Grid input: select on press, fill-handle double-click, whole-line references (#900, #877, #872, #873, #875)

- A press selects its cell when the button goes down and a drag extends from it; Shift/Ctrl act
  on the press; checkboxes and links act on the click; the selection border, a selected column
  header, objects and Page Layout headers/footers wait for the drag or click (#900).
- Double-clicking the fill handle fills down to the bottom of the data region around the source,
  stopping above the first filled cell under it: new `edit.autoFillToData`, tested against 13
  cases observed in Excel (#877). The old double-click handler was never reached.
- While typing a formula, column and row headings point `B:B`, `B:D`, `3:3` into it (#872);
  whole-column and whole-row references are coloured and outlined (#873, #875); F4 toggles them
  `$B:$D` / `B:D` as Excel does.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

.github/workflows/flatpak-pages.yml

@@ -0,0 +1,176 @@
+name: Publish Flatpak repository to Pages
+
+on:
+  release:
+    types: [published]
+  workflow_dispatch:
+    inputs:
+      release_tag:
+        description: "Published GitHub release tag to publish (for example, v1.2.3)"
+        required: true
+        type: string
+
+permissions:
+  contents: read
+
+concurrency:
+  group: flatpak-pages-${{ github.repository }}
+  cancel-in-progress: false
+
+jobs:
+  build:
+    name: Build Flatpak repository
+    # Pre-releases (rc builds) never reach the stable branch: a published pre-release is skipped
+    # here, and the validation step below refuses a manual tag with a pre-release suffix.
+    if: github.event_name != 'release' || !github.event.release.prerelease
+    runs-on: ubuntu-24.04
+    permissions:
+      contents: read
+      # configure-pages only reads the Pages configuration (base_url); deploy needs write.
+      pages: read
+    env:
+      GH_TOKEN: ${{ github.token }}
+      RELEASE_TAG: ${{ github.event.release.tag_name || inputs.release_tag }}
+      APP_ID: ai.storyteller.gridcraft
+    steps:
+      - name: Configure Pages
+        id: pages
+        uses: actions/configure-pages@45bfe0192ca1faeb007ade9deae92b16b8254a0d # v6.0.0
+
+      - name: Install Flatpak repository tools
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends flatpak ostree
+
+      - name: Download and validate release bundles
+        shell: bash
+        run: |
+          set -euo pipefail
+          tag="$RELEASE_TAG"
+          if ! printf '%s' "$tag" | grep -Eq '^v(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)(-((0|[1-9][0-9]*|[0-9]*[A-Za-z-][0-9A-Za-z-]*)(\.(0|[1-9][0-9]*|[0-9]*[A-Za-z-][0-9A-Za-z-]*))*))?(\+[0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*)?$'; then
+            echo "::error::Release tag '$tag' is not strict SemVer prefixed with v"
+            exit 1
+          fi
+          # A pre-release has a "-" before any "+build" metadata (v1.2.3-rc.1).
+          case "${tag%%+*}" in
+            *-*)
+              echo "::error::$tag is a pre-release; only stable releases are published to the Flatpak repository"
+              exit 1
+              ;;
+          esac
+          published_tag="$(gh api "repos/$GITHUB_REPOSITORY/releases/tags/$tag" --jq \
+            'select(.draft == false and .prerelease == false and .published_at != null) | .tag_name')"
+          if [[ "$published_tag" != "$tag" ]]; then
+            echo "::error::$tag is not a published stable (non-pre-release) release in $GITHUB_REPOSITORY"
+            exit 1
+          fi
+
+          version="${tag#v}"
+          mkdir -p bundles
+          gh release download "$tag" --repo "$GITHUB_REPOSITORY" \
+            --pattern SHA256SUMS.txt --dir bundles
+          for arch in x86_64 aarch64; do
+            asset="gridcraft-$version-linux-$arch.flatpak"
+            gh release download "$tag" --repo "$GITHUB_REPOSITORY" \
+              --pattern "$asset" --dir bundles
+            test -s "bundles/$asset"
+            (
+              cd bundles
+              awk -v file="$asset" '$2 == file || $2 == "*" file { print; found=1 } END { exit !found }' \
+                SHA256SUMS.txt | sha256sum --check -
+            )
+          done
+          test "$(find bundles -maxdepth 1 -type f -name '*.flatpak' | wc -l)" -eq 2
+
+          for arch in x86_64 aarch64; do
+            asset="bundles/gridcraft-$version-linux-$arch.flatpak"
+            validation_repo="$(mktemp -d)"
+            ostree --repo="$validation_repo" init --mode=archive-z2
+            flatpak build-import-bundle "$validation_repo" "$asset"
+            expected_ref="app/$APP_ID/$arch/stable"
+            ostree --repo="$validation_repo" refs | grep -Fxq "$expected_ref" || {
+              echo "::error::$(basename "$asset") does not contain $expected_ref"
+              exit 1
+            }
+            rm -rf "$validation_repo"
+          done
+
+      - name: Build repository and site
+        shell: bash
+        env:
+          PAGES_BASE_URL: ${{ steps.pages.outputs.base_url }}
+        run: |
+          set -euo pipefail
+          site="$RUNNER_TEMP/site"
+          repo_dir="$site/flatpak/repo"
+          mkdir -p "$repo_dir"
+          ostree --repo="$repo_dir" init --mode=archive-z2
+
+          previous_url="${PAGES_BASE_URL%/}/flatpak/repo"
+          if curl --fail --silent --show-error --location \
+            --output /dev/null "$previous_url/summary"; then
+            ostree --repo="$repo_dir" remote add --no-gpg-verify previous "$previous_url"
+            ostree --repo="$repo_dir" pull --mirror previous
+            ostree --repo="$repo_dir" remote delete previous
+          fi
+
+          version="${RELEASE_TAG#v}"
+          for arch in x86_64 aarch64; do
+            flatpak build-import-bundle "$repo_dir" \
+              "bundles/gridcraft-$version-linux-$arch.flatpak"
+          done
+          # Prune unreachable objects and keep at most 3 commits per ref, so the Pages repository
+          # (re-mirrored and re-deployed on every release) does not grow without bound.
+          flatpak build-update-repo \
+            --prune --prune-depth=3 \
+            --title="GridCraft" \
+            --comment='Official GridCraft releases' \
+            --description='Official Flatpak repository for GridCraft' \
+            --homepage="https://github.com/$GITHUB_REPOSITORY" \
+            --default-branch=stable \
+            "$repo_dir"
+
+          for arch in x86_64 aarch64; do
+            ostree --repo="$repo_dir" rev-parse "app/$APP_ID/$arch/stable" >/dev/null
+          done
+          test -s "$repo_dir/summary"
+
+          base_url="${PAGES_BASE_URL%/}"
+          repo_url="$base_url/flatpak/repo/"
+          cat >"$site/flatpak/gridcraft.flatpakrepo" <<META
+          [Flatpak Repo]
+          Title=GridCraft
+          Comment=Official GridCraft releases
+          Description=Official Flatpak repository for GridCraft
+          Url=$repo_url
+          Homepage=https://github.com/$GITHUB_REPOSITORY
+          META
+          cat >"$site/flatpak/index.html" <<HTML
+          <!doctype html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1"><title>GridCraft Flatpak repository</title></head><body><main><h1>GridCraft Flatpak repository</h1><p>Latest published release: <strong>$RELEASE_TAG</strong></p><p><a href="gridcraft.flatpakrepo">Add the GridCraft repository</a></p><pre>flatpak remote-add --if-not-exists gridcraft $base_url/flatpak/gridcraft.flatpakrepo
+          flatpak install gridcraft $APP_ID</pre></main></body></html>
+          HTML
+          cat >"$site/index.html" <<HTML
+          <!doctype html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1"><title>GridCraft downloads</title></head><body><main><h1>GridCraft downloads</h1><p><a href="flatpak/">Flatpak repository</a></p><p><a href="https://github.com/$GITHUB_REPOSITORY/releases/tag/$RELEASE_TAG">Release assets</a></p></main></body></html>
+          HTML
+          touch "$site/.nojekyll"
+
+      - name: Upload Pages artifact
+        uses: actions/upload-pages-artifact@fc324d3547104276b827a68afc52ff2a11cc49c9 # v5.0.0
+        with:
+          path: ${{ runner.temp }}/site
+          include-hidden-files: true
+
+  deploy:
+    name: Deploy Pages
+    needs: build
+    runs-on: ubuntu-24.04
+    permissions:
+      pages: write
+      id-token: write
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@368f82528645a54fb793d4d04e342629a3f51346 # v5.0.1

.github/workflows/freebsd.yml

@@ -1,27 +1,95 @@
 # Builds and tests the workspace on FreeBSD, inside a FreeBSD VM on a Linux runner
 # (GitHub has no FreeBSD runners). GPU tests skip themselves when the VM has no adapter.
+# Test builds run only from the `release` branch (a manual run from any other branch is skipped).
+# Packaging runs (release.yml calls it that way) run from any branch, so a release.yml dry run
+# from a branch builds the tarball too; they need no secrets.
+#
+# With `package: true` (release.yml calls it that way, or a manual run) it instead builds the
+# release binaries and uploads `gridcraft-<version>-freebsd-x86_64.tar.gz` as the
+# `release-freebsd` artifact (packaging/freebsd/package.sh), which release.yml attaches to the
+# draft GitHub Release.
 name: FreeBSD
 
 on:
-  push:
-    branches: [release]
-  pull_request:
-    paths:
-      - .github/workflows/freebsd.yml
-      - packaging/freebsd/**
-      - packaging/env.sh
   workflow_dispatch:
+    inputs:
+      package:
+        description: "Build the release tarball instead of running the tests"
+        type: boolean
+        default: false
+  workflow_call:
+    inputs:
+      version:
+        description: "Version for the artifact name (empty: Cargo.toml)"
+        type: string
+        default: ""
+      version_override:
+        description: "Also write the version into Cargo.toml before building (test runs)"
+        type: boolean
+        default: false
+      package:
+        type: boolean
+        default: false
 
 concurrency:
-  group: freebsd-${{ github.ref }}
-  cancel-in-progress: true
+  # Called from release.yml, github.workflow is the caller's name; keep the groups apart.
+  group: freebsd-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.workflow == 'FreeBSD' }}
 
 permissions:
   contents: read
 
 jobs:
   freebsd:
-    # Intentionally tracked at @main (not SHA-pinned) so org-wide CI improvements, security fixes, and build optimizations propagate without PR churn across all craftapp repos.
-    uses: storytold/craft-common-actions/.github/workflows/freebsd.yml@main
-    with:
-      craft-fonts-ref: abb83316d96aa59c1cf64784289e378fe9fa5695
+    name: FreeBSD 14 (${{ inputs.package && 'package' || 'build + test' }})
+    if: github.ref == 'refs/heads/release' || inputs.package
+    runs-on: ubuntu-latest
+    timeout-minutes: 300
+    env:
+      GRIDCRAFT_VERSION: ${{ inputs.version }}
+      GRIDCRAFT_VERSION_OVERRIDE: ${{ inputs.version_override && '1' || '' }}
+      GRIDCRAFT_PACKAGE: ${{ inputs.package && '1' || '' }}
+      GRIDCRAFT_BUILD_SHA: ${{ github.sha }}
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Check out craft-fonts
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          repository: storytold/craft-fonts
+          ref: abb83316d96aa59c1cf64784289e378fe9fa5695
+          path: craft-fonts
+      - name: Build in a FreeBSD VM
+        uses: vmactions/freebsd-vm@c46abacb49f09938ca4e1702d15d836285d694cc # v1.5.9
+        with:
+          release: "14.3"
+          usesh: true
+          cpu: 4
+          mem: 12288
+          envs: "GRIDCRAFT_VERSION GRIDCRAFT_VERSION_OVERRIDE GRIDCRAFT_PACKAGE GRIDCRAFT_BUILD_SHA"
+          # Only the packaging run brings files back (dist/release). The target dir lives outside
+          # the synced checkout, because copying it out of the VM fails on large builds.
+          copyback: ${{ inputs.package }}
+          prepare: |
+            pkg install -y bash git curl pkgconf cmake python3 libxkbcommon wayland libX11 libXcursor libXrandr libXi libxcb mesa-libs vulkan-loader gtk3 fontconfig freetype2
+            curl -fsSL https://sh.rustup.rs | sh -s -- -y --profile minimal
+          run: |
+            . "$HOME/.cargo/env"
+            # The checkout is synced in under another owner; let tests that call git read it.
+            git config --global --add safe.directory "*"
+            export CARGO_TARGET_DIR=/var/tmp/gridcraft-target CARGO_PROFILE_DEV_DEBUG=0
+            rustc --version
+            if [ -n "$GRIDCRAFT_PACKAGE" ]; then
+              if [ -n "$GRIDCRAFT_VERSION_OVERRIDE" ]; then
+                cargo run -q -p xtask --no-default-features -- version set "$GRIDCRAFT_VERSION"
+              fi
+              CRAFT_FONTS_DIR="$PWD/craft-fonts" CRAFT_FONTS_REQUIRED=1 bash packaging/freebsd/package.sh
+            else
+              cargo build --workspace --all-targets --locked
+              CRAFT_FONTS_DIR="$PWD/craft-fonts" cargo test --workspace --locked
+            fi
+      - uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        if: inputs.package
+        with:
+          name: release-freebsd
+          path: dist/release/*
+          if-no-files-found: error

.github/workflows/nix.yml

@@ -1,33 +0,0 @@
-# Evaluates the Nix flake (no build, about a minute): `nix build` / `nix develop` stop at evaluation
-# when Cargo.lock gains something nix/package.nix can't vendor, and nothing else would notice.
-name: Nix
-
-on:
-  push:
-    branches: [main]
-    paths: ["flake.nix", "flake.lock", "nix/**", "Cargo.lock", ".github/workflows/nix.yml"]
-  pull_request:
-    paths: ["flake.nix", "flake.lock", "nix/**", "Cargo.lock", ".github/workflows/nix.yml"]
-  workflow_dispatch:
-
-permissions:
-  contents: read
-
-concurrency:
-  group: nix-${{ github.ref }}
-  cancel-in-progress: true
-
-jobs:
-  eval:
-    runs-on: ubuntu-latest
-    timeout-minutes: 15
-    steps:
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-      - uses: cachix/install-nix-action@13d8dd58da0234aa297dedd986986ccb8e7f3e24 # v31.11.1
-      - name: nix flake check --no-build
-        run: |
-          if [ -f flake.nix ]; then
-            nix flake check --no-build --all-systems
-          else
-            echo "No flake.nix present in this repository; skipping check."
-          fi

Cargo.lock

@@ -1496,7 +1496,7 @@ dependencies = [
 
 [[package]]
 name = "gridcraft"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "arboard",
  "craft-print",
@@ -1518,7 +1518,7 @@ dependencies = [
 
 [[package]]
 name = "gridcraft-calc"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "gridcraft-core",
  "gridcraft-formula",
@@ -1530,7 +1530,7 @@ dependencies = [
 
 [[package]]
 name = "gridcraft-chart"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "gridcraft-calc",
  "gridcraft-core",
@@ -1541,7 +1541,7 @@ dependencies = [
 
 [[package]]
 name = "gridcraft-cli"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "gridcraft-engine",
  "gridcraft-mcp",
@@ -1553,7 +1553,7 @@ dependencies = [
 
 [[package]]
 name = "gridcraft-core"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "js-sys",
  "serde",
@@ -1563,7 +1563,7 @@ dependencies = [
 
 [[package]]
 name = "gridcraft-engine"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "gridcraft-calc",
  "gridcraft-chart",
@@ -1584,7 +1584,7 @@ dependencies = [
 
 [[package]]
 name = "gridcraft-formula"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "gridcraft-core",
  "serde",
@@ -1593,7 +1593,7 @@ dependencies = [
 
 [[package]]
 name = "gridcraft-functions"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "gridcraft-core",
  "regex",
@@ -1601,7 +1601,7 @@ dependencies = [
 
 [[package]]
 name = "gridcraft-mcp"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "gridcraft-engine",
  "log",
@@ -1610,7 +1610,7 @@ dependencies = [
 
 [[package]]
 name = "gridcraft-model"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "gridcraft-core",
  "gridcraft-formula",
@@ -1622,18 +1622,18 @@ dependencies = [
 
 [[package]]
 name = "gridcraft-numfmt"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "gridcraft-core",
 ]
 
 [[package]]
 name = "gridcraft-pdf"
-version = "0.8.0"
+version = "0.6.1"
 
 [[package]]
 name = "gridcraft-ui-egui"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "craft-ui",
  "egui",
@@ -1655,7 +1655,7 @@ dependencies = [
 
 [[package]]
 name = "gridcraft-web"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "eframe",
  "egui",
@@ -1672,7 +1672,7 @@ dependencies = [
 
 [[package]]
 name = "gridcraft-xlsx"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "aes",
  "gridcraft-core",
@@ -4526,7 +4526,7 @@ checksum = "e450f9b2ed1dff33c94c12589a87338689467b9c4f5d8a5710bd09a847d2c8a7"
 
 [[package]]
 name = "xtask"
-version = "0.8.0"
+version = "0.6.1"
 dependencies = [
  "gridcraft-engine",
  "serde_json",

Cargo.toml

@@ -4,7 +4,7 @@ members = ["crates/*", "apps/*", "xtask"]
 default-members = ["crates/*", "apps/gridcraft", "apps/gridcraft-cli", "xtask"]
 
 [workspace.package]
-version = "0.8.0"
+version = "0.6.1"
 edition = "2024"
 license = "MIT OR Apache-2.0"
 rust-version = "1.90"

apps/gridcraft/src/control_server.rs

@@ -1,11 +1,7 @@
 //! Localhost JSON-lines control server. Each connection may send many requests; each line
 //! `{"id":…, "method":…, "params":…}` gets one reply line `{"id":…, "ok":…, …}`.
-//!
-//! The server only reads requests: a line that is not a JSON object with a string `method` (an
-//! HTTP request line, a stray `nc`, binary data) gets one error reply and the connection is
-//! closed, so nothing sent after it runs.
 
-use std::io::{BufRead, BufReader, Read, Write};
+use std::io::{BufRead, BufReader, Write};
 use std::net::{TcpListener, TcpStream};
 use std::sync::mpsc::{Receiver, Sender, channel};
 use std::time::Duration;
@@ -17,13 +13,6 @@ const MAX_LINE: usize = 64 * 1024 * 1024;
 
 pub fn start(port: u16, ctx: egui::Context) -> std::io::Result<Receiver<ControlRequest>> {
     let listener = TcpListener::bind(("127.0.0.1", port))?;
-    let rx = serve_listener(listener, ctx)?;
-    log::info!("control channel listening on 127.0.0.1:{port}");
-    Ok(rx)
-}
-
-/// Accept connections on `listener`; requests arrive on the returned receiver.
-fn serve_listener(listener: TcpListener, ctx: egui::Context) -> std::io::Result<Receiver<ControlRequest>> {
     let (tx, rx) = channel();
     std::thread::Builder::new().name("control".into()).spawn(move || {
         for stream in listener.incoming().flatten() {
@@ -32,184 +21,47 @@ fn serve_listener(listener: TcpListener, ctx: egui::Context) -> std::io::Result<
             let _ = std::thread::Builder::new().name("control-conn".into()).spawn(move || serve(stream, tx, ctx));
         }
     })?;
+    log::info!("control channel listening on 127.0.0.1:{port}");
     Ok(rx)
 }
 
-/// Read one `\n`-terminated line of at most `max` bytes into `buf` (newline stripped).
-/// `Ok(false)` at end of stream; `Err` when the line is too long or the read fails.
-fn read_bounded_line(reader: &mut impl BufRead, buf: &mut Vec<u8>, max: usize) -> Result<bool, String> {
-    buf.clear();
-    // `take` bounds the bytes buffered for one line: a peer can't make us allocate more than `max`.
-    let limit = u64::try_from(max).unwrap_or(u64::MAX).saturating_add(1);
-    let n = reader.take(limit).read_until(b'\n', buf).map_err(|e| e.to_string())?;
-    if n == 0 {
-        return Ok(false);
-    }
-    if buf.last() == Some(&b'\n') {
-        buf.pop();
-        return Ok(true);
-    }
-    if buf.len() > max {
-        return Err(format!("request too large (over {max} bytes); closing the connection"));
-    }
-    // Last line without a newline, then end of stream.
-    Ok(true)
-}
-
-/// One request line, parsed.
-enum Line {
-    Request {
-        id: Json,
-        method: String,
-        params: Json,
-    },
-    Blank,
-    /// Not a request: reply with this error and close the connection.
-    Reject(String),
-}
-
-fn parse_line(bytes: &[u8]) -> Line {
-    let Ok(text) = std::str::from_utf8(bytes) else {
-        return Line::Reject("not a control request (invalid UTF-8); closing the connection".into());
-    };
-    let text = text.trim();
-    if text.is_empty() {
-        return Line::Blank;
-    }
-    if is_http_request_line(text) {
-        return Line::Reject("HTTP is not served here: this port takes JSON lines; closing the connection".into());
-    }
-    let msg = match serde_json::from_str::<Json>(text) {
-        Ok(v) => v,
-        Err(e) => return Line::Reject(format!("invalid JSON ({e}); expected one JSON request object per line; closing the connection")),
-    };
-    let Some(obj) = msg.as_object() else {
-        return Line::Reject("not a control request (expected a JSON object); closing the connection".into());
-    };
-    let Some(method) = obj.get("method").and_then(Json::as_str) else {
-        return Line::Reject("not a control request (missing string `method`); closing the connection".into());
-    };
-    Line::Request {
-        id: obj.get("id").cloned().unwrap_or(Json::Null),
-        method: method.to_string(),
-        params: obj.get("params").cloned().unwrap_or(json!({})),
-    }
-}
-
-/// An HTTP/1 request line (`POST / HTTP/1.1`) or the HTTP/2 preface (`PRI * HTTP/2.0`).
-fn is_http_request_line(text: &str) -> bool {
-    const METHODS: [&str; 10] = ["GET", "HEAD", "POST", "PUT", "DELETE", "CONNECT", "OPTIONS", "TRACE", "PATCH", "PRI"];
-    text.split_once(' ').is_some_and(|(method, _)| METHODS.contains(&method))
-        || text.rsplit_once(' ').is_some_and(|(_, version)| version.starts_with("HTTP/"))
-}
-
 fn serve(stream: TcpStream, tx: Sender<ControlRequest>, ctx: egui::Context) {
     let Ok(read) = stream.try_clone() else { return };
     let mut out = stream;
-    let mut reader = BufReader::new(read);
-    let mut buf = Vec::new();
-    loop {
-        let reject = match read_bounded_line(&mut reader, &mut buf, MAX_LINE) {
-            Ok(false) => break,
-            // The peer is gone before sending a line: nobody to tell.
-            Err(_) if buf.is_empty() => break,
-            Err(e) => e,
-            Ok(true) => match parse_line(&buf) {
-                Line::Blank => continue,
-                Line::Reject(e) => e,
-                Line::Request { id, method, params } => {
-                    let (req, rx) = ControlRequest::new(method, params);
-                    if tx.send(req).is_err() {
-                        break;
-                    }
-                    // Wake the UI thread: egui only runs frames when something happens.
-                    ctx.request_repaint();
-                    let mut reply = rx
-                        .recv_timeout(Duration::from_secs(60))
-                        .unwrap_or_else(|_| json!({"ok": false, "error": "timed out waiting for the UI (is the window minimised?)"}));
-                    if let Some(o) = reply.as_object_mut() {
-                        o.insert("id".into(), id);
-                    }
-                    if writeln!(out, "{reply}").is_err() {
-                        break;
-                    }
-                    continue;
-                }
-            },
-        };
-        // The connection closes either way; a peer that can't read the reason loses nothing.
-        let _ = writeln!(out, "{}", json!({"ok": false, "error": reject}));
-        break;
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    /// Send `input` on a new connection and read reply lines until the server closes it.
-    fn exchange(addr: std::net::SocketAddr, input: &[u8]) -> Vec<Json> {
-        let mut c = TcpStream::connect(addr).unwrap();
-        c.set_read_timeout(Some(Duration::from_secs(5))).unwrap();
-        c.write_all(input).unwrap();
-        // A read timeout ends the list too: the server kept the connection open.
-        BufReader::new(c).lines().map_while(Result::ok).map(|l| serde_json::from_str(&l).unwrap()).collect()
-    }
-
-    fn serve_on_loopback() -> (std::net::SocketAddr, Receiver<ControlRequest>) {
-        let listener = TcpListener::bind(("127.0.0.1", 0)).unwrap();
-        let addr = listener.local_addr().unwrap();
-        (addr, serve_listener(listener, egui::Context::default()).unwrap())
-    }
-
-    /// A browser can POST to the port: its request line closes the connection before the JSON
-    /// line in its body is read, so nothing is dispatched.
-    #[test]
-    fn an_http_request_closes_the_connection_before_its_body_is_dispatched() {
-        let (addr, rx) = serve_on_loopback();
-        let http = b"POST / HTTP/1.1\r\nHost: 127.0.0.1:7979\r\nContent-Type: text/plain\r\n\r\n\
-            {\"id\":1,\"method\":\"engine.execute\",\"params\":{\"command\":\"cell.set\",\"params\":{\"cell\":\"A1\",\"input\":\"x\"}}}\n";
-        let replies = exchange(addr, http);
-        assert_eq!(replies.len(), 1, "{replies:?}");
-        assert!(replies[0]["error"].as_str().unwrap().contains("closing the connection"), "{replies:?}");
-        assert!(rx.try_recv().is_err(), "the body was dispatched");
-    }
-
-    #[test]
-    fn a_line_that_is_not_a_request_closes_the_connection() {
-        let (addr, rx) = serve_on_loopback();
-        std::thread::spawn(move || {
-            for req in rx {
-                let _ = req.reply.send(json!({"ok": true}));
+    let reader = BufReader::new(read);
+    for line in reader.lines() {
+        let Ok(line) = line else { break };
+        if line.trim().is_empty() {
+            continue;
+        }
+        if line.len() > MAX_LINE {
+            let _ = writeln!(out, "{}", json!({"ok": false, "error": "request too large"}));
+            continue;
+        }
+        let msg: Json = match serde_json::from_str(&line) {
+            Ok(v) => v,
+            Err(e) => {
+                let _ = writeln!(out, "{}", json!({"ok": false, "error": format!("invalid JSON: {e}")}));
+                continue;
             }
-        });
-        let mut c = TcpStream::connect(addr).unwrap();
-        c.set_read_timeout(Some(Duration::from_secs(5))).unwrap();
-        c.write_all(b"{\"id\":1,\"method\":\"a\"}\r\n\n{\"id\":2,\"method\":\"b\"}\n").unwrap();
-        let mut r = BufReader::new(c);
-        for id in [1, 2] {
-            let mut line = String::new();
-            r.read_line(&mut line).unwrap();
-            assert_eq!(serde_json::from_str::<Json>(&line).unwrap()["id"], id, "{line}");
+        };
+        let id = msg.get("id").cloned().unwrap_or(Json::Null);
+        let method = msg.get("method").and_then(Json::as_str).unwrap_or("").to_string();
+        let params = msg.get("params").cloned().unwrap_or(json!({}));
+        let (req, rx) = ControlRequest::new(method, params);
+        if tx.send(req).is_err() {
+            break;
         }
-        for junk in [&b"hello\n"[..], b"[1,2]\n", b"{\"id\":1}\n", b"{\"method\":5}\n", b"\xff\xfe\n", b"GET /x HTTP/1.1\n"] {
-            let mut input = junk.to_vec();
-            input.extend_from_slice(b"{\"id\":2,\"method\":\"b\"}\n");
-            let replies = exchange(addr, &input);
-            assert_eq!(replies.len(), 1, "{replies:?}");
-            assert_eq!(replies[0]["ok"], false);
+        // Wake the UI thread: egui only runs frames when something happens.
+        ctx.request_repaint();
+        let mut reply = rx
+            .recv_timeout(Duration::from_secs(60))
+            .unwrap_or_else(|_| json!({"ok": false, "error": "timed out waiting for the UI (is the window minimised?)"}));
+        if let Some(o) = reply.as_object_mut() {
+            o.insert("id".into(), id);
+        }
+        if writeln!(out, "{reply}").is_err() {
+            break;
         }
-        assert!(is_http_request_line("OPTIONS * HTTP/1.1"));
-        assert!(is_http_request_line("PRI * HTTP/2.0"));
-        assert!(!is_http_request_line("{\"method\":\"GET /\"}"));
-    }
-
-    #[test]
-    fn an_overlong_line_is_refused_without_reading_the_rest() {
-        let mut buf = Vec::new();
-        let long = [b'x'; 100];
-        let mut input: &[u8] = &long;
-        assert!(read_bounded_line(&mut input, &mut buf, 10).is_err());
-        assert_eq!(input.len(), 100 - 11, "the rest of the line is left unread");
     }
 }

crates/engine/src/cmd/edit.rs

@@ -83,6 +83,15 @@ pub fn specs() -> Vec<CommandSpec> {
             has_doc,
             auto_fill
         ),
+        cmd!(
+            "edit.autoFillToData",
+            "AutoFill to Adjacent Data",
+            [],
+            None,
+            "{source?: \"B1:B4\", mode?: series|alternate|copy|formats|values}: the fill-handle double-click: fills the source down to the bottom of the data region around it, stopping above the first filled cell under it; {target: null} when there is nothing to fill",
+            has_doc,
+            auto_fill_to_data
+        ),
         cmd!(
             "edit.fillSeries",
             "Series…",
@@ -1246,9 +1255,6 @@ fn clear(s: &mut Session, p: &Json, what: &str) -> Result<Json> {
             };
             let cells: Vec<(CellRef, Cell)> =
                 cx.wb.sheet(sheet).map(|sh| sh.cells.iter_range(r).map(|(c, x)| (c, x.clone())).collect()).unwrap_or_default();
-            // Report every stored cell we touch, even beyond a million coordinates in a sparse
-            // selection. Removed formula anchors must also reach calc so their spills disappear.
-            cx.changed.extend(cells.iter().map(|(c, _)| (sheet, *c)));
             let mut cells = cells;
             if what == "contents" {
                 for (_, cell) in cells.iter_mut() {
@@ -1287,24 +1293,10 @@ fn clear(s: &mut Session, p: &Json, what: &str) -> Result<Json> {
                 sh.hyperlinks.retain(|c, _| !r.contains(*c));
             }
             if matches!(what, "all" | "formats") {
-                let mut unmerged = false;
-                sh.merges.retain(|m| {
-                    let keep = !r.contains_range(m);
-                    unmerged |= !keep;
-                    keep
-                });
-                if unmerged {
-                    // An empty merge can block a spill without storing any cells in this range.
-                    // As in Unmerge, retry blocked formula anchors that could reach the freed area.
-                    let reach = RangeRef::new(CellRef::new(0, 0), r.end);
-                    let blocked: Vec<_> = sh
-                        .cells
-                        .iter_range(reach)
-                        .filter(|(_, cell)| cell.formula.is_some() && cell.value == Value::Error(gridcraft_core::CellError::Spill))
-                        .map(|(c, _)| (sheet, c))
-                        .collect();
-                    cx.changed.extend(blocked);
-                }
+                sh.merges.retain(|m| !r.contains_range(m));
+            }
+            for c in r.iter().take(1_000_000) {
+                cx.changed.push((sheet, c));
             }
         }
         Ok(Json::Null)
@@ -1369,6 +1361,19 @@ fn auto_fill(s: &mut Session, p: &Json) -> Result<Json> {
     })
 }
 
+fn auto_fill_to_data(s: &mut Session, p: &Json) -> Result<Json> {
+    let sheet = target_sheet(s, p)?;
+    let src = str_param(p, "source").and_then(RangeRef::parse).map_or_else(|| target_range(s, p), Ok)?;
+    let sh = s.doc()?.wb.sheets.get(sheet).ok_or_else(|| bad("edit.autoFillToData", "no such sheet"))?;
+    let Some(target) = crate::selection::fill_down_extent(sh, src) else { return Ok(json!({"target": null})) };
+    let mut params = json!({"source": src.a1(), "target": target.a1(), "sheet": sheet});
+    if let Some(mode) = str_param(p, "mode") {
+        params["mode"] = json!(mode);
+    }
+    auto_fill(s, &params)?;
+    Ok(json!({"target": target.a1()}))
+}
+
 fn fill_series(s: &mut Session, p: &Json) -> Result<Json> {
     let sheet = target_sheet(s, p)?;
     let r = target_range(s, p)?;

crates/engine/src/selection.rs

@@ -186,11 +186,16 @@ pub fn jump(sheet: &Sheet, from: CellRef, dr: i64, dc: i64) -> CellRef {
 
 /// The contiguous data region around `c` (Ctrl+A / Ctrl+Shift+8, AutoSum, sort, tables).
 pub fn current_region(sheet: &Sheet, c: CellRef) -> RangeRef {
+    current_region_of(sheet, RangeRef::cell(c))
+}
+
+/// [`current_region`] grown from a whole range rather than one cell.
+pub fn current_region_of(sheet: &Sheet, from: RangeRef) -> RangeRef {
     let filled = |c: CellRef| sheet.cell(c).is_some_and(|x| !x.value.is_empty() || x.formula.is_some()) || sheet.spill.contains_key(&c);
     // Whether a row (or column) has a filled cell between two columns (rows), inclusive.
     let row_has = |row: u32, a: u32, b: u32| (a..=b).any(|col| filled(CellRef::new(row, col)));
     let col_has = |col: u32, a: u32, b: u32| (a..=b).any(|row| filled(CellRef::new(row, col)));
-    let (mut r0, mut r1, mut c0, mut c1) = (c.row, c.row, c.col, c.col);
+    let (mut r0, mut r1, mut c0, mut c1) = (from.start.row, from.end.row, from.start.col, from.end.col);
     // Grow one side at a time while the line next to it (diagonals included) has data. Each
     // pass scans only the lines next to the region, so tall regions take linear time.
     loop {
@@ -216,6 +221,27 @@ pub fn current_region(sheet: &Sheet, c: CellRef) -> RangeRef {
     RangeRef::new(CellRef::new(r0, c0), CellRef::new(r1, c1))
 }
 
+/// Where a double-click on the fill handle fills `src` to, as observed in Excel: down to the last
+/// row of the data region around it (its current region, so a column of data on either side, or
+/// one reached only diagonally, counts), stopping above the first filled cell under the source.
+/// `None` when there is nothing to fill.
+pub fn fill_down_extent(sheet: &Sheet, src: RangeRef) -> Option<RangeRef> {
+    let region = current_region_of(sheet, src);
+    let mut last = region.end.row;
+    if last <= src.end.row {
+        return None;
+    }
+    // A filled cell under the source ends the fill just above it. Only stored cells are visited,
+    // so a tall region costs what the sheet holds, not its height.
+    let under = RangeRef::new(CellRef::new(src.end.row + 1, src.start.col), CellRef::new(last, src.end.col));
+    let first_cell = sheet.cells.iter_range(under).find(|(_, x)| !x.value.is_empty() || x.formula.is_some()).map(|(c, _)| c.row);
+    let first_spill = sheet.spill.range(under.start..=under.end).map(|(c, _)| *c).find(|c| under.contains(*c)).map(|c| c.row);
+    if let Some(r) = first_cell.into_iter().chain(first_spill).min() {
+        last = r - 1;
+    }
+    (last > src.end.row).then(|| RangeRef::new(src.start, CellRef::new(last, src.end.col)))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

crates/engine/src/tests.rs

@@ -734,6 +734,127 @@ fn fill_series() {
     assert_eq!(v(&s, "C2"), Value::from("Item 10"));
 }
 
+/// The fill-handle double-click (#877), case by case as observed in Excel 365 for Windows.
+#[test]
+#[allow(clippy::disallowed_methods)] // times the tall fill; native-only test
+fn fill_handle_double_click_fills_to_adjacent_data() {
+    // The column of a cell, rows 1..=n, with `.` for empty.
+    let col = |s: &Session, c: &str, n: u32| -> String {
+        (1..=n)
+            .map(|r| match v(s, &format!("{c}{r}")) {
+                Value::Empty => ".".to_string(),
+                Value::Number(x) => format!("{x}"),
+                Value::Text(t) => t.to_string(),
+                x => format!("{x:?}"),
+            })
+            .collect::<Vec<_>>()
+            .join(",")
+    };
+    let nums = |s: &mut Session, c: &str, rows: &[u32]| {
+        for r in rows {
+            s.execute("cell.set", json!({"cell": format!("{c}{r}"), "input": r.to_string()})).unwrap();
+        }
+    };
+    let dbl = |s: &mut Session, src: &str| s.execute("edit.autoFillToData", json!({"source": src})).unwrap();
+
+    // The issue's sheet: a 2, 4, 6, 8 series next to 1..10 continues to row 10.
+    let mut s = self::s();
+    nums(&mut s, "A", &(1..=10).collect::<Vec<_>>());
+    s.execute("range.setValues", json!({"range": "B1", "values": [[2], [4], [6], [8]]})).unwrap();
+    assert_eq!(dbl(&mut s, "B1:B4"), json!({"target": "B1:B10"}));
+    assert_eq!(col(&s, "B", 12), "2,4,6,8,10,12,14,16,18,20,.,.");
+    assert_eq!(s.doc().unwrap().selection.current().a1(), "B1:B10");
+    // Undo takes the whole fill back in one step.
+    s.execute("edit.undo", json!({})).unwrap();
+    assert_eq!(col(&s, "B", 12), "2,4,6,8,.,.,.,.,.,.,.,.");
+
+    // Its last cell alone copies.
+    assert_eq!(dbl(&mut s, "B4"), json!({"target": "B4:B10"}));
+    assert_eq!(col(&s, "B", 12), "2,4,6,8,8,8,8,8,8,8,.,.");
+
+    // Data only on the right counts.
+    let mut s = self::s();
+    nums(&mut s, "D", &(1..=8).collect::<Vec<_>>());
+    s.execute("cell.set", json!({"cell": "C1", "input": "5"})).unwrap();
+    dbl(&mut s, "C1");
+    assert_eq!(col(&s, "C", 10), "5,5,5,5,5,5,5,5,.,.");
+
+    // A filled cell under the source stops the fill above it.
+    let mut s = self::s();
+    nums(&mut s, "A", &(1..=10).collect::<Vec<_>>());
+    s.execute("cell.set", json!({"cell": "B1", "input": "7"})).unwrap();
+    s.execute("cell.set", json!({"cell": "B6", "input": "x"})).unwrap();
+    dbl(&mut s, "B1");
+    assert_eq!(col(&s, "B", 12), "7,7,7,7,7,x,.,.,.,.,.,.");
+    // ... and right under it, nothing happens.
+    let mut s = self::s();
+    nums(&mut s, "A", &(1..=6).collect::<Vec<_>>());
+    s.execute("range.setValues", json!({"range": "B1", "values": [[7], [9]]})).unwrap();
+    assert_eq!(dbl(&mut s, "B1"), json!({"target": null}));
+    assert_eq!(col(&s, "B", 8), "7,9,.,.,.,.,.,.");
+
+    // A gap in the neighbouring column ends the region.
+    let mut s = self::s();
+    nums(&mut s, "A", &[1, 2, 3, 4, 5, 7, 8, 9, 10]);
+    s.execute("cell.set", json!({"cell": "B1", "input": "7"})).unwrap();
+    dbl(&mut s, "B1");
+    assert_eq!(col(&s, "B", 12), "7,7,7,7,7,.,.,.,.,.,.,.");
+
+    // The longer side wins: 3 rows on the left, 9 on the right.
+    let mut s = self::s();
+    nums(&mut s, "A", &[1, 2, 3]);
+    nums(&mut s, "C", &(1..=9).collect::<Vec<_>>());
+    s.execute("cell.set", json!({"cell": "B1", "input": "7"})).unwrap();
+    dbl(&mut s, "B1");
+    assert_eq!(col(&s, "B", 12), "7,7,7,7,7,7,7,7,7,.,.,.");
+
+    // Data reached only diagonally belongs to the region too (A1:A3, then C4:C9).
+    let mut s = self::s();
+    nums(&mut s, "A", &[1, 2, 3]);
+    nums(&mut s, "C", &[4, 5, 6, 7, 8, 9]);
+    s.execute("cell.set", json!({"cell": "B1", "input": "7"})).unwrap();
+    dbl(&mut s, "B1");
+    assert_eq!(col(&s, "B", 12), "7,7,7,7,7,7,7,7,7,.,.,.");
+
+    // A column further away doesn't.
+    let mut s = self::s();
+    nums(&mut s, "D", &(1..=9).collect::<Vec<_>>());
+    s.execute("cell.set", json!({"cell": "B1", "input": "7"})).unwrap();
+    assert_eq!(dbl(&mut s, "B1"), json!({"target": null}));
+
+    // From the middle of the data, and at its end (nothing to do).
+    let mut s = self::s();
+    nums(&mut s, "A", &(1..=10).collect::<Vec<_>>());
+    s.execute("cell.set", json!({"cell": "B5", "input": "7"})).unwrap();
+    dbl(&mut s, "B5");
+    assert_eq!(col(&s, "B", 12), ".,.,.,.,7,7,7,7,7,7,.,.");
+    let mut s = self::s();
+    nums(&mut s, "A", &[1, 2, 3]);
+    s.execute("cell.set", json!({"cell": "B3", "input": "7"})).unwrap();
+    assert_eq!(dbl(&mut s, "B3"), json!({"target": null}));
+
+    // Formulas fill with their references moving.
+    let mut s = self::s();
+    nums(&mut s, "A", &(1..=5).collect::<Vec<_>>());
+    s.execute("cell.set", json!({"cell": "B1", "input": "=A1*2"})).unwrap();
+    dbl(&mut s, "B1");
+    assert_eq!(v(&s, "B5"), Value::Number(10.0));
+
+    // A whole data column a million rows tall is fine (and quick: only stored cells are visited).
+    let mut s = self::s();
+    let tall: Vec<Vec<f64>> = (0..200_000).map(|i| vec![i as f64]).collect();
+    s.execute("range.setValues", json!({"range": "A1", "values": tall})).unwrap();
+    s.execute("cell.set", json!({"cell": "B1", "input": "1"})).unwrap();
+    let t = std::time::Instant::now();
+    assert_eq!(dbl(&mut s, "B1"), json!({"target": "B1:B200000"}));
+    assert!(t.elapsed().as_secs_f64() < 20.0, "double-click fill of 200,000 rows took {:?}", t.elapsed());
+    assert_eq!(v(&s, "B200000"), Value::Number(1.0));
+
+    // Programmatic calls with nothing selected or empty params don't fail.
+    let mut s = self::s();
+    assert_eq!(s.execute("edit.autoFillToData", json!({})).unwrap(), json!({"target": null}));
+}
+
 #[test]
 fn ctrl_drag_fill_swaps_copy_and_series() {
     // Issue #264: Ctrl+drag fills a lone number as a series, and copies what a plain drag extends.

crates/engine/tests/command_sequence_fuzz.rs

@@ -748,6 +748,7 @@ const CURATED: &[(&str, usize)] = &[
     ("edit.fillDown", 2),
     ("edit.fillRight", 1),
     ("edit.autoFill", 2),
+    ("edit.autoFillToData", 1),
     ("edit.fillSeries", 1),
     ("home.bold", 1),
     ("home.fillColor", 1),
@@ -845,6 +846,7 @@ fn curated_params(rng: &mut Rng, wb: &Workbook, id: &str) -> Json {
             let tgt = RangeRef::new(src.start, CellRef::new(src.end.row + rng.int(0, 6) as u32, src.end.col + rng.int(0, 1) as u32));
             json!({"source": src.a1(), "target": tgt.a1(), "mode": rng.pick(&["series", "copy", "alternate", "formats", "values"])})
         }
+        "edit.autoFillToData" => json!({"source": near_range(rng).a1(), "mode": rng.pick(&["series", "copy"])}),
         "edit.fillSeries" => json!({"range": near_range(rng).a1(), "type": rng.pick(&["linear", "growth", "autofill"]), "step": rng.int(-2, 3)}),
         "home.bold" => json!({"range": range(rng)}),
         "home.fillColor" => json!({"range": range(rng), "color": color(rng)}),

crates/engine/tests/sparse_clear_invalidation.rs

@@ -1,87 +0,0 @@
-//! Clearing a large sparse selection must invalidate every changed cell (issue #1032).
-
-use gridcraft_core::{CellError, CellRef, Value};
-use gridcraft_engine::Session;
-use serde_json::json;
-
-fn value(s: &Session, address: &str) -> Value {
-    s.doc().unwrap().wb.active().unwrap().value(CellRef::parse(address).unwrap())
-}
-
-#[test]
-fn large_clear_updates_distant_direct_and_transitive_dependents() {
-    for command in ["edit.clearContents", "edit.clearAll"] {
-        let mut s = Session::new();
-        s.new_workbook();
-        for (cell, input) in [("A1000001", "7"), ("B1", "=A1000001"), ("C1", "=B1*2")] {
-            s.execute("cell.set", json!({"cell": cell, "input": input})).unwrap();
-        }
-        assert_eq!((value(&s, "B1"), value(&s, "C1")), (Value::Number(7.0), Value::Number(14.0)));
-
-        // B1 stretches the used range to row 1; the changed source lies just past the old cap.
-        s.execute(command, json!({"range": "A1:A1000001"})).unwrap();
-        assert_eq!(value(&s, "A1000001"), Value::Empty, "{command}");
-        assert_eq!((value(&s, "B1"), value(&s, "C1")), (Value::Number(0.0), Value::Number(0.0)), "{command}");
-
-        s.execute("edit.undo", json!({})).unwrap();
-        assert_eq!(value(&s, "A1000001"), Value::Number(7.0), "{command} undo");
-        assert_eq!((value(&s, "B1"), value(&s, "C1")), (Value::Number(7.0), Value::Number(14.0)), "{command} undo");
-        s.execute("edit.redo", json!({})).unwrap();
-        assert_eq!(value(&s, "A1000001"), Value::Empty, "{command} redo");
-        assert_eq!((value(&s, "B1"), value(&s, "C1")), (Value::Number(0.0), Value::Number(0.0)), "{command} redo");
-    }
-}
-
-#[test]
-fn large_clear_removes_a_distant_formulas_spill_and_updates_its_dependent() {
-    for command in ["edit.clearContents", "edit.clearAll"] {
-        let mut s = Session::new();
-        s.new_workbook();
-        s.execute("cell.set", json!({"cell": "A1000001", "input": "=SEQUENCE(2)"})).unwrap();
-        s.execute("cell.set", json!({"cell": "B1", "input": "=A1000002"})).unwrap();
-        assert_eq!((value(&s, "A1000002"), value(&s, "B1")), (Value::Number(2.0), Value::Number(2.0)));
-
-        // The spill lies outside the selection, but must disappear when its anchor is cleared.
-        s.execute(command, json!({"range": "A1:A1000001"})).unwrap();
-        assert_eq!(value(&s, "A1000001"), Value::Empty, "{command}");
-        assert_eq!(value(&s, "A1000002"), Value::Empty, "{command}");
-        assert_eq!(value(&s, "B1"), Value::Number(0.0), "{command}");
-    }
-}
-
-#[test]
-fn clearing_an_empty_merge_unblocks_a_spill() {
-    for command in ["edit.clearFormats", "edit.clearAll"] {
-        let mut s = Session::new();
-        s.new_workbook();
-        s.execute("cell.set", json!({"cell": "A1", "input": "=SEQUENCE(3)"})).unwrap();
-        // Keep the empty merged area inside the used range after the spill becomes blocked.
-        s.execute("cell.set", json!({"cell": "C4", "input": "1"})).unwrap();
-        s.execute("home.mergeCells", json!({"range": "A2:B3"})).unwrap();
-        assert_eq!(value(&s, "A1"), Value::Error(CellError::Spill));
-
-        s.execute(command, json!({"range": "A2:B3"})).unwrap();
-        assert_eq!((value(&s, "A1"), value(&s, "A3")), (Value::Number(1.0), Value::Number(3.0)), "{command}");
-        assert!(s.doc().unwrap().wb.active().unwrap().merges.is_empty(), "{command}");
-    }
-}
-
-#[test]
-fn clearing_a_distant_styled_blocker_unblocks_a_spill() {
-    let mut s = Session::new();
-    s.new_workbook();
-    s.execute("cell.set", json!({"cell": "A1", "input": "=SEQUENCE(100)"})).unwrap();
-    s.execute("cell.set", json!({"cell": "A90", "input": "x"})).unwrap();
-    s.execute("home.bold", json!({"range": "A90", "on": true})).unwrap();
-    assert_eq!(value(&s, "A1"), Value::Error(CellError::Spill));
-
-    // The cleared blocker stays stored for its style and lies beyond the local 64-row scan.
-    s.execute("edit.clearContents", json!({"range": "A2:A100"})).unwrap();
-    assert_eq!(value(&s, "A1"), Value::Number(1.0));
-    assert_eq!(value(&s, "A90"), Value::Number(90.0));
-    assert_eq!(value(&s, "A100"), Value::Number(100.0));
-    let wb = &s.doc().unwrap().wb;
-    let cell = wb.active().unwrap().cell(CellRef::parse("A90").unwrap()).unwrap();
-    assert_eq!(cell.value, Value::Empty);
-    assert!(wb.styles.get(cell.style).font.bold);
-}

crates/formula/src/lib.rs

@@ -12,7 +12,7 @@ pub mod printer;
 
 pub use ast::{Anchor, BinOp, Expr, RefKind, Reference, SheetSel, StructItem, StructRef, TrimMode, UnOp};
 pub use input::{FormulaLocale, parse_input, print_input};
-pub use parser::{MAX_FORMULA_LEN, ParseError, normalize_function_name, parse};
+pub use parser::{ParseError, normalize_function_name, parse};
 pub use printer::{print, print_r1c1, quote_sheet};
 
 #[cfg(test)]

crates/formula/src/parser.rs

@@ -17,11 +17,6 @@ pub struct ParseError {
 
 pub(crate) const MAX_DEPTH: usize = 256;
 
-/// Longest formula accepted, in characters: Excel's limit for formula contents. It also bounds
-/// the depth of the trees long operator chains build (`1+1+…`), which dropping and evaluating
-/// walk recursively; without it a formula of a few hundred kilobytes in a file overflows the stack.
-pub const MAX_FORMULA_LEN: usize = 8_192;
-
 /// Parses formula text. A leading `=` (or `+`/`-` as Lotus users type) is accepted and skipped
 /// for `=`.
 pub fn parse(src: &str) -> Result<Expr, ParseError> {
@@ -30,9 +25,6 @@ pub fn parse(src: &str) -> Result<Expr, ParseError> {
 
 pub(crate) fn parse_syntax(src: &str, locale: crate::FormulaLocale) -> Result<Expr, ParseError> {
     let body = src.strip_prefix('=').unwrap_or(src);
-    if body.len() > MAX_FORMULA_LEN && body.chars().count() > MAX_FORMULA_LEN {
-        return Err(ParseError { msg: format!("formula is longer than {MAX_FORMULA_LEN} characters"), pos: 0 });
-    }
     let toks = tokenize_locale(body, locale).map_err(|e| ParseError { msg: e.msg, pos: e.pos })?;
     let toks = significant_spaces(toks);
     let mut p = Parser { toks, i: 0, depth: 0, input: locale == crate::FormulaLocale::Es };
@@ -168,18 +160,11 @@ impl Parser {
             return Err(self.err("formula is nested too deeply"));
         }
         let mut lhs = self.prefix(allow_union)?;
-        // Postfix operators (`%`, invoking a result) wrap `lhs` without recursing: they count
-        // towards the nesting limit, so `1%%%…` can't build a tree deeper than it.
-        let mut postfix = 0;
         loop {
             if *self.peek() == Tok::Op("%") {
                 if 70 < min_bp {
                     break;
                 }
-                postfix += 1;
-                if self.depth + postfix > MAX_DEPTH {
-                    return Err(self.err("formula is nested too deeply"));
-                }
                 self.next();
                 lhs = Expr::Unary(UnOp::Percent, Box::new(lhs));
                 continue;
@@ -189,10 +174,6 @@ impl Parser {
                 if let Expr::Name(_) = lhs {
                     // A name followed by '(' was lexed as Func; this is `(name)(…)` only.
                 }
-                postfix += 1;
-                if self.depth + postfix > MAX_DEPTH {
-                    return Err(self.err("formula is nested too deeply"));
-                }
                 self.next();
                 let args = self.args()?;
                 lhs = Expr::Invoke(Box::new(lhs), args);

crates/formula/src/tests.rs

@@ -366,38 +366,3 @@ fn prints_long_flat_chain_without_deep_recursion() {
     assert_eq!(text, vec!["1"; 20001].join("+"));
     assert_eq!(r1c1, text);
 }
-
-#[test]
-fn hostile_formulas_are_errors_not_stack_overflows() {
-    // A small stack: parsing must fail cleanly instead of building trees deeper than the nesting
-    // limit, which dropping, printing and evaluating walk recursively.
-    let handle = std::thread::Builder::new()
-        .stack_size(512 * 1024)
-        .spawn(|| {
-            let percents = format!("1{}", "%".repeat(1_000));
-            let invokes = format!("LAMBDA(x,x)(1){}", "(1)".repeat(1_000));
-            let long_chain = format!("1{}", "+1".repeat(100_000));
-            let huge_percents = format!("1{}", "%".repeat(1_000_000));
-            (parse(&percents).is_err(), parse(&invokes).is_err(), parse(&long_chain).is_err(), parse(&huge_percents).is_err())
-        })
-        .expect("spawn");
-    assert_eq!(handle.join().expect("parsing must not overflow the stack"), (true, true, true, true));
-    // Within the limits these still parse.
-    assert!(parse(&format!("1{}", "%".repeat(100))).is_ok());
-    assert!(parse("LAMBDA(x,x)(1)(2)").is_ok());
-}
-
-#[test]
-fn formulas_longer_than_excel_allows_are_refused() {
-    let at_limit = format!("1{}", "+1".repeat((crate::MAX_FORMULA_LEN - 1) / 2));
-    assert_eq!(at_limit.chars().count(), crate::MAX_FORMULA_LEN - 1);
-    assert!(parse(&at_limit).is_ok());
-    assert!(parse(&format!("={at_limit}")).is_ok(), "the leading = does not count");
-    let over = format!("{at_limit}+1");
-    let err = parse(&over).unwrap_err();
-    assert!(err.msg.contains("8192"), "{}", err.msg);
-    // Characters, not bytes: 8,000 two-byte characters in a text literal are within the limit.
-    let text = format!("\"{}\"", "é".repeat(8_000));
-    assert!(text.len() > crate::MAX_FORMULA_LEN);
-    assert!(parse(&text).is_ok());
-}

crates/ui-egui/src/editor.rs

@@ -222,22 +222,59 @@ pub fn formula_refs(text: &str) -> Vec<(usize, usize, RangeRef, Option<String>,
             } else {
                 i = j + 1;
             }
-            let key = body.get(start..end).unwrap_or("").replace('$', "").to_ascii_uppercase();
-            let idx = match seen.iter().position(|k| *k == key) {
-                Some(k) => k,
-                None => {
-                    seen.push(key);
-                    seen.len() - 1
-                }
-            };
+            let idx = colour_index(&mut seen, body.get(start..end).unwrap_or(""));
             out.push((start + offset, end + offset, range, sheet, idx % REF_COLORS.len()));
             continue;
         }
+        // Whole columns and rows (`A:A`, `$B:$D`, `2:2`, `Sheet2!3:5`) are references too.
+        if let Some(t) = toks.get(j)
+            && let Some(range) = whole_line_ref(&t.tok, toks.get(j + 1).map(|t| &t.tok), toks.get(j + 2).map(|t| &t.tok))
+            && let Some(last) = toks.get(j + 2)
+        {
+            let end = last.end;
+            let idx = colour_index(&mut seen, body.get(start..end).unwrap_or(""));
+            out.push((start + offset, end + offset, range, sheet, idx % REF_COLORS.len()));
+            i = j + 3;
+            continue;
+        }
         i += 1;
     }
     out
 }
 
+/// The colour slot of a reference: the same text (ignoring `$` and case) keeps its colour.
+fn colour_index(seen: &mut Vec<String>, text: &str) -> usize {
+    let key = text.replace('$', "").to_ascii_uppercase();
+    match seen.iter().position(|k| *k == key) {
+        Some(k) => k,
+        None => {
+            seen.push(key);
+            seen.len() - 1
+        }
+    }
+}
+
+/// `A:C` or `2:5` as three tokens (the lexer splits them around the colon): whole columns or
+/// whole rows, the same words the formula parser accepts there.
+fn whole_line_ref(
+    a: &gridcraft_engine::formula::lexer::Tok,
+    colon: Option<&gridcraft_engine::formula::lexer::Tok>,
+    b: Option<&gridcraft_engine::formula::lexer::Tok>,
+) -> Option<RangeRef> {
+    use gridcraft_engine::formula::lexer::Tok;
+    if !matches!(colon, Some(Tok::Colon | Tok::Trim(_))) {
+        return None;
+    }
+    let word = |t: &Tok| match t {
+        Tok::Word(w) => Some(w.clone()),
+        Tok::Number(n) if n.fract() == 0.0 && *n >= 1.0 => Some(format!("{n}")),
+        _ => None,
+    };
+    let (w1, w2) = (word(a)?, word(b?)?);
+    let range = RangeRef::parse(&format!("{w1}:{w2}"))?;
+    (range.is_full_cols() || range.is_full_rows()).then_some(range)
+}
+
 /// Excel-style AutoComplete: the one distinct text entry in the same column (contiguous data
 /// above and below) that starts with `typed` (case-insensitive). `None` when ambiguous.
 pub fn column_completion(sheet: &gridcraft_engine::model::Sheet, at: CellRef, typed: &str) -> Option<String> {
@@ -329,4 +366,31 @@ mod tests {
         assert_eq!(r[1].2.a1(), "B2:C3");
         assert_eq!(r[3].3.as_deref(), Some("Sheet2"));
     }
+
+    /// Whole columns and rows are coloured and outlined like any reference (#873, #875).
+    #[test]
+    fn whole_column_and_row_refs() {
+        use gridcraft_engine::core::{MAX_COLS, MAX_ROWS};
+        let text = "=SUM(A:A)+SUM(2:2)+COUNT($B:$D,Sheet2!3:5,a:a)";
+        let r = formula_refs(text);
+        let spans: Vec<&str> = r.iter().map(|x| &text[x.0..x.1]).collect();
+        assert_eq!(spans, ["A:A", "2:2", "$B:$D", "Sheet2!3:5", "a:a"]);
+        assert_eq!(r[0].2, RangeRef::cols(0, 0));
+        assert_eq!(r[1].2, RangeRef::rows(1, 1));
+        assert_eq!(r[2].2, RangeRef::cols(1, 3));
+        assert_eq!((r[3].2, r[3].3.as_deref()), (RangeRef::rows(2, 4), Some("Sheet2")));
+        // Distinct references get distinct colours; the same one (any case or `$`) keeps its own.
+        assert_eq!([r[0].4, r[1].4, r[2].4, r[3].4], [0, 1, 2, 3]);
+        assert_eq!(r[4].4, r[0].4);
+        // The outline spans the whole sheet's height or width.
+        assert_eq!(r[0].2.end.row, MAX_ROWS - 1);
+        assert_eq!(r[1].2.end.col, MAX_COLS - 1);
+        // Mixed with cells, in order of appearance.
+        let r = formula_refs("=A1+B:B*C2:D3+10:10");
+        assert_eq!(r.iter().map(|x| x.2.a1()).collect::<Vec<_>>(), ["A1", "B:B", "C2:D3", "10:10"]);
+        // Not references: a name, numbers around a colon in text, beyond the sheet, half a range.
+        for text in ["=SUM(Sales)", "=\"1:2\"&A", "=SUM(XFE:XFE)", "=SUM(0:0)", "=SUM(1048577:1048577)", "=SUM(A:", "=A:"] {
+            assert!(formula_refs(text).is_empty(), "{text}: {:?}", formula_refs(text));
+        }
+    }
 }

crates/ui-egui/src/formula_bar.rs

@@ -422,25 +422,7 @@ fn cycle_anchor(ed: &mut crate::editor::EditState) {
     for (a, b, ..) in formula_refs(&ed.text) {
         if a <= caret_b && caret_b <= b {
             let Some(r) = ed.text.get(a..b) else { return };
-            let cycled: String = r
-                .split(':')
-                .map(|part| {
-                    let p = part.split('!').next_back().unwrap_or(part);
-                    let prefix = &part[..part.len() - p.len()];
-                    let bare = p.replace('$', "");
-                    let letters: String = bare.chars().take_while(|c| c.is_ascii_alphabetic()).collect();
-                    let digits = &bare[letters.len()..];
-                    let state = (p.starts_with('$'), p[letters.len().min(p.len())..].contains('$') || p.trim_start_matches('$').contains('$'));
-                    let next = match state {
-                        (false, false) => format!("${letters}${digits}"),
-                        (true, true) => format!("{letters}${digits}"),
-                        (false, true) => format!("${letters}{digits}"),
-                        (true, false) => format!("{letters}{digits}"),
-                    };
-                    format!("{prefix}{next}")
-                })
-                .collect::<Vec<_>>()
-                .join(":");
+            let cycled = cycle_ref(r);
             let (Some(x), Some(y)) = (ed.text.get(..a), ed.text.get(b..)) else { return };
             ed.text = format!("{x}{cycled}{y}");
             ed.caret = ed.text.get(..a + cycled.len()).map(|s| s.chars().count()).unwrap_or(ed.caret);
@@ -452,6 +434,46 @@ fn cycle_anchor(ed: &mut crate::editor::EditState) {
     }
 }
 
+/// F4 on one reference: `A1` → `$A$1` → `A$1` → `$A1` → `A1`. Whole columns and rows have one
+/// coordinate, so they toggle: `B:D` ⇄ `$B:$D`, `2:3` ⇄ `$2:$3` (as Excel does).
+fn cycle_ref(r: &str) -> String {
+    let unqualified = |part: &str| part.split('!').next_back().unwrap_or(part).to_string();
+    let first = unqualified(r.split(':').next().unwrap_or(r));
+    let first_bare = first.replace('$', "");
+    let whole_line = r.contains(':') && (first_bare.chars().all(|c| c.is_ascii_alphabetic()) || first_bare.chars().all(|c| c.is_ascii_digit()));
+    if whole_line {
+        let anchored = first.starts_with('$');
+        return r
+            .split(':')
+            .map(|part| {
+                let p = unqualified(part);
+                let prefix = &part[..part.len() - p.len()];
+                let bare = p.replace('$', "");
+                if anchored { format!("{prefix}{bare}") } else { format!("{prefix}${bare}") }
+            })
+            .collect::<Vec<_>>()
+            .join(":");
+    }
+    r.split(':')
+        .map(|part| {
+            let p = part.split('!').next_back().unwrap_or(part);
+            let prefix = &part[..part.len() - p.len()];
+            let bare = p.replace('$', "");
+            let letters: String = bare.chars().take_while(|c| c.is_ascii_alphabetic()).collect();
+            let digits = &bare[letters.len()..];
+            let state = (p.starts_with('$'), p[letters.len().min(p.len())..].contains('$') || p.trim_start_matches('$').contains('$'));
+            let next = match state {
+                (false, false) => format!("${letters}${digits}"),
+                (true, true) => format!("{letters}${digits}"),
+                (false, true) => format!("${letters}{digits}"),
+                (true, false) => format!("{letters}{digits}"),
+            };
+            format!("{prefix}{next}")
+        })
+        .collect::<Vec<_>>()
+        .join(":")
+}
+
 fn function_names() -> Vec<String> {
     static NAMES: std::sync::OnceLock<Vec<String>> = std::sync::OnceLock::new();
     NAMES
@@ -474,3 +496,32 @@ pub fn function_signature(name: &str) -> Option<String> {
 pub fn function_description(name: &str) -> Option<String> {
     function_info(name).and_then(|f| f["description"].as_str().map(str::to_string))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::cycle_ref;
+
+    #[test]
+    fn f4_cycles_cells_through_four_states() {
+        let mut r = "A1".to_string();
+        let mut seen = vec![];
+        for _ in 0..4 {
+            r = cycle_ref(&r);
+            seen.push(r.clone());
+        }
+        assert_eq!(seen, ["$A$1", "A$1", "$A1", "A1"]);
+        assert_eq!(cycle_ref("B2:C3"), "$B$2:$C$3");
+        assert_eq!(cycle_ref("Sheet2!B2"), "Sheet2!$B$2");
+    }
+
+    /// As observed in Excel: F4 on a whole column or row toggles its `$` (#873).
+    #[test]
+    fn f4_toggles_whole_columns_and_rows() {
+        assert_eq!(cycle_ref("B:B"), "$B:$B");
+        assert_eq!(cycle_ref("$B:$B"), "B:B");
+        assert_eq!(cycle_ref("2:3"), "$2:$3");
+        assert_eq!(cycle_ref("$2:$3"), "2:3");
+        assert_eq!(cycle_ref("Sheet2!C:E"), "Sheet2!$C:$E");
+        assert_eq!(cycle_ref("'My Sheet'!$4:$4"), "'My Sheet'!4:4");
+    }
+}

crates/ui-egui/src/grid.rs

@@ -63,6 +63,12 @@ pub enum Drag {
     Select,
     Rows(u32),
     Cols(u32),
+    /// Point mode while editing a formula: dragging over the column (`cols`) or row headers from
+    /// `anchor` puts `B:D` or `2:5` into the formula.
+    PointLines {
+        cols: bool,
+        anchor: u32,
+    },
     /// Reordering one contiguous whole-column selection by its header.
     MoveCols {
         source: RangeRef,
@@ -118,6 +124,12 @@ pub struct GridState {
     /// The selection outline on its way to a new selection.
     pub glide: crate::selection_glide::SelectionGlide,
     pub last_click: Option<(CellRef, f64)>,
+    /// The grid acted on the current press when the button went down (#900): its drag start or
+    /// click must not act again. Cleared when the button is up.
+    pub press_consumed: bool,
+    /// The cell a plain press selected: releasing over it without dragging is a click, which
+    /// toggles its checkbox or follows its hyperlink.
+    pub click_cell: Option<CellRef>,
     pub hover_cell: Option<CellRef>,
     pub autosave: bool,
     pub last_autosave: f64,
@@ -1775,6 +1787,10 @@ pub(crate) fn paint_headers(
 const OBJECT_RESIZE_RADIUS: f32 = 10.0;
 
 fn interact(app: &mut SheetApp, ui: &mut egui::Ui, resp: &egui::Response, geo: &Geo, sh: &Sheet, wb: &Workbook) {
+    // A press the grid acted on lasts through its release, however the release is handled.
+    if ui.input(|i| !i.pointer.any_down() && !i.pointer.any_pressed() && !i.pointer.any_released()) {
+        app.grid.press_consumed = false;
+    }
     // Text selection and editing must not also move the object or edit worksheet cells.
     if app.text_box_editor.is_some() || app.grid.hf_edit.is_some() {
         return;
@@ -1966,38 +1982,67 @@ fn interact(app: &mut SheetApp, ui: &mut egui::Ui, resp: &egui::Response, geo: &
         }
     }
 
-    // Double-click the fill handle: a double-click is also a click, so run it before the handle press returns.
+    // A double-click on the fill handle fills down as far as the data next to the source goes
+    // (#877). It arrives with the second release, after that press armed a fill drag.
     if resp.double_clicked()
-        && let Some(p) = pos
+        && app.editor.is_none()
+        && let Some(p) = pointer.press_origin().map(|p| geo.mirror_pos(p)).or(pos)
         && on_handle(p)
     {
-        // Fill down as far as the neighbouring column goes.
-        let src = sel.current();
-        let neighbour = if src.start.col > 0 { src.start.col - 1 } else { src.end.col + 1 };
-        let mut last = src.end.row;
-        while last + 1 < MAX_ROWS && sh.value_ref(CellRef::new(last + 1, neighbour)).is_some_and(|v| !v.is_empty()) && last - src.end.row < 1_000_000
-        {
-            last += 1;
-        }
-        if last > src.end.row {
-            let target = RangeRef::new(src.start, CellRef::new(last, src.end.col));
-            let _ = app.run("edit.autoFill", json!({"source": src.a1(), "target": target.a1()}));
-        }
         app.grid.drag = Drag::None;
         app.grid.drag_select = false;
-        resp.request_focus();
+        app.grid.click_cell = None;
+        app.run_or_alert("edit.autoFillToData", json!({"source": sel.current().a1()}));
         return;
     }
 
+    // A press acts when the button goes down, as in Excel (#900): the cell under it is selected
+    // at once and a drag extends from it. Targets that behave like buttons (the outline band) or
+    // whose press may still turn into a drag of something else (the selection border, a selected
+    // column header, an object) wait for the drag to start or for the click.
+    let press_now = resp.hovered() && pointer.primary_pressed() && app.grid.drag == Drag::None;
+    let follow_up = !press_now && (resp.drag_started() || primary_clicked) && app.grid.drag == Drag::None && !app.grid.press_consumed;
+    if press_now {
+        app.grid.press_consumed = true;
+        app.grid.click_cell = None;
+    }
+    // Releasing a plain press without dragging away from its cell clicks it.
+    if primary_clicked
+        && !press_now
+        && let Some(c) = app.grid.click_cell.take()
+        && let Some(p) = pos
+        && in_cells
+        && geo.cell_at(sh, p) == c
+        && app.editor.is_none()
+    {
+        click_cell(app, geo, sh, c, p, mods);
+    }
+    // Leaves this press to its drag start or its click.
+    let defer = |app: &mut SheetApp| {
+        if press_now && !primary_clicked {
+            app.grid.press_consumed = false;
+            true
+        } else {
+            false
+        }
+    };
+
     // Press: decide the drag mode.
-    if resp.drag_started() || (primary_clicked && app.grid.drag == Drag::None) {
+    if press_now || follow_up {
         // Where the press began (a drag is only recognised after the pointer has moved).
         let Some(p) = pointer.press_origin().map(|p| geo.mirror_pos(p)).or(pos) else { return };
+        // Objects take their press on its drag start or click (above), and a header or footer
+        // in Page Layout view on its click (`paper_view`).
+        if (crate::chartview::hit(app, geo, sh, p).is_some() || crate::paper_view::over_header_footer(geo, geo.mirror_pos(p))) && defer(app) {
+            return;
+        }
         // The outline band's − / + and level buttons act on release, like buttons.
         if let Some(action) = crate::outline::hit(geo, sh, p) {
             if primary_clicked {
                 let (command, params) = action.command();
                 app.run_or_alert(command, params);
+            } else {
+                defer(app);
             }
             return;
         }
@@ -2016,17 +2061,20 @@ fn interact(app: &mut SheetApp, ui: &mut egui::Ui, resp: &egui::Response, geo: &
                 return;
             }
             let c = geo.col_at(sh, p.x);
-            if point_header(app, wb, sh, RangeRef::cols(c, c)) {
+            // Point mode: a column header puts the whole column into the formula (`C:C`).
+            if point_lines(app, wb, sh, true, c, c) {
+                app.grid.drag = Drag::PointLines { cols: true, anchor: c };
                 return;
             }
-            if resp.drag_started()
-                && !mods.any()
-                && sel.ranges.len() == 1
-                && sel.current().is_full_cols()
-                && sel.current().contains(CellRef::new(0, c))
-            {
-                app.grid.drag = Drag::MoveCols { source: sel.current(), before: None };
-                return;
+            if !mods.any() && sel.ranges.len() == 1 && sel.current().is_full_cols() && sel.current().contains(CellRef::new(0, c)) {
+                // A selected column: dragging it moves the columns, a click selects just it.
+                if resp.drag_started() {
+                    app.grid.drag = Drag::MoveCols { source: sel.current(), before: None };
+                    return;
+                }
+                if defer(app) {
+                    return;
+                }
             }
             let range = if mods.shift { RangeRef::cols(sel.anchor.col.min(c), sel.anchor.col.max(c)) } else { RangeRef::cols(c, c) };
             select_ranges(app, range, mods.command, CellRef::new(geo.row_at(sh, geo.cells.top() + 1.0), c));
@@ -2039,7 +2087,8 @@ fn interact(app: &mut SheetApp, ui: &mut egui::Ui, resp: &egui::Response, geo: &
                 return;
             }
             let r = geo.row_at(sh, p.y);
-            if point_header(app, wb, sh, RangeRef::rows(r, r)) {
+            if point_lines(app, wb, sh, false, r, r) {
+                app.grid.drag = Drag::PointLines { cols: false, anchor: r };
                 return;
             }
             let range = if mods.shift { RangeRef::rows(sel.anchor.row.min(r), sel.anchor.row.max(r)) } else { RangeRef::rows(r, r) };
@@ -2091,9 +2140,15 @@ fn interact(app: &mut SheetApp, ui: &mut egui::Ui, resp: &egui::Response, geo: &
             app.grid.drag = Drag::Fill { target: None };
             return;
         }
-        if on_cur_border(p) && resp.drag_started() {
-            app.grid.drag = Drag::Move { grab: c, to: None };
-            return;
+        if on_cur_border(p) {
+            // The selection's border drags it to a new place; a click on it selects the cell.
+            if resp.drag_started() {
+                app.grid.drag = Drag::Move { grab: c, to: None };
+                return;
+            }
+            if defer(app) {
+                return;
+            }
         }
         // Double-click edits.
         let now = crate::now_ms();
@@ -2117,18 +2172,10 @@ fn interact(app: &mut SheetApp, ui: &mut egui::Ui, resp: &egui::Response, geo: &
             select_ranges(app, RangeRef::cell(c), true, c);
         } else {
             let _ = app.session.run("selection.set", json!({"cell": c.a1()}));
-            if primary_clicked && wb.styles.get(sh.style_id(c)).num_fmt.as_str() == "checkbox" {
-                let _ = app.run("cell.toggleCheckbox", json!({"cell": c.a1()}));
-            }
-            // A click on a hyperlink's text follows it (like Excel); elsewhere in the cell selects.
-            if let Some(h) = sh.hyperlinks.get(&c).cloned()
-                && primary_clicked
-                && !mods.any()
-            {
-                let r = geo.cell_rect(sh, c);
-                if p.x < r.left() + r.width() * 0.8 {
-                    follow_link(app, &h.target);
-                }
+            if primary_clicked {
+                click_cell(app, geo, sh, c, p, mods);
+            } else {
+                app.grid.click_cell = Some(c);
             }
         }
         app.grid.drag = Drag::Select;
@@ -2182,6 +2229,11 @@ fn interact(app: &mut SheetApp, ui: &mut egui::Ui, resp: &egui::Response, geo: &
                     app.session.run("selection.set", json!({"range": RangeRef::cols(anchor.min(c), anchor.max(c)).a1(), "active": sel.active.a1()}));
                 scroll_by(app, vec2(auto.x, 0.0));
             }
+            Drag::PointLines { cols, anchor } => {
+                let to = if cols { geo.col_at(sh, p.x) } else { geo.row_at(sh, p.y) };
+                point_lines(app, wb, sh, cols, anchor, to);
+                scroll_by(app, if cols { vec2(auto.x, 0.0) } else { vec2(0.0, auto.y) });
+            }
             Drag::MoveCols { source, .. } => {
                 let col = geo.col_at(sh, p.x.clamp(geo.cells.left() + 1.0, geo.cells.right() - 1.0));
                 let midpoint = geo.x(sh, col) + sh.col_width(col) * geo.z * 0.5;
@@ -2324,22 +2376,14 @@ fn interact(app: &mut SheetApp, ui: &mut egui::Ui, resp: &egui::Response, geo: &
         }
     }
 
-    if primary_clicked || resp.drag_started() {
+    // The grid takes the keyboard, except from a formula being pointed at (its press already
+    // handed focus back to the editor).
+    if (primary_clicked || resp.drag_started()) && app.editor.is_none() {
         resp.request_focus();
     }
     keyboard(app, &ctx, resp, geo, sh);
 }
 
-/// Point mode on a header: inserts the whole-column or whole-row reference instead of selecting.
-fn point_header(app: &mut SheetApp, wb: &Workbook, sh: &Sheet, range: RangeRef) -> bool {
-    let Some(ed) = app.editor.as_mut().filter(|ed| ed.can_point()) else { return false };
-    let r = range.a1();
-    let r = if ed.sheet != wb.active_sheet { format!("{}!{r}", gridcraft_engine::formula::quote_sheet(&sh.name)) } else { r };
-    ed.insert_ref(&r);
-    ed.request_focus = true;
-    true
-}
-
 fn select_to_pointer(app: &mut SheetApp, geo: &Geo, sh: &Sheet, wb: &Workbook, p: Pos2) {
     let cell = CellRef::new(
         geo.row_at(sh, p.y.clamp(geo.cells.top() + 1.0, geo.cells.bottom() - 1.0)),
@@ -2369,6 +2413,23 @@ fn select_to_pointer(app: &mut SheetApp, geo: &Geo, sh: &Sheet, wb: &Workbook, p
     }
 }
 
+/// Point mode on the headers: puts whole columns (`cols`, `B:D`) or rows (`2:5`) from `a` to `b`
+/// into the formula being edited, as Excel does for a click or drag on the headings. `false`
+/// (nothing changed) when not editing a formula where a reference can go.
+fn point_lines(app: &mut SheetApp, wb: &Workbook, sh: &Sheet, cols: bool, a: u32, b: u32) -> bool {
+    let Some(ed) = app.editor.as_mut() else { return false };
+    if !ed.can_point() {
+        return false;
+    }
+    let range = if cols { RangeRef::cols(a.min(b), a.max(b)) } else { RangeRef::rows(a.min(b), a.max(b)) };
+    let text = range.a1();
+    let text = if ed.sheet != wb.active_sheet { format!("{}!{text}", gridcraft_engine::formula::quote_sheet(&sh.name)) } else { text };
+    ed.insert_ref(&text);
+    ed.point_cell = None;
+    ed.request_focus = true;
+    true
+}
+
 fn coalesce_last_undo(app: &mut SheetApp) {
     // Merge consecutive drag steps into one undo entry.
     if let Some(d) = app.session.active_mut()
@@ -2524,6 +2585,23 @@ fn delete_selected_object(app: &mut SheetApp, sh: &Sheet) -> bool {
     true
 }
 
+/// What a click on a cell does beyond selecting it: toggles its checkbox, or follows its
+/// hyperlink when the click is on the link's text (like Excel; elsewhere in the cell it selects).
+fn click_cell(app: &mut SheetApp, geo: &Geo, sh: &Sheet, c: CellRef, p: Pos2, mods: egui::Modifiers) {
+    let checkbox = app.session.active().is_some_and(|d| d.wb.styles.get(sh.style_id(c)).num_fmt.as_str() == "checkbox");
+    if checkbox {
+        let _ = app.run("cell.toggleCheckbox", json!({"cell": c.a1()}));
+    }
+    if let Some(h) = sh.hyperlinks.get(&c).cloned()
+        && !mods.any()
+    {
+        let r = geo.cell_rect(sh, c);
+        if p.x < r.left() + r.width() * 0.8 {
+            follow_link(app, &h.target);
+        }
+    }
+}
+
 /// A click on a hyperlink. References select; web and e-mail addresses ask first (the dialog's
 /// OK runs `link.open`); every other kind is refused with a message. The decision is the
 /// engine's ([`gridcraft_engine::links::classify`]), the same one `link.open` applies.
@@ -2573,8 +2651,7 @@ fn keyboard(app: &mut SheetApp, ctx: &egui::Context, resp: &egui::Response, geo:
         resp.request_focus();
     }
     let other_focus = ctx.memory(|m| m.focused()).is_some_and(|f| f != resp.id && (editing || !stale.contains(&f)));
-    // An open filter menu owns the keyboard even when a click inside it left focus on nothing (#1516).
-    if editing || app.dialog.is_some() || other_focus || app.message.is_some() || app.grid.filter_menu.is_some() {
+    if editing || app.dialog.is_some() || other_focus || app.message.is_some() {
         return;
     }
     if ctx.memory(|m| m.focused()).is_none() {
@@ -2769,24 +2846,16 @@ fn filter_menu(app: &mut SheetApp, ui: &mut egui::Ui, geo: &Geo, was_open: bool)
     let values = gridcraft_engine::cmd::data::filter_values(&wb, si, col);
     let key = egui::Id::new(("filter_sel", col));
     let search_key = egui::Id::new(("filter_search", col));
-    let buttons_key = egui::Id::new(("filter_buttons", col));
-    // Enter is the menu's OK, as in Excel: taken before the search box (which would only drop its
-    // focus) and the value checkboxes (which would toggle) see it. A focused button keeps it as its click.
-    let buttons: Vec<egui::Id> = ui.ctx().data_mut(|d| d.get_temp(buttons_key)).unwrap_or_default();
-    let on_button = ui.ctx().memory(|m| m.focused()).is_some_and(|f| buttons.contains(&f));
-    let enter = !on_button && ui.input_mut(|i| i.consume_key(egui::Modifiers::NONE, egui::Key::Enter));
     let mut close = false;
     let area = egui::Area::new(egui::Id::new("filter_menu")).fixed_pos(at + vec2(-180.0, 10.0)).order(egui::Order::Foreground);
     let response = area.show(ui.ctx(), |ui| {
         egui::Frame::popup(ui.style()).show(ui, |ui| {
             ui.set_width(230.0);
-            let ascending = ui.button("↑  Sort Ascending");
-            if ascending.clicked() {
+            if ui.button("↑  Sort Ascending").clicked() {
                 let _ = app.run("data.sortAscending", json!({"column": col_to_letters(col)}));
                 close = true;
             }
-            let descending = ui.button("↓  Sort Descending");
-            if descending.clicked() {
+            if ui.button("↓  Sort Descending").clicked() {
                 let _ = app.run("data.sortDescending", json!({"column": col_to_letters(col)}));
                 close = true;
             }
@@ -2823,16 +2892,11 @@ fn filter_menu(app: &mut SheetApp, ui: &mut egui::Ui, geo: &Geo, was_open: bool)
             let checks: Vec<(String, bool)> = checks.iter().map(|(v, on)| (v.clone(), *on && matches(v))).collect();
             ui.separator();
             ui.horizontal(|ui| {
-                let clear = ui.button("Clear Filter");
-                if clear.clicked() {
+                if ui.button("Clear Filter").clicked() {
                     let _ = app.run("data.filterBy", json!({"column": col_to_letters(col), "clear": true}));
                     close = true;
                 }
-                // Nothing checked would hide every row, so Enter (unlike a click on Apply) does nothing then.
-                let any = checks.iter().any(|(_, on)| *on);
-                let apply = ui.button("Apply");
-                ui.ctx().data_mut(|d| d.insert_temp(buttons_key, vec![ascending.id, descending.id, clear.id, apply.id]));
-                if apply.clicked() || (enter && any) {
+                if ui.button("Apply").clicked() {
                     let blanks = checks.iter().any(|(v, on)| v == "(Blanks)" && *on);
                     let vals: Vec<String> = checks.iter().filter(|(v, on)| *on && v != "(Blanks)").map(|(v, _)| v.clone()).collect();
                     let p = if checks.iter().all(|(_, b)| *b) {
@@ -2850,7 +2914,6 @@ fn filter_menu(app: &mut SheetApp, ui: &mut egui::Ui, geo: &Geo, was_open: bool)
         ui.ctx().data_mut(|d| {
             d.remove::<Vec<(String, bool)>>(key);
             d.remove::<String>(search_key);
-            d.remove::<Vec<egui::Id>>(buttons_key);
         });
         app.grid.filter_menu = None;
     }

crates/ui-egui/src/paper_view.rs

@@ -306,6 +306,13 @@ pub(crate) fn interact(app: &mut SheetApp, ui: &mut egui::Ui, resp: &egui::Respo
     editor(app, ui, geo, &pg);
 }
 
+/// Whether `p` (screen) is over a header or footer zone, which a click edits in place.
+pub fn over_header_footer(geo: &crate::grid::Geo, p: egui::Pos2) -> bool {
+    let Some(pg) = geo.paper.as_ref() else { return false };
+    let (x, y) = (geo.scroll.x as f64 + ((p.x - geo.cells.left()) / geo.z) as f64, geo.scroll.y as f64 + ((p.y - geo.cells.top()) / geo.z) as f64);
+    geo.cells.contains(p) && pg.hf_zone_at(x, y).is_some()
+}
+
 /// The `pageLayout.headerFooter` parameter holding one kind of page's header or footer.
 fn hf_key(kind: HfPage, footer: bool) -> &'static str {
     match (kind, footer) {

crates/ui-egui/tests/fill_handle_double_click.rs

@@ -1,4 +1,4 @@
-//! Double-clicking the fill handle fills down to the neighbouring column's last used row,
+//! Double-clicking the fill handle fills down to the bottom of the data beside it (`edit.autoFillToData`),
 //! even with the pointer up for a frame between the two clicks.
 
 use egui::{Event, Modifiers, PointerButton, Pos2, vec2};
@@ -55,5 +55,5 @@ fn double_click_on_the_fill_handle_fills_down_with_a_frame_between_the_clicks()
 
     assert_eq!([number(&h, 3), number(&h, 4), number(&h, 5)], [Value::Number(40.0), Value::Number(50.0), Value::Number(60.0)]);
     assert_eq!(h.state().session.active().unwrap().selection.a1(), "B1:B6");
-    assert_eq!(h.state().session.journal.iter().filter(|(id, _)| id == "edit.autoFill").count(), 1);
+    assert_eq!(h.state().session.journal.iter().filter(|(id, _)| id == "edit.autoFillToData").count(), 1);
 }

crates/ui-egui/tests/filter_menu_enter.rs

@@ -1,87 +0,0 @@
-//! Enter in the AutoFilter menu works like its Apply button, as Excel's OK (issue #1516): from the
-//! search box or with a value focused it applies the filter and closes the menu, and the key never
-//! reaches the grid underneath.
-
-use egui::{Event, Key, Modifiers, PointerButton};
-use egui_kittest::kittest::Queryable;
-use gridcraft_engine::Session;
-use gridcraft_ui_egui::SheetApp;
-use serde_json::json;
-
-type Harness = egui_kittest::Harness<'static, SheetApp>;
-
-/// A1:A4 holds a header and three fruits under an AutoFilter, with the menu opened by Alt+Down on A1.
-fn filter_menu_open() -> Harness {
-    let mut session = Session::new();
-    session.new_workbook();
-    session.execute("range.setValues", json!({"range": "A1", "values": [["Fruit"], ["Apple"], ["Banana"], ["Cherry"]]})).unwrap();
-    session.execute("data.filter", json!({"range": "A1:A4"})).unwrap();
-    session.execute("selection.set", json!({"cell": "A1"})).unwrap();
-    let mut h = egui_kittest::Harness::builder().with_size(egui::vec2(1200.0, 800.0)).build_ui_state(
-        |ui, app: &mut SheetApp| {
-            app.logic(ui.ctx());
-            app.ui(ui);
-        },
-        SheetApp::new(session, Default::default()),
-    );
-    h.run_steps(4);
-    key(&mut h, Key::ArrowDown, Modifiers::ALT);
-    assert!(h.state().grid.filter_menu.is_some(), "Alt+Down opens the filter menu");
-    h
-}
-
-fn key(h: &mut Harness, k: Key, m: Modifiers) {
-    h.input_mut().events.push(Event::Key { key: k, physical_key: Some(k), pressed: true, repeat: false, modifiers: m });
-    h.input_mut().events.push(Event::Key { key: k, physical_key: Some(k), pressed: false, repeat: false, modifiers: m });
-    h.run_steps(2);
-}
-
-/// Rows 2..=4 (Apple, Banana, Cherry): which ones the filter hides.
-fn hidden(h: &Harness) -> Vec<bool> {
-    let sh = h.state().session.active().unwrap().wb.active().unwrap();
-    (1..=3).map(|r| sh.is_row_hidden(r)).collect()
-}
-
-fn active(h: &Harness) -> String {
-    h.state().session.active().unwrap().selection.active.a1()
-}
-
-#[test]
-fn enter_in_the_search_box_applies_the_filter() {
-    let mut h = filter_menu_open();
-    h.input_mut().events.push(Event::Text("an".into()));
-    h.run_steps(2);
-    key(&mut h, Key::Enter, Modifiers::NONE);
-    assert_eq!(hidden(&h), [true, false, true], "only Banana matches the search");
-    assert!(h.state().grid.filter_menu.is_none(), "Enter closes the menu");
-    assert_eq!(active(&h), "A1", "Enter must not move the active cell");
-}
-
-#[test]
-fn enter_with_a_value_clicked_applies_the_filter() {
-    let mut h = filter_menu_open();
-    let apple = h.get_by_label("Apple").rect().center();
-    h.input_mut().events.push(Event::PointerMoved(apple));
-    for pressed in [true, false] {
-        h.input_mut().events.push(Event::PointerButton { pos: apple, button: PointerButton::Primary, pressed, modifiers: Modifiers::NONE });
-    }
-    h.run_steps(2);
-    assert!(h.state().grid.filter_menu.is_some(), "clicking a value keeps the menu open");
-    key(&mut h, Key::Enter, Modifiers::NONE);
-    // Enter applies the list as it is: it must not toggle the value back on.
-    assert_eq!(hidden(&h), [true, false, false], "Apple was unchecked");
-    assert!(h.state().grid.filter_menu.is_none(), "Enter closes the menu");
-    assert_eq!(active(&h), "A1", "Enter must not move the active cell");
-}
-
-#[test]
-fn enter_with_nothing_checked_keeps_the_menu_open() {
-    let mut h = filter_menu_open();
-    // A search that matches nothing leaves no value to show, as Excel's OK is then disabled.
-    h.input_mut().events.push(Event::Text("Bananna".into()));
-    h.run_steps(2);
-    key(&mut h, Key::Enter, Modifiers::NONE);
-    assert_eq!(hidden(&h), [false, false, false], "an empty selection must not hide every row");
-    assert!(h.state().grid.filter_menu.is_some(), "the menu stays open");
-    assert_eq!(active(&h), "A1");
-}

crates/ui-egui/tests/press_select.rs

@@ -0,0 +1,348 @@
+//! A press on a cell selects it when the button goes down, as in Excel (#900), and a double-click
+//! on the fill handle fills down to the data next to it (#877).
+
+use egui::{Event, Modifiers, PointerButton, Pos2};
+use gridcraft_engine::Session;
+use gridcraft_engine::core::{CellRef, RangeRef, Value};
+use gridcraft_ui_egui::{SheetApp, grid::Geo};
+use serde_json::json;
+
+type Harness = egui_kittest::Harness<'static, SheetApp>;
+
+fn harness(session: Session) -> Harness {
+    // 60 frames a second, so two clicks a few frames apart are a double-click to egui.
+    let mut h = Harness::builder().with_size(egui::vec2(1200.0, 800.0)).with_step_dt(1.0 / 60.0).build_ui_state(
+        |ui, app: &mut SheetApp| {
+            let ctx = ui.ctx().clone();
+            app.logic(&ctx);
+            app.ui(ui);
+        },
+        SheetApp::new(session, Default::default()),
+    );
+    h.run_steps(4);
+    h
+}
+
+fn blank() -> Session {
+    let mut s = Session::new();
+    s.new_workbook();
+    s
+}
+
+fn geo(h: &Harness) -> Geo {
+    let app = h.state();
+    let sheet = app.session.active().unwrap().wb.active().unwrap();
+    Geo::new(sheet, app.grid.rect.unwrap(), app.view().scroll)
+}
+
+fn rect(h: &Harness, a1: &str) -> egui::Rect {
+    let app = h.state();
+    let sheet = app.session.active().unwrap().wb.active().unwrap();
+    geo(h).cell_rect(sheet, CellRef::parse(a1).unwrap())
+}
+
+fn frame(h: &mut Harness, event: Event) {
+    h.input_mut().events.push(event);
+    h.run_steps(1);
+}
+
+fn button(pos: Pos2, pressed: bool, modifiers: Modifiers) -> Event {
+    Event::PointerButton { pos, button: PointerButton::Primary, pressed, modifiers }
+}
+
+fn down(h: &mut Harness, at: Pos2, modifiers: Modifiers) {
+    h.input_mut().events.push(Event::ModifiersChanged(modifiers));
+    frame(h, Event::PointerMoved(at));
+    frame(h, button(at, true, modifiers));
+}
+
+fn up(h: &mut Harness, at: Pos2, modifiers: Modifiers) {
+    frame(h, button(at, false, modifiers));
+    h.input_mut().events.push(Event::ModifiersChanged(Modifiers::NONE));
+    h.run_steps(2);
+}
+
+/// Waits out the double-click window (the grid times it on the wall clock).
+fn pause(h: &mut Harness) {
+    std::thread::sleep(std::time::Duration::from_millis(500));
+    h.run_steps(2);
+}
+
+fn selection(h: &Harness) -> (String, String, Vec<String>) {
+    let s = &h.state().session.active().unwrap().selection;
+    (s.active.a1(), s.anchor.a1(), s.ranges.iter().map(RangeRef::a1).collect())
+}
+
+fn value(h: &Harness, a1: &str) -> Value {
+    h.state().session.active().unwrap().wb.active().unwrap().value(CellRef::parse(a1).unwrap())
+}
+
+#[test]
+fn the_press_selects_before_the_release() {
+    let mut h = harness(blank());
+    let c3 = rect(&h, "C3").center();
+    down(&mut h, c3, Modifiers::NONE);
+    assert_eq!(selection(&h).0, "C3", "the cell is selected while the button is still down");
+    up(&mut h, c3, Modifiers::NONE);
+    assert_eq!(selection(&h), ("C3".into(), "C3".into(), vec!["C3".into()]));
+}
+
+#[test]
+fn a_press_that_wobbles_inside_its_cell_still_selects_it() {
+    let mut h = harness(blank());
+    let r = rect(&h, "C3");
+    let at = r.left_top() + egui::vec2(4.0, 4.0);
+    down(&mut h, at, Modifiers::NONE);
+    // Further than egui's click distance, but still inside C3: a drag that never leaves the cell.
+    for step in 1..=6 {
+        frame(&mut h, Event::PointerMoved(at + egui::vec2(step as f32 * 5.0, step as f32 * 1.5)));
+    }
+    up(&mut h, at + egui::vec2(30.0, 9.0), Modifiers::NONE);
+    assert_eq!(selection(&h), ("C3".into(), "C3".into(), vec!["C3".into()]));
+}
+
+#[test]
+fn a_long_press_without_moving_selects_the_cell() {
+    let mut h = harness(blank());
+    let c3 = rect(&h, "C3").center();
+    down(&mut h, c3, Modifiers::NONE);
+    // Longer than egui's longest click: the release is no longer a click.
+    h.run_steps(60);
+    up(&mut h, c3, Modifiers::NONE);
+    assert_eq!(selection(&h).2, vec!["C3".to_string()]);
+}
+
+#[test]
+fn dragging_from_the_press_extends_live_then_stays() {
+    let mut h = harness(blank());
+    let c3 = rect(&h, "C3").center();
+    down(&mut h, c3, Modifiers::NONE);
+    let e5 = rect(&h, "E5").center();
+    frame(&mut h, Event::PointerMoved(c3.lerp(e5, 0.5)));
+    frame(&mut h, Event::PointerMoved(e5));
+    assert_eq!(selection(&h), ("C3".into(), "C3".into(), vec!["C3:E5".into()]), "the range follows the pointer while held");
+    up(&mut h, e5, Modifiers::NONE);
+    assert_eq!(selection(&h), ("C3".into(), "C3".into(), vec!["C3:E5".into()]));
+}
+
+#[test]
+fn shift_and_ctrl_presses_act_on_the_press() {
+    let mut h = harness(blank());
+    let b2 = rect(&h, "B2").center();
+    down(&mut h, b2, Modifiers::NONE);
+    up(&mut h, b2, Modifiers::NONE);
+    pause(&mut h);
+    let d4 = rect(&h, "D4").center();
+    down(&mut h, d4, Modifiers::SHIFT);
+    assert_eq!(selection(&h).2, vec!["B2:D4".to_string()], "Shift+press extends at once");
+    up(&mut h, d4, Modifiers::SHIFT);
+    assert_eq!(selection(&h).2, vec!["B2:D4".to_string()]);
+    pause(&mut h);
+    let f6 = rect(&h, "F6").center();
+    let ctrl = Modifiers { ctrl: true, command: true, ..Modifiers::NONE };
+    down(&mut h, f6, ctrl);
+    assert_eq!(selection(&h).2, vec!["B2:D4".to_string(), "F6".to_string()], "Ctrl+press adds an area at once");
+    up(&mut h, f6, ctrl);
+    assert_eq!(selection(&h).2, vec!["B2:D4".to_string(), "F6".to_string()], "and the release doesn't add it twice");
+}
+
+#[test]
+fn a_checkbox_toggles_on_the_click_not_the_press() {
+    let mut s = blank();
+    s.execute("insert.checkbox", json!({"range": "B2"})).unwrap();
+    let mut h = harness(s);
+    let b2 = rect(&h, "B2").center();
+    down(&mut h, b2, Modifiers::NONE);
+    assert_eq!(selection(&h).0, "B2");
+    assert_eq!(value(&h, "B2"), Value::Bool(false), "pressing doesn't toggle yet");
+    up(&mut h, b2, Modifiers::NONE);
+    assert_eq!(value(&h, "B2"), Value::Bool(true), "the click toggles once");
+    pause(&mut h);
+    // A press that is dragged off the cell is not a click.
+    down(&mut h, b2, Modifiers::NONE);
+    let d2 = rect(&h, "D2").center();
+    frame(&mut h, Event::PointerMoved(d2));
+    up(&mut h, d2, Modifiers::NONE);
+    assert_eq!(value(&h, "B2"), Value::Bool(true));
+    assert_eq!(selection(&h).2, vec!["B2:D2".to_string()]);
+}
+
+#[test]
+fn double_click_still_edits_the_cell() {
+    let mut s = blank();
+    s.execute("cell.set", json!({"cell": "C3", "input": "hello"})).unwrap();
+    let mut h = harness(s);
+    let c3 = rect(&h, "C3").center();
+    for _ in 0..2 {
+        down(&mut h, c3, Modifiers::NONE);
+        frame(&mut h, button(c3, false, Modifiers::NONE));
+    }
+    h.run_steps(2);
+    let editor = h.state().editor.as_ref().expect("a double-click edits");
+    assert_eq!((editor.cell.a1(), editor.text.as_str()), ("C3".to_string(), "hello"));
+}
+
+#[test]
+fn a_click_on_the_selection_border_selects_the_cell_and_a_drag_moves_it() {
+    let mut s = blank();
+    s.execute("cell.set", json!({"cell": "B2", "input": "7"})).unwrap();
+    s.execute("selection.set", json!({"range": "B2"})).unwrap();
+    let mut h = harness(s);
+    // On B2's right border, which belongs to the move handle: nothing happens on the press.
+    let r = rect(&h, "B2");
+    let border = egui::pos2(r.right(), r.center().y);
+    down(&mut h, border, Modifiers::NONE);
+    assert_eq!(selection(&h).0, "B2");
+    let d4 = rect(&h, "D4").center();
+    frame(&mut h, Event::PointerMoved(border + egui::vec2(20.0, 0.0)));
+    frame(&mut h, Event::PointerMoved(d4));
+    up(&mut h, d4, Modifiers::NONE);
+    assert_eq!(value(&h, "B2"), Value::Empty, "dragging the border moved the cell");
+    assert_eq!(value(&h, "D4"), Value::Number(7.0));
+}
+
+#[test]
+fn double_clicking_the_fill_handle_fills_to_the_data_beside_it() {
+    // The sheet from #877: 1..10 in A, 2, 4, 6, 8 in B1:B4.
+    let mut s = blank();
+    let a: Vec<Vec<f64>> = (1..=10).map(|i| vec![i as f64]).collect();
+    s.execute("range.setValues", json!({"range": "A1", "values": a})).unwrap();
+    s.execute("range.setValues", json!({"range": "B1", "values": [[2], [4], [6], [8]]})).unwrap();
+    s.execute("selection.set", json!({"range": "B1:B4"})).unwrap();
+    let mut h = harness(s);
+    let handle = rect(&h, "B4").right_bottom() - egui::vec2(1.0, 1.0);
+    frame(&mut h, Event::PointerMoved(handle));
+    frame(&mut h, button(handle, true, Modifiers::NONE));
+    frame(&mut h, button(handle, false, Modifiers::NONE));
+    // A few frames between the clicks, as a real double-click has (still well inside egui's window).
+    h.run_steps(4);
+    frame(&mut h, button(handle, true, Modifiers::NONE));
+    frame(&mut h, button(handle, false, Modifiers::NONE));
+    h.run_steps(3);
+    assert_eq!(value(&h, "B10"), Value::Number(20.0));
+    assert_eq!(value(&h, "B11"), Value::Empty);
+    assert_eq!(selection(&h).2, vec!["B1:B10".to_string()]);
+    // One undo step.
+    h.state_mut().run("edit.undo", json!({})).unwrap();
+    assert_eq!(value(&h, "B5"), Value::Empty);
+    assert_eq!(value(&h, "B4"), Value::Number(8.0));
+}
+
+fn header_point(h: &Harness, col: Option<&str>, row: Option<u32>) -> Pos2 {
+    let g = geo(h);
+    let app = h.state();
+    let sheet = app.session.active().unwrap().wb.active().unwrap();
+    match (col, row) {
+        (Some(c), _) => {
+            let x = g.cell_rect(sheet, CellRef::parse(&format!("{c}1")).unwrap()).center().x;
+            egui::pos2(x, g.cells.top() - g.header_h / 2.0)
+        }
+        (_, Some(r)) => {
+            let y = g.cell_rect(sheet, CellRef::new(r - 1, 0)).center().y;
+            egui::pos2(g.cells.left() - g.header_w / 2.0, y)
+        }
+        _ => unreachable!(),
+    }
+}
+
+fn start_typing(h: &mut Harness, cell: &str, text: &str) {
+    h.state_mut().session.execute("selection.set", json!({"cell": cell})).unwrap();
+    h.run_steps(2);
+    h.input_mut().events.push(Event::Text(text.into()));
+    h.run_steps(3);
+}
+
+fn editor_text(h: &Harness) -> String {
+    h.state().editor.as_ref().map(|e| e.text.clone()).unwrap_or_default()
+}
+
+fn enter(h: &mut Harness) {
+    h.input_mut().events.push(Event::Key { key: egui::Key::Enter, physical_key: None, pressed: true, repeat: false, modifiers: Modifiers::NONE });
+    h.input_mut().events.push(Event::Key { key: egui::Key::Enter, physical_key: None, pressed: false, repeat: false, modifiers: Modifiers::NONE });
+    h.run_steps(3);
+}
+
+fn formula(h: &Harness, a1: &str) -> Option<String> {
+    let sheet = h.state().session.active().unwrap().wb.active().unwrap();
+    sheet.cell(CellRef::parse(a1).unwrap()).and_then(|c| c.formula.as_ref().map(|f| f.text.clone()))
+}
+
+/// While typing a formula, the headings point like cells do, as observed in Excel: a column
+/// heading puts `B:B` in, a drag across headings `B:D`, a row heading `3:3` (#872).
+#[test]
+fn headings_put_whole_columns_and_rows_into_a_formula() {
+    let mut s = blank();
+    s.execute("range.setValues", json!({"range": "B1", "values": [[1, 10, 100], [2, 20, 200], [3, 30, 300]]})).unwrap();
+    let mut h = harness(s);
+
+    start_typing(&mut h, "F1", "=SUM(");
+    let b = header_point(&h, Some("B"), None);
+    down(&mut h, b, Modifiers::NONE);
+    assert_eq!(editor_text(&h), "=SUM(B:B", "the press points");
+    up(&mut h, b, Modifiers::NONE);
+    assert_eq!(editor_text(&h), "=SUM(B:B");
+    assert_eq!(h.state().session.active().unwrap().selection.active.a1(), "F1", "the selection stays on the edited cell");
+    h.input_mut().events.push(Event::Text(")".into()));
+    h.run_steps(2);
+    enter(&mut h);
+    assert_eq!(formula(&h, "F1").as_deref(), Some("SUM(B:B)"));
+    assert_eq!(value(&h, "F1"), Value::Number(6.0));
+
+    // A drag across the headings widens it, and back again.
+    pause(&mut h);
+    start_typing(&mut h, "F2", "=SUM(");
+    let (b, c, d) = (header_point(&h, Some("B"), None), header_point(&h, Some("C"), None), header_point(&h, Some("D"), None));
+    down(&mut h, b, Modifiers::NONE);
+    frame(&mut h, Event::PointerMoved(c));
+    frame(&mut h, Event::PointerMoved(d));
+    assert_eq!(editor_text(&h), "=SUM(B:D");
+    frame(&mut h, Event::PointerMoved(c));
+    assert_eq!(editor_text(&h), "=SUM(B:C");
+    up(&mut h, c, Modifiers::NONE);
+    h.input_mut().events.push(Event::Text(")".into()));
+    h.run_steps(2);
+    enter(&mut h);
+    assert_eq!(value(&h, "F2"), Value::Number(66.0));
+
+    // A row heading.
+    pause(&mut h);
+    start_typing(&mut h, "F4", "=SUM(");
+    let r3 = header_point(&h, None, Some(3));
+    down(&mut h, r3, Modifiers::NONE);
+    up(&mut h, r3, Modifiers::NONE);
+    assert_eq!(editor_text(&h), "=SUM(3:3");
+    h.input_mut().events.push(Event::Text(")".into()));
+    h.run_steps(2);
+    enter(&mut h);
+    assert_eq!(value(&h, "F4"), Value::Number(333.0));
+
+    // Not in point mode (after a reference was typed), a heading click ends the edit and selects.
+    pause(&mut h);
+    start_typing(&mut h, "F5", "=A1");
+    let c = header_point(&h, Some("C"), None);
+    down(&mut h, c, Modifiers::NONE);
+    up(&mut h, c, Modifiers::NONE);
+    assert_ne!(editor_text(&h), "=A1C:C");
+}
+
+/// Pointing at cells while typing a formula still works with presses: the press puts the
+/// reference in, a drag widens it, and the keyboard stays with the formula.
+#[test]
+fn cells_point_into_a_formula_on_the_press() {
+    let mut s = blank();
+    s.execute("range.setValues", json!({"range": "B1", "values": [[1], [2], [3]]})).unwrap();
+    let mut h = harness(s);
+    start_typing(&mut h, "D1", "=SUM(");
+    let (b1, b3) = (rect(&h, "B1").center(), rect(&h, "B3").center());
+    down(&mut h, b1, Modifiers::NONE);
+    assert_eq!(editor_text(&h), "=SUM(B1");
+    frame(&mut h, Event::PointerMoved(b1.lerp(b3, 0.5)));
+    frame(&mut h, Event::PointerMoved(b3));
+    up(&mut h, b3, Modifiers::NONE);
+    assert_eq!(editor_text(&h), "=SUM(B1:B3");
+    h.input_mut().events.push(Event::Text(")".into()));
+    h.run_steps(2);
+    enter(&mut h);
+    assert_eq!(formula(&h, "D1").as_deref(), Some("SUM(B1:B3)"));
+    assert_eq!(value(&h, "D1"), Value::Number(6.0));
+}

crates/xlsx/src/tests/malformed.rs

@@ -227,32 +227,3 @@ fn hyperlinks_past_the_cell_cap_are_reported() {
     assert_eq!(wb.sheet(0).unwrap().hyperlinks.len(), 3);
     assert!(rep.warnings.is_empty(), "{:?}", rep.warnings);
 }
-
-/// Formula text built to overflow a recursive parser or tree walk (a million `%`, a 200,000-term
-/// sum): the cells keep their formula text and cached value, nothing overflows the stack.
-#[test]
-fn hostile_formula_text_does_not_overflow_the_stack() {
-    let percents = format!("1{}", "%".repeat(1_000_000));
-    let chain = format!("1{}", "+1".repeat(100_000));
-    let body = format!(r#"<sheetData><row r="1"><c r="A1"><f>{percents}</f><v>3</v></c><c r="B1"><f>{chain}</f><v>4</v></c></row></sheetData>"#);
-    let names = format!(r#"<definedNames><definedName name="Deep">{percents}</definedName></definedNames>"#);
-    let bytes = minimal(&body, &[], "", &names);
-    let handle = std::thread::Builder::new()
-        .stack_size(1024 * 1024)
-        .spawn(move || {
-            let (wb, _) = read_xlsx(&bytes).expect("readable");
-            let s = wb.sheet(0).expect("sheet");
-            let a1 = s.cell(gridcraft_core::CellRef::new(0, 0)).and_then(|c| c.formula.clone()).expect("formula kept");
-            let b1 = s.cell(gridcraft_core::CellRef::new(0, 1)).and_then(|c| c.formula.clone()).expect("formula kept");
-            let kept = (a1.expr.is_none(), b1.expr.is_none(), a1.text.len(), s.value(gridcraft_core::CellRef::new(0, 0)));
-            assert_eq!(wb.names.first().map(|n| n.formula.len()), Some(1_000_001));
-            let out = write_xlsx(&wb).expect("writable");
-            drop(wb);
-            (kept, !out.is_empty())
-        })
-        .expect("spawn");
-    let ((a_unparsed, b_unparsed, a_len, a_value), written) = handle.join().expect("no stack overflow");
-    assert!(a_unparsed && b_unparsed && written);
-    assert_eq!(a_len, 1_000_001);
-    assert_eq!(a_value, gridcraft_core::Value::Number(3.0));
-}

docs/control-protocol.md

@@ -15,10 +15,6 @@ Then send newline-delimited JSON to `127.0.0.1:7979`. Every request line gets on
 
 Errors come back as `{"id": …, "ok": false, "error": "…"}`.
 
-A line that is not a JSON object with a string `method` (an HTTP request, text that isn't JSON,
-bytes that aren't UTF-8, a line over 64 MiB) gets one error reply and the server closes the
-connection; nothing sent after it runs. Blank lines are skipped.
-
 ## Methods
 
 | Method | Params | What it does |

docs/file-format-parity.md

@@ -1,6 +1,6 @@
 # File-format parity
 
-> **Last reviewed:** 2026-10-11 · **Last updated:** 2026-10-14 · **Change:** trivial (formulas over Excel's 8,192 characters, and `%` or call chains past the nesting limit, are parse errors instead of stack overflows when a file is opened; previously trivial: XLSX chart sheets are kept on save (#727)) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
+> **Last reviewed:** 2026-10-11 · **Last updated:** 2026-10-12 · **Change:** trivial (XLSX chart sheets are kept on save (#727); previously minor: CSV save keeps the separator it was opened with) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
 
 Every format Excel opens or saves, with GridCraft's read and write support, fidelity and tests.
 Part of [target-app-parity.md](target-app-parity.md). **File formats: ~50% ready, 80–120 h**
@@ -85,7 +85,6 @@ refresh. Counted under features (Get & Transform, ~10% ready), not here.
 
 | Date | Change | Summary |
 |---|---|---|
-| 2026-10-14 | trivial | Formula parser: text longer than Excel's 8,192 characters, and postfix chains (`1%%%…`, `f(1)(1)…`) past the 256-level nesting limit, are parse errors (the cell keeps its formula text and cached value) instead of trees deep enough to overflow the stack when a hostile file is opened, saved or dropped |
 | 2026-10-12 | trivial | XLSX chart sheets are kept on save (#727) |
 | 2026-10-12 | trivial | CSV and TSV export is capped at 512 MiB and refuses a larger used range with an error (#528) |
 | 2026-10-12 | minor | `.xls` import reads the calculation settings (CalcMode, CalcIter, CalcCount, CalcDelta, CalcPrecision), so circular models calculate instead of showing `#CIRC!` (#724) |

docs/function-parity.md

@@ -1,6 +1,6 @@
 # Function parity: worksheet functions and formulas
 
-> **Last reviewed:** 2026-10-11 · **Last updated:** 2026-10-13 · **Change:** minor (clearing large sparse ranges recalculates every changed cell's dependents, #1032) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
+> **Last reviewed:** 2026-10-11 · **Last updated:** 2026-10-12 · **Change:** minor (USDOLLAR added as a compatibility function; MIRR, COUNTIF and INDIRECT edge cases match Excel 365) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
 
 Excel's worksheet functions, category by category, against GridCraft's function library. Part of
 [target-app-parity.md](target-app-parity.md); gaps feed [gaps.md](gaps.md).
@@ -76,7 +76,6 @@ PIVOTBY, REGEXTEST…) are all present.
 | Structured references (`Table1[Col]`, `[#Totals]`, `@`; the unbracketed `[[#This Row],Col]` some writers emit) | done |
 | Defined names (workbook and sheet scope), Create from Selection | done |
 | Dynamic arrays, spill, `#SPILL!`, spill operator `A1#` | done; stale-spill bugs (#133, #139; PRs #148, #157) |
-| Recalculation after clearing large sparse ranges | every stored cell changed by Clear is reported to recalculation, without a million-coordinate cutoff; removed formula spills are cleared, and removing empty merges still unblocks spills (#1032) |
 | Implicit intersection `@`, legacy CSE array formulas | done; legacy array range fill (PR #156) |
 | Trim references `A1:.E10` (trailing), `A1.:E10` (leading), `A1.:.E10` (both), also on whole rows/columns (`A:.A`) | done; evaluated as `TRIMRANGE(range, code, code)`, adjusted on insert/delete; files store `_xlfn.TRIMRANGE(range,code,code)` (Excel's own file spelling unconfirmed in public docs), `_xlfn._TRO_ALL/_TRO_LEADING/_TRO_TRAILING(...)` read too |
 | LET, LAMBDA, named LAMBDAs, ISOMITTED, MAP/REDUCE/SCAN/BYROW/BYCOL/MAKEARRAY | done |
@@ -109,7 +108,6 @@ workbooks; results checked in as data, not Excel files) and fixing what it finds
 
 | Date | Change | Summary |
 |---|---|---|
-| 2026-10-13 | minor | Clear reports changed stored cells sparsely, including those beyond the first million coordinates; dependent formulas and removed spills update, while clearing empty merges still unblocks spills (#1032) |
 | 2026-10-12 | minor | USDOLLAR added as a Compatibility function (not on Microsoft's list, so the counts don't change); MIRR with no positive flow is -1, COUNTIF's bare `"<="` / `">="` skip empty strings, INDIRECT with `a1` = FALSE gives `#REF!` for A1-style text (#738) |
 | 2026-10-11 | minor | TEXT / number formats fixed against Excel-cached results: fraction literals and zero fractions, `0` denominators zero padded, `?` pads the thousands separator, booleans use the text section (226 mismatches → 0 in 352 TEXT cells) |
 | 2026-10-11 | minor | Iterative calculation: circular references iterate up to Maximum Iterations / Maximum Change when enabled |

docs/ui-parity.md

@@ -1,6 +1,6 @@
 # UI parity
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-13 · **Change:** minor (horizontal scrollbar in the sheet tab bar, #840) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
+> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-13 · **Change:** minor (presses select on button-down, fill-handle double-click, whole-line references in point mode; observed against Windows Excel) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
 
 Interaction, controls and feel, against Excel. Part of [target-app-parity.md](target-app-parity.md).
 **UI/UX fidelity: ~55% ready, 50–80 h** (estimated). Ribbon command coverage is measured
@@ -43,12 +43,12 @@ this logic, with one undo step.
 
 | Behaviour | Status |
 |---|---|
-| Click/drag/Shift/Ctrl selection, multi-area selection | rectangular drag works in one direction only in some cases (#28) |
+| Click/drag/Shift/Ctrl selection, multi-area selection | done; a press selects when the button goes down and a drag extends from it, as in Excel; clicks on checkboxes and links act on release (#900). Rectangular drag works in one direction only in some cases (#28) |
 | Selection outline glides to a new selection (Excel: "Provide feedback with animation") | done (10-11): 0.12 s, decelerating, with the fill and fill handle; View ▸ Animations (`view.animations`) turns it off. The timing is an estimate, not yet measured against Excel; the system's reduced-motion setting isn't followed yet |
-| Fill handle: drag to fill series, double-click to fill down, right-drag menu | fill done (Ctrl+drag swaps copy and series); right-drag menu missing |
+| Fill handle: drag to fill series, double-click to fill down, right-drag menu | fill done (Ctrl+drag swaps copy and series); double-click fills to the bottom of the data region around the source and stops above a filled cell, matching 13 cases observed in Excel (`edit.autoFillToData`, #877); right-drag menu missing |
 | Drag-move and drag-copy cells (border drag, Ctrl/Option, Shift to insert) | done (M3) |
 | In-cell editing, Enter/Tab movement, Alt/Option+Enter line breaks | done |
-| Point mode (click/drag/arrow references), reference colouring, F4 | done |
+| Point mode (click/drag/arrow references), reference colouring, F4 | done; headings point whole columns and rows (`B:D`, `3:3`), which are coloured and outlined, and F4 toggles them `$B:$D` ⇄ `B:D` as in Excel (#872, #873, #875) |
 | AutoComplete in columns, function autocomplete and argument tips | done; cell helpers clip to the worksheet and hide when the editor scrolls out (#200) |
 | Header resize and double-click AutoFit | done (#42, #88 for header dividers) |
 | Outline symbols for grouped rows / columns (band beside the headers, brackets, − / +, level buttons 1…n+1) | done (#373): clicks run `data.hideDetail` / `data.showDetail` / `data.showLevels`, frozen panes and right-to-left sheets included; summary rows/columns are always below/right (the "Summary rows below detail" setting isn't modelled), no "Show outline symbols" option yet, and a block of cells still groups rows without the Rows / Columns dialog |
@@ -161,6 +161,7 @@ scrollbar bugs 2–4 · pixel/feel pass against observed Excel 7–12.
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-10-13 | minor | Presses select on button-down (#900); fill-handle double-click fills to the adjacent data (#877); headings point `A:A`/`2:2` into formulas, coloured, outlined and toggled by F4 (#872, #873, #875) |
 | 2026-10-12 | minor | The File view's recent list tells when each workbook was last changed, read off the UI thread |
 | 2026-10-13 | minor | Horizontal scrollbar in the sheet tab bar: drag, track click pages, frozen columns excluded from the page (#840) |
 | 2026-10-12 | minor | Ctrl+wheel zoom steps along a ladder of percentages about 20% apart that never skips 100%, gliding to each step with animations on, so a notch out undoes a notch in (it drifted: 100 → 122 → 101); Excel steps 15 points, see decisions.md |