app icon: calico cat in a polka-dot scarf (owner's ArtCraft drawing), Dock/taskbar/launcher wiring, palette docs

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-24 02:06:54 -06:00 · 2026-10-02 09:44:07 -04:00
parent 7143973f52
commit b97828eb50
27 changed files with 336 additions and 1 deletions
@@ -38,6 +38,22 @@ Generated-in-code art is original and has no file to list: the UI icon set (`cra
 | `crates/render/tests/golden/feather.png` | DesignCraft contributors (generated) | rendered by DesignCraft's own renderer (`crates/render/tests/effects.rs`, synthetic shapes and bundled fonts) | MIT OR Apache-2.0 | Golden test image for soft effects |
 | `crates/render/tests/golden/inner-shadow.png` | DesignCraft contributors (generated) | rendered by DesignCraft's own renderer (`crates/render/tests/effects.rs`, synthetic shapes and bundled fonts) | MIT OR Apache-2.0 | Golden test image for soft effects |
 | `crates/render/tests/golden/outer-glow.png` | DesignCraft contributors (generated) | rendered by DesignCraft's own renderer (`crates/render/tests/effects.rs`, synthetic shapes and bundled fonts) | MIT OR Apache-2.0 | Golden test image for soft effects |
+| `assets/app-icon/LICENSE.txt` | (licence text) | this project | — | Licence for the app icon |
+| `assets/app-icon/designcraft-1024.png` | DesignCraft project owner (drawn in ArtCraft) | rendered from `assets/app-icon/designcraft.svg` by `packaging/icons.sh` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/designcraft-macos-512.png` | DesignCraft project owner (drawn in ArtCraft) | rendered from `assets/app-icon/designcraft.svg` by `packaging/icons.sh` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/designcraft-small.svg` | DesignCraft project owner (drawn in ArtCraft) | owner's ArtCraft drawing, vectorised with craftrules `assets/logo-options/_tools/vectorize_tile.py` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/designcraft.icns` | DesignCraft project owner (drawn in ArtCraft) | rendered from `assets/app-icon/designcraft.svg` by `packaging/icons.sh` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/designcraft.ico` | DesignCraft project owner (drawn in ArtCraft) | rendered from `assets/app-icon/designcraft.svg` by `packaging/icons.sh` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/designcraft.svg` | DesignCraft project owner (drawn in ArtCraft) | owner's ArtCraft drawing, vectorised with craftrules `assets/logo-options/_tools/vectorize_tile.py` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/hicolor/128x128/apps/ai.storyteller.designcraft.png` | DesignCraft project owner (drawn in ArtCraft) | rendered from `assets/app-icon/designcraft.svg` by `packaging/icons.sh` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/hicolor/16x16/apps/ai.storyteller.designcraft.png` | DesignCraft project owner (drawn in ArtCraft) | rendered from `assets/app-icon/designcraft.svg` by `packaging/icons.sh` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/hicolor/24x24/apps/ai.storyteller.designcraft.png` | DesignCraft project owner (drawn in ArtCraft) | rendered from `assets/app-icon/designcraft.svg` by `packaging/icons.sh` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/hicolor/256x256/apps/ai.storyteller.designcraft.png` | DesignCraft project owner (drawn in ArtCraft) | rendered from `assets/app-icon/designcraft.svg` by `packaging/icons.sh` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/hicolor/32x32/apps/ai.storyteller.designcraft.png` | DesignCraft project owner (drawn in ArtCraft) | rendered from `assets/app-icon/designcraft.svg` by `packaging/icons.sh` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/hicolor/48x48/apps/ai.storyteller.designcraft.png` | DesignCraft project owner (drawn in ArtCraft) | rendered from `assets/app-icon/designcraft.svg` by `packaging/icons.sh` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/hicolor/512x512/apps/ai.storyteller.designcraft.png` | DesignCraft project owner (drawn in ArtCraft) | rendered from `assets/app-icon/designcraft.svg` by `packaging/icons.sh` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/hicolor/64x64/apps/ai.storyteller.designcraft.png` | DesignCraft project owner (drawn in ArtCraft) | rendered from `assets/app-icon/designcraft.svg` by `packaging/icons.sh` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
+| `assets/app-icon/hicolor/scalable/apps/ai.storyteller.designcraft.svg` | DesignCraft project owner (drawn in ArtCraft) | owner's ArtCraft drawing, vectorised with craftrules `assets/logo-options/_tools/vectorize_tile.py` | MIT OR Apache-2.0 (`assets/app-icon/LICENSE.txt`) | App icon: calico cat in a polka-dot scarf (see `assets/app-icon/README.md`) |
 | `docs/brand/artcraft-logo.svg`, `docs/brand/artcraft-logo.png` | ArtCraft / Storyteller | ArtCraft brand kit (project owner) | ArtCraft trademark — used with the owner's permission; not covered by the code licence | ArtCraft wordmark (README header) |
 | `docs/brand/artcraft-logo-white.svg`, `docs/brand/artcraft-logo-white.png` | ArtCraft / Storyteller | ArtCraft brand kit (project owner) | ArtCraft trademark — used with the owner's permission; not covered by the code licence | Wordmark for dark backgrounds |
 | `docs/brand/artcraft-mark.svg`, `docs/brand/artcraft-mark.png` | ArtCraft / Storyteller | ArtCraft brand kit (project owner) | ArtCraft trademark — used with the owner's permission; not covered by the code licence | The mark; its outline is drawn in code by `crates/ui-egui/src/about.rs` (About splash, start screen) |
@@ -853,6 +853,7 @@ dependencies = [
 "muda",
 "rfd",
 "serde_json",
+ "winresource",
 ]

 [[package]]
@@ -4070,10 +4071,12 @@ version = "1.1.6+spec-1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "920602543f0911ab71da12c50d59701da54c196d1a2bf5cb4b75667f137a406a"
 dependencies = [
+ "indexmap",
 "serde_core",
 "serde_spanned",
 "toml_datetime",
 "toml_parser",
+ "toml_writer",
 "winnow",
 ]

@@ -4107,6 +4110,12 @@ dependencies = [
 "winnow",
 ]

+[[package]]
+name = "toml_writer"
+version = "1.1.2+spec-1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7d56353a2a665ad0f41a421187180aab746c8c325620617ad883a99a1cbe66d2"
+
 [[package]]
 name = "tracing"
 version = "0.1.44"
@@ -5152,6 +5161,16 @@ dependencies = [
 "memchr",
 ]

+[[package]]
+name = "winresource"
+version = "0.1.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0986a8b1d586b7d3e4fe3d9ea39fb451ae22869dcea4aa109d287a374d866087"
+dependencies = [
+ "toml",
+ "version_check",
+]
+
 [[package]]
 name = "wit-bindgen"
 version = "0.57.1"
@@ -7,6 +7,10 @@
  </a>
 </p>

+<p align="center">
+  <img alt="DesignCraft app icon: a calico cat wearing a polka-dot scarf" src="assets/app-icon/hicolor/256x256/apps/ai.storyteller.designcraft.png" width="128">
+</p>
+
 <h1 align="center">DesignCraft</h1>

 <p align="center">
@@ -139,6 +143,7 @@ egui frontend is a separate crate, so the UI can be swapped without touching the
 - **Status and milestones:** [ROADMAP.md](ROADMAP.md)
 - **Contributor and agent rules** (clean-room, asset policy, quality gates): [`AGENTS.md`](AGENTS.md)
 - **Bundled assets:** every one is listed with its licence in [`ASSETS.md`](ASSETS.md)
+- **App icon and colour:** a calico cat in a polka-dot scarf on DesignCraft green `#7bb51c`; see [`assets/app-icon/`](assets/app-icon/README.md)

 ## The Crafting Apps

@@ -17,6 +17,10 @@ egui = { workspace = true }
 serde_json = { workspace = true }
 log = { workspace = true }

+[build-dependencies]
+# Icon + VERSIONINFO for designcraft.exe; build.rs only uses it when the target is Windows.
+winresource = "0.1"
+
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 rfd = { workspace = true }

@@ -0,0 +1,29 @@
+//! Windows only: embed the app icon and version info (VERSIONINFO) into `designcraft.exe`, so it
+//! shows in Explorer, the taskbar, the Start menu and Alt-Tab.
+//!
+//! On every other target this does nothing. A missing resource compiler is a warning, so a
+//! cross-compile from macOS or Linux still links, unless `DESIGNCRAFT_REQUIRE_WINRES=1` turns it
+//! into an error (for release builds).
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-changed=../../assets/app-icon/designcraft.ico");
+    println!("cargo:rerun-if-env-changed=DESIGNCRAFT_REQUIRE_WINRES");
+    if std::env::var("CARGO_CFG_TARGET_OS").as_deref() != Ok("windows") {
+        return;
+    }
+    let mut res = winresource::WindowsResource::new();
+    res.set_icon("../../assets/app-icon/designcraft.ico")
+        .set("ProductName", "DesignCraft")
+        .set("FileDescription", "DesignCraft page layout")
+        .set("CompanyName", "Learning Machines LLC")
+        .set("LegalCopyright", "Copyright (c) the DesignCraft authors. MIT OR Apache-2.0.")
+        .set("OriginalFilename", "designcraft.exe")
+        .set("InternalName", "designcraft");
+    if let Err(e) = res.compile() {
+        if std::env::var_os("DESIGNCRAFT_REQUIRE_WINRES").is_some() {
+            panic!("embedding Windows resources failed: {e}");
+        }
+        println!("cargo:warning=designcraft.exe built without icon/version resources: {e}");
+    }
+}
@@ -99,6 +99,19 @@ fn services() -> Services {
    }
 }

+/// Desktop app ID: the Linux `.desktop` file name and hicolor icon name (Wayland matches windows by it).
+const APP_ID: &str = "ai.storyteller.designcraft";
+
+/// The window, Dock, taskbar and Alt-Tab icon. macOS gets Apple's icon grid (transparent margin);
+/// elsewhere the full tile. Regenerate with `packaging/icons.sh`.
+fn app_icon() -> Option<egui::IconData> {
+    #[cfg(target_os = "macos")]
+    let png: &[u8] = include_bytes!("../../../assets/app-icon/designcraft-macos-512.png");
+    #[cfg(not(target_os = "macos"))]
+    let png: &[u8] = include_bytes!("../../../assets/app-icon/hicolor/256x256/apps/ai.storyteller.designcraft.png");
+    eframe::icon_data::from_png_bytes(png).map_err(|e| log::warn!("app icon: {e}")).ok()
+}
+
 fn main() -> eframe::Result {
    let mut control_port: Option<u16> = std::env::var("DESIGNCRAFT_CONTROL_PORT").ok().and_then(|p| p.parse().ok());
    let mut files = Vec::new();
@@ -115,7 +128,7 @@ fn main() -> eframe::Result {
            _ => files.push(a),
        }
    }
-    let options = eframe::NativeOptions {
+    let mut options = eframe::NativeOptions {
        viewport: egui::ViewportBuilder::default()
            .with_title("DesignCraft")
            .with_inner_size([1440.0, 900.0])
@@ -126,6 +139,10 @@ fn main() -> eframe::Result {
            .with_title_shown(false),
        ..Default::default()
    };
+    options.viewport = options.viewport.with_app_id(APP_ID);
+    if let Some(icon) = app_icon() {
+        options.viewport = options.viewport.with_icon(icon);
+    }
    eframe::run_native(
        "DesignCraft",
        options,
@@ -0,0 +1,13 @@
+DesignCraft app icon (designcraft.svg, designcraft-small.svg and every file derived from them in
+this directory: designcraft-1024.png, designcraft-macos-512.png, designcraft.icns, designcraft.ico,
+hicolor/).
+
+Original artwork made for this project by the project owner in ArtCraft, then vectorised. No
+third-party material. Licensed like the rest of DesignCraft, under either of
+
+  * Apache License, Version 2.0 (https://www.apache.org/licenses/LICENSE-2.0)
+  * MIT license (https://opensource.org/licenses/MIT)
+
+at your option.
+
+Regenerate the derived files with packaging/icons.sh.
@@ -0,0 +1,50 @@
+# DesignCraft app icon
+
+**A calico cat wearing a polka-dot scarf**, as an engraving-style head-and-shoulders portrait in the
+Crafting Apps' owl-template framing: a full-bleed colour field, the cat in three-quarter view, its
+shoulders running off the bottom edge.
+
+## Palette
+
+Exactly three colours:
+
+| Colour | Hex | Used for |
+|---|---|---|
+| Ink | `#0b0b0c` | Line work and contour |
+| Paper | `#efe9dc` | The figure (the cat and its scarf) |
+| DesignCraft green (app colour) | `#7bb51c` | The full-bleed background field |
+
+## Geometry
+
+A 512 × 512 viewBox, clipped to a rounded square with `rx=112`. Windows and Linux use the full tile. The
+macOS icons (`.icns`, `designcraft-macos-512.png`) sit on Apple's grid: an 824/1024 body with a
+transparent margin.
+
+## Provenance
+
+The owner drew the cat in ArtCraft. The 2880 px drawing, keyed to the three-colour palette, lives
+outside this repo in craftrules at `assets/app-icons/designcraft/source.png`. It was vectorised with
+craftrules' `assets/logo-options/_tools/vectorize_tile.py`: `designcraft.svg` is traced at 2048 px and
+`designcraft-small.svg` at 1024 px. Design rules: craftrules `standards/icon-design.md`.
+
+## Files
+
+| File | Use |
+|---|---|
+| `designcraft.svg` | Canonical artwork (about 680 KB) |
+| `designcraft-small.svg` | Lighter vector (about 350 KB); also `hicolor/scalable` |
+| `designcraft-1024.png` | 1024 px render of the full tile |
+| `designcraft-macos-512.png` | Runtime Dock icon on macOS (embedded by `apps/designcraft`) |
+| `designcraft.icns` | macOS bundle icon (`CFBundleIconFile`) |
+| `designcraft.ico` | Windows exe icon, 16–256 px (embedded by `apps/designcraft/build.rs`) |
+| `hicolor/<size>/apps/ai.storyteller.designcraft.png` | Linux icon theme, 16–512 px; the 256 px one is also the runtime window icon on Windows and Linux |
+| `hicolor/scalable/apps/ai.storyteller.designcraft.svg` | Linux scalable icon |
+| `LICENSE.txt` | MIT OR Apache-2.0 |
+
+The app ID is `ai.storyteller.designcraft`. It's used for the hicolor icon names, the Wayland app ID and
+`packaging/linux/ai.storyteller.designcraft.desktop`.
+
+## Regenerate
+
+Edit `designcraft.svg` (or `designcraft-small.svg`), then run `packaging/icons.sh`. It needs `resvg`, and
+`iconutil` for the `.icns` (macOS only). It packs the `.ico` with `cargo xtask ico`.
@@ -0,0 +1,58 @@
+#!/usr/bin/env bash
+# Regenerate every app icon from assets/app-icon/designcraft.svg.
+#
+# Needs: resvg (brew install resvg / cargo install resvg). On macOS, iconutil also writes the
+# .icns. The outputs are committed, so builds and packaging never need these tools.
+#
+#   packaging/icons.sh
+set -euo pipefail
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+DIR="$ROOT/assets/app-icon"
+SVG="$DIR/designcraft.svg"
+ID="ai.storyteller.designcraft"
+TMP="$(mktemp -d)"
+trap 'rm -rf "$TMP"' EXIT
+
+command -v resvg >/dev/null || { echo "error: resvg not found (brew install resvg)" >&2; exit 1; }
+
+# The artwork is a full-bleed 512 tile (rx=112). Windows and Linux use it as is. macOS icons sit on
+# Apple's grid: an 824/1024 body with a transparent margin, so widen the viewBox to 512*1024/824.
+MAC="$TMP/mac.svg"
+sed 's/viewBox="0 0 512 512"/viewBox="-62.136 -62.136 636.272 636.272"/' "$SVG" >"$MAC"
+grep -q 'viewBox="-62.136' "$MAC" || { echo "error: expected viewBox=\"0 0 512 512\" in $SVG" >&2; exit 1; }
+
+render() { resvg -w "$2" -h "$2" "$1" "$3" </dev/null; }
+
+render "$SVG" 1024 "$DIR/designcraft-1024.png"
+# Runtime window/Dock icon on macOS (embedded by apps/designcraft); other platforms use hicolor 256.
+render "$MAC" 512 "$DIR/designcraft-macos-512.png"
+
+# Linux hicolor theme.
+for s in 16 24 32 48 64 128 256 512; do
+  mkdir -p "$DIR/hicolor/${s}x${s}/apps"
+  render "$SVG" "$s" "$DIR/hicolor/${s}x${s}/apps/$ID.png"
+done
+mkdir -p "$DIR/hicolor/scalable/apps"
+cp "$DIR/designcraft-small.svg" "$DIR/hicolor/scalable/apps/$ID.svg"
+
+# Windows .ico.
+ICO_PNGS=()
+for s in 16 20 24 32 40 48 64 128 256; do
+  render "$SVG" "$s" "$TMP/ico-$s.png"
+  ICO_PNGS+=("$TMP/ico-$s.png")
+done
+(cd "$ROOT" && cargo run -q -p xtask -- ico "$DIR/designcraft.ico" "${ICO_PNGS[@]}")
+
+# macOS .icns.
+if command -v iconutil >/dev/null; then
+  SET="$TMP/designcraft.iconset"
+  mkdir -p "$SET"
+  for s in 16 32 128 256 512; do
+    render "$MAC" "$s" "$SET/icon_${s}x${s}.png"
+    render "$MAC" $((s * 2)) "$SET/icon_${s}x${s}@2x.png"
+  done
+  iconutil -c icns -o "$DIR/designcraft.icns" "$SET"
+else
+  echo "warning: iconutil not found (macOS only); designcraft.icns not regenerated" >&2
+fi
+echo "icons written to $DIR"
@@ -0,0 +1,13 @@
+[Desktop Entry]
+Type=Application
+Name=DesignCraft
+GenericName=Page Layout
+Comment=Lay out magazines, books and print documents
+Exec=designcraft %F
+TryExec=designcraft
+Icon=ai.storyteller.designcraft
+Terminal=false
+StartupNotify=true
+StartupWMClass=ai.storyteller.designcraft
+Categories=Graphics;Publishing;
+Keywords=layout;page;desktop publishing;dtp;magazine;book;indesign;idml;typesetting;
@@ -0,0 +1,104 @@
+//! `cargo xtask ico <out.ico> <in.png>…`: pack PNG images into a Windows `.ico`.
+//!
+//! Vista and later read PNG-compressed icon entries, so each PNG is stored as is. The size comes
+//! from the PNG's IHDR chunk; 256 px is written as 0, per the ICO format.
+
+use std::path::Path;
+
+/// Width and height from a PNG's IHDR chunk.
+pub fn png_size(png: &[u8]) -> Result<(u32, u32), String> {
+    const SIG: &[u8] = b"\x89PNG\r\n\x1a\n";
+    if png.len() < 24 || &png[..8] != SIG || &png[12..16] != b"IHDR" {
+        return Err("not a PNG file".into());
+    }
+    let w = u32::from_be_bytes([png[16], png[17], png[18], png[19]]);
+    let h = u32::from_be_bytes([png[20], png[21], png[22], png[23]]);
+    Ok((w, h))
+}
+
+/// An ICO file holding `pngs`, which must be square and at most 256 px.
+pub fn pack(pngs: &[Vec<u8>]) -> Result<Vec<u8>, String> {
+    if pngs.is_empty() || pngs.len() > u16::MAX as usize {
+        return Err("need at least one PNG".into());
+    }
+    let mut out = Vec::new();
+    out.extend_from_slice(&0u16.to_le_bytes()); // reserved
+    out.extend_from_slice(&1u16.to_le_bytes()); // type: icon
+    out.extend_from_slice(&(pngs.len() as u16).to_le_bytes());
+    let mut offset = 6 + 16 * pngs.len();
+    for png in pngs {
+        let (w, h) = png_size(png)?;
+        if w != h || w == 0 || w > 256 {
+            return Err(format!("icon images must be square and at most 256 px, got {w}x{h}"));
+        }
+        let dim = if w == 256 { 0 } else { w as u8 };
+        out.extend_from_slice(&[dim, dim, 0, 0]); // width, height, palette size, reserved
+        out.extend_from_slice(&1u16.to_le_bytes()); // colour planes
+        out.extend_from_slice(&32u16.to_le_bytes()); // bits per pixel
+        out.extend_from_slice(&(png.len() as u32).to_le_bytes());
+        out.extend_from_slice(&(offset as u32).to_le_bytes());
+        offset += png.len();
+    }
+    for png in pngs {
+        out.extend_from_slice(png);
+    }
+    Ok(out)
+}
+
+pub fn run(args: &[&str]) -> Result<(), String> {
+    let [out, inputs @ ..] = args else {
+        return Err("usage: cargo xtask ico <out.ico> <in.png>…".into());
+    };
+    let pngs = inputs.iter().map(|p| std::fs::read(p).map_err(|e| format!("read {p}: {e}"))).collect::<Result<Vec<_>, _>>()?;
+    let ico = pack(&pngs)?;
+    std::fs::write(Path::new(out), &ico).map_err(|e| format!("write {out}: {e}"))?;
+    println!("{out}: {} images, {} bytes", pngs.len(), ico.len());
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn fake_png(size: u32) -> Vec<u8> {
+        let mut v = b"\x89PNG\r\n\x1a\n\0\0\0\x0dIHDR".to_vec();
+        v.extend_from_slice(&size.to_be_bytes());
+        v.extend_from_slice(&size.to_be_bytes());
+        v.extend_from_slice(&[8, 6, 0, 0, 0, 1, 2, 3, 4]);
+        v
+    }
+
+    #[test]
+    fn packs_directory_and_payloads() {
+        let a = fake_png(16);
+        let b = fake_png(256);
+        let ico = pack(&[a.clone(), b.clone()]).unwrap();
+        assert_eq!(&ico[..6], &[0, 0, 1, 0, 2, 0]);
+        // Entry 0: 16 px at offset 6 + 32.
+        assert_eq!(&ico[6..8], &[16, 16]);
+        assert_eq!(u32::from_le_bytes(ico[14..18].try_into().unwrap()), a.len() as u32);
+        assert_eq!(u32::from_le_bytes(ico[18..22].try_into().unwrap()), 38);
+        // Entry 1: 256 px stored as 0, right after the first payload.
+        assert_eq!(&ico[22..24], &[0, 0]);
+        assert_eq!(u32::from_le_bytes(ico[34..38].try_into().unwrap()), 38 + a.len() as u32);
+        assert_eq!(&ico[38..38 + a.len()], &a[..]);
+        assert_eq!(&ico[38 + a.len()..], &b[..]);
+    }
+
+    #[test]
+    fn rejects_bad_input() {
+        assert!(pack(&[]).is_err());
+        assert!(pack(&[fake_png(512)]).is_err());
+        assert!(pack(&[b"GIF89a".to_vec()]).is_err());
+        assert_eq!(png_size(&fake_png(48)).unwrap(), (48, 48));
+    }
+
+    #[test]
+    fn committed_icon_is_valid() {
+        let path = crate::root().join("assets/app-icon/designcraft.ico");
+        let Ok(ico) = std::fs::read(&path) else { return };
+        assert_eq!(&ico[..4], &[0, 0, 1, 0]);
+        let n = u16::from_le_bytes([ico[4], ico[5]]) as usize;
+        assert!(n >= 4, "expected several sizes in {}", path.display());
+    }
+}
@@ -4,6 +4,7 @@
 //! invoked through `std::process::Command`.

 mod assets;
+mod ico;
 mod layers;
 mod parity;
 mod stats;
@@ -23,6 +24,8 @@ commands:
                  show where test corpora live; --download fetches PngSuite into corpus/pngsuite
  stats [--exact] count tests and lines per crate (--exact: ask the test harness via `-- --list`)
  parity          recompute the InDesign feature-parity summary in docs/parity.md
+  ico <out.ico> <in.png>...
+                  pack square PNGs (<= 256 px) into a Windows .ico (see packaging/icons.sh)
 ";

 fn main() -> ExitCode {
@@ -36,6 +39,7 @@ fn main() -> ExitCode {
        Some("corpus") => cmd_corpus(rest.contains(&"--download")),
        Some("stats") => stats::run(&root(), rest.contains(&"--exact")),
        Some("parity") => parity::run(&root()),
+        Some("ico") => ico::run(&rest),
        Some("-h" | "--help" | "help") | None => {
            print!("{USAGE}");
            Ok(())