feat(web): startup option in effectcraft-config.json

A startup key (last, empty or demo) chooses the project the page opens on load. empty restores the last visit's project and otherwise starts blank, never with the demo; demo always opens the demo project; last, or no key, is the current behaviour. ?empty and ?demo still win. The config file is fetched once per page load and the service worker never caches it.

apps/effectcraft-web/Cargo.toml

@@ -51,6 +51,10 @@ web-sys = { version = "0.3", features = [
     "HtmlInputElement",
     "Location",
     "Navigator",
+    "Request",
+    "RequestCache",
+    "RequestInit",
+    "Response",
     "Url",
     "UrlSearchParams",
     "Window",

apps/effectcraft-web/src/app.rs

@@ -6,7 +6,7 @@ use std::sync::atomic::{AtomicBool, Ordering};
 
 use effectcraft_engine::Session;
 
-use crate::{api, audio, browse, diskcache, files, frames, persist, storage, worker};
+use crate::{api, audio, browse, config_file, diskcache, files, frames, persist, storage, worker};
 use effectcraft_ui_egui::EffectcraftApp;
 use serde_json::json;
 use wasm_bindgen::prelude::*;
@@ -220,6 +220,8 @@ pub async fn start(canvas_id: String) -> Result<(), JsValue> {
     };
     api::set_info("storage", json!({"backend": persist::backend(), "entries": stored, "loadMs": t0.elapsed().as_secs_f64() * 1000.0}));
     audio::install_unlock();
+    // `./effectcraft-config.json`: what to open on load.
+    let startup = config_file::startup().await;
     browse::restore();
     diskcache::init();
     storage::refresh();
@@ -255,10 +257,11 @@ pub async fn start(canvas_id: String) -> Result<(), JsValue> {
                 let mut session = session();
                 session.load_settings();
                 let recovery = session.begin_recovery();
-                // `?empty`: a blank project; `?demo`: the demo project; otherwise the last visit's
-                // project (the demo on a first visit).
-                let restored = !empty && !query_flag("demo") && persist::restore(&mut session);
-                if !restored && !empty {
+                // `?empty`: a blank project; `?demo`: the demo project; otherwise what the config's
+                // `startup` says (default: the last visit's project, the demo on a first visit).
+                let demo = query_flag("demo");
+                let restored = !empty && !demo && startup.restores() && persist::restore(&mut session);
+                if !restored && !empty && (demo || startup.demo_when_nothing_restored()) {
                     let _ = session.execute("file.openDemoProject", json!({}));
                 }
                 api::set_info("restored", json!(restored));

apps/effectcraft-web/src/config_file.rs

@@ -0,0 +1,44 @@
+//! `./effectcraft-config.json`, fetched once per page load and shared by whoever reads a key.
+
+use std::cell::RefCell;
+
+use wasm_bindgen::JsCast;
+use wasm_bindgen_futures::JsFuture;
+
+use crate::startup::{self, Startup};
+
+thread_local! {
+    /// `None`: not fetched yet; `Some(None)`: no usable file.
+    static FILE: RefCell<Option<Option<Vec<u8>>>> = const { RefCell::new(None) };
+}
+
+async fn fetch() -> Option<Vec<u8>> {
+    let init = web_sys::RequestInit::new();
+    // Always ask the server: the file is the operator's switch, never a cached copy.
+    init.set_cache(web_sys::RequestCache::NoCache);
+    let req = web_sys::Request::new_with_str_and_init("effectcraft-config.json", &init).ok()?;
+    let resp: web_sys::Response = JsFuture::from(web_sys::window()?.fetch_with_request(&req)).await.ok()?.dyn_into().ok()?;
+    if resp.status() != 200 {
+        return None;
+    }
+    let buf = JsFuture::from(resp.array_buffer().ok()?).await.ok()?;
+    let a = js_sys::Uint8Array::new(&buf);
+    (a.length() as usize <= startup::CONFIG_MAX).then(|| a.to_vec())
+}
+
+/// The config file's bytes (`None` when there is none), fetched on the first call.
+pub async fn bytes() -> Option<Vec<u8>> {
+    if let Some(done) = FILE.with(|f| f.borrow().clone()) {
+        return done;
+    }
+    let got = fetch().await;
+    FILE.with(|f| *f.borrow_mut() = Some(got.clone()));
+    got
+}
+
+/// The configured startup behaviour.
+pub async fn startup() -> Startup {
+    let s = bytes().await.map(|b| startup::parse(&b)).unwrap_or_default();
+    log::info!("startup: {s:?}");
+    s
+}

apps/effectcraft-web/src/lib.rs

@@ -18,10 +18,11 @@
 //! | cpal audio output | Web Audio: an AudioWorklet fed from the preview mixdown (`audio`) |
 //! | TCP control channel / MCP | `window.effectcraft` JavaScript API (`api`) |
 //!
-//! [`store`] is portable (unit-tested natively); everything else is `wasm32`-only.
+//! [`store`] and [`startup`] are portable (unit-tested natively); everything else is `wasm32`-only.
 
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
 
+pub mod startup;
 pub mod store;
 
 #[cfg(target_arch = "wasm32")]
@@ -33,6 +34,8 @@ pub mod audio;
 #[cfg(target_arch = "wasm32")]
 pub mod browse;
 #[cfg(target_arch = "wasm32")]
+pub mod config_file;
+#[cfg(target_arch = "wasm32")]
 pub mod diskcache;
 #[cfg(target_arch = "wasm32")]
 pub mod files;

apps/effectcraft-web/src/startup.rs

@@ -0,0 +1,49 @@
+//! The `startup` key of `./effectcraft-config.json`: which project the page opens on load.
+//!
+//! | Value | On load |
+//! |---|---|
+//! | `"last"` (and absent) | the last visit's project; the demo project on a first visit |
+//! | `"empty"` | the last visit's project; a blank project on a first visit, never the demo |
+//! | `"demo"` | the demo project, whatever the last visit left |
+//!
+//! The `?empty` and `?demo` URL flags still win. Anything else (a missing key, another type, an
+//! unknown value, a config that is not JSON) is the default, `"last"`.
+
+use serde_json::Value;
+
+/// What the page opens on load.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub enum Startup {
+    #[default]
+    Last,
+    Empty,
+    Demo,
+}
+
+/// The largest config file read (bytes).
+pub const CONFIG_MAX: usize = 64 * 1024;
+
+/// The `startup` key of a config file's bytes.
+pub fn parse(bytes: &[u8]) -> Startup {
+    if bytes.len() > CONFIG_MAX {
+        return Startup::default();
+    }
+    let Ok(v) = serde_json::from_slice::<Value>(bytes) else { return Startup::default() };
+    match v.get("startup").and_then(Value::as_str) {
+        Some("empty") => Startup::Empty,
+        Some("demo") => Startup::Demo,
+        _ => Startup::Last,
+    }
+}
+
+impl Startup {
+    /// Whether the last visit's project is restored (off for the demo).
+    pub fn restores(self) -> bool {
+        self != Startup::Demo
+    }
+
+    /// Whether the demo project opens when nothing was restored (off for a blank start).
+    pub fn demo_when_nothing_restored(self) -> bool {
+        self != Startup::Empty
+    }
+}

apps/effectcraft-web/tests/it/main.rs

@@ -0,0 +1 @@
+mod startup_tests;

apps/effectcraft-web/tests/it/startup_tests.rs

@@ -0,0 +1,40 @@
+//! The `startup` key of the config file.
+
+use effectcraft_web::startup::{CONFIG_MAX, Startup, parse};
+
+#[test]
+fn the_three_values() {
+    assert_eq!(parse(br#"{"startup":"empty"}"#), Startup::Empty);
+    assert_eq!(parse(br#"{"startup":"demo"}"#), Startup::Demo);
+    assert_eq!(parse(br#"{"startup":"last"}"#), Startup::Last);
+}
+
+#[test]
+fn absent_or_invalid_is_the_default() {
+    for bytes in
+        [&b"{}"[..], b"", b"not json", b"[]", b"null", br#"{"startup":1}"#, br#"{"startup":"Empty"}"#, br#"{"startup":null}"#, br#"{"startup":["empty"]}"#]
+    {
+        assert_eq!(parse(bytes), Startup::Last, "{:?}", String::from_utf8_lossy(bytes));
+    }
+}
+
+#[test]
+fn a_config_with_other_keys_still_has_its_startup() {
+    assert_eq!(parse(br#"{"remote":{"mounts":[]},"startup":"empty"}"#), Startup::Empty);
+    assert_eq!(parse(br#"{"startup":"demo","unknown":{"a":1}}"#), Startup::Demo);
+}
+
+#[test]
+fn an_oversized_file_is_the_default() {
+    let mut big = br#"{"startup":"empty","pad":""#.to_vec();
+    big.extend(std::iter::repeat_n(b'x', CONFIG_MAX));
+    big.extend_from_slice(br#""}"#);
+    assert_eq!(parse(&big), Startup::Last);
+}
+
+#[test]
+fn what_each_value_does_on_load() {
+    assert!(Startup::Last.restores() && Startup::Last.demo_when_nothing_restored());
+    assert!(Startup::Empty.restores() && !Startup::Empty.demo_when_nothing_restored());
+    assert!(!Startup::Demo.restores() && Startup::Demo.demo_when_nothing_restored());
+}

apps/effectcraft-web/web/sw.js

@@ -3,7 +3,8 @@
 // `cargo xtask web` fills in the build's file list and version. Every file is precached into a
 // cache named after the version, served cache-first (responses keep the server's headers, so
 // the page stays cross-origin isolated: COOP/COEP), and old versions are dropped once the new
-// one activates. Anything else same-origin is fetched from the network and cached for next time.
+// one activates. Anything else same-origin is fetched from the network and cached for next time,
+// except the config file, which must stay live.
 const VERSION = "__EC_VERSION__";
 const FILES = __EC_FILES__;
 const CACHE = `effectcraft-${VERSION}`;
@@ -30,6 +31,7 @@ self.addEventListener("fetch", (event) => {
   const req = event.request;
   const url = new URL(req.url);
   if (req.method !== "GET" || url.origin !== self.location.origin) return;
+  if (url.pathname.endsWith("/effectcraft-config.json")) return;
   event.respondWith(
     (async () => {
       const cache = await caches.open(CACHE).catch(() => null);

docs/web.md

@@ -242,6 +242,25 @@ Window ▸ Media Browser browses a virtual tree (`src/browse.rs`):
 
 `mediaBrowser.list` reports the places and these actions; `mediaBrowser.action {action}` runs one.
 
+### Startup project
+
+By default the page opens the last visit's project, and the demo project on a first visit. A
+`startup` key in `effectcraft-config.json` (next to `index.html`) changes that:
+
+```json
+{"startup":"empty"}
+```
+
+| Value | On load |
+|---|---|
+| `"last"` (or no key) | the last visit's project; the demo project on a first visit |
+| `"empty"` | the last visit's project; a blank project on a first visit, never the demo |
+| `"demo"` | the demo project, whatever the last visit left |
+
+The `?empty` and `?demo` URL flags still win. A missing, invalid or non-JSON file, or an unknown
+value, is the default. The file is fetched once per page load; serve it with
+`Cache-Control: no-cache` (the service worker never caches it).
+
 ### Audio
 
 Audio preview goes through **Web Audio**: an AudioWorklet (`audio-worklet.js`; a

packaging/web/README.md

@@ -58,6 +58,19 @@ location /effectcraft/ {
 
 Local test: `python3 -m http.server 8765` inside the folder, then open http://localhost:8765/.
 
+## Startup project (optional)
+
+To choose what the page opens on load, add an `effectcraft-config.json` next to `index.html`:
+
+```json
+{"startup":"empty"}
+```
+
+`"empty"` restores the last visit's project and otherwise starts blank (never the demo); `"demo"`
+always opens the demo project; `"last"` (the default) restores the last visit's project and shows
+the demo on a first visit. Serve the file with `Cache-Control: no-cache`. Details:
+[docs/web.md](../../docs/web.md#startup-project).
+
 ## Embedding in a page (iframe)
 
 ```html

packaging/web/_headers

@@ -12,3 +12,6 @@
 
 /index.html
   Cache-Control: no-cache
+
+/effectcraft-config.json
+  Cache-Control: no-cache