Add APNG Studio canvas extension (#2272)

* Add APNG Studio canvas extension

APNG Studio is an interactive GitHub Copilot canvas extension for building
Animated PNG (APNG) files from frames: draw or upload frames, tune per-frame
timing and compositing, preview live, send the result to a phone by QR, and
export an animated .png.

Adds extensions/apng-studio/ with the required .github/plugin/plugin.json and
assets/preview.png, and regenerates .github/plugin/marketplace.json.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Address review feedback for APNG Studio

Security and robustness (extension.mjs):
- Reject "." and ".." project ids so canvas/action input cannot resolve
  outside artifacts/.
- Bound request bodies (1 MiB JSON, 40 MiB frame upload); return 413 when
  exceeded.
- Reject malformed JSON with 400 instead of coercing to {}, so a truncated
  body cannot trigger destructive routes such as /frames/clear.
- Scope shares per project so one canvas cannot rotate or stop another's
  share; the LAN server is shared and torn down once no shares remain.
- get_state treats hiddenFirst as active only with >=2 frames, matching the
  encoder, so a single-frame project reports the correct duration.

Accessibility (web/):
- Expose Pen/Eraser state with aria-pressed and keep it in sync in setTool.
- Mark the toast as an aria-live status region.

Packaging:
- Add extensions/apng-studio/.gitignore with artifacts/ so the documented
  runtime-data exclusion holds for this extension.
- Update the README install section to reference the committed awesome-copilot
  extension path.

Regenerated .github/plugin/marketplace.json.

* Use "GitHub Copilot app" wording

Update the plugin description (and regenerated marketplace entry) to refer to
the host as the GitHub Copilot app.

* Address deeper review for APNG Studio

Security:
- Require a per-server access token on every loopback data/mutation request
  (minted per canvas server, carried in the iframe URL, attached to every
  renderer request). Static assets stay public. Blocks a local process or
  cross-origin page from reading state or driving mutations.

Concurrency and durability:
- Serialize the load-mutate-save cycle per project; dedupe concurrent first
  loads; write project.json via temp file + rename.

Lifecycle:
- Track SSE clients per instance and end them before server.close().
- Stop a project's LAN share only when no other panel references it.

Correctness:
- Report exact numerator/denominator total duration; handle pointercancel.

QR and accessibility:
- Place QR version bits least-significant-bit first (versions 7-10).
- Associate delay/fps/dispose/blend labels with their inputs via for=.

* Address deeper concurrency and validation review for APNG Studio

- Run assemble() under the project lock; add_color_frame renders and appends
  within one lock.
- Validate uploaded frames (PNG chunk scan, size + dimension checks) before
  writing; first frame stores real dimensions; CanvasError maps to 400.
- Validate move delta; clear frames in memory before deleting files.
- Route the open-handler rename through applySettings.
- Deduplicate LAN share startup; clean up if the canvas closes mid-start.
- End SSE streams before server.close(); skip dead streams in broadcast.
- Exact fractional duration; drawing surface stays >= 1px; refresh state before
  re-seeding "start from last frame".

* Address review: PNG format validation, share bind, limits, a11y

- Validate uploaded frames are 8-bit RGBA non-interlaced PNGs (standard
  compression/filter); reject formats the codec can't encode.
- Cap projects at 600 frames (add + duplicate).
- Bind the LAN share server to the private address, not 0.0.0.0; require a
  private address and rebind when it changes while idle; build the URL from the
  bound address.
- Align width/height inputs and clampSize to the 2048 maximum.
- Size the drawing surface by width + aspect ratio for narrow panels.
- set_frame with an unknown frameId returns a validation error.

* Address review: encoded-byte budget, timing modes, id keys, load errors

- 256 MiB aggregate encoded-byte budget (add + duplicate); per-frame size
  tracked and backfilled on load, so a frame count alone no longer bounds
  assembly memory.
- Frame timing is one exclusive mode (delayMs | fps | delayNum/delayDen);
  combinations are rejected instead of producing hybrid delays.
- Collision-resistant project storage keys: safe ids are used verbatim (existing
  projects still load) and only unsafe ids get a hash suffix, so "foo/bar" and
  "foo?bar" can't share a directory.
- Load only treats a missing file as a new project; other read/parse errors
  surface instead of silently overwriting real data.
- Share server binds to a real LAN interface (skips virtual/VPN/container,
  prefers physical NICs and common ranges).
- Generated export names get millisecond + random suffix to avoid same-second
  overwrite.
- PNG validator accepts the encoder's Uint8Array so agent solid-color frames
  aren't rejected.

* Address review: crash-safe frame writes, server startup, APNG first frame

- Write the PNG before mutating project metadata on add/duplicate, and delete
  after persisting, so an interrupted disk op can't dangle a reference or
  advance unsaved state.
- Evict a project from the in-memory cache if its save fails, so a transient
  write error can't desync the live session from disk.
- Reject on the loopback server's listen error and drop a half-initialized
  instance so startup failures clean up and can retry.
- Normalize APNG dispose_op PREVIOUS to BACKGROUND on the first animated frame
  (spec requirement).
- Release decoded ImageBitmaps after use so a large upload batch doesn't retain
  native image memory.
- Surface otherwise-silent async UI failures via a toast; check the state
  response is ok before parsing it.

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
Andrea Liliana Griffiths
2026-07-13 01:53:55 +02:00
committed by GitHub
parent f8d98b41d1
commit 0916fe444d
14 changed files with 3618 additions and 0 deletions
+669
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"use strict";
// ---- tiny helpers -------------------------------------------------------
const $ = (id) => document.getElementById(id);
const nonce = () => Date.now().toString(36) + Math.random().toString(36).slice(2, 6);
// The server mints a per-session access token and passes it in this iframe's
// URL. Attach it to every data request so other local origins that guess the
// port cannot read state or drive mutations.
const ACCESS_KEY = new URLSearchParams(location.search).get("k") || "";
function withKey(path) {
const u = new URL(path, location.origin);
if (ACCESS_KEY) u.searchParams.set("k", ACCESS_KEY);
return u.pathname + u.search;
}
async function api(path, body) {
const res = await fetch(withKey(path), {
method: "POST",
headers: { "Content-Type": "application/json" },
body: JSON.stringify(body || {}),
});
if (!res.ok) throw new Error((await res.text()) || res.statusText);
const text = await res.text();
return text ? JSON.parse(text) : {};
}
function toast(msg, ms = 2600) {
const t = $("toast");
t.textContent = msg;
t.hidden = false;
clearTimeout(toast._t);
toast._t = setTimeout(() => (t.hidden = true), ms);
}
// Surface any otherwise-unhandled async-handler failure to the user instead of
// letting it become a silent unhandled rejection with no feedback.
if (typeof window !== "undefined") {
window.addEventListener("unhandledrejection", (e) => {
toast("Error: " + (e.reason?.message || e.reason || "something went wrong"));
});
}
function clampSize(w, h, max = 2048) {
w = Math.max(1, Math.round(w));
h = Math.max(1, Math.round(h));
const longer = Math.max(w, h);
if (longer > max) {
const s = max / longer;
w = Math.max(1, Math.round(w * s));
h = Math.max(1, Math.round(h * s));
}
return { w, h };
}
// ---- state --------------------------------------------------------------
let state = { name: "animation", width: 256, height: 256, loops: 0, hiddenFirst: false, frames: [] };
let assetNonce = nonce();
function defaultDelay() {
const v = parseInt($("in-delay-all").value, 10);
return Number.isFinite(v) && v >= 0 ? v : 120;
}
async function refreshState() {
const res = await fetch(withKey("/state"));
if (!res.ok) throw new Error((await res.text()) || res.statusText);
state = await res.json();
assetNonce = nonce();
render();
}
// ---- rendering ----------------------------------------------------------
function render() {
renderPreview();
renderMeta();
renderSettings();
renderFrames();
syncDrawStage();
}
function renderPreview() {
const img = $("preview");
const empty = $("empty-preview");
const has = state.frames.length > 0;
empty.hidden = has;
if (has) {
img.src = withKey(`/preview.png?n=${assetNonce}`);
img.hidden = false;
img.classList.toggle("pixelated", Math.max(state.width, state.height) < 96);
} else {
img.hidden = true;
}
}
function renderMeta() {
const n = state.frames.length;
const hidden = state.hiddenFirst && n >= 2;
const animated = hidden ? state.frames.slice(1) : state.frames;
const totalMs = Math.round(
animated.reduce((a, f) => a + (f.delayNum || 0) / (f.delayDen || 1000), 0) * 1000
);
$("meta-frames").textContent = `${n} frame${n === 1 ? "" : "s"}${hidden ? " · 1 static" : ""}`;
$("meta-duration").textContent = `${(totalMs / 1000).toFixed(1)}s`;
$("meta-loops").textContent = state.loops === 0 ? "loops ∞" : `loops ${state.loops}`;
const busy = n === 0;
$("btn-export").disabled = busy;
$("btn-download").disabled = busy;
$("btn-restart").disabled = busy;
$("btn-share").disabled = busy;
}
function renderSettings() {
const n = state.frames.length;
const hasFrames = n > 0;
const w = $("in-width"),
h = $("in-height"),
l = $("in-loops");
if (document.activeElement !== w) w.value = state.width;
if (document.activeElement !== h) h.value = state.height;
if (document.activeElement !== l) l.value = state.loops;
w.disabled = hasFrames;
h.disabled = hasFrames;
$("dim-hint").style.display = hasFrames ? "block" : "none";
const hf = $("in-hidden-first");
hf.checked = !!state.hiddenFirst;
hf.disabled = n < 2;
$("hidden-first-label").classList.toggle("disabled", n < 2);
$("hidden-first-hint").hidden = !(state.hiddenFirst && n >= 2);
for (const id of ["btn-delay-all", "btn-fps", "btn-ops-all"]) $(id).disabled = !hasFrames;
}
function renderFrames() {
const strip = $("frame-strip");
const empty = $("empty-frames");
strip.innerHTML = "";
empty.hidden = state.frames.length > 0;
const hidden = state.hiddenFirst && state.frames.length >= 2;
state.frames.forEach((f, i) => {
const isStatic = hidden && i === 0;
const card = document.createElement("div");
card.className = "frame-card" + (isStatic ? " is-static" : "");
const thumbWrap = document.createElement("div");
thumbWrap.className = "checker frame-thumb-wrap";
const thumb = document.createElement("img");
thumb.className = "frame-thumb";
thumb.alt = `Frame ${i + 1}`;
thumb.src = withKey(`/frame?id=${encodeURIComponent(f.id)}&n=${assetNonce}`);
thumbWrap.appendChild(thumb);
if (isStatic) {
const badge = document.createElement("span");
badge.className = "static-badge";
badge.textContent = "STATIC";
thumbWrap.appendChild(badge);
}
const body = document.createElement("div");
body.className = "frame-body";
const idx = document.createElement("div");
idx.className = "frame-index";
idx.textContent = isStatic ? `#${i + 1} · fallback` : `#${i + 1}`;
// Inputs (declared first so the shared commit closure can read them).
const numIn = numberInput(f.delayNum, 0, 65535, "Delay numerator");
const denIn = numberInput(f.delayDen, 1, 65535, "Delay denominator");
const disposeSel = selectEl(
[[0, "None"], [1, "Background"], [2, "Previous"]],
f.disposeOp,
"Dispose op — what to do with the canvas after this frame"
);
const blendSel = selectEl(
[[0, "Source"], [1, "Over"]],
f.blendOp,
"Blend op — how this frame is drawn onto the canvas"
);
const msHint = document.createElement("span");
msHint.className = "ms-hint muted";
const updateHint = () => {
const num = parseInt(numIn.value, 10) || 0;
const den = parseInt(denIn.value, 10) || 1000;
const ms = Math.round((num / den) * 1000);
const fps = num > 0 ? den / num : 0;
const fpsTxt = fps ? ` · ${Number.isInteger(fps) ? fps : fps.toFixed(1)} fps` : "";
msHint.textContent = `= ${ms} ms${fpsTxt}`;
};
updateHint();
const commit = () =>
api("/frames/props", {
id: f.id,
delayNum: parseInt(numIn.value, 10) || 0,
delayDen: parseInt(denIn.value, 10) || 1000,
disposeOp: parseInt(disposeSel.value, 10) || 0,
blendOp: parseInt(blendSel.value, 10) || 0,
}).catch((e) => toast("Error: " + e.message));
numIn.addEventListener("input", updateHint);
denIn.addEventListener("input", updateHint);
numIn.addEventListener("change", commit);
denIn.addEventListener("change", commit);
disposeSel.addEventListener("change", commit);
blendSel.addEventListener("change", commit);
const delayRow = document.createElement("div");
delayRow.className = "frame-field";
delayRow.append(fieldLabel("delay"), numIn, slash(), denIn, msHint);
const opsRow = document.createElement("div");
opsRow.className = "frame-field";
opsRow.append(fieldLabel("dispose"), disposeSel);
const blendRow = document.createElement("div");
blendRow.className = "frame-field";
blendRow.append(fieldLabel("blend"), blendSel);
const actions = document.createElement("div");
actions.className = "frame-actions";
actions.append(
iconBtn("◀", "Move left", i === 0, () => api("/frames/move", { id: f.id, delta: -1 })),
iconBtn("▶", "Move right", i === state.frames.length - 1, () =>
api("/frames/move", { id: f.id, delta: 1 })
),
iconBtn("⧉", "Duplicate", false, () => api("/frames/duplicate", { id: f.id })),
iconBtn("✕", "Delete", false, () => api("/frames/delete", { id: f.id }), true)
);
if (isStatic) {
[numIn, denIn, disposeSel, blendSel].forEach((el) => (el.disabled = true));
msHint.textContent = "not animated";
}
body.append(idx, delayRow, opsRow, blendRow, actions);
card.append(thumbWrap, body);
strip.appendChild(card);
});
}
function numberInput(value, min, max, title) {
const el = document.createElement("input");
el.type = "number";
el.className = "num-in";
el.min = String(min);
el.max = String(max);
el.step = "1";
el.value = value;
el.title = title;
return el;
}
function selectEl(options, value, title) {
const s = document.createElement("select");
s.className = "frame-select";
s.title = title;
for (const [val, text] of options) {
const o = document.createElement("option");
o.value = String(val);
o.textContent = text;
s.appendChild(o);
}
s.value = String(value);
return s;
}
function fieldLabel(text) {
const s = document.createElement("span");
s.className = "frame-label muted";
s.textContent = text;
return s;
}
function slash() {
const s = document.createElement("span");
s.className = "slash muted";
s.textContent = "/";
return s;
}
function iconBtn(label, title, disabled, onClick, danger) {
const b = document.createElement("button");
b.className = "icon-btn" + (danger ? " danger" : "");
b.textContent = label;
b.title = title;
b.setAttribute("aria-label", title);
b.disabled = !!disabled;
b.addEventListener("click", async () => {
try {
await onClick();
} catch (e) {
toast("Error: " + e.message);
}
});
return b;
}
// ---- settings handlers --------------------------------------------------
async function commitLoops() {
await api("/settings", { loops: parseInt($("in-loops").value, 10) || 0 });
}
async function commitDim() {
if (state.frames.length > 0) return;
const w = parseInt($("in-width").value, 10);
const h = parseInt($("in-height").value, 10);
const { w: cw, h: ch } = clampSize(w || state.width, h || state.height);
await api("/settings", { width: cw, height: ch });
}
function debounce(fn, ms) {
let t = null;
return () => {
clearTimeout(t);
t = setTimeout(fn, ms);
};
}
// Commit on `input` (fires for stepper buttons and arrow keys in every engine,
// including the host WebKit view where `change` is unreliable for steppers) as
// well as `change` (final blur/Enter). The `input` path is debounced so holding
// an arrow or typing a value doesn't spam the server.
const commitDimSoon = debounce(commitDim, 300);
const commitLoopsSoon = debounce(commitLoops, 300);
for (const id of ["in-width", "in-height"]) {
$(id).addEventListener("input", commitDimSoon);
$(id).addEventListener("change", commitDim);
}
$("in-loops").addEventListener("input", commitLoopsSoon);
$("in-loops").addEventListener("change", commitLoops);
$("in-hidden-first").addEventListener("change", async (e) => {
await api("/settings", { hiddenFirst: e.target.checked });
});
$("btn-delay-all").addEventListener("click", async () => {
const ms = defaultDelay();
await api("/frames/props-all", { delayMs: ms });
toast(`All delays set to ${ms} ms`);
});
$("btn-fps").addEventListener("click", async () => {
const fps = Math.max(1, Math.min(120, parseInt($("in-fps").value, 10) || 12));
await api("/frames/props-all", { fps });
toast(`All frames set to ${fps} fps`);
});
$("btn-ops-all").addEventListener("click", async () => {
await api("/frames/props-all", {
disposeOp: parseInt($("in-dispose-all").value, 10) || 0,
blendOp: parseInt($("in-blend-all").value, 10) || 0,
});
toast("Applied dispose & blend to all frames");
});
$("btn-clear").addEventListener("click", async () => {
if (!state.frames.length) return;
if (!confirm("Remove all frames?")) return;
await api("/frames/clear", {});
});
// ---- export / download --------------------------------------------------
$("btn-export").addEventListener("click", async () => {
try {
const r = await api("/export", {});
$("saved-path").hidden = false;
$("saved-path").textContent = "Saved: " + r.path;
toast("Exported " + r.name);
} catch (e) {
toast("Export failed: " + e.message);
}
});
$("btn-download").addEventListener("click", async () => {
const res = await fetch(withKey(`/preview.png?n=${nonce()}`));
const blob = await res.blob();
const a = document.createElement("a");
a.href = URL.createObjectURL(blob);
a.download = (state.name || "animation").replace(/[^\w.-]+/g, "_") + ".png";
document.body.appendChild(a);
a.click();
a.remove();
setTimeout(() => URL.revokeObjectURL(a.href), 4000);
});
$("btn-restart").addEventListener("click", () => {
// Re-assigning an identical src is a no-op, so bump the nonce to force a
// fresh fetch and restart the animation from the first frame.
assetNonce = nonce();
renderPreview();
});
// ---- send to phone ------------------------------------------------------
let shareCountdown = null;
$("btn-share").addEventListener("click", async () => {
const btn = $("btn-share");
btn.disabled = true;
try {
const info = await api("/share/start", {});
openSharePanel(info);
} catch (e) {
toast("Couldn't start sharing: " + e.message);
} finally {
btn.disabled = state.frames.length === 0;
}
});
$("btn-share-stop").addEventListener("click", stopSharing);
function openSharePanel(info) {
$("share-panel").hidden = false;
// Cache-bust the QR so a new token's code is fetched each time.
$("share-qr-img").src = withKey(`/share/qr.png?ts=${Date.now()}`);
const link = $("share-url");
link.href = info.url;
link.textContent = info.url.replace(/^https?:\/\//, "");
startShareCountdown(info.expiresAt);
}
function startShareCountdown(expiresAt) {
clearInterval(shareCountdown);
const tick = () => {
const ms = expiresAt - Date.now();
if (ms <= 0) {
clearInterval(shareCountdown);
$("share-panel").hidden = true;
toast("Phone link expired");
api("/share/stop", {}).catch(() => {});
return;
}
const m = Math.floor(ms / 60000);
const s = Math.floor((ms % 60000) / 1000);
$("share-expiry").textContent = `Expires in ${m}:${String(s).padStart(2, "0")}`;
};
tick();
shareCountdown = setInterval(tick, 1000);
}
async function stopSharing() {
clearInterval(shareCountdown);
$("share-panel").hidden = true;
try {
await api("/share/stop", {});
} catch (_) {
/* server may have already expired the share */
}
}
// ---- upload -------------------------------------------------------------
$("btn-upload").addEventListener("click", () => $("file-input").click());
$("file-input").addEventListener("change", async (e) => {
const files = [...e.target.files];
e.target.value = "";
if (files.length) await addFiles(files);
});
async function addFiles(files) {
try {
toast(`Adding ${files.length} image${files.length === 1 ? "" : "s"}`);
if (state.frames.length === 0) {
const first = await createImageBitmap(files[0]);
const { w, h } = clampSize(first.width, first.height);
first.close?.();
await api("/settings", { width: w, height: h });
await refreshState();
}
for (const f of files) await addImageFile(f);
toast("Frames added");
} catch (e) {
toast("Upload error: " + e.message);
}
}
async function addImageFile(file) {
const bmp = await createImageBitmap(file);
const c = document.createElement("canvas");
c.width = state.width;
c.height = state.height;
try {
drawContain(c.getContext("2d"), bmp, state.width, state.height);
} finally {
// Release the decoded bitmap right after the synchronous draw so a large
// batch doesn't retain native image memory until GC.
bmp.close?.();
}
const blob = await new Promise((r) => c.toBlob(r, "image/png"));
await postFrame(blob, defaultDelay());
}
function drawContain(ctx, img, W, H) {
const s = Math.min(W / img.width, H / img.height);
const dw = img.width * s;
const dh = img.height * s;
ctx.clearRect(0, 0, W, H);
ctx.drawImage(img, (W - dw) / 2, (H - dh) / 2, dw, dh);
}
async function postFrame(blob, delayMs) {
const res = await fetch(withKey(`/frames?delayMs=${delayMs || 0}`), { method: "POST", body: blob });
if (!res.ok) throw new Error(await res.text());
}
// ---- drawing ------------------------------------------------------------
const drawCanvas = $("draw-canvas");
const dctx = drawCanvas.getContext("2d");
let drawTool = "pen";
let drawing = false;
let lastPt = null;
$("btn-toggle-draw").addEventListener("click", () => {
const panel = $("draw-panel");
panel.hidden = !panel.hidden;
if (!panel.hidden) initDrawCanvas();
});
$("btn-cancel-draw").addEventListener("click", () => ($("draw-panel").hidden = true));
$("tool-pen").addEventListener("click", () => setTool("pen"));
$("tool-eraser").addEventListener("click", () => setTool("eraser"));
function setTool(t) {
drawTool = t;
$("tool-pen").classList.toggle("active", t === "pen");
$("tool-eraser").classList.toggle("active", t === "eraser");
$("tool-pen").setAttribute("aria-pressed", String(t === "pen"));
$("tool-eraser").setAttribute("aria-pressed", String(t === "eraser"));
}
$("btn-clear-draw").addEventListener("click", () => {
dctx.clearRect(0, 0, drawCanvas.width, drawCanvas.height);
});
$("btn-fill").addEventListener("click", () => {
dctx.save();
dctx.globalCompositeOperation = "source-over";
dctx.fillStyle = $("draw-color").value;
dctx.fillRect(0, 0, drawCanvas.width, drawCanvas.height);
dctx.restore();
});
$("opt-onion").addEventListener("change", syncOnion);
$("opt-from-last").addEventListener("change", initDrawCanvas);
function syncDrawStage() {
// Size the drawing surface to the project dimensions and scale for display.
if (drawCanvas.width !== state.width || drawCanvas.height !== state.height) {
drawCanvas.width = state.width;
drawCanvas.height = state.height;
}
const longer = Math.max(state.width, state.height) || 1;
const scale = Math.min(360, Math.max(200, longer)) / longer;
const dispW = Math.max(1, Math.round(state.width * scale));
// Drive the display size from the width plus the intrinsic aspect ratio and
// let height follow, so a narrow side panel (CSS max-width) shrinks the
// surface proportionally instead of stretching a fixed height.
const ratio = `${state.width} / ${state.height}`;
drawCanvas.style.width = dispW + "px";
drawCanvas.style.height = "auto";
drawCanvas.style.aspectRatio = ratio;
drawCanvas.style.imageRendering = scale > 1.4 ? "pixelated" : "auto";
const onion = $("onion-img");
onion.style.width = dispW + "px";
onion.style.height = "auto";
onion.style.aspectRatio = ratio;
if (!$("draw-panel").hidden) syncOnion();
}
function lastFrame() {
return state.frames.length ? state.frames[state.frames.length - 1] : null;
}
function syncOnion() {
const onion = $("onion-img");
const lf = lastFrame();
if ($("opt-onion").checked && lf) {
onion.src = withKey(`/frame?id=${encodeURIComponent(lf.id)}&n=${assetNonce}`);
onion.hidden = false;
} else {
onion.hidden = true;
}
}
function initDrawCanvas() {
syncDrawStage();
dctx.clearRect(0, 0, drawCanvas.width, drawCanvas.height);
const lf = lastFrame();
if ($("opt-from-last").checked && lf) {
const img = new Image();
img.onload = () => dctx.drawImage(img, 0, 0, drawCanvas.width, drawCanvas.height);
img.src = withKey(`/frame?id=${encodeURIComponent(lf.id)}&n=${assetNonce}`);
}
syncOnion();
}
function canvasPoint(e) {
const rect = drawCanvas.getBoundingClientRect();
return {
x: (e.clientX - rect.left) * (drawCanvas.width / rect.width),
y: (e.clientY - rect.top) * (drawCanvas.height / rect.height),
};
}
function strokeTo(pt) {
dctx.globalCompositeOperation = drawTool === "eraser" ? "destination-out" : "source-over";
dctx.strokeStyle = $("draw-color").value;
dctx.fillStyle = $("draw-color").value;
dctx.lineWidth = parseInt($("draw-size").value, 10) || 6;
dctx.lineCap = "round";
dctx.lineJoin = "round";
if (lastPt) {
dctx.beginPath();
dctx.moveTo(lastPt.x, lastPt.y);
dctx.lineTo(pt.x, pt.y);
dctx.stroke();
} else {
dctx.beginPath();
dctx.arc(pt.x, pt.y, dctx.lineWidth / 2, 0, Math.PI * 2);
dctx.fill();
}
lastPt = pt;
}
drawCanvas.addEventListener("pointerdown", (e) => {
drawing = true;
lastPt = null;
drawCanvas.setPointerCapture(e.pointerId);
strokeTo(canvasPoint(e));
});
drawCanvas.addEventListener("pointermove", (e) => {
if (drawing) strokeTo(canvasPoint(e));
});
function endStroke() {
drawing = false;
lastPt = null;
}
drawCanvas.addEventListener("pointerup", endStroke);
drawCanvas.addEventListener("pointerleave", endStroke);
drawCanvas.addEventListener("pointercancel", endStroke);
$("btn-add-drawing").addEventListener("click", async () => {
const blob = await new Promise((r) => drawCanvas.toBlob(r, "image/png"));
await postFrame(blob, defaultDelay());
toast("Frame added");
if ($("opt-from-last").checked) {
// Pull the just-added frame into state before re-seeding the canvas, so
// "start from last frame" copies it instead of the previous frame (or a
// blank canvas on the first add), which the async SSE update may not
// have delivered yet.
await refreshState();
initDrawCanvas();
}
});
// ---- live updates -------------------------------------------------------
let eventSource = null;
function connectEvents() {
try {
if (eventSource) eventSource.close();
eventSource = new EventSource(withKey("/events"));
eventSource.onmessage = () => refreshState();
} catch (_) {
eventSource = null; /* SSE unavailable; manual reload still works */
}
}
$("btn-reload").addEventListener("click", async () => {
const btn = $("btn-reload");
const glyph = $("reload-glyph");
btn.disabled = true;
glyph.classList.add("spinning");
try {
// Recover a dropped live-update stream, then pull the latest state and
// rebuild the preview + thumbnails against a fresh cache-busting nonce.
if (!eventSource || eventSource.readyState === 2) connectEvents();
await refreshState();
toast("Reloaded");
} catch (e) {
toast("Reload failed: " + e.message);
} finally {
glyph.classList.remove("spinning");
btn.disabled = false;
}
});
connectEvents();
refreshState();
+189
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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>APNG Studio</title>
<link rel="stylesheet" href="styles.css" />
</head>
<body>
<header class="app-header">
<div>
<h1>APNG Studio</h1>
<p class="muted" id="subtitle">Assemble an animated PNG from frames.</p>
</div>
<div class="header-actions">
<button class="btn btn-sm" id="btn-reload"
title="Reload — re-sync frames and rebuild the preview">
<span class="reload-glyph" id="reload-glyph"></span> Reload
</button>
<span class="badge" id="mime-badge">image/apng</span>
</div>
</header>
<!-- Preview -->
<section class="card">
<div class="preview-wrap checker">
<img id="preview" alt="APNG preview" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" />
<div class="empty-preview" id="empty-preview">
<span>No frames yet</span>
<small class="muted">Upload images or draw a frame below.</small>
</div>
</div>
<div class="preview-meta">
<span id="meta-frames">0 frames</span>
<span class="dot">·</span>
<span id="meta-duration">0.0s</span>
<span class="dot">·</span>
<span id="meta-loops">loops ∞</span>
</div>
<div class="row gap">
<button class="btn btn-primary" id="btn-export">Export .png</button>
<button class="btn" id="btn-download">Download</button>
<button class="btn" id="btn-share">Send to phone</button>
<button class="btn btn-ghost" id="btn-restart" title="Restart animation">↺ Replay</button>
</div>
<p class="saved-path muted" id="saved-path" hidden></p>
<!-- Send to phone -->
<div class="share-panel" id="share-panel" hidden>
<div class="share-qr checker">
<img id="share-qr-img" alt="QR code — scan with your phone camera to open the animation" />
</div>
<div class="share-body">
<div class="share-title">Scan with your phone camera</div>
<p class="muted tiny">Your phone must be on the same WiFi as this computer.</p>
<a class="share-url" id="share-url" href="#" target="_blank" rel="noopener"></a>
<div class="share-foot">
<span class="muted tiny" id="share-expiry"></span>
<button class="btn btn-sm btn-ghost" id="btn-share-stop">Stop</button>
</div>
</div>
</div>
</section>
<!-- Settings -->
<section class="card">
<div class="section-title">Settings</div>
<div class="settings-grid">
<label class="field">
<span>Width</span>
<input type="number" id="in-width" min="1" max="2048" step="1" />
</label>
<label class="field">
<span>Height</span>
<input type="number" id="in-height" min="1" max="2048" step="1" />
</label>
<label class="field">
<span>Loops <small class="muted">(0 = ∞)</small></span>
<input type="number" id="in-loops" min="0" max="65535" step="1" />
</label>
<div class="field">
<span>First frame</span>
<label class="chk" id="hidden-first-label">
<input type="checkbox" id="in-hidden-first" /> Static fallback
</label>
</div>
</div>
<p class="muted tiny" id="dim-hint">Canvas size can only change while there are no frames.</p>
<p class="muted tiny" id="hidden-first-hint" hidden>
Frame&nbsp;1 is shown by viewers without APNG support and is not part of the loop.
</p>
<div class="subsection">
<div class="subsection-title">Apply to all frames</div>
<div class="apply-rows">
<span class="inline">
<label class="mini" for="in-delay-all">Delay</label>
<input type="number" id="in-delay-all" min="0" max="65535" step="10" value="120" />
<span class="mini">ms</span>
<button class="btn btn-sm" id="btn-delay-all">Apply</button>
</span>
<span class="inline">
<label class="mini" for="in-fps">Frame rate</label>
<input type="number" id="in-fps" min="1" max="120" step="1" value="12" />
<span class="mini">fps</span>
<button class="btn btn-sm" id="btn-fps">Set</button>
</span>
<span class="inline">
<label class="mini" for="in-dispose-all">Dispose</label>
<select id="in-dispose-all">
<option value="0">None</option>
<option value="1">Background</option>
<option value="2">Previous</option>
</select>
<label class="mini" for="in-blend-all">Blend</label>
<select id="in-blend-all">
<option value="0">Source</option>
<option value="1">Over</option>
</select>
<button class="btn btn-sm" id="btn-ops-all">Apply</button>
</span>
</div>
<details class="help">
<summary>What do dispose &amp; blend do?</summary>
<ul>
<li><b>Blend · Source</b> replaces the canvas region with this frame (alpha included). <b>Over</b> composites this frame on top of what's already there — use it with transparency to build an image up frame by frame.</li>
<li><b>Dispose · None</b> keeps the frame on screen for the next one. <b>Background</b> clears it to transparent first. <b>Previous</b> restores whatever was there before this frame.</li>
</ul>
</details>
</div>
</section>
<!-- Frames -->
<section class="card">
<div class="section-title row between">
<span>Frames</span>
<button class="btn btn-sm btn-ghost danger" id="btn-clear">Clear all</button>
</div>
<div class="frame-strip" id="frame-strip"></div>
<div class="empty-frames muted" id="empty-frames">Frames you add appear here in order.</div>
</section>
<!-- Add frames -->
<section class="card">
<div class="section-title">Add frames</div>
<div class="row gap wrap">
<button class="btn" id="btn-upload">⬆ Upload images</button>
<button class="btn" id="btn-toggle-draw">✎ Draw a frame</button>
<input type="file" id="file-input" accept="image/*" multiple hidden />
</div>
<!-- Draw panel -->
<div class="draw-panel" id="draw-panel" hidden>
<div class="draw-tools">
<label class="tool">
<span>Color</span>
<input type="color" id="draw-color" value="#3b82f6" />
</label>
<label class="tool">
<span>Size</span>
<input type="range" id="draw-size" min="1" max="48" value="6" />
</label>
<div class="tool-group" role="group" aria-label="Tool">
<button class="btn btn-sm tool-btn active" id="tool-pen" aria-pressed="true">Pen</button>
<button class="btn btn-sm tool-btn" id="tool-eraser" aria-pressed="false">Eraser</button>
</div>
<button class="btn btn-sm" id="btn-fill">Fill</button>
<button class="btn btn-sm" id="btn-clear-draw">Clear</button>
</div>
<div class="draw-options">
<label class="chk"><input type="checkbox" id="opt-onion" /> Onion skin</label>
<label class="chk"><input type="checkbox" id="opt-from-last" /> Start from last frame</label>
</div>
<div class="canvas-stage checker" id="canvas-stage">
<img id="onion-img" class="onion" alt="" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" hidden />
<canvas id="draw-canvas"></canvas>
</div>
<div class="row gap">
<button class="btn btn-primary btn-sm" id="btn-add-drawing">Add frame</button>
<button class="btn btn-sm btn-ghost" id="btn-cancel-draw">Close</button>
</div>
</div>
</section>
<div class="toast" id="toast" role="status" aria-live="polite" hidden></div>
<script src="app.js"></script>
</body>
</html>
+620
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:root {
--radius: 10px;
--radius-sm: 7px;
--gap: 12px;
--card-bg: var(--background-color-default, #ffffff);
--muted: var(--text-color-muted, #59636e);
--border: var(--border-color-default, #d1d9e0);
--fg: var(--text-color-default, #1f2328);
--accent: var(--true-color-blue, #0969da);
--danger: var(--true-color-red, #cf222e);
}
* {
box-sizing: border-box;
}
/* Ensure the `hidden` attribute always wins over element display rules. */
[hidden] {
display: none !important;
}
body {
margin: 0;
padding: 14px 14px 40px;
background: var(--background-color-default, #ffffff);
color: var(--fg);
font-family: var(--font-sans, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif);
font-size: var(--text-body-medium, 14px);
line-height: var(--leading-body-medium, 20px);
-webkit-font-smoothing: antialiased;
}
h1 {
font-family: var(--font-sans-display, var(--font-sans, sans-serif));
font-size: var(--text-title-medium, 18px);
font-weight: var(--font-weight-semibold, 600);
line-height: 1.2;
margin: 0;
}
.app-header {
display: flex;
align-items: flex-start;
justify-content: space-between;
gap: var(--gap);
margin-bottom: 14px;
}
.header-actions {
display: flex;
align-items: center;
gap: 8px;
flex-shrink: 0;
}
.reload-glyph {
display: inline-block;
}
.reload-glyph.spinning {
animation: apng-spin 0.6s linear infinite;
}
@keyframes apng-spin {
to {
transform: rotate(360deg);
}
}
.muted {
color: var(--muted);
}
.tiny {
font-size: var(--text-caption, 11px);
}
.muted.tiny {
margin: 8px 0 0;
}
.badge {
font-family: var(--font-mono, monospace);
font-size: var(--text-code-inline, 12px);
color: var(--muted);
border: 1px solid var(--border);
border-radius: 999px;
padding: 2px 9px;
white-space: nowrap;
}
#subtitle {
margin: 3px 0 0;
font-size: var(--text-body-small, 12px);
}
.card {
background: var(--card-bg);
border: 1px solid var(--border);
border-radius: var(--radius);
padding: 14px;
margin-bottom: 14px;
}
.section-title {
font-weight: var(--font-weight-semibold, 600);
margin-bottom: 12px;
}
.row {
display: flex;
align-items: center;
}
.row.gap {
gap: 8px;
}
.row.wrap {
flex-wrap: wrap;
}
.row.between,
.between {
justify-content: space-between;
}
/* Buttons */
.btn {
appearance: none;
border: 1px solid var(--border);
background: var(--background-color-default, #fff);
color: var(--fg);
border-radius: var(--radius-sm);
padding: 7px 12px;
font-size: var(--text-body-small, 13px);
font-weight: 500;
cursor: pointer;
transition: background 120ms ease, border-color 120ms ease, opacity 120ms ease;
}
.btn:hover {
background: var(--n-2-10, rgba(0, 0, 0, 0.04));
}
.btn:active {
transform: translateY(0.5px);
}
.btn:disabled {
opacity: 0.45;
cursor: not-allowed;
}
.btn-sm {
padding: 4px 9px;
font-size: var(--text-caption, 12px);
}
.btn-primary {
background: var(--accent);
border-color: var(--accent);
color: var(--color-white, #fff);
}
.btn-primary:hover {
filter: brightness(1.06);
background: var(--accent);
}
.btn-ghost {
background: transparent;
border-color: transparent;
}
.btn-ghost:hover {
background: var(--n-2-10, rgba(0, 0, 0, 0.05));
}
.danger {
color: var(--danger);
}
/* Preview */
.preview-wrap {
position: relative;
border-radius: var(--radius-sm);
border: 1px solid var(--border);
min-height: 160px;
max-height: 320px;
display: flex;
align-items: center;
justify-content: center;
overflow: hidden;
padding: 10px;
}
#preview {
max-width: 100%;
max-height: 300px;
image-rendering: auto;
display: block;
}
#preview.pixelated {
image-rendering: pixelated;
}
.empty-preview {
position: absolute;
inset: 0;
display: flex;
flex-direction: column;
gap: 4px;
align-items: center;
justify-content: center;
background: var(--background-color-default, #fff);
text-align: center;
}
.preview-meta {
display: flex;
align-items: center;
gap: 7px;
justify-content: center;
color: var(--muted);
font-size: var(--text-body-small, 12px);
margin: 10px 0 12px;
}
.preview-meta .dot {
opacity: 0.5;
}
.saved-path {
margin: 10px 0 0;
font-family: var(--font-mono, monospace);
font-size: var(--text-caption, 11px);
word-break: break-all;
}
/* Checkerboard for transparency */
.checker {
--checker-base: var(--background-color-default, #fff);
--checker-square: var(--border-color-default, #d9dbe0);
background-color: var(--checker-base);
background-image:
linear-gradient(45deg, var(--checker-square) 25%, transparent 25%),
linear-gradient(-45deg, var(--checker-square) 25%, transparent 25%),
linear-gradient(45deg, transparent 75%, var(--checker-square) 75%),
linear-gradient(-45deg, transparent 75%, var(--checker-square) 75%);
background-size: 16px 16px;
background-position: 0 0, 0 8px, 8px -8px, -8px 0;
}
/* Send to phone */
.share-panel {
display: flex;
gap: var(--gap);
align-items: center;
margin-top: 12px;
padding: 12px;
border: 1px solid var(--border);
border-radius: var(--radius);
background: var(--card-bg);
}
.share-qr {
flex-shrink: 0;
padding: 8px;
border-radius: var(--radius-sm);
line-height: 0;
}
.share-qr img {
width: 132px;
height: 132px;
image-rendering: pixelated;
display: block;
}
.share-body {
display: flex;
flex-direction: column;
gap: 4px;
min-width: 0;
}
.share-title {
font-weight: var(--font-weight-semibold, 600);
}
.share-url {
font-family: var(--font-mono, monospace);
font-size: var(--text-code-inline, 12px);
color: var(--accent);
word-break: break-all;
text-decoration: none;
margin-top: 2px;
}
.share-url:hover {
text-decoration: underline;
}
.share-foot {
display: flex;
align-items: center;
justify-content: space-between;
gap: 8px;
margin-top: 6px;
}
/* Settings */
.settings-grid {
display: grid;
grid-template-columns: repeat(2, minmax(0, 1fr));
gap: 10px;
}
.field {
display: flex;
flex-direction: column;
gap: 4px;
font-size: var(--text-body-small, 12px);
color: var(--muted);
}
.field .inline {
display: flex;
gap: 6px;
}
input[type="number"],
input[type="text"] {
width: 100%;
padding: 6px 8px;
border: 1px solid var(--border);
border-radius: var(--radius-sm);
background: var(--background-color-default, #fff);
color: var(--fg);
font-size: var(--text-body-medium, 13px);
font-family: inherit;
}
input:focus-visible,
.btn:focus-visible,
select:focus-visible {
outline: 2px solid var(--color-focus-outline, var(--accent));
outline-offset: 1px;
}
/* hidden-first checkbox living inside the settings grid */
.field .chk {
color: var(--fg);
font-size: var(--text-body-small, 12px);
padding: 4px 0;
}
.field .chk.disabled {
opacity: 0.45;
cursor: not-allowed;
}
/* Settings subsection: apply-to-all controls */
.subsection {
margin-top: 14px;
padding-top: 12px;
border-top: 1px dashed var(--border);
}
.subsection-title {
font-size: var(--text-caption, 11px);
text-transform: uppercase;
letter-spacing: 0.04em;
color: var(--muted);
font-weight: 600;
margin-bottom: 8px;
}
.apply-rows {
display: flex;
flex-direction: column;
gap: 8px;
}
.apply-rows .inline {
display: flex;
align-items: center;
flex-wrap: wrap;
gap: 6px;
}
.apply-rows .inline input[type="number"] {
width: 68px;
}
.apply-rows select {
padding: 5px 7px;
border: 1px solid var(--border);
border-radius: var(--radius-sm);
background: var(--background-color-default, #fff);
color: var(--fg);
font-size: var(--text-body-small, 12px);
font-family: inherit;
}
.mini {
font-size: 11px;
color: var(--muted);
}
.help {
margin-top: 12px;
font-size: var(--text-body-small, 12px);
}
.help summary {
cursor: pointer;
color: var(--accent);
font-size: var(--text-caption, 11px);
}
.help ul {
margin: 8px 0 0;
padding-left: 18px;
color: var(--muted);
}
.help li {
margin-bottom: 5px;
}
.help b {
color: var(--fg);
}
/* Frame strip */
.frame-strip {
display: flex;
gap: 10px;
overflow-x: auto;
padding-bottom: 6px;
}
.frame-card {
flex: 0 0 auto;
width: 168px;
border: 1px solid var(--border);
border-radius: var(--radius-sm);
overflow: hidden;
background: var(--card-bg);
}
.frame-card.is-static {
border-color: var(--accent);
border-style: dashed;
}
.frame-thumb-wrap {
position: relative;
border-bottom: 1px solid var(--border);
}
.frame-thumb {
width: 100%;
height: 88px;
object-fit: contain;
display: block;
}
.static-badge {
position: absolute;
top: 5px;
left: 5px;
background: var(--accent);
color: var(--color-white, #fff);
font-size: 9px;
font-weight: 700;
letter-spacing: 0.04em;
padding: 1px 5px;
border-radius: 4px;
}
.frame-body {
padding: 7px;
display: flex;
flex-direction: column;
gap: 6px;
}
.frame-index {
font-size: var(--text-caption, 11px);
color: var(--muted);
font-weight: 600;
}
.frame-field {
display: flex;
align-items: center;
flex-wrap: wrap;
gap: 4px;
}
.frame-label {
font-size: 10px;
text-transform: uppercase;
letter-spacing: 0.03em;
min-width: 46px;
}
.num-in {
width: 52px !important;
padding: 3px 4px !important;
font-size: var(--text-caption, 11px) !important;
text-align: center;
}
.slash {
font-size: 11px;
}
.ms-hint {
flex-basis: 100%;
font-size: 10px;
}
.frame-select {
flex: 1;
min-width: 0;
padding: 3px 4px;
border: 1px solid var(--border);
border-radius: 5px;
background: var(--background-color-default, #fff);
color: var(--fg);
font-size: var(--text-caption, 11px);
font-family: inherit;
}
.frame-actions {
display: flex;
gap: 3px;
margin-top: 1px;
}
.icon-btn {
flex: 1;
appearance: none;
border: 1px solid var(--border);
background: transparent;
color: var(--fg);
border-radius: 5px;
padding: 3px 0;
cursor: pointer;
font-size: 12px;
line-height: 1;
}
.icon-btn:hover {
background: var(--n-2-10, rgba(0, 0, 0, 0.05));
}
.icon-btn.danger:hover {
background: var(--true-color-red-muted, rgba(207, 34, 46, 0.1));
}
.icon-btn:disabled {
opacity: 0.35;
cursor: not-allowed;
}
.empty-frames {
font-size: var(--text-body-small, 12px);
padding: 4px 0 0;
}
/* Draw panel */
.draw-panel {
margin-top: 14px;
padding-top: 14px;
border-top: 1px dashed var(--border);
}
.draw-tools {
display: flex;
flex-wrap: wrap;
align-items: center;
gap: 10px;
margin-bottom: 10px;
}
.tool {
display: flex;
align-items: center;
gap: 5px;
font-size: var(--text-caption, 12px);
color: var(--muted);
}
.tool input[type="color"] {
width: 30px;
height: 26px;
padding: 0;
border: 1px solid var(--border);
border-radius: 6px;
background: none;
cursor: pointer;
}
.tool-group {
display: inline-flex;
gap: 0;
}
.tool-group .tool-btn {
border-radius: 0;
margin-left: -1px;
}
.tool-group .tool-btn:first-child {
border-radius: var(--radius-sm) 0 0 var(--radius-sm);
margin-left: 0;
}
.tool-group .tool-btn:last-child {
border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}
.tool-btn.active {
background: var(--accent);
border-color: var(--accent);
color: var(--color-white, #fff);
}
.draw-options {
display: flex;
gap: 16px;
margin-bottom: 10px;
}
.chk {
display: flex;
align-items: center;
gap: 6px;
font-size: var(--text-body-small, 12px);
cursor: pointer;
}
.canvas-stage {
position: relative;
border: 1px solid var(--border);
border-radius: var(--radius-sm);
overflow: hidden;
margin-bottom: 10px;
display: flex;
justify-content: center;
}
.canvas-stage .onion,
.canvas-stage canvas {
position: relative;
max-width: 100%;
display: block;
touch-action: none;
}
.canvas-stage .onion {
position: absolute;
inset: 0;
margin: auto;
opacity: 0.28;
pointer-events: none;
object-fit: contain;
}
#draw-canvas {
cursor: crosshair;
}
/* Toast */
.toast {
position: fixed;
left: 50%;
bottom: 18px;
transform: translateX(-50%);
background: var(--fg);
color: var(--background-color-default, #fff);
padding: 8px 14px;
border-radius: 999px;
font-size: var(--text-body-small, 12px);
box-shadow: 0 4px 16px rgba(0, 0, 0, 0.22);
z-index: 50;
max-width: 90%;
text-align: center;
}
.toast[hidden] {
display: none;
}