New architecture

This commit is contained in:
2026-04-03 18:45:08 +02:00
parent 4613b8e5dd
commit 0d0e9fe043
24 changed files with 2747 additions and 908 deletions

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node_modules/

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/**
* build.cjs — esbuild script for the PDF viewer TypeScript bundle.
*
* Produces two output files in ../assets/viewer/:
* viewer.bundle.js — main viewer (IIFE, no PDF.js included)
* render-worker.bundle.js — render worker (pdf.min.js prepended + IIFE)
*
* Usage:
* node build.cjs — one-shot production build (minified)
* node build.cjs --watch — watch mode for development (unminified)
*/
const esbuild = require("esbuild");
const fs = require("fs");
const path = require("path");
const isWatch = process.argv.includes("--watch");
const minify = !isWatch;
const ROOT = __dirname;
const PDFJS_WORKER_MIN = path.join(ROOT, "../viewer/pdfjs/pdf.worker.min.js");
const PDFJS_MIN = path.join(ROOT, "../viewer/pdfjs/pdf.min.js");
const OUT_DIR = path.join(ROOT, "../viewer");
// Preamble prepended to the render-worker bundle.
//
// Sets `globalThis.window = globalThis` before pdf.worker.min.js runs so that:
// 1. pdf.worker.min.js does NOT auto-call WorkerMessageHandler.initializeFromPort(self)
// (which would hijack our render-worker's own onmessage handler).
// 2. pdf.worker.min.js DOES set globalThis.pdfjsWorker.WorkerMessageHandler as usual.
// 3. pdf.min.js's _mainThreadWorkerMessageHandler getter then finds the handler via
// globalThis.pdfjsWorker and uses it inline — no document.createElement needed.
const RENDER_WORKER_PREAMBLE = Buffer.from("globalThis.window=globalThis;\n");
// ── Render-worker plugin: prepend preamble + pdf.worker.min.js + pdf.min.js ───
//
// Bundle order matters:
// 1. Preamble — sets globalThis.window = globalThis
// 2. pdf.worker.min.js — sets globalThis.pdfjsWorker.WorkerMessageHandler
// (skips auto-setup because window is now defined)
// 3. pdf.min.js — sets globalThis.pdfjsLib; fake-worker path reads pdfjsWorker
// 4. Compiled TS — our render-worker code
function prependPdfjsPlugin() {
const pdfjsWorkerMin = fs.readFileSync(PDFJS_WORKER_MIN);
const pdfjsMin = fs.readFileSync(PDFJS_MIN);
const NL = Buffer.from("\n");
return {
name: "prepend-pdfjs",
setup(build) {
build.onEnd(result => {
if (result.errors.length > 0 || !result.outputFiles) return;
const compiled = Buffer.from(result.outputFiles[0].contents);
const combined = Buffer.concat([
RENDER_WORKER_PREAMBLE,
pdfjsWorkerMin, NL,
pdfjsMin, NL,
compiled,
]);
fs.writeFileSync(path.join(OUT_DIR, "render-worker.bundle.js"), combined);
if (!isWatch) console.log("[viewer-src] render-worker.bundle.js written");
});
},
};
}
async function main() {
const sharedOptions = { bundle: true, format: "iife", target: "es2020", minify };
if (isWatch) {
const viewerCtx = await esbuild.context({
...sharedOptions,
entryPoints: ["src/viewer.ts"],
outfile: path.join(OUT_DIR, "viewer.bundle.js"),
});
const workerCtx = await esbuild.context({
...sharedOptions,
entryPoints: ["src/render-worker.ts"],
write: false,
plugins: [prependPdfjsPlugin()],
});
await viewerCtx.watch();
await workerCtx.watch();
console.log("[viewer-src] watching for changes…");
// Keep the process alive
return;
}
// One-shot build
await esbuild.build({
...sharedOptions,
entryPoints: ["src/viewer.ts"],
outfile: path.join(OUT_DIR, "viewer.bundle.js"),
});
console.log("[viewer-src] viewer.bundle.js written");
// Render worker: build to memory then prepend preamble + worker + pdf.min.js
const workerResult = await esbuild.build({
...sharedOptions,
entryPoints: ["src/render-worker.ts"],
write: false,
});
const pdfjsWorkerMin = fs.readFileSync(PDFJS_WORKER_MIN);
const pdfjsMin = fs.readFileSync(PDFJS_MIN);
const NL = Buffer.from("\n");
const compiled = Buffer.from(workerResult.outputFiles[0].contents);
fs.writeFileSync(
path.join(OUT_DIR, "render-worker.bundle.js"),
Buffer.concat([RENDER_WORKER_PREAMBLE, pdfjsWorkerMin, NL, pdfjsMin, NL, compiled]),
);
console.log("[viewer-src] render-worker.bundle.js written");
}
main().catch(e => { console.error(e); process.exit(1); });

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{
"name": "brittle-viewer",
"lockfileVersion": 3,
"requires": true,
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}

View File

@@ -0,0 +1,15 @@
{
"name": "brittle-viewer",
"private": true,
"scripts": {
"build": "tsc --noEmit && node build.cjs",
"build:no-check": "node build.cjs",
"dev": "node build.cjs --watch",
"typecheck": "tsc --noEmit"
},
"devDependencies": {
"esbuild": "^0.25.0",
"pdfjs-dist": "^4.10.38",
"typescript": "^5.8.0"
}
}

View File

@@ -0,0 +1,275 @@
/**
* PageManager — page lifecycle: PLACEHOLDER → RENDERING → RENDERED → PLACEHOLDER
*
* Each page is a sized div (placeholder). When a page enters the buffer zone,
* a render job is dispatched to the render worker. When the worker returns an
* ImageBitmap, it is swapped into the DOM atomically (old canvas removed and
* new canvas appended in the same synchronous turn) so there is never a blank
* frame between the old blurry canvas and the new sharp one.
*
* During CSS zoom (Phase 1 of ZoomController), canvas teardown is suppressed
* to prevent dark flashes while intersection data is still settling.
*/
import { PageState } from "./types.js";
import type { PageDimensions } from "./types.js";
const MAX_CANVAS_PIXELS = 16_777_216; // 4096 × 4096
/**
* Clamp render scale so the canvas pixel count stays within budget.
* CSS dimensions stay correct — pages appear at the right size, just at
* reduced effective DPI when zoomed very high. Same strategy as Chrome's viewer.
*/
function clampedRenderScale(
vpWidth: number,
vpHeight: number,
desiredScale: number,
dpr: number,
): number {
const w = vpWidth * desiredScale * dpr;
const h = vpHeight * desiredScale * dpr;
const pixels = w * h;
if (pixels <= MAX_CANVAS_PIXELS) return desiredScale * dpr;
return desiredScale * dpr * Math.sqrt(MAX_CANVAS_PIXELS / pixels);
}
/** Called by viewer.ts to send a render job to the worker. */
export type DispatchRender = (pageNum: number, scale: number, gen: number) => void;
export class PageManager {
private readonly _wrapper: HTMLElement;
private readonly _dims: PageDimensions[];
private readonly _dpr: number;
private readonly _dispatchRender: DispatchRender;
private readonly _wrappers: HTMLElement[] = [];
// _states[i] tracks the render state of page i+1 (0-indexed).
private readonly _states: PageState[];
// _canvases[i] is the canvas currently in the DOM for page i+1, or null.
private readonly _canvases: (HTMLCanvasElement | null)[];
private _scale: number;
private _renderGen: number = 0;
private _inFlight: number = 0;
private _zooming: boolean = false;
constructor(
wrapper: HTMLElement,
dims: PageDimensions[],
initialScale: number,
dpr: number,
dispatchRender: DispatchRender,
) {
this._wrapper = wrapper;
this._dims = dims;
this._scale = initialScale;
this._dpr = dpr;
this._dispatchRender = dispatchRender;
this._states = new Array<PageState>(dims.length).fill(PageState.PLACEHOLDER);
this._canvases = new Array<HTMLCanvasElement | null>(dims.length).fill(null);
this._buildPlaceholders();
}
get pageWrappers(): readonly HTMLElement[] { return this._wrappers; }
get numPages(): number { return this._dims.length; }
get renderGen(): number { return this._renderGen; }
/** True when no renders are currently in flight (all visible pages are sharp). */
get allRendered(): boolean { return this._inFlight === 0; }
/** Called by ZoomController to suppress canvas teardown during Phase 1 CSS zoom. */
setZooming(z: boolean): void { this._zooming = z; }
private _buildPlaceholders(): void {
for (let i = 0; i < this._dims.length; i++) {
const dim = this._dims[i]!;
const wrap = document.createElement("div");
wrap.className = "page-wrapper";
wrap.dataset["page"] = String(i + 1);
wrap.style.width = dim.width * this._scale + "px";
wrap.style.height = dim.height * this._scale + "px";
this._wrapper.appendChild(wrap);
this._wrappers.push(wrap);
}
}
/**
* Called on each IntersectionObserver tick.
* Dispatches renders for pages entering the buffer (visible pages first).
* Cleans up pages that have left the buffer (unless zooming).
*/
reconcile(
bufferSet: ReadonlySet<number>,
visibleSet: ReadonlySet<number>,
): void {
const gen = this._renderGen;
// Visible pages first, then off-screen buffered pages.
const toRender: number[] = [
...[...visibleSet].sort((a, b) => a - b),
...[...bufferSet].filter(p => !visibleSet.has(p)).sort((a, b) => a - b),
];
for (const pageNum of toRender) {
const i = pageNum - 1;
if (i < 0 || i >= this._dims.length) continue;
if (this._states[i] === PageState.PLACEHOLDER) {
this._startRender(i, gen);
}
}
for (let i = 0; i < this._dims.length; i++) {
const pageNum = i + 1;
// Skip teardown during active CSS zoom — IntersectionObserver may report
// stale data while layout is still settling, causing premature canvas removal.
// onScaleChange (Phase 2) performs the authoritative cleanup.
if (!this._zooming && !bufferSet.has(pageNum) && this._states[i] === PageState.RENDERED) {
this._cleanup(i);
}
// Cancel in-flight renders that are now out of the buffer.
// Leave the canvas in place — removing it would cause a dark flash between
// Phase 1 (CSS zoom) and Phase 2 (debounced re-render).
if (!bufferSet.has(pageNum) && this._states[i] === PageState.RENDERING) {
this._inFlight--;
this._states[i] = PageState.PLACEHOLDER;
}
}
}
private _startRender(i: number, gen: number): void {
const dim = this._dims[i]!;
const scale = clampedRenderScale(dim.width, dim.height, this._scale, this._dpr);
this._states[i] = PageState.RENDERING;
this._inFlight++;
this._dispatchRender(i + 1, scale, gen);
}
private _cleanup(i: number): void {
if (this._states[i] === PageState.RENDERING) this._inFlight--;
this._states[i] = PageState.PLACEHOLDER;
const canvas = this._canvases[i];
if (canvas) {
canvas.remove();
this._canvases[i] = null;
}
}
/**
* Called when the render worker returns a finished bitmap.
*
* Double-buffer swap: the old canvas stays in the DOM until the new one is
* ready, then both mutations happen in the same synchronous JS turn so the
* browser produces exactly one paint frame for the transition.
*/
onRendered(pageNum: number, gen: number, bitmap: ImageBitmap): void {
if (gen !== this._renderGen) { bitmap.close(); return; }
const i = pageNum - 1;
if (
i < 0 ||
i >= this._dims.length ||
this._states[i] !== PageState.RENDERING
) {
bitmap.close();
return;
}
this._inFlight--;
const dim = this._dims[i]!;
const wrap = this._wrappers[i]!;
const cssW = dim.width * this._scale;
const cssH = dim.height * this._scale;
// Build new canvas off-screen (not in DOM yet).
const canvas = document.createElement("canvas");
canvas.width = bitmap.width;
canvas.height = bitmap.height;
canvas.style.width = cssW + "px";
canvas.style.height = cssH + "px";
canvas.style.display = "block";
// Zero-copy display via bitmaprenderer; fall back to drawImage if unavailable.
const bitmapCtx = canvas.getContext("bitmaprenderer");
if (bitmapCtx) {
bitmapCtx.transferFromImageBitmap(bitmap);
} else {
(canvas.getContext("2d") as CanvasRenderingContext2D).drawImage(bitmap, 0, 0);
bitmap.close();
}
wrap.style.width = cssW + "px";
wrap.style.height = cssH + "px";
// Do NOT reset wrap's CSS zoom here — ZoomController may have advanced it
// since the last onScaleChange. The explicit canvas CSS dimensions already
// counteract the zoom; resetting it would cause a brief visual scale jump.
// Atomic DOM swap: old removed + new appended in the same synchronous turn
// → the browser paints exactly one frame for the change.
const old = this._canvases[i];
if (old) old.remove();
wrap.appendChild(canvas);
this._canvases[i] = canvas;
this._states[i] = PageState.RENDERED;
}
/**
* Called after the zoom debounce fires (Phase 2).
* Increments renderGen to cancel all stale in-flight renders, resizes
* placeholders, then re-dispatches renders for the buffer zone.
*/
onScaleChange(
newScale: number,
bufferSet: ReadonlySet<number>,
visibleSet: ReadonlySet<number>,
): void {
this._scale = newScale;
this._renderGen++;
for (let i = 0; i < this._dims.length; i++) {
const pageNum = i + 1;
const dim = this._dims[i]!;
const wrap = this._wrappers[i]!;
const cssW = dim.width * newScale;
const cssH = dim.height * newScale;
wrap.style.width = cssW + "px";
wrap.style.height = cssH + "px";
wrap.style.setProperty("zoom", "1");
if (bufferSet.has(pageNum)) {
// Keep old canvas stretched to the new CSS size so there is no blank
// flash while the new render is in flight. onRendered() will replace
// it atomically in the same synchronous JS turn when done.
const canvas = this._canvases[i];
if (canvas) {
canvas.style.width = cssW + "px";
canvas.style.height = cssH + "px";
}
if (this._states[i] === PageState.RENDERING) this._inFlight--;
this._states[i] = PageState.PLACEHOLDER;
} else {
// Off-screen: safe to discard immediately (no visible flash).
const canvas = this._canvases[i];
if (canvas) { canvas.remove(); this._canvases[i] = null; }
this._states[i] = PageState.PLACEHOLDER;
}
}
this.reconcile(bufferSet, visibleSet);
}
/** Returns the 1-based page number of the topmost visible page. */
getCurrentPage(visibleSet: ReadonlySet<number>): number {
if (visibleSet.size > 0) return Math.min(...visibleSet);
// Fall back to scroll position when no page is intersecting.
const top = this._wrapper.parentElement?.getBoundingClientRect().top ?? 0;
for (const wrap of this._wrappers) {
if (wrap.getBoundingClientRect().bottom > top + 4) {
return parseInt(wrap.dataset["page"]!, 10);
}
}
return 1;
}
}

View File

@@ -0,0 +1,204 @@
/**
* render-worker.ts — off-main-thread PDF rendering via Web Worker.
*
* NOTE: pdf.min.js is prepended to the compiled output of this file at build
* time by build.cjs (see prependPdfjsPlugin). It sets `self.pdfjsLib` as a
* global, which this module reads via the declaration below.
*
* Worker message protocol
* ────────────────────────
* Main → Worker:
* { type: "init", pdfData: ArrayBuffer } (transferred, not copied)
* { type: "render", pageNum, scale, gen }
* { type: "cleanup" } — pdfDoc.cleanup(): free internal caches
* { type: "destroy" } — pdfDoc.destroy() + self.close()
*
* Worker → Main:
* { type: "ready", numPages, dims } — page-1 dim used as stub for all pages
* { type: "rendered", pageNum, gen, bitmap } (bitmap as transferable)
* { type: "error", message }
*
* WebKit nested-worker constraint
* ────────────────────────────────
* WebKit forbids nested workers (a worker spawning a worker). PDF.js normally
* spawns pdf.worker.min.js from wherever it is used — which here would be a
* nested worker. Instead, pdf.worker.min.js is bundled into this file (by
* build.cjs) preceded by a preamble that sets globalThis.window = globalThis.
* This causes pdf.worker.min.js to expose its WorkerMessageHandler on
* globalThis.pdfjsWorker without auto-calling initializeFromPort(self). PDF.js
* detects the pre-loaded handler via _mainThreadWorkerMessageHandler and runs
* inline in this thread — no nested worker creation attempted at all.
*
* Render queue
* ────────────
* With disableFontFace: true, every text glyph becomes canvas path operations.
* A text-heavy page can require 20 000+ synchronous canvas calls. Running
* multiple page renders concurrently exhausts the worker thread and causes
* system-wide CPU saturation (perceived UI lock). The queue serialises renders
* so exactly one page is active at a time. Incoming render messages for the
* same page supersede any queued (but not yet started) request.
*/
import type { PDFDocumentProxy } from "pdfjs-dist";
import type { WorkerInbound, WorkerOutbound, PageDimensions } from "./types.js";
// pdf.min.js is prepended at build time and sets globalThis.pdfjsLib.
declare const pdfjsLib: typeof import("pdfjs-dist");
let pdfDoc: PDFDocumentProxy | null = null;
// Custom canvas factory that uses OffscreenCanvas instead of
// document.createElement("canvas"). Required because this file runs in a Web
// Worker where `document` is not available. PDF.js uses the factory to create
// intermediate canvases (e.g. for scaling inline images during page rendering).
const offscreenCanvasFactory = {
create(width: number, height: number) {
const canvas = new OffscreenCanvas(width, height);
const context = canvas.getContext("2d")!;
return { canvas, context };
},
reset(
item: { canvas: OffscreenCanvas; context: OffscreenCanvasRenderingContext2D | null },
width: number,
height: number,
) {
item.canvas.width = width;
item.canvas.height = height;
},
destroy(
item: { canvas: OffscreenCanvas; context: OffscreenCanvasRenderingContext2D | null },
) {
// Release memory by shrinking the canvas; nulling context is cosmetic.
item.canvas.width = 1;
item.canvas.height = 1;
item.context = null;
},
};
// ── Render queue ──────────────────────────────────────────────────────────────
interface RenderJob { pageNum: number; scale: number; gen: number; }
const renderQueue: RenderJob[] = [];
let activeRenders = 0;
const MAX_CONCURRENT = 1;
function enqueueRender(pageNum: number, scale: number, gen: number): void {
// Supersede any already-queued (not yet started) job for the same page.
const dup = renderQueue.findIndex(j => j.pageNum === pageNum);
if (dup >= 0) renderQueue.splice(dup, 1);
renderQueue.push({ pageNum, scale, gen });
drainQueue();
}
function drainQueue(): void {
while (activeRenders < MAX_CONCURRENT && renderQueue.length > 0) {
const job = renderQueue.shift()!;
activeRenders++;
handleRender(job.pageNum, job.scale, job.gen).finally(() => {
activeRenders--;
drainQueue();
});
}
}
// ── Message dispatch ──────────────────────────────────────────────────────────
self.onmessage = async (ev: MessageEvent<WorkerInbound>): Promise<void> => {
const msg = ev.data;
switch (msg.type) {
case "init":
await handleInit(msg.pdfData);
break;
case "render":
// Enqueue and return immediately; drainQueue() handles concurrency.
enqueueRender(msg.pageNum, msg.scale, msg.gen);
break;
case "cleanup":
await pdfDoc?.cleanup();
break;
case "destroy":
renderQueue.length = 0; // cancel pending jobs
if (pdfDoc) { await pdfDoc.destroy(); pdfDoc = null; }
self.close();
break;
}
};
// ── Handlers ──────────────────────────────────────────────────────────────────
async function handleInit(pdfData: ArrayBuffer): Promise<void> {
try {
// pdf.worker.min.js is bundled into this file (prepended by build.cjs).
// It sets globalThis.pdfjsWorker.WorkerMessageHandler, which PDF.js detects
// via its _mainThreadWorkerMessageHandler getter and uses as an inline fake
// worker — no nested-worker creation attempted.
pdfjsLib.GlobalWorkerOptions.workerSrc =
"brittle://app/pdfjs/build/pdf.worker.min.js";
// disableFontFace: PDF.js normally registers custom fonts via
// document.fonts.add() (the Font Loading API). In a Web Worker, `document`
// is undefined, so font registration fails and text is invisible. Setting
// disableFontFace: true makes PDF.js render all glyphs as canvas vector
// paths instead — no browser font API needed, text renders correctly.
//
// canvasFactory: the installed pdfjs-dist types omit this parameter even
// though the runtime API accepts it. `any` cast bypasses the type check.
// eslint-disable-next-line @typescript-eslint/no-explicit-any
pdfDoc = await pdfjsLib.getDocument({
data: new Uint8Array(pdfData),
canvasFactory: offscreenCanvasFactory,
disableFontFace: true,
} as any).promise;
const numPages = pdfDoc.numPages;
// Fetch page-1 dimensions so the main thread can lay out placeholders.
// Page-1 dims are used as a uniform stub for all pages — accurate for most
// academic PDFs (uniform paper size). We deliberately do NOT fetch dims for
// every page here: that would tie up the worker with N getPage() calls while
// render jobs are already arriving, causing further delays.
const firstPage = await pdfDoc.getPage(1);
const firstVp = firstPage.getViewport({ scale: 1.0 });
firstPage.cleanup();
const stubDim: PageDimensions = { width: firstVp.width, height: firstVp.height };
const stubDims: PageDimensions[] = Array.from({ length: numPages }, () => stubDim);
const out: WorkerOutbound = { type: "ready", numPages, dims: stubDims };
self.postMessage(out);
} catch (e) {
const out: WorkerOutbound = { type: "error", message: String(e) };
self.postMessage(out);
}
}
async function handleRender(
pageNum: number,
scale: number,
gen: number,
): Promise<void> {
if (!pdfDoc) return;
let page = null;
try {
page = await pdfDoc.getPage(pageNum);
const vp = page.getViewport({ scale });
const width = Math.round(vp.width);
const height = Math.round(vp.height);
const offscreen = new OffscreenCanvas(width, height);
// OffscreenCanvasRenderingContext2D is assignable to the canvasContext
// parameter of page.render(); the cast satisfies the type checker.
const ctx = offscreen.getContext("2d") as unknown as CanvasRenderingContext2D;
await page.render({ canvasContext: ctx, viewport: vp }).promise;
const bitmap = offscreen.transferToImageBitmap();
const out: WorkerOutbound = { type: "rendered", pageNum, gen, bitmap };
(self as unknown as Worker).postMessage(out, [bitmap]);
} catch (e) {
if ((e as Error)?.name !== "RenderingCancelledException") {
console.warn("[render-worker] render error page", pageNum, e);
}
} finally {
page?.cleanup();
}
}

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// ── Page lifecycle ────────────────────────────────────────────────────────────
export const PageState = {
PLACEHOLDER: 0,
RENDERING: 1,
RENDERED: 2,
} as const;
export type PageState = typeof PageState[keyof typeof PageState];
/** Page dimensions at scale=1 (fetched from the render worker at init). */
export interface PageDimensions {
width: number;
height: number;
}
// ── Render worker message protocol ────────────────────────────────────────────
/** Messages the main thread sends to the render worker. */
export type WorkerInbound =
| { type: "init"; pdfData: ArrayBuffer }
| { type: "render"; pageNum: number; scale: number; gen: number }
| { type: "cleanup" }
| { type: "destroy" };
/**
* Messages the render worker sends to the main thread.
*
* "ready" includes all page dims so the main thread can lay out placeholders
* without a second round-trip.
*/
export type WorkerOutbound =
| { type: "ready"; numPages: number; dims: PageDimensions[] }
| { type: "rendered"; pageNum: number; gen: number; bitmap: ImageBitmap }
| { type: "error"; message: string };
// ── iframe ↔ parent postMessage protocol ─────────────────────────────────────
/** Messages the PDF viewer iframe sends up to the parent Leptos app. */
export type OutboundMessage =
| { type: "brittle:viewer-state"; refId: string; zoom: number; scrollTop: number }
| { type: "brittle:keydown"; key: string; ctrlKey: boolean; shiftKey: boolean; altKey: boolean; metaKey: boolean };

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/**
* viewer.ts — PDF viewer orchestrator.
*
* Rendering is entirely off the main thread: a render worker (render-worker.ts,
* with pdf.min.js bundled in) handles all PDF.js calls and canvas rasterisation
* via OffscreenCanvas. The main thread only performs DOM manipulation and
* receives finished ImageBitmaps for zero-copy display.
*
* Init sequence:
* 1. Fetch render-worker.bundle.js → blob URL → new Worker()
* 2. Fetch raw PDF bytes → transfer ArrayBuffer to worker
* 3. Worker loads PDF.js, fetches page dims → posts "ready" with dims
* 4. Create PageManager (placeholder divs) with received dims
* 5. Wire render worker onmessage → pageManager.onRendered()
* 6. Create ViewportTracker → IntersectionObserver fires → initial reconcile
* 7. Create ZoomController
* 8. Register toolbar, keyboard, scroll, and lifecycle handlers
*/
import { PageManager } from "./page-manager.js";
import { ViewportTracker } from "./viewport-tracker.js";
import { ZoomController } from "./zoom-controller.js";
import type { WorkerInbound, WorkerOutbound, OutboundMessage, PageDimensions } from "./types.js";
// requestIdleCallback polyfill for older WebKitGTK builds.
if (typeof requestIdleCallback === "undefined") {
(self as unknown as Record<string, unknown>)["requestIdleCallback"] =
(cb: IdleRequestCallback): ReturnType<typeof setTimeout> =>
setTimeout(() => cb({ timeRemaining: () => 50, didTimeout: false }), 1);
}
// ── DOM refs ──────────────────────────────────────────────────────────────────
const container = document.getElementById("canvas-container")!;
const pagesWrapper = document.getElementById("pages-wrapper")!;
const statusEl = document.getElementById("status")!;
const zoomLabel = document.getElementById("zoom-label")!;
const pageIndicator = document.getElementById("page-indicator")!;
// ── URL params ─────────────────────────────────────────────────────────────────
const params = new URLSearchParams(location.search);
const refId = params.get("ref_id") ?? "";
const savedZoom = parseFloat(params.get("zoom") ?? "");
const savedScrollTop = parseFloat(params.get("scroll_top") ?? "");
const DPR = window.devicePixelRatio || 1;
// ── Mutable state ─────────────────────────────────────────────────────────────
let pageManager: PageManager | null = null;
let viewportTracker: ViewportTracker | null = null;
let zoomController: ZoomController | null = null;
let renderWorker: Worker | null = null;
let currentBufferSet: ReadonlySet<number> = new Set();
let currentVisibleSet: ReadonlySet<number> = new Set();
// ── Utilities ──────────────────────────────────────────────────────────────────
function setStatus(msg: string): void { statusEl.textContent = msg; }
function showError(msg: string): void {
const b = document.getElementById("error-banner")!;
b.textContent = msg;
b.style.display = "block";
setStatus("Error");
}
function refreshPageIndicator(): void {
if (!pageManager) return;
const cur = pageManager.getCurrentPage(currentVisibleSet);
pageIndicator.textContent = `${cur} / ${pageManager.numPages}`;
}
function scrollToPage(pageNum: number): void {
if (!pageManager) return;
const wrap = pageManager.pageWrappers[pageNum - 1];
if (!wrap) return;
container.scrollTop +=
wrap.getBoundingClientRect().top - container.getBoundingClientRect().top;
}
function sendViewerState(): void {
if (!zoomController || window.parent === window) return;
const msg: OutboundMessage = {
type: "brittle:viewer-state",
refId,
zoom: zoomController.scale,
scrollTop: container.scrollTop,
};
window.parent.postMessage(msg, "*");
}
/** Send a render job to the worker. Called by PageManager via dispatchRender. */
function dispatchRender(pageNum: number, scale: number, gen: number): void {
const msg: WorkerInbound = { type: "render", pageNum, scale, gen };
renderWorker?.postMessage(msg);
}
// ── Visibility change callback ─────────────────────────────────────────────────
function onVisibilityChange(
bufferSet: ReadonlySet<number>,
visibleSet: ReadonlySet<number>,
): void {
currentBufferSet = bufferSet;
currentVisibleSet = visibleSet;
pageManager?.reconcile(bufferSet, visibleSet);
refreshPageIndicator();
}
// ── Fit-to-page scale computation ─────────────────────────────────────────────
function fitScale(dims: PageDimensions[]): number {
const dim = dims[0] ?? { width: 595, height: 842 }; // A4 fallback
return Math.max(0.1, Math.min(5.0, Math.min(
(container.clientWidth - 40) / dim.width,
(container.clientHeight - 40) / dim.height,
)));
}
// ── Main init ──────────────────────────────────────────────────────────────────
async function load(): Promise<void> {
if (!refId) { showError("No ref_id in URL."); return; }
setStatus("Loading…");
try {
// 1. Fetch the worker bundle and the PDF bytes in parallel — they are
// independent, so there is no reason to wait for one before starting
// the other. The worker is created from a blob URL because Tauri's
// WebView requires workers to be same-origin; blob URLs satisfy that.
const [workerBlob, pdfBuf] = await Promise.all([
fetch("brittle://app/viewer/render-worker.bundle.js").then(r => r.blob()),
fetch(`brittle://app/pdf?ref_id=${encodeURIComponent(refId)}`).then(r => r.arrayBuffer()),
]);
renderWorker = new Worker(URL.createObjectURL(workerBlob));
// 2. Send init message; wait for "ready" (stub dims based on page 1).
// The worker posts "ready" immediately after loading the PDF so the
// main thread unblocks and creates placeholders right away. A follow-up
// "dims" message with real per-page dimensions arrives shortly after.
const { numPages, dims } = await new Promise<{
numPages: number;
dims: PageDimensions[];
}>((resolve, reject) => {
renderWorker!.onmessage = (ev: MessageEvent<WorkerOutbound>) => {
const msg = ev.data;
if (msg.type === "ready") resolve({ numPages: msg.numPages, dims: msg.dims });
if (msg.type === "error") reject(new Error(msg.message));
};
renderWorker!.onerror = e => reject(new Error(e.message));
const initMsg: WorkerInbound = { type: "init", pdfData: pdfBuf };
renderWorker!.postMessage(initMsg, [pdfBuf]);
});
// 3. Compute initial scale (saved zoom if valid, otherwise fit-to-page).
const fitted = fitScale(dims);
const initialScale = (savedZoom > 0)
? Math.max(0.1, Math.min(5.0, savedZoom))
: fitted;
// 4. PageManager — creates N placeholder divs in #pages-wrapper.
pageManager = new PageManager(
pagesWrapper, dims, initialScale, DPR, dispatchRender,
);
// 5. Wire worker onmessage for ongoing renders and dim corrections.
renderWorker.onmessage = (ev: MessageEvent<WorkerOutbound>) => {
const msg = ev.data;
if (msg.type === "rendered") {
pageManager?.onRendered(msg.pageNum, msg.gen, msg.bitmap);
refreshPageIndicator();
if (pageManager?.allRendered) setStatus("Ready");
} else if (msg.type === "error") {
console.warn("[viewer] worker error:", msg.message);
}
};
// 6. ViewportTracker — IntersectionObserver fires once placeholders are in
// the DOM, triggering the initial reconcile automatically.
viewportTracker = new ViewportTracker(
container,
[...pageManager.pageWrappers],
onVisibilityChange,
);
// 7. ZoomController — on Phase 2 re-render, also save state.
zoomController = new ZoomController(
container,
pageManager,
(newScale, bufferSet, visibleSet) => {
pageManager!.onScaleChange(newScale, bufferSet, visibleSet);
sendViewerState();
},
() => ({ bufferSet: currentBufferSet, visibleSet: currentVisibleSet }),
zoomLabel,
initialScale,
);
// 9. Toolbar buttons
document.getElementById("btn-zoom-out")!.addEventListener("click",
() => zoomController!.applyScale(zoomController!.scale / 1.25));
document.getElementById("btn-zoom-in")!.addEventListener("click",
() => zoomController!.applyScale(zoomController!.scale * 1.25));
document.getElementById("btn-zoom-fit")!.addEventListener("click",
() => zoomController!.applyScale(fitScale(dims)));
// 10. Keyboard shortcuts + forwarding to parent for global keybindings.
document.addEventListener("keydown", ev => {
if ((ev.target as HTMLElement).tagName === "INPUT") return;
if (ev.key === "+" || ev.key === "=") {
ev.preventDefault();
zoomController!.applyScale(zoomController!.scale * 1.25);
}
if (ev.key === "-") {
ev.preventDefault();
zoomController!.applyScale(zoomController!.scale / 1.25);
}
if (ev.key === "0") {
ev.preventDefault();
zoomController!.applyScale(fitScale(dims));
}
// Forward to parent Leptos app for global keybinding dispatch.
if (window.parent !== window) {
const msg: OutboundMessage = {
type: "brittle:keydown",
key: ev.key,
ctrlKey: ev.ctrlKey,
shiftKey: ev.shiftKey,
altKey: ev.altKey,
metaKey: ev.metaKey,
};
window.parent.postMessage(msg, "*");
}
});
// 11. Scroll → update page indicator + debounced state save.
let scrollSaveTimer: ReturnType<typeof setTimeout> | null = null;
container.addEventListener("scroll", () => {
refreshPageIndicator();
if (scrollSaveTimer !== null) clearTimeout(scrollSaveTimer);
scrollSaveTimer = setTimeout(sendViewerState, 500);
}, { passive: true });
// 12. Restore saved scroll position (rAF ensures layout is ready).
if (savedScrollTop > 0) {
requestAnimationFrame(() => { container.scrollTop = savedScrollTop; });
}
// 13. Inbound postMessage from parent Leptos app (page navigation commands).
window.addEventListener("message", ev => {
if (ev.data === "pdf.page.next") {
scrollToPage(Math.min(
pageManager!.getCurrentPage(currentVisibleSet) + 1, numPages,
));
}
if (ev.data === "pdf.page.prev") {
scrollToPage(Math.max(
pageManager!.getCurrentPage(currentVisibleSet) - 1, 1,
));
}
});
// 14. Tab visibility lifecycle: free caches when hidden, re-reconcile on show.
document.addEventListener("visibilitychange", () => {
if (document.hidden) {
renderWorker?.postMessage({ type: "cleanup" } satisfies WorkerInbound);
} else {
pageManager?.reconcile(currentBufferSet, currentVisibleSet);
}
});
// 15. DPR change (e.g., window moved to a different-DPI monitor).
matchMedia(`(resolution: ${DPR}dppx)`).addEventListener("change", () => {
if (pageManager && zoomController) {
pageManager.onScaleChange(
zoomController.scale, currentBufferSet, currentVisibleSet,
);
}
});
// 16. Teardown on unload.
window.addEventListener("beforeunload", () => {
viewportTracker?.disconnect();
renderWorker?.postMessage({ type: "destroy" } satisfies WorkerInbound);
renderWorker = null;
});
pageIndicator.textContent = `1 / ${numPages}`;
setStatus("Rendering…");
} catch (e) {
showError("Could not load PDF: " + ((e as Error).message ?? String(e)));
}
}
load();

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/**
* ViewportTracker — dual IntersectionObserver for page visibility detection.
*
* - visibleSet: pages currently on screen (rootMargin "0px")
* - bufferSet: pages within ~2 viewport heights above/below (rootMargin "200% 0px")
*
* Both observers schedule a single rAF-deferred notification to prevent stale
* data when the two observers fire in separate microtasks for the same layout
* change (e.g. buffer removes a page before visible has also removed it).
*
* Hard invariant enforced before every callback: every visible page is also
* in the buffer set.
*/
type OnVisibilityChange = (
bufferSet: ReadonlySet<number>,
visibleSet: ReadonlySet<number>,
) => void;
export class ViewportTracker {
private readonly _onChange: OnVisibilityChange;
private readonly _visibleSet: Set<number> = new Set();
private readonly _bufferSet: Set<number> = new Set();
private _visibleObserver: IntersectionObserver | null = null;
private _bufferObserver: IntersectionObserver | null = null;
private _rafPending: number | null = null;
constructor(
root: HTMLElement,
pageWrappers: HTMLElement[],
onChange: OnVisibilityChange,
) {
this._onChange = onChange;
this._observe(root, pageWrappers);
}
private _observe(root: HTMLElement, pageWrappers: HTMLElement[]): void {
const scheduleNotify = (): void => {
if (this._rafPending !== null) return;
this._rafPending = requestAnimationFrame(() => {
this._rafPending = null;
// Hard invariant: every visible page must also be in the buffer.
for (const p of this._visibleSet) this._bufferSet.add(p);
this._onChange(new Set(this._bufferSet), new Set(this._visibleSet));
});
};
this._visibleObserver = new IntersectionObserver(entries => {
for (const e of entries) {
const page = parseInt((e.target as HTMLElement).dataset["page"]!, 10);
if (e.isIntersecting) this._visibleSet.add(page);
else this._visibleSet.delete(page);
}
scheduleNotify();
}, { root, rootMargin: "0px", threshold: 0 });
this._bufferObserver = new IntersectionObserver(entries => {
for (const e of entries) {
const page = parseInt((e.target as HTMLElement).dataset["page"]!, 10);
if (e.isIntersecting) this._bufferSet.add(page);
else this._bufferSet.delete(page);
}
scheduleNotify();
}, { root, rootMargin: "200% 0px", threshold: 0 });
for (const wrap of pageWrappers) {
this._visibleObserver.observe(wrap);
this._bufferObserver.observe(wrap);
}
}
/** Observe a newly-added page wrapper (unused currently, kept for extensibility). */
observe(wrap: HTMLElement): void {
this._visibleObserver?.observe(wrap);
this._bufferObserver?.observe(wrap);
}
disconnect(): void {
this._visibleObserver?.disconnect();
this._bufferObserver?.disconnect();
this._visibleSet.clear();
this._bufferSet.clear();
if (this._rafPending !== null) {
cancelAnimationFrame(this._rafPending);
this._rafPending = null;
}
}
}

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/**
* ZoomController — two-phase zoom pipeline.
*
* Phase 1 (instant, every event):
* CSS `zoom` property on each .page-wrapper = newScale / renderScale
* Scroll position adjusted to keep the anchor point fixed
* Zoom label updated immediately
*
* Phase 2 (debounced, 250ms after last event):
* pageManager.onScaleChange(newScale, bufferSet, visibleSet)
* Pages re-rendered at native resolution via the render worker
*
* Ctrl+Scroll events within a single frame are coalesced via rAF; the 250ms
* debounce starts from inside the rAF callback so it begins after the last
* event in a burst.
*/
import type { PageManager } from "./page-manager.js";
// Must match the CSS constants in index.html:
// #pages-wrapper { padding: 20px 0; gap: 12px; }
const CONTENT_PADDING_TOP = 20;
const PAGE_GAP = 12;
export interface BufferSnapshot {
bufferSet: ReadonlySet<number>;
visibleSet: ReadonlySet<number>;
}
type OnReRender = (
newScale: number,
bufferSet: ReadonlySet<number>,
visibleSet: ReadonlySet<number>,
) => void;
export class ZoomController {
static readonly ZOOM_MIN = 0.1;
static readonly ZOOM_MAX = 5.0;
private readonly _container: HTMLElement;
private readonly _pm: PageManager;
private readonly _onReRender: OnReRender;
private readonly _getBuffer: () => BufferSnapshot;
private readonly _zoomLabel: HTMLElement;
private _scale: number;
private _renderScale: number;
private _debounce: ReturnType<typeof setTimeout> | null = null;
private _rafPending: number | null = null;
constructor(
container: HTMLElement,
pageManager: PageManager,
onReRender: OnReRender,
getBuffer: () => BufferSnapshot,
zoomLabel: HTMLElement,
initialScale: number,
) {
this._container = container;
this._pm = pageManager;
this._onReRender = onReRender;
this._getBuffer = getBuffer;
this._zoomLabel = zoomLabel;
this._scale = initialScale;
this._renderScale = initialScale;
this._updateLabel();
this._bindScrollZoom();
}
get scale(): number { return this._scale; }
clamp(s: number): number {
return Math.max(ZoomController.ZOOM_MIN, Math.min(ZoomController.ZOOM_MAX, s));
}
private _updateLabel(): void {
this._zoomLabel.textContent = Math.round(this._scale * 100) + "%";
}
/**
* Apply a new zoom level.
*
* @param newScale - Target zoom scale.
* @param anchorY - Pixel offset within container to hold fixed (default: center).
* @param anchorX - Pixel offset within container to hold fixed (default: center).
*/
applyScale(newScale: number, anchorY?: number, anchorX?: number): void {
const container = this._container;
const oldScale = this._scale;
this._scale = this.clamp(newScale);
this._updateLabel();
this._pm.setZooming(true);
if (anchorY === undefined) anchorY = container.clientHeight / 2;
if (anchorX === undefined) anchorX = container.clientWidth / 2;
// Compute the non-scaling portion of content above the anchor point.
// Gaps and padding are fixed-size (do not scale with zoom), so a naive
// `(scrollTop + anchorY) × ratio` formula accumulates one error of
// `GAP × (ratio 1)` per gap above the anchor — enough to visibly drift
// the anchor point on long documents.
const anchorContentY = container.scrollTop + anchorY;
let fixedAbove = CONTENT_PADDING_TOP;
let cumY = CONTENT_PADDING_TOP;
for (const wrap of this._pm.pageWrappers) {
const zoom = parseFloat(wrap.style.getPropertyValue("zoom") || "1") || 1;
const h = parseFloat(wrap.style.height) * zoom;
if (cumY + h > anchorContentY) break;
cumY += h + PAGE_GAP;
fixedAbove += PAGE_GAP;
}
// Phase 1: instant CSS zoom feedback (no re-render yet)
const cssZoom = this._scale / this._renderScale;
for (const wrap of this._pm.pageWrappers) {
wrap.style.setProperty("zoom", String(cssZoom));
}
// Exact scroll anchor: scale only the page-content portion; the fixed
// portion (gaps + padding) does not change.
// T_new = fixedAbove + (T_old + anchorY fixedAbove) × ratio anchorY
const ratio = this._scale / oldScale;
const scalable = container.scrollTop + anchorY - fixedAbove;
container.scrollTop = Math.max(0, fixedAbove + scalable * ratio - anchorY);
container.scrollLeft = Math.max(0, (container.scrollLeft + anchorX) * ratio - anchorX);
this._scheduleReRender();
}
private _scheduleReRender(): void {
if (this._rafPending !== null) cancelAnimationFrame(this._rafPending);
this._rafPending = requestAnimationFrame(() => {
this._rafPending = null;
if (this._debounce !== null) clearTimeout(this._debounce);
this._debounce = setTimeout(() => this._triggerReRender(), 250);
});
}
private _triggerReRender(): void {
this._pm.setZooming(false); // Phase 2: onScaleChange handles the cleanup
this._renderScale = this._scale;
const { bufferSet, visibleSet } = this._getBuffer();
this._onReRender(this._scale, bufferSet, visibleSet);
}
private _bindScrollZoom(): void {
this._container.addEventListener("wheel", ev => {
if (!ev.ctrlKey) return;
ev.preventDefault();
const rect = this._container.getBoundingClientRect();
const anchorY = ev.clientY - rect.top;
const anchorX = ev.clientX - rect.left;
this.applyScale(
this._scale * (ev.deltaY < 0 ? 1.1 : 1 / 1.1),
anchorY,
anchorX,
);
}, { passive: false });
}
}

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{
"compilerOptions": {
"target": "ES2020",
"module": "ES2020",
"moduleResolution": "bundler",
"lib": ["ES2020", "DOM", "DOM.Iterable", "WebWorker"],
"strict": true,
"noUncheckedIndexedAccess": true,
"skipLibCheck": true
},
"include": ["src"]
}