feat(editor): add canvas worker renderer dev entry (#9719)

blocksuite/playground/examples/renderer/canvas.worker.ts

@@ -0,0 +1,88 @@
+import { type ParagraphLayout } from './types.js';
+
+const meta = {
+  emSize: 2048,
+  hHeadAscent: 1984,
+  hHeadDescent: -494,
+};
+
+const font = new FontFace(
+  'Inter',
+  `url(https://fonts.gstatic.com/s/inter/v18/UcCo3FwrK3iLTcviYwYZ8UA3.woff2)`
+);
+// @ts-expect-error worker env
+self.fonts && self.fonts.add(font);
+font.load().catch(console.error);
+
+function getBaseline() {
+  const fontSize = 15;
+  const lineHeight = 1.2 * fontSize;
+
+  const A = fontSize * (meta.hHeadAscent / meta.emSize); // ascent
+  const D = fontSize * (meta.hHeadDescent / meta.emSize); // descent
+  const AD = A + Math.abs(D); // ascent + descent
+  const L = lineHeight - AD; // leading
+  const y = A + L / 2;
+  return y;
+}
+
+class CanvasWorkerManager {
+  private canvas: OffscreenCanvas | null = null;
+  private ctx: OffscreenCanvasRenderingContext2D | null = null;
+
+  init(width: number, height: number, dpr: number) {
+    this.canvas = new OffscreenCanvas(width * dpr, height * dpr);
+    this.ctx = this.canvas.getContext('2d')!;
+    this.ctx.scale(dpr, dpr);
+    this.ctx.fillStyle = 'lightgrey';
+    this.ctx.fillRect(0, 0, width, height);
+  }
+
+  draw(paragraphs: ParagraphLayout[], hostRect: DOMRect) {
+    const { canvas, ctx } = this;
+    if (!canvas || !ctx) return;
+
+    ctx.font = '15px Inter';
+    const baselineY = getBaseline();
+
+    paragraphs.forEach(paragraph => {
+      paragraph.sentences.forEach(sentence => {
+        ctx.strokeStyle = 'yellow';
+        sentence.rects.forEach(textRect => {
+          const x = textRect.rect.left - hostRect.left;
+          const y = textRect.rect.top - hostRect.top;
+          ctx.strokeRect(x, y, textRect.rect.width, textRect.rect.height);
+        });
+
+        ctx.fillStyle = 'black';
+        sentence.rects.forEach(textRect => {
+          const x = textRect.rect.left - hostRect.left;
+          const y = textRect.rect.top - hostRect.top;
+          ctx.fillText(textRect.text, x, y + baselineY);
+        });
+      });
+    });
+
+    const bitmap = canvas.transferToImageBitmap();
+    self.postMessage({ type: 'render', bitmap }, { transfer: [bitmap] });
+  }
+}
+
+const manager = new CanvasWorkerManager();
+
+self.onmessage = async (e: MessageEvent) => {
+  const { type, data } = e.data;
+  switch (type) {
+    case 'init': {
+      const { width, height, dpr } = data;
+      manager.init(width, height, dpr);
+      break;
+    }
+    case 'draw': {
+      await font.load();
+      const { paragraphs, hostRect } = data;
+      manager.draw(paragraphs, hostRect);
+      break;
+    }
+  }
+};