feat(renderer): draw transparent artboard checkerboard

renderer/renderer.ts

@@ -23,16 +23,50 @@ export function createRenderer(canvas: HTMLCanvasElement, backend: RendererBacke
     throw new Error("WebGL2 is not available");
   }
 
+  const clearRect = (x: number, y: number, w: number, h: number, color: [number, number, number, number]) => {
+    context.scissor(x, canvas.height - y - h, w, h);
+    context.clearColor(...color);
+    context.clear(context.COLOR_BUFFER_BIT);
+  };
+
   return {
     render(frame) {
       const { w, h } = frame.editor.viewport.size;
+      const { center, zoom } = frame.editor.viewport;
 
       if (canvas.width !== w) canvas.width = w;
       if (canvas.height !== h) canvas.height = h;
 
       context.viewport(0, 0, w, h);
-      context.clearColor(0, 0, 0, 0);
+      context.disable(context.SCISSOR_TEST);
+      context.clearColor(0.18, 0.18, 0.2, 1);
       context.clear(context.COLOR_BUFFER_BIT);
+      context.enable(context.SCISSOR_TEST);
+
+      for (const artboard of frame.document.artboards) {
+        const x = Math.round(w / 2 + (artboard.bounds.x - center.x) * zoom);
+        const y = Math.round(h / 2 + (artboard.bounds.y - center.y) * zoom);
+        const width = Math.max(0, Math.round(artboard.bounds.w * zoom));
+        const height = Math.max(0, Math.round(artboard.bounds.h * zoom));
+
+        if (artboard.backgroundColor === "transparent") {
+          const squareSize = Math.max(4, Math.round(12 * zoom));
+          for (let py = y; py < y + height; py += squareSize) {
+            for (let px = x; px < x + width; px += squareSize) {
+              const sx = Math.max(0, px);
+              const sy = Math.max(0, py);
+              const sw = Math.min(px + squareSize, x + width, w) - sx;
+              const sh = Math.min(py + squareSize, y + height, h) - sy;
+              if (sw <= 0 || sh <= 0) continue;
+
+              const checker = (Math.floor((px - x) / squareSize) + Math.floor((py - y) / squareSize)) % 2 === 0;
+              clearRect(sx, sy, sw, sh, checker ? [0.82, 0.82, 0.86, 1] : [0.94, 0.94, 0.97, 1]);
+            }
+          }
+        }
+      }
+
+      context.disable(context.SCISSOR_TEST);
     },
     dispose() {},
   };