A ResizeObserver HD-DPI example

I'm not sure if adding image-rendering fits here. Maybe that should be a separate example?
webgpu · Mar 7, 2024 · ab99174 · ab99174
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diff --git a/sample/resizeObserverHDDPI/checker.wgsl b/sample/resizeObserverHDDPI/checker.wgsl
@@ -0,0 +1,25 @@
+struct Uniforms {
+  color0: vec4f,
+  color1: vec4f,
+  size: u32,
+};
+
+@group(0) @binding(0) var<uniform> uni: Uniforms;
+
+@vertex
+fn vs(@builtin(vertex_index) vertexIndex : u32) -> @builtin(position) vec4f {
+  const pos = array(
+    vec2f(-1.0, -1.0),
+    vec2f( 3.0, -1.0),
+    vec2f(-1.0,  3.0),
+  );
+  return vec4f(pos[vertexIndex], 0.0, 1.0);
+}
+
+@fragment
+fn fs(@builtin(position) position: vec4f) -> @location(0) vec4f {
+  let grid = vec2u(position.xy) / uni.size;
+  let checker = (grid.x + grid.y) % 2 == 1;
+  return select(uni.color0, uni.color1, checker);
+}
+
diff --git a/sample/resizeObserverHDDPI/index.html b/sample/resizeObserverHDDPI/index.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
+    <title>webgpu-samples: resizeObserverHDDPI</title>
+    <style>
+      html, body {
+        margin: 0;      /* remove default margin */
+        height: 100%;   /* make body fill the browser window */
+      }
+      canvas {
+        width: 100%;
+        height: 100%;
+        display: block;
+      }
+      .fit-container {
+        width: 100%;
+        height: 100%;
+      }
+      .resizable {
+        resize: both;
+        overflow: scroll;  /* required because resize doesn't work with overflow: visible, the default */
+        max-width: 100%;
+        max-height: 100%;
+      }
+    </style>
+    <script defer src="main.js" type="module"></script>
+    <gscript defer type="module" src="../../js/iframe-helper.js"></script>
+  </head>
+  <body>
+    <div id="container" class="fit-container">
+      <canvas></canvas>
+    </div>
+  </body>
+</html>
diff --git a/sample/resizeObserverHDDPI/main.ts b/sample/resizeObserverHDDPI/main.ts
@@ -0,0 +1,164 @@
+import { GUI } from 'dat.gui';
+import checkerWGSL from './checker.wgsl';
+
+const canvas = document.querySelector('canvas') as HTMLCanvasElement;
+const adapter = await navigator.gpu.requestAdapter();
+const device = await adapter.requestDevice();
+
+const context = canvas.getContext('webgpu') as GPUCanvasContext;
+
+const presentationFormat = navigator.gpu.getPreferredCanvasFormat();
+
+context.configure({
+  device,
+  format: presentationFormat,
+  alphaMode: 'premultiplied',
+});
+
+const module = device.createShaderModule({
+  code: checkerWGSL,
+});
+const pipeline = device.createRenderPipeline({
+  layout: 'auto',
+  vertex: { module },
+  fragment: {
+    module,
+    targets: [
+      {
+        format: presentationFormat,
+      },
+    ],
+  },
+});
+
+// These offsets are in f32/u32 offset.
+enum UniformOffset {
+  color0 = 0,
+  color1 = 4,
+  size = 8,
+}
+
+const uniformValuesAsF32 = new Float32Array(12); // 2 vec4fs, 1 u32, 3 padding
+const uniformValuesAsU32 = new Uint32Array(uniformValuesAsF32.buffer);
+const uniformBuffer = device.createBuffer({
+  size: uniformValuesAsF32.byteLength,
+  usage: GPUBufferUsage.UNIFORM | GPUBufferUsage.COPY_DST,
+});
+
+const bindGroup = device.createBindGroup({
+  layout: pipeline.getBindGroupLayout(0),
+  entries: [
+    {
+      binding: 0,
+      resource: { buffer: uniformBuffer },
+    },
+  ],
+});
+
+const settings = {
+  color0: '#FF0000',
+  color1: '#00FFFF',
+  size: 1,
+  resizable: false,
+  fullscreen() {
+    if (document.fullscreenElement) {
+      document.exitFullscreen();
+    } else {
+      document.body.requestFullscreen();
+    }
+  },
+};
+
+const containerElem = document.querySelector('#container') as HTMLElement;
+
+const gui = new GUI();
+gui.addColor(settings, 'color0').onChange(frame);
+gui.addColor(settings, 'color1').onChange(frame);
+gui.add(settings, 'size', 1, 32, 1).name('checker size').onChange(frame);
+gui.add(settings, 'fullscreen');
+gui.add(settings, 'resizable').onChange(() => {
+  const { resizable } = settings;
+  // Get these before we adjust the CSS because our canvas is sized in device pixels
+  // and so will expand if we stop constraining it with CSS
+  const width = containerElem.clientWidth;
+  const height = containerElem.clientHeight;
+
+  containerElem.classList.toggle('resizable', resizable);
+  containerElem.classList.toggle('fit-container', !resizable);
+
+  containerElem.style.width = resizable ? `${width}px` : '';
+  containerElem.style.height = resizable ? `${height}px` : '';
+});
+
+// Given a CSS color, returns the color in 0 to 1 RGBA values.
+const cssColorToRGBA = (function () {
+  const ctx = new OffscreenCanvas(1, 1).getContext('2d', {
+    willReadFrequently: true,
+  });
+  return function (color: string) {
+    ctx.clearRect(0, 0, 1, 1);
+    ctx.fillStyle = color;
+    ctx.fillRect(0, 0, 1, 1);
+    return [...ctx.getImageData(0, 0, 1, 1).data].map((v) => v / 255);
+  };
+})();
+
+function frame() {
+  uniformValuesAsF32.set(cssColorToRGBA(settings.color0), UniformOffset.color0);
+  uniformValuesAsF32.set(cssColorToRGBA(settings.color1), UniformOffset.color1);
+  uniformValuesAsU32[UniformOffset.size] = settings.size;
+
+  device.queue.writeBuffer(uniformBuffer, 0, uniformValuesAsF32);
+
+  const commandEncoder = device.createCommandEncoder();
+
+  const renderPassDescriptor: GPURenderPassDescriptor = {
+    colorAttachments: [
+      {
+        view: context.getCurrentTexture().createView(),
+        clearValue: { r: 0.2, g: 0.2, b: 0.2, a: 1.0 },
+        loadOp: 'clear',
+        storeOp: 'store',
+      },
+    ],
+  };
+
+  const passEncoder = commandEncoder.beginRenderPass(renderPassDescriptor);
+  passEncoder.setPipeline(pipeline);
+  passEncoder.setBindGroup(0, bindGroup);
+  passEncoder.draw(3);
+  passEncoder.end();
+
+  device.queue.submit([commandEncoder.finish()]);
+}
+
+function getDevicePixelContentBoxSize(entry: ResizeObserverEntry) {
+  // Safari does not support devicePixelContentBoxSize
+  if (entry.devicePixelContentBoxSize) {
+    return {
+      width: entry.devicePixelContentBoxSize[0].inlineSize,
+      height: entry.devicePixelContentBoxSize[0].blockSize,
+    };
+  } else {
+    // These values not correct but they're as close as you can get in Safari
+    return {
+      width: entry.contentBoxSize[0].inlineSize * devicePixelRatio,
+      height: entry.contentBoxSize[0].blockSize * devicePixelRatio,
+    };
+  }
+}
+
+const { maxTextureDimension2D } = device.limits;
+const observer = new ResizeObserver(([entry]) => {
+  // Note: If you are using requestAnimationFrame you should
+  // only record the size here but set it in the requestAnimationFrame callback
+  // otherwise you'll get flicker when resizing.
+  const { width, height } = getDevicePixelContentBoxSize(entry);
+
+  // A size of 0 will cause an error when we call getCurrentTexture.
+  // A size > maxTextureDimension2D will also an error when we call getCurrentTexture.
+  canvas.width = Math.max(1, Math.min(width, maxTextureDimension2D));
+  canvas.height = Math.max(1, Math.min(height, maxTextureDimension2D));
+  frame();
+});
+observer.observe(canvas);
diff --git a/sample/resizeObserverHDDPI/meta.ts b/sample/resizeObserverHDDPI/meta.ts
@@ -0,0 +1,6 @@
+export default {
+  name: 'ResizeObserver HD-DPI Fullscreen',
+  description: `This example shows how use ResizeObserver, handle HD-DPI correctly, and Fullscreen`,
+  filename: 'sample/resizeObserverHDDPI',
+  sources: [{ path: 'main.ts' }, { path: 'checker.wgsl' }],
+};
diff --git a/src/samples.ts b/src/samples.ts
@@ -16,6 +16,7 @@ import normalMap from '../sample/normalMap/meta';
 import particles from '../sample/particles/meta';
 import renderBundles from '../sample/renderBundles/meta';
 import resizeCanvas from '../sample/resizeCanvas/meta';
+import resizeObserverHDDPI from '../sample/resizeObserverHDDPI/meta';
 import reversedZ from '../sample/reversedZ/meta';
 import rotatingCube from '../sample/rotatingCube/meta';
 import samplerParameters from '../sample/samplerParameters/meta';
@@ -118,6 +119,7 @@ export const pageCategories: PageCategory[] = [
       'Demos integrating WebGPU with other functionalities of the web platform.',
     samples: {
       resizeCanvas,
+      resizeObserverHDDPI,
       videoUploading,
       worker,
     },