From 61bd698c9c67129e71cbdf7a62b6b76412e47ddb Mon Sep 17 00:00:00 2001
From: Gregg Tavares <github@greggman.com>
Date: Thu, 9 Jan 2025 10:37:57 -0800
Subject: [PATCH] add dpr test

---
 .../dpr-zoom-test-with-visualviewport.html    | 166 ++++++++++++++++++
 1 file changed, 166 insertions(+)
 create mode 100644 test/devicepixelcontentbox-with-visualviewport-scale/dpr-zoom-test-with-visualviewport.html
diff --git a/test/devicepixelcontentbox-with-visualviewport-scale/dpr-zoom-test-with-visualviewport.html b/test/devicepixelcontentbox-with-visualviewport-scale/dpr-zoom-test-with-visualviewport.html
new file mode 100644
index 0000000..4eebdfd
--- /dev/null
+++ b/test/devicepixelcontentbox-with-visualviewport-scale/dpr-zoom-test-with-visualviewport.html
@@ -0,0 +1,166 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <title>WebGPU Resize Canvas - Pixel Perfect</title>
+    <style>
+@import url(https://webgpufundamentals.org/webgpu/resources/webgpu-lesson.css);
+html, body {
+  margin: 0;       /* remove the default margin          */
+  height: 100%;    /* make the html,body fill the page   */
+}
+canvas {
+  display: block;  /* make the canvas act like a block   */
+  width: 100%;     /* make the canvas fill its container */
+  height: 100%;
+}
+#info {
+  position: absolute;
+  left: 0;
+  top: 0;
+  padding: 0.5em;
+  margin: 0;
+  background-color: rgba(0, 0, 0, 0.7);
+  color: white;
+}
+    </style>
+  </head>
+  <body>
+<canvas></canvas>
+<pre id="info"></pre>
+  </body>
+  <script>
+// WebGPU Resize Canvas - Pixel Perfect
+// from https://webgpufundamentals.org/webgpu/webgpu-resize-pixel-perfect.html
+
+const info = document.querySelector('#info');
+
+async function main() {
+  const adapter = await navigator.gpu?.requestAdapter();
+  const device = await adapter?.requestDevice();
+  if (!device) {
+    fail('need a browser that supports WebGPU');
+    return;
+  }
+
+  // Get a WebGPU context from the canvas and configure it
+  const canvas = document.querySelector('canvas');
+  const context = canvas.getContext('webgpu');
+  const presentationFormat = navigator.gpu.getPreferredCanvasFormat();
+  context.configure({
+    device,
+    format: presentationFormat,
+  });
+
+  const module = device.createShaderModule({
+    label: 'hardcoded checkerboard triangle shaders',
+    code: `
+      struct OurVertexShaderOutput {
+        @builtin(position) position: vec4f,
+      };
+
+      @vertex fn vs(
+        @builtin(vertex_index) vertexIndex : u32
+      ) -> OurVertexShaderOutput {
+        let pos = array(
+          vec2f(-1.0,  3.0),
+          vec2f( 3.0, -1.0),
+          vec2f(-1.0, -1.0),
+        );
+
+        var vsOutput: OurVertexShaderOutput;
+        vsOutput.position = vec4f(pos[vertexIndex], 0.0, 1.0);
+        return vsOutput;
+      }
+
+      @fragment fn fs(fsInput: OurVertexShaderOutput) -> @location(0) vec4f {
+        let hv = vec2f(floor(fsInput.position.xy % 2));
+        return vec4f(1, 0, 1, 1) * hv.x +
+               vec4f(0, 1, 0, 1) * hv.y;
+      }
+    `,
+  });
+
+  const pipeline = device.createRenderPipeline({
+    label: 'hardcoded checkerboard triangle pipeline',
+    layout: 'auto',
+    vertex: {
+      module,
+    },
+    fragment: {
+      module,
+      targets: [{ format: presentationFormat }],
+    },
+  });
+
+  const renderPassDescriptor = {
+    label: 'our basic canvas renderPass',
+    colorAttachments: [
+      {
+        // view: <- to be filled out when we render
+        clearValue: [0.3, 0.3, 0.3, 1],
+        loadOp: 'clear',
+        storeOp: 'store',
+      },
+    ],
+  };
+
+  let renderCount = 0;
+  const elemSizes = new WeakMap();
+  function render() {
+    const { width, height } = elemSizes.get(canvas);
+    canvas.width = Math.max(1, Math.min(Math.round(width * visualViewport.scale), device.limits.maxTextureDimension2D));
+    canvas.height = Math.max(1, Math.min(Math.round(height * visualViewport.scale), device.limits.maxTextureDimension2D));
+
+    info.textContent = `\
+    devicePixelRatio: ${devicePixelRatio}
+         canvas size: ${canvas.width}x${canvas.height}
+visualViewport.scale: ${visualViewport.scale}
+`;
+
+    // Get the current texture from the canvas context and
+    // set it as the texture to render to.
+    renderPassDescriptor.colorAttachments[0].view =
+        context.getCurrentTexture().createView();
+
+    const encoder = device.createCommandEncoder({ label: 'our encoder' });
+    const pass = encoder.beginRenderPass(renderPassDescriptor);
+    pass.setPipeline(pipeline);
+    pass.draw(3);  // call our vertex shader 3 times
+    pass.end();
+
+    const commandBuffer = encoder.finish();
+    device.queue.submit([commandBuffer]);
+  }
+
+  const observer = new ResizeObserver(entries => {
+    for (const entry of entries) {
+      const width = (entry.devicePixelContentBoxSize?.[0].inlineSize ||
+                    entry.contentBoxSize[0].inlineSize * devicePixelRatio);
+      const height = (entry.devicePixelContentBoxSize?.[0].blockSize ||
+                     entry.contentBoxSize[0].blockSize * devicePixelRatio);
+      elemSizes.set(entry.target, { width, height });
+      // re-render
+      render();
+    }
+  });
+
+  visualViewport.addEventListener('resize', render);
+
+  try {
+    observer.observe(canvas, { box: 'device-pixel-content-box' });
+  } catch {
+    observer.observe(canvas, { box: 'content-box' });
+  }
+}
+
+function fail(msg) {
+  // eslint-disable-next-line no-alert
+  alert(msg);
+}
+
+main();
+  
+  </script>
+</html>
