Add perf-test for many paint layers.

Now that we've removed UpdateLayerPositionsAfterLayout, add a perf test so that nobody in the future adds code which iterates over all the paint layers (or similar) after each layout. Bug: 504567 Change-Id: Ie379f5e4ec0228ac8318e9e589fdcfaf0dc88e21 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4994412 Commit-Queue: Morten Stenshorne <mstensho@chromium.org> Auto-Submit: Ian Kilpatrick <ikilpatrick@chromium.org> Reviewed-by: Morten Stenshorne <mstensho@chromium.org> Cr-Commit-Position: refs/heads/main@{#1217915}
qweri0p · Oct 31, 2023 · 1f286ad · 1f286ad
1 parent aca20b4
commit 1f286ad
Showing 1 changed file with 42 additions and 0 deletions.
diff --git a/third_party/blink/perf_tests/layout/layer-overhead.html b/third_party/blink/perf_tests/layout/layer-overhead.html
@@ -0,0 +1,42 @@
+<!DOCTYPE html>
+<title>Tests the overhead of many paint layers - don't add code which iterates over every paint layer upon each layout!</title>
+<style>
+#container {
+  position: relative;
+  width: 100px;
+  height: 200px;
+  overflow: hidden;
+}
+#container > div {
+  overflow: hidden;
+}
+#target {
+  position: relative;
+  width: 100px;
+  height: 100px;
+  overflow: hidden;
+  top: 0px;
+}
+</style>
+<script src="../resources/runner.js"></script>
+<body>
+  <pre id="log"></pre>
+  <div id="container"></div>
+  <div id="target"></div>
+  <script>
+    let container = document.getElementById('container');
+    for (let i = 0; i < 50000; i++) {
+      container.appendChild(document.createElement('div'));
+    }
+    PerfTestRunner.measureRunsPerSecond({
+      description: 'Measures performance of many paint layers existing in the DOM',
+      run: () => {
+        let target = document.getElementById('target');
+        target.style.top = '10px';
+        PerfTestRunner.forceLayout();
+        target.style.top = '0px';
+        PerfTestRunner.forceLayout();
+      },
+    });
+  </script>
+</body>