Missing layout invalidation for position-fallback changes

When the position-fallback property changes, the layout may change. Add the property to computed_style_diff_functions.json5. Bug: 1381609 Change-Id: I3d3d88ef7cbb512ca4e6ca3ad0213d8b872bd9a9 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4020512 Commit-Queue: Rune Lillesveen <futhark@chromium.org> Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org> Cr-Commit-Position: refs/heads/main@{#1070568}
chromium · Nov 11, 2022 · dcc4b23 · dcc4b23
1 parent 5effd94
commit dcc4b23
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diff --git a/third_party/blink/renderer/core/style/computed_style_diff_functions.json5 b/third_party/blink/renderer/core/style/computed_style_diff_functions.json5
@@ -101,7 +101,8 @@
                 "BaselineShiftType", "baseline-shift", "dominant-baseline",
                 "CssDominantBaseline", "text-anchor",
                 "stroke-width", "stroke-miterlimit", "stroke-linecap", "stroke-linejoin",
-                "marker-end", "marker-mid", "marker-start", "scrollbar-width", "object-view-box"],
+                "marker-end", "marker-mid", "marker-start", "scrollbar-width", "object-view-box",
+                "position-fallback"],
         methods_to_diff: [
           {
             method: "BorderLeftWidth()",

diff --git a/...party/blink/web_tests/external/wpt/css/css-anchor-position/position-fallback-dynamic.html b/...party/blink/web_tests/external/wpt/css/css-anchor-position/position-fallback-dynamic.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<title>CSS Anchor Positioning Test: Dynamically change position via position-fallback property</title>
+<link rel="help" href="https://drafts.csswg.org/css-anchor-1/#fallback">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<style>
+  body { margin: 0; }
+
+  @position-fallback --fallback1 {
+    @try {
+      left: anchor(--a1 right);
+    }
+  }
+  #anchor {
+    anchor-name: --a1;
+    width: 100px;
+    height: 100px;
+  }
+  #anchored {
+    position: absolute;
+    width: 100px;
+    height: 100px;
+  }
+</style>
+<div id="anchor"></div>
+<div id="anchored"></div>
+<script>
+  test(() => {
+    assert_equals(anchored.offsetLeft, 0);
+  }, "Initial static left position is 0");
+
+  test(() => {
+    anchored.style.positionFallback = "--fallback1";
+    assert_equals(anchored.offsetLeft, 100);
+  }, "Left position set to right edge of anchor with @position-fallback");
+</script>