Avoid scheduling rendering updates for SVG animations on elements

nullhook · nullhook · commit b70eabc44142 · 2025-12-19T03:16:38.000-08:00
without renderers https://bugs.webkit.org/show_bug.cgi?id=298217 rdar://159647563 Reviewed by Antoine Quint. When SVG elements with SMIL animations (like animateTransform) are inside containers with hidden attribute, the legacy SVG engine was scheduling full page rendering updates every animation frame despite the elements having no renderer. Now when animations run on elements without renderers, we skip scheduling rendering updates entirely. * LayoutTests/svg/animations/animateTransform-hidden-no-rendering-updates-expected.txt: Added. * LayoutTests/svg/animations/animateTransform-hidden-no-rendering-updates.html: Added. * Source/WebCore/svg/SVGGraphicsElement.cpp: (WebCore::SVGGraphicsElement::svgAttributeChanged): Canonical link: https://commits.webkit.org/304744@main
diff --git a/LayoutTests/svg/animations/animateTransform-hidden-no-rendering-updates-expected.txt b/LayoutTests/svg/animations/animateTransform-hidden-no-rendering-updates-expected.txt
@@ -0,0 +1,10 @@
+Test that SVG animations on hidden elements do not trigger rendering updates.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS updateCount <= 5 is true
+PASS successfullyParsed is true
+
+TEST COMPLETE
+
diff --git a/LayoutTests/svg/animations/animateTransform-hidden-no-rendering-updates.html b/LayoutTests/svg/animations/animateTransform-hidden-no-rendering-updates.html
@@ -0,0 +1,69 @@
+<!DOCTYPE HTML>
+<html>
+
+<head>
+    <script src="../../resources/js-test.js"></script>
+    <style>
+        #container {
+            width: 100px;
+            height: 100px;
+        }
+    </style>
+</head>
+
+<body>
+    <div id="container" hidden>
+        <svg viewBox="0 0 100 100" width="100" height="100">
+            <circle cx="50" cy="50" fill="none" r="35" stroke="currentColor"
+                stroke-dasharray="164.93361431346415 56.97787143782138" stroke-width="6">
+                <animateTransform attributeName="transform" type="rotate" repeatCount="indefinite" dur="1s"
+                    values="0 50 50;90 50 50;180 50 50;360 50 50" keyTimes="0;0.40;0.65;1"></animateTransform>
+            </circle>
+        </svg>
+    </div>
+    <div id="console"></div>
+    <script>
+        window.jsTestIsAsync = true;
+
+        let updateCount = 0;
+
+        function sleepFor(duration) {
+            return new Promise(resolve => setTimeout(resolve, duration));
+        }
+
+        async function waitForRenderingUpdateCountToSettle() {
+            let renderingUpdateCount = 0;
+            do {
+                renderingUpdateCount = internals.renderingUpdateCount();
+                // Wait slightly more than 2 frames at 60fps (~33.33ms) to ensure
+                // any pending rendering updates have completed.
+                await sleepFor(34);
+            } while (internals.renderingUpdateCount() != renderingUpdateCount);
+
+            internals.startTrackingRenderingUpdates();
+        }
+
+        window.addEventListener('load', async () => {
+            if (!window.internals) {
+                finishJSTest();
+                return;
+            }
+
+            description('Test that SVG animations on hidden elements do not trigger rendering updates.');
+
+            internals.setSpeculativeTilingDelayDisabledForTesting(true);
+            
+            await waitForRenderingUpdateCountToSettle();
+
+            await sleepFor(250);
+
+            updateCount = internals.renderingUpdateCount();
+
+            shouldBeTrue('updateCount <= 5');
+
+            finishJSTest();
+        }, false);
+    </script>
+</body>
+
+</html>
diff --git a/Source/WebCore/svg/SVGGraphicsElement.cpp b/Source/WebCore/svg/SVGGraphicsElement.cpp
@@ -155,9 +155,10 @@ void SVGGraphicsElement::svgAttributeChanged(const QualifiedName& attrName)
             return;
         }
 
-        if (CheckedPtr renderer = this->renderer())
+        if (CheckedPtr renderer = this->renderer()) {
             renderer->setNeedsTransformUpdate();
-        updateSVGRendererForElementChange();
+            updateSVGRendererForElementChange();
+        }
         return;
     }
 

Original file line number	Diff line number	Diff line change
`@@ -155,9 +155,10 @@ void SVGGraphicsElement::svgAttributeChanged(const QualifiedName& attrName)`
`155`	`155`	`return;`
`156`	`156`	`}`
`157`	`157`
`158`		`- if (CheckedPtr renderer = this->renderer())`
	`158`	`+ if (CheckedPtr renderer = this->renderer()) {`
`159`	`159`	`renderer->setNeedsTransformUpdate();`
`160`		`- updateSVGRendererForElementChange();`
	`160`	`+ updateSVGRendererForElementChange();`
	`161`	`+ }`
`161`	`162`	`return;`
`162`	`163`	`}`
`163`	`164`