Scroll To Text Fragement re-loads after every dynamic style sheet loa…

…d, and fights user scrolls to do so. https://bugs.webkit.org/show_bug.cgi?id=264195 rdar://112608578 Reviewed by Simon Fraser. In order to account for style changes adjusting the scroll of the page, after each dynamic style sheet load, we recall scrollToFragment to set the page at the correct position again. We need to stop automatically scrolling after the user has scrolled, as user scroll should trump all URL programatic scrolls. So we reset the flag that causes scrolls to happen when a user scroll is detected. * LayoutTests/http/tests/scroll-to-text-fragment/no-scroll-after-stylesheet-load-expected.txt: Added. * LayoutTests/http/tests/scroll-to-text-fragment/no-scroll-after-stylesheet-load.html: Added. * LayoutTests/resources/ui-helper.js: (window.UIHelper.async initiateUserScroll): * Source/WebCore/dom/Document.cpp: (WebCore::Document::didRemoveAllPendingStylesheet): * Source/WebCore/page/LocalFrameView.cpp: (WebCore::LocalFrameView::scrollToFragment): (WebCore::LocalFrameView::setWasScrolledByUser): * Source/WebCore/page/LocalFrameView.h: Canonical link: https://commits.webkit.org/272151@main
WebKit · Dec 16, 2023 · 2dd5d4c · 2dd5d4c
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diff --git a/LayoutTests/http/tests/scroll-to-text-fragment/no-scroll-after-stylesheet-load-expected.txt b/LayoutTests/http/tests/scroll-to-text-fragment/no-scroll-after-stylesheet-load-expected.txt
@@ -0,0 +1,3 @@
+PASS: Page scrolls to correct Text Fragment.
+PASS: Addition of dynamic style element did not adjust scroll.
+
diff --git a/LayoutTests/http/tests/scroll-to-text-fragment/no-scroll-after-stylesheet-load.html b/LayoutTests/http/tests/scroll-to-text-fragment/no-scroll-after-stylesheet-load.html
@@ -0,0 +1,98 @@
+<!DOCTYPE html>
+<meta charset="utf-8" />
+<title>Scroll to text fragment - ensure that loading a stylesheet doesn't cause the page to re-scroll</title>
+<meta name="assert" content="This test checks that loading a stylesheet doesn't cause the page to re-scroll.">
+
+<head>
+<script src="/js-test-resources/ui-helper.js"></script>
+
+<script>
+
+    document.addEventListener('readystatechange', () => {
+        if (document.readyState !== 'interactive')
+            return;
+        const link = document.createElement('link');
+        link.rel = 'stylesheet';
+        link.type = 'text/css';
+        link.media = 'all';
+        link.property = 'stylesheet';
+        link.href = 'not-even-a-file.css';
+        document.body.appendChild(link);
+    });
+
+    function adjustStyle() {
+        const head = document.head || document.getElementsByTagName("head")[0];
+        const styleElement = document.createElement('style');
+
+        styleElement.type = "text/css";
+        head.appendChild(styleElement);
+        const css = '#matches-nothing-in-dom {}';
+        const cssNode = document.createTextNode(css);
+        const childNodes = styleElement.childNodes;
+        const child = childNodes[0];
+
+        if (child)
+            styleElement.replaceChild(cssNode, child);
+        else
+            styleElement.appendChild(cssNode);
+    }
+
+    if (window.testRunner) {
+    testRunner.dumpAsText();
+    testRunner.waitUntilDone();
+    }
+
+
+ async function runTest()
+ {
+    if (!testRunner.runUIScript)
+        return;
+
+    location.href = "#:~:text=Scroll%20Point";
+    var output = "";
+
+    await UIHelper.ensurePresentationUpdate();
+
+    if (window.pageYOffset > 0)
+      output += "PASS: Page scrolls to correct Text Fragment.";
+    else 
+      output += "FAIL: Page does not scroll to correct Text Fragment.";
+    output += '<br>';
+
+    var scrollOffset = window.pageYOffset;
+
+    await UIHelper.initiateUserScroll();
+
+    adjustStyle();
+
+    await UIHelper.renderingUpdate();
+
+    if (window.pageYOffset != scrollOffset)
+      output += "PASS: Addition of dynamic style element did not adjust scroll.";
+    else
+      output += "FAIL: Addition of dynamic style element causes page to re-scroll. First Scroll: " + scrollOffset + " Second Scroll: " + window.pageYOffset;
+    output += '<br>';
+
+    var target = document.getElementById('target');
+    target.innerHTML = output;
+    target.style.paddingTop = "0px";
+
+    if (window.testRunner)
+        testRunner.notifyDone();
+  }
+
+  window.addEventListener('load', () => {
+    runTest();
+  }, false);
+</script>
+</head>
+
+<body>
+    <div id="target" style="padding-top: 10000px;">
+
+        <p>Scroll Point</p>
+
+    </div>
+</body>
+</html>
+
diff --git a/LayoutTests/platform/gtk/TestExpectations b/LayoutTests/platform/gtk/TestExpectations
@@ -2648,6 +2648,8 @@ fast/canvas/font-family-system-ui-canvas.html [ Skip ]
 
 fast/line-grid [ Skip ]
 
+http/tests/scroll-to-text-fragment/no-scroll-after-stylesheet-load.html [ Skip ]
+
 # Flaky tests Nov2023
 webkit.org/b/264680 compositing/transitions/transform-on-large-layer.html [ ImageOnlyFailure Pass ]
 webkit.org/b/264680 fast/canvas/offscreen-backing-store-attached.html [ ImageOnlyFailure Pass ]

diff --git a/LayoutTests/resources/ui-helper.js b/LayoutTests/resources/ui-helper.js
@@ -521,6 +521,16 @@ window.UIHelper = class UIHelper {
         return new Promise(resolve => setTimeout(resolve, ms));
     }
 
+    static async initiateUserScroll()
+    {
+        if (this.isIOSFamily()) {
+            await UIHelper.scrollTo(0, 10);
+        }
+        else {
+            await UIHelper.statelessMouseWheelScrollAt(10, 10, 0, 10);
+        }
+    }
+
     static scrollTo(x, y, unconstrained)
     {
         if (!this.isWebKit2()) {

diff --git a/Source/WebCore/page/LocalFrameView.cpp b/Source/WebCore/page/LocalFrameView.cpp
@@ -4665,6 +4665,10 @@ void LocalFrameView::setWasScrolledByUser(bool wasScrolledByUser)
     cancelScheduledScrolls();
     if (currentScrollType() == ScrollType::Programmatic)
         return;
+
+    if (wasScrolledByUser)
+        m_frame->document()->setGotoAnchorNeededAfterStylesheetsLoad(false);
+
     m_maintainScrollPositionAnchor = nullptr;
     if (m_wasScrolledByUser == wasScrolledByUser)
         return;

diff --git a/Source/WebKit/UIProcess/WebPageProxy.cpp b/Source/WebKit/UIProcess/WebPageProxy.cpp
@@ -12261,6 +12261,7 @@ void WebPageProxy::detectDataInAllFrames(OptionSet<WebCore::DataDetectorType> ty
         completionHandler({ });
         return;
     }
+
     sendWithAsyncReply(Messages::WebPage::DetectDataInAllFrames(types), WTFMove(completionHandler));
 }