[Filters] Filters with outsets have to repaint all the filterRegion i…

…f GraphicsStyles are used https://bugs.webkit.org/show_bug.cgi?id=261856 rdar://115817290 Reviewed by Simon Fraser. The bounding box of a target element might all be clipped. But a filter effect, like drop shadow, may still be visible in the current viewport. If GraphicsStyles are used, we need to redraw the whole filterRegion. * LayoutTests/css3/filters/drop-shadow-target-clipped-expected.html: Added. * LayoutTests/css3/filters/drop-shadow-target-clipped.html: Added. * Source/WebCore/rendering/RenderLayerFilters.cpp: (WebCore::RenderLayerFilters::needsRedrawSourceImage const): (WebCore::RenderLayerFilters::beginFilterEffect): * Source/WebCore/rendering/RenderLayerFilters.h: Canonical link: https://commits.webkit.org/268282@main
WebKit · Sep 21, 2023 · 39763b0 · 39763b0
1 parent 3e1f054
commit 39763b0
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Showing 4 changed files with 66 additions and 1 deletion.
diff --git a/LayoutTests/css3/filters/drop-shadow-target-clipped-expected.html b/LayoutTests/css3/filters/drop-shadow-target-clipped-expected.html
@@ -0,0 +1,28 @@
+<style>
+    .box {
+        width: 300px;
+        height: 300px;
+        position: absolute;
+    }
+    .background-red {
+        top: 0;
+        left: 0;
+        background-color: red;
+    }
+    .background-green {
+        top: -100px;
+        left: -100px;
+        background-color: green;
+    }
+    .background-blue {
+        top: -200px;
+        left: -200px;
+        background-color: blue;
+    }
+</style>
+<body>
+    Three overlapping boxes should be displayed.
+    <div class="box background-red"></div>
+    <div class="box background-green"></div>
+    <div class="box background-blue"></div>
+</body>
diff --git a/LayoutTests/css3/filters/drop-shadow-target-clipped.html b/LayoutTests/css3/filters/drop-shadow-target-clipped.html
@@ -0,0 +1,30 @@
+<!-- webkit-test-runner [ GraphicsContextFiltersEnabled=true ] -->
+<style>
+    .box {
+        width: 300px;
+        height: 300px;
+        position: absolute;
+        background-color: black;
+    }
+    .drop-shadow-red {
+        top: -1000px;
+        left: -1000px;
+        filter: drop-shadow(1000px 1000px 0 red);
+    }
+    .drop-shadow-green {
+        top: -1000px;
+        left: -1000px;
+        filter: drop-shadow(900px 900px 0 green);
+    }
+    .drop-shadow-blue {
+        top: -1000px;
+        left: -1000px;
+        filter: drop-shadow(800px 800px 0 blue);
+    }
+</style>
+<body>
+    Three overlapping boxes should be displayed.
+    <div class="box drop-shadow-red"></div>
+    <div class="box drop-shadow-green"></div>
+    <div class="box drop-shadow-blue"></div>
+</body>
diff --git a/Source/WebCore/rendering/RenderLayerFilters.cpp b/Source/WebCore/rendering/RenderLayerFilters.cpp
@@ -62,6 +62,11 @@ bool RenderLayerFilters::hasFilterThatShouldBeRestrictedBySecurityOrigin() const
     return m_filter && m_filter->hasFilterThatShouldBeRestrictedBySecurityOrigin();
 }
 
+bool RenderLayerFilters::needsRedrawSourceImage() const
+{
+    return m_targetSwitcher && m_targetSwitcher->needsRedrawSourceImage();
+}
+
 void RenderLayerFilters::notifyFinished(CachedResource&, const NetworkLoadMetrics&)
 {
     // FIXME: This really shouldn't have to invalidate layer composition,
@@ -173,7 +178,7 @@ GraphicsContext* RenderLayerFilters::beginFilterEffect(RenderElement& renderer,
 
     if (!filter.hasFilterThatMovesPixels())
         m_repaintRect = dirtyRect;
-    else if (hasUpdatedBackingStore)
+    else if (hasUpdatedBackingStore || needsRedrawSourceImage())
         m_repaintRect = filterRegion;
     else {
         m_repaintRect = dirtyRect;

diff --git a/Source/WebCore/rendering/RenderLayerFilters.h b/Source/WebCore/rendering/RenderLayerFilters.h
@@ -73,6 +73,8 @@ class RenderLayerFilters final : private CachedSVGDocumentClient {
     void applyFilterEffect(GraphicsContext& destinationContext);
 
 private:
+    bool needsRedrawSourceImage() const;
+
     void notifyFinished(CachedResource&, const NetworkLoadMetrics&) final;
     void resetDirtySourceRect() { m_dirtySourceRect = LayoutRect(); }