Don't always make backing store for -webkit-backface-visibility:hidden

https://bugs.webkit.org/show_bug.cgi?id=132420 Reviewed by Sam Weinig. Source/WebCore: Previously, -webkit-backface-visibility:hidden unconditionally created compositing layers with backing store. This results in high memory use on pages with this style applied to many elements (a cargo-cult "optimization"). Fix by only having -webkit-backface-visibility:hidden create compositing layers if some ancestor has a 3D transform. That's the only scenario in which the element can be flipped around to reveal the back side, so the only time we need to do compositing for this property. In future, we could be smarter, and only consider 3D transforms in the current preserve-3d context. Tests: compositing/backing/backface-visibility-in-3dtransformed.html compositing/backing/backface-visibility-in-transformed.html compositing/backing/backface-visibility.html * rendering/RenderLayer.cpp: (WebCore::RenderLayer::RenderLayer): (WebCore::RenderLayer::updateLayerPositions): (WebCore::RenderLayer::hitTestLayer): * rendering/RenderLayer.h: * rendering/RenderLayerCompositor.cpp: (WebCore::RenderLayerCompositor::requiresCompositingLayer): (WebCore::RenderLayerCompositor::requiresOwnBackingStore): (WebCore::RenderLayerCompositor::requiresCompositingForBackfaceVisibility): * rendering/RenderLayerCompositor.h: LayoutTests: Dump layers for elements with backface-visibility: hidden with various types of ancestors. * compositing/backing/backface-visibility-expected.txt: Added. * compositing/backing/backface-visibility-in-3dtransformed-expected.txt: Added. * compositing/backing/backface-visibility-in-3dtransformed.html: Added. * compositing/backing/backface-visibility-in-transformed-expected.txt: Added. * compositing/backing/backface-visibility-in-transformed.html: Added. * compositing/backing/backface-visibility.html: Added. * inspector-protocol/layers/layers-anonymous.html: Don't use backface-visibility for force a layer. Canonical link: https://commits.webkit.org/150473@main git-svn-id: https://svn.webkit.org/repository/webkit/trunk@168119 268f45cc-cd09-0410-ab3c-d52691b4dbfc
WebKit · May 1, 2014 · 90191e2 · 90191e2
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diff --git a/LayoutTests/ChangeLog b/LayoutTests/ChangeLog
@@ -1,3 +1,22 @@
+2014-05-01  Simon Fraser  <simon.fraser@apple.com>
+
+        Don't always make backing store for -webkit-backface-visibility:hidden
+        https://bugs.webkit.org/show_bug.cgi?id=132420
+
+        Reviewed by Sam Weinig.
+
+        Dump layers for elements with backface-visibility: hidden with various types
+        of ancestors.
+
+        * compositing/backing/backface-visibility-expected.txt: Added.
+        * compositing/backing/backface-visibility-in-3dtransformed-expected.txt: Added.
+        * compositing/backing/backface-visibility-in-3dtransformed.html: Added.
+        * compositing/backing/backface-visibility-in-transformed-expected.txt: Added.
+        * compositing/backing/backface-visibility-in-transformed.html: Added.
+        * compositing/backing/backface-visibility.html: Added.
+        * inspector-protocol/layers/layers-anonymous.html: Don't use backface-visibility
+        for force a layer.
+
 2014-05-01  Brent Fulgham  <bfulgham@apple.com>
 
         Fix handling of attributes prior to compiling shader

diff --git a/LayoutTests/compositing/backing/backface-visibility-expected.txt b/LayoutTests/compositing/backing/backface-visibility-expected.txt
@@ -0,0 +1,3 @@
+Should be no layers here.
+
+
diff --git a/LayoutTests/compositing/backing/backface-visibility-in-3dtransformed-expected.txt b/LayoutTests/compositing/backing/backface-visibility-in-3dtransformed-expected.txt
@@ -0,0 +1,28 @@
+Should be several layers here.
+
+(GraphicsLayer
+  (bounds 800.00 600.00)
+  (children 1
+    (GraphicsLayer
+      (bounds 800.00 600.00)
+      (contentsOpaque 1)
+      (children 1
+        (GraphicsLayer
+          (position 8.00 50.00)
+          (bounds 122.00 122.00)
+          (drawsContent 1)
+          (transform [1.00 0.00 0.00 0.00] [0.00 1.00 0.00 0.00] [0.00 0.00 1.00 0.00] [0.00 0.00 10.00 1.00])
+          (children 1
+            (GraphicsLayer
+              (position 11.00 11.00)
+              (bounds 100.00 100.00)
+              (contentsOpaque 1)
+              (backfaceVisibility hidden)
+            )
+          )
+        )
+      )
+    )
+  )
+)
+
diff --git a/LayoutTests/compositing/backing/backface-visibility-in-3dtransformed.html b/LayoutTests/compositing/backing/backface-visibility-in-3dtransformed.html
@@ -0,0 +1,46 @@
+<!DOCTYPE html>
+
+<html>
+<head>
+    <style>
+        .container {
+            height: 100px;
+            width: 100px;
+            padding: 10px;
+            border: 1px solid gray;
+        }
+        .box {
+          width: 100px;
+          height: 100px;
+          background-color: silver;
+        }
+
+        .transformed {
+            -webkit-transform: translateZ(10px);
+        }
+        .backface-hidden {
+            -webkit-backface-visibility: hidden;
+        }
+    </style>
+    <script>
+        if (window.testRunner)
+            testRunner.dumpAsText();
+
+        function dumpLayers()
+        {
+            var layersResult = document.getElementById('layers');
+            if (window.testRunner)
+                layersResult.innerText = window.internals.layerTreeAsText(document);
+
+        }
+        window.addEventListener('load', dumpLayers, false)
+    </script>
+</head>
+<body>
+    <p>Should be several layers here.</p>
+    <div class="transformed container">
+        <div class="backface-hidden box"></div>
+    </div>
+<pre id="layers"></pre>
+</body>
+</html>
diff --git a/LayoutTests/compositing/backing/backface-visibility-in-transformed-expected.txt b/LayoutTests/compositing/backing/backface-visibility-in-transformed-expected.txt
@@ -0,0 +1,3 @@
+Should be no layers here.
+
+
diff --git a/LayoutTests/compositing/backing/backface-visibility-in-transformed.html b/LayoutTests/compositing/backing/backface-visibility-in-transformed.html
@@ -0,0 +1,46 @@
+<!DOCTYPE html>
+
+<html>
+<head>
+    <style>
+        .container {
+            height: 100px;
+            width: 100px;
+            padding: 10px;
+            border: 1px solid gray;
+        }
+        .box {
+          width: 100px;
+          height: 100px;
+          background-color: silver;
+        }
+
+        .transformed {
+            -webkit-transform: translate(10px, 10px);
+        }
+        .backface-hidden {
+            -webkit-backface-visibility: hidden;
+        }
+    </style>
+    <script>
+        if (window.testRunner)
+            testRunner.dumpAsText();
+
+        function dumpLayers()
+        {
+            var layersResult = document.getElementById('layers');
+            if (window.testRunner)
+                layersResult.innerText = window.internals.layerTreeAsText(document);
+
+        }
+        window.addEventListener('load', dumpLayers, false)
+    </script>
+</head>
+<body>
+    <p>Should be no layers here.</p>
+    <div class="transformed container">
+        <div class="backface-hidden box"></div>
+    </div>
+<pre id="layers"></pre>
+</body>
+</html>
diff --git a/LayoutTests/compositing/backing/backface-visibility.html b/LayoutTests/compositing/backing/backface-visibility.html
@@ -0,0 +1,35 @@
+<!DOCTYPE html>
+
+<html>
+<head>
+    <style>
+        .box {
+          width: 100px;
+          height: 100px;
+          background-color: silver;
+        }
+
+        .backface-hidden {
+            -webkit-backface-visibility: hidden;
+        }
+    </style>
+    <script>
+        if (window.testRunner)
+            testRunner.dumpAsText();
+
+        function dumpLayers()
+        {
+            var layersResult = document.getElementById('layers');
+            if (window.testRunner)
+                layersResult.innerText = window.internals.layerTreeAsText(document);
+
+        }
+        window.addEventListener('load', dumpLayers, false)
+    </script>
+</head>
+<body>
+    <p>Should be no layers here.</p>
+    <div class="backface-hidden box"></div>
+<pre id="layers"></pre>
+</body>
+</html>
diff --git a/LayoutTests/inspector-protocol/layers/layers-anonymous.html b/LayoutTests/inspector-protocol/layers/layers-anonymous.html
@@ -127,7 +127,7 @@
 
     #first-letter::first-letter {
         float: left;
-        -webkit-backface-visibility: hidden;
+        -webkit-transform: translateZ(0);
     }
 
 </style>

diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
@@ -1,3 +1,35 @@
+2014-05-01  Simon Fraser  <simon.fraser@apple.com>
+
+        Don't always make backing store for -webkit-backface-visibility:hidden
+        https://bugs.webkit.org/show_bug.cgi?id=132420
+
+        Reviewed by Sam Weinig.
+
+        Previously, -webkit-backface-visibility:hidden unconditionally created
+        compositing layers with backing store. This results in high memory use
+        on pages with this style applied to many elements (a cargo-cult "optimization").
+
+        Fix by only having -webkit-backface-visibility:hidden create compositing layers
+        if some ancestor has a 3D transform. That's the only scenario in which the
+        element can be flipped around to reveal the back side, so the only time we need
+        to do compositing for this property. In future, we could be smarter, and only
+        consider 3D transforms in the current preserve-3d context.
+
+        Tests: compositing/backing/backface-visibility-in-3dtransformed.html
+               compositing/backing/backface-visibility-in-transformed.html
+               compositing/backing/backface-visibility.html
+
+        * rendering/RenderLayer.cpp:
+        (WebCore::RenderLayer::RenderLayer):
+        (WebCore::RenderLayer::updateLayerPositions):
+        (WebCore::RenderLayer::hitTestLayer):
+        * rendering/RenderLayer.h:
+        * rendering/RenderLayerCompositor.cpp:
+        (WebCore::RenderLayerCompositor::requiresCompositingLayer):
+        (WebCore::RenderLayerCompositor::requiresOwnBackingStore):
+        (WebCore::RenderLayerCompositor::requiresCompositingForBackfaceVisibility):
+        * rendering/RenderLayerCompositor.h:
+
 2014-05-01  Alex Christensen  <achristensen@webkit.org>
 
         Finish updating ANGLE.

diff --git a/Source/WebCore/rendering/RenderLayer.cpp b/Source/WebCore/rendering/RenderLayer.cpp
@@ -169,6 +169,8 @@ RenderLayer::RenderLayer(RenderLayerModelObject& rendererLayerModelObject)
     , m_3DTransformedDescendantStatusDirty(true)
     , m_has3DTransformedDescendant(false)
     , m_hasCompositingDescendant(false)
+    , m_hasTransformedAncestor(false)
+    , m_has3DTransformedAncestor(false)
     , m_indirectCompositingReason(NoIndirectCompositingReason)
     , m_viewportConstrainedNotCompositedReason(NoNotCompositedReason)
 #if PLATFORM(IOS)
@@ -449,6 +451,8 @@ void RenderLayer::updateLayerPositions(RenderGeometryMap* geometryMap, UpdateLay
         clearRepaintRects();
 
     m_repaintStatus = NeedsNormalRepaint;
+    m_hasTransformedAncestor = flags & SeenTransformedLayer;
+    m_has3DTransformedAncestor = flags & Seen3DTransformedLayer;
 
     // Go ahead and update the reflection's position and size.
     if (m_reflection)
@@ -467,6 +471,12 @@ void RenderLayer::updateLayerPositions(RenderGeometryMap* geometryMap, UpdateLay
     if (renderer().hasColumns())
         flags |= UpdatePagination;
 
+    if (transform()) {
+        flags |= SeenTransformedLayer;
+        if (!transform()->isAffine())
+            flags |= Seen3DTransformedLayer;
+    }
+
     for (RenderLayer* child = firstChild(); child; child = child->nextSibling())
         child->updateLayerPositions(geometryMap, flags);
 
@@ -4931,7 +4941,7 @@ RenderLayer* RenderLayer::hitTestLayer(RenderLayer* rootLayer, RenderLayer* cont
         // We computed the correct state in the caller (above code), so just reference it.
         ASSERT(transformState);
         localTransformState = const_cast<HitTestingTransformState*>(transformState);
-    } else if (transformState || m_has3DTransformedDescendant || preserves3D()) {
+    } else if (transformState || has3DTransformedDescendant() || preserves3D()) {
         // We need transform state for the first time, or to offset the container state, so create it here.
         localTransformState = createLocalTransformState(rootLayer, containerLayer, hitTestRect, hitTestLocation, transformState);
     }

diff --git a/Source/WebCore/rendering/RenderLayer.h b/Source/WebCore/rendering/RenderLayer.h
@@ -499,7 +499,9 @@ class RenderLayer final : public ScrollableArea {
         NeedsFullRepaintInBacking = 1 << 1,
         IsCompositingUpdateRoot = 1 << 2,
         UpdateCompositingLayers = 1 << 3,
-        UpdatePagination = 1 << 4
+        UpdatePagination = 1 << 4,
+        SeenTransformedLayer = 1 << 5,
+        Seen3DTransformedLayer = 1 << 6
     };
     typedef unsigned UpdateLayerPositionsFlags;
     static const UpdateLayerPositionsFlags defaultFlags = CheckForRepaint | IsCompositingUpdateRoot | UpdateCompositingLayers;
@@ -1113,10 +1115,11 @@ class RenderLayer final : public ScrollableArea {
     void updateDescendantDependentFlags(HashSet<const RenderObject*>* outOfFlowDescendantContainingBlocks = 0);
     bool checkIfDescendantClippingContextNeedsUpdate(bool isClipping);
 
-    // This flag is computed by RenderLayerCompositor, which knows more about 3d hierarchies than we do.
-    void setHas3DTransformedDescendant(bool b) { m_has3DTransformedDescendant = b; }
     bool has3DTransformedDescendant() const { return m_has3DTransformedDescendant; }
-
+
+    bool hasTransformedAncestor() const { return m_hasTransformedAncestor; }
+    bool has3DTransformedAncestor() const { return m_has3DTransformedAncestor; }
+
     void dirty3DTransformedDescendantStatus();
     // Both updates the status, and returns true if descendants of this have 3d.
     bool update3DTransformedDescendantStatus();
@@ -1253,6 +1256,10 @@ class RenderLayer final : public ScrollableArea {
     bool m_has3DTransformedDescendant : 1;  // Set on a stacking context layer that has 3D descendants anywhere
                                             // in a preserves3D hierarchy. Hint to do 3D-aware hit testing.
     bool m_hasCompositingDescendant : 1; // In the z-order tree.
+
+    bool m_hasTransformedAncestor : 1;
+    bool m_has3DTransformedAncestor : 1;
+
     unsigned m_indirectCompositingReason : 3;
     unsigned m_viewportConstrainedNotCompositedReason : 2;
 

diff --git a/Source/WebCore/rendering/RenderLayerCompositor.cpp b/Source/WebCore/rendering/RenderLayerCompositor.cpp
@@ -2032,7 +2032,7 @@ bool RenderLayerCompositor::requiresCompositingLayer(const RenderLayer& layer, R
         || requiresCompositingForCanvas(*renderer)
         || requiresCompositingForPlugin(*renderer)
         || requiresCompositingForFrame(*renderer)
-        || (canRender3DTransforms() && renderer->style().backfaceVisibility() == BackfaceVisibilityHidden)
+        || requiresCompositingForBackfaceVisibility(*renderer)
         || clipsCompositingDescendants(*renderer->layer())
         || requiresCompositingForAnimation(*renderer)
         || requiresCompositingForFilters(*renderer)
@@ -2075,7 +2075,7 @@ bool RenderLayerCompositor::requiresOwnBackingStore(const RenderLayer& layer, co
         || requiresCompositingForCanvas(renderer)
         || requiresCompositingForPlugin(renderer)
         || requiresCompositingForFrame(renderer)
-        || (canRender3DTransforms() && renderer.style().backfaceVisibility() == BackfaceVisibilityHidden)
+        || requiresCompositingForBackfaceVisibility(renderer)
         || requiresCompositingForAnimation(renderer)
         || requiresCompositingForFilters(renderer)
         || requiresCompositingForPosition(renderer, layer)
@@ -2342,6 +2342,14 @@ bool RenderLayerCompositor::requiresCompositingForTransform(RenderLayerModelObje
     return renderer.hasTransform() && renderer.style().transform().has3DOperation();
 }
 
+bool RenderLayerCompositor::requiresCompositingForBackfaceVisibility(RenderLayerModelObject& renderer) const
+{
+    if (!(m_compositingTriggers & ChromeClient::ThreeDTransformTrigger))
+        return false;
+
+    return renderer.style().backfaceVisibility() == BackfaceVisibilityHidden && renderer.layer()->has3DTransformedAncestor();
+}
+
 bool RenderLayerCompositor::requiresCompositingForVideo(RenderLayerModelObject& renderer) const
 {
     if (!(m_compositingTriggers & ChromeClient::VideoTrigger))

diff --git a/Source/WebCore/rendering/RenderLayerCompositor.h b/Source/WebCore/rendering/RenderLayerCompositor.h
@@ -392,6 +392,7 @@ class RenderLayerCompositor : public GraphicsLayerClient, public GraphicsLayerUp
     // Whether a running transition or animation enforces the need for a compositing layer.
     bool requiresCompositingForAnimation(RenderLayerModelObject&) const;
     bool requiresCompositingForTransform(RenderLayerModelObject&) const;
+    bool requiresCompositingForBackfaceVisibility(RenderLayerModelObject&) const;
     bool requiresCompositingForVideo(RenderLayerModelObject&) const;
     bool requiresCompositingForCanvas(RenderLayerModelObject&) const;
     bool requiresCompositingForPlugin(RenderLayerModelObject&) const;

diff --git a/WebKit.xcworkspace/xcshareddata/xcschemes/All Source (target WebProcess).xcscheme b/WebKit.xcworkspace/xcshareddata/xcschemes/All Source (target WebProcess).xcscheme
@@ -115,9 +115,9 @@
             buildForAnalyzing = "YES">
             <BuildableReference
                BuildableIdentifier = "primary"
-               BlueprintIdentifier = "1AD7451818D0D26C006F3A1E"
-               BuildableName = "WebKit.framework"
-               BlueprintName = "WebKit"
+               BlueprintIdentifier = "9398100A0824BF01008DF038"
+               BuildableName = "WebKitLegacy.framework"
+               BlueprintName = "WebKitLegacy"
                ReferencedContainer = "container:Source/WebKit/WebKit.xcodeproj">
             </BuildableReference>
          </BuildActionEntry>

diff --git a/WebKit.xcworkspace/xcshareddata/xcschemes/All Source.xcscheme b/WebKit.xcworkspace/xcshareddata/xcschemes/All Source.xcscheme
@@ -115,9 +115,9 @@
             buildForAnalyzing = "YES">
             <BuildableReference
                BuildableIdentifier = "primary"
-               BlueprintIdentifier = "1AD7451818D0D26C006F3A1E"
-               BuildableName = "WebKit.framework"
-               BlueprintName = "WebKit"
+               BlueprintIdentifier = "9398100A0824BF01008DF038"
+               BuildableName = "WebKitLegacy.framework"
+               BlueprintName = "WebKitLegacy"
                ReferencedContainer = "container:Source/WebKit/WebKit.xcodeproj">
             </BuildableReference>
          </BuildActionEntry>