Make ::backdrop renderers use background layers when possible

https://bugs.webkit.org/show_bug.cgi?id=248148 rdar://102566049 Reviewed by Simon Fraser. Right now, when rotating in fullscreen on iPad, there are white gaps around the edges. This was avoided by RenderFullscreen using "background layers" that are 3x the size with a negative offset. Now that RenderFullscreen is gone, we need to target ::backdrop pseudo elements that have: - The same rect as the RenderView - position: fixed, since position: absolute can allow scrolling away from the ::backdrop, since the containing block is the ICB - No transforms/clips/masks (since they intentionally do not cover the whole screen) Also clean up remainders of RenderFullscreen which has been removed in 255641@main. * LayoutTests/compositing/no-compositing-when-full-screen-is-present-expected.txt: * LayoutTests/compositing/no-compositing-when-full-screen-is-present.html: * LayoutTests/platform/gtk/compositing/no-compositing-when-full-screen-is-present-expected.txt: Update test expectations to reflect that ::backdrop is now layer backed in fullscreen. * LayoutTests/TestExpectations: * LayoutTests/fullscreen/full-screen-layer-dump-expected.txt: * LayoutTests/fullscreen/full-screen-layer-dump.html: Make test expectation more clear in the description to avoid regressing this test again, and update test expectation to reflect that "background layers" now work again. * Source/WebCore/rendering/RenderElement.cpp: (WebCore::RenderElement::propagateStyleToAnonymousChildren): * Source/WebCore/rendering/RenderLayerBacking.cpp: (WebCore::RenderLayerBacking::RenderLayerBacking): * Source/WebCore/rendering/RenderLayerCompositor.cpp: (WebCore::isDescendantOfFullScreenLayer): Consider the fullscreen element's associated ::backdrop as fullscreen layer, otherwise the renderer is never layer-backed meaning we can't use "background layers". We avoid backing non-fullscreen layers to optimize for power usage. * Source/WebCore/rendering/RenderObject.h: (WebCore::RenderObject::isAttachment const): (WebCore::RenderObject::isAnonymousBlock const): (WebCore::RenderObject::isRenderFullScreen const): Deleted. (WebCore::RenderObject::isRenderFullScreenPlaceholder const): Deleted. Canonical link: https://commits.webkit.org/257538@main
WebKit · Dec 8, 2022 · 2a5bd0f · 2a5bd0f
1 parent 60342c9
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diff --git a/LayoutTests/TestExpectations b/LayoutTests/TestExpectations
@@ -6176,9 +6176,6 @@ imported/w3c/web-platform-tests/xhr/send-after-setting-document-domain.htm [ Ski
 fast/text/text-edge-no-half-leading-simple.html [ Skip ]
 fast/text/text-edge-no-half-leading-with-line-height-simple.html [ Skip ]
 
-# This test isn't working as expected, it will be fixed in webkit.org/b/248148.
-webkit.org/b/248148 fullscreen/full-screen-layer-dump.html [ Failure ]
-
 # CSS Nesting
 imported/w3c/web-platform-tests/css/css-nesting/conditional-properties.html [ ImageOnlyFailure ]
 imported/w3c/web-platform-tests/css/css-nesting/conditional-rules.html [ ImageOnlyFailure ]

diff --git a/LayoutTests/compositing/no-compositing-when-full-screen-is-present-expected.txt b/LayoutTests/compositing/no-compositing-when-full-screen-is-present-expected.txt
@@ -1,4 +1,4 @@
-Test that only elements in fullscreen subtree get layer backed.
+Test that only elements in fullscreen subtree and the associated backdrop get layer backed.
 
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
@@ -17,7 +17,28 @@ foobar
       (bounds 800.00 600.00)
       (contentsOpaque 1)
       (backingStoreAttached 1)
-      (children 1
+      (children 2
+        (GraphicsLayer
+          (preserves3D 1)
+          (backingStoreAttached 0)
+          (children 1
+            (GraphicsLayer
+              (bounds 800.00 600.00)
+              (backingStoreAttached 1)
+              (children 2
+                (GraphicsLayer
+                  (anchor 0.00 0.00)
+                  (bounds 800.00 600.00)
+                  (backingStoreAttached 1)
+                )
+                (GraphicsLayer
+                  (bounds 800.00 600.00)
+                  (backingStoreAttached 1)
+                )
+              )
+            )
+          )
+        )
         (GraphicsLayer
           (preserves3D 1)
           (backingStoreAttached 0)

diff --git a/LayoutTests/compositing/no-compositing-when-full-screen-is-present.html b/LayoutTests/compositing/no-compositing-when-full-screen-is-present.html
@@ -9,7 +9,7 @@
 <script src="../resources/js-test.js"></script>
 <script>
 
-description("Test that only elements in fullscreen subtree get layer backed.");
+description("Test that only elements in fullscreen subtree and the associated backdrop get layer backed.");
 
 function goFullscreen() {
     host.webkitRequestFullscreen();

diff --git a/LayoutTests/fullscreen/full-screen-layer-dump-expected.txt b/LayoutTests/fullscreen/full-screen-layer-dump-expected.txt
@@ -1,24 +1,42 @@
+Test passes if you see a contents layer 3x the size and with a negative offset equal to the size:
+
 (GraphicsLayer
   (anchor 0.00 0.00)
   (bounds 800.00 600.00)
   (children 1
     (GraphicsLayer
       (bounds 800.00 600.00)
       (contentsOpaque 1)
-      (children 1
+      (children 2
         (GraphicsLayer
           (preserves3D 1)
           (children 1
             (GraphicsLayer
               (bounds 800.00 600.00)
-              (contentsOpaque 1)
-              (contents layer (background color)
-                (position 0.00 0.00)
-                (bounds 800.00 600.00)
+              (children 2
+                (GraphicsLayer
+                  (anchor 0.00 0.00)
+                  (bounds 800.00 600.00)
+                  (contents layer (background color)
+                    (position -800.00 -600.00)
+                    (bounds 2400.00 1800.00)
+                  )
+                )
+                (GraphicsLayer
+                  (bounds 800.00 600.00)
+                )
               )
             )
           )
         )
+        (GraphicsLayer
+          (preserves3D 1)
+          (children 1
+            (GraphicsLayer
+              (bounds 800.00 600.00)
+            )
+          )
+        )
       )
     )
   )

diff --git a/LayoutTests/fullscreen/full-screen-layer-dump.html b/LayoutTests/fullscreen/full-screen-layer-dump.html
@@ -23,7 +23,8 @@
         document.addEventListener('webkitfullscreenchange', event => {
             if (document.webkitIsFullScreen) {
                 setTimeout(() => {
-                    out.innerText = internals.layerTreeAsText(document, internals.LAYER_TREE_INCLUDES_CONTENT_LAYERS);
+                    out.innerText = "Test passes if you see a contents layer 3x the size and with a negative offset equal to the size:\n\n";
+                    out.innerText += internals.layerTreeAsText(document, internals.LAYER_TREE_INCLUDES_CONTENT_LAYERS);
                     document.webkitCancelFullScreen();
                 }, 0)
             } else 

diff --git a/LayoutTests/platform/gtk/compositing/no-compositing-when-full-screen-is-present-expected.txt b/LayoutTests/platform/gtk/compositing/no-compositing-when-full-screen-is-present-expected.txt
@@ -1,4 +1,4 @@
-Test that only elements in fullscreen subtree get layer backed.
+Test that only elements in fullscreen subtree and the associated backdrop get layer backed.
 
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
@@ -17,7 +17,28 @@ foobar
       (bounds 800.00 600.00)
       (contentsOpaque 1)
       (backingStoreAttached 1)
-      (children 1
+      (children 2
+        (GraphicsLayer
+          (preserves3D 1)
+          (backingStoreAttached 1)
+          (children 1
+            (GraphicsLayer
+              (bounds 800.00 600.00)
+              (backingStoreAttached 1)
+              (children 2
+                (GraphicsLayer
+                  (anchor 0.00 0.00)
+                  (bounds 800.00 600.00)
+                  (backingStoreAttached 1)
+                )
+                (GraphicsLayer
+                  (bounds 800.00 600.00)
+                  (backingStoreAttached 1)
+                )
+              )
+            )
+          )
+        )
         (GraphicsLayer
           (preserves3D 1)
           (backingStoreAttached 1)

diff --git a/Source/WebCore/rendering/RenderElement.cpp b/Source/WebCore/rendering/RenderElement.cpp
@@ -757,11 +757,6 @@ void RenderElement::propagateStyleToAnonymousChildren(StylePropagationType propa
         if (propagationType == PropagateToBlockChildrenOnly && !is<RenderBlock>(elementChild))
             continue;
 
-#if ENABLE(FULLSCREEN_API)
-        if (elementChild.isRenderFullScreen() || elementChild.isRenderFullScreenPlaceholder())
-            continue;
-#endif
-
         // RenderFragmentedFlows are updated through the RenderView::styleDidChange function.
         if (is<RenderFragmentedFlow>(elementChild))
             continue;

diff --git a/Source/WebCore/rendering/RenderLayerBacking.cpp b/Source/WebCore/rendering/RenderLayerBacking.cpp
@@ -205,10 +205,24 @@ RenderLayerBacking::RenderLayerBacking(RenderLayer& layer)
         m_isMainFrameRenderViewLayer = renderer().frame().isMainFrame();
         m_isFrameLayerWithTiledBacking = renderer().page().chrome().client().shouldUseTiledBackingForFrameView(renderer().view().frameView());
     }
-    
+
     createPrimaryGraphicsLayer();
 #if ENABLE(FULLSCREEN_API)
-    setRequiresBackgroundLayer(layer.renderer().isRenderFullScreen());
+    auto isFullsizeBackdrop = [](const RenderElement& renderer) -> bool {
+        auto& style = renderer.style();
+        if (style.styleType() != PseudoId::Backdrop || style.position() != PositionType::Fixed)
+            return false;
+
+        if (style.hasTransform() || style.hasClip() || style.hasMask())
+            return false;
+
+        if (!is<RenderBox>(renderer))
+            return false;
+
+        auto rendererRect = downcast<RenderBox>(renderer).frameRect();
+        return rendererRect == renderer.view().frameRect();
+    };
+    setRequiresBackgroundLayer(isFullsizeBackdrop(layer.renderer()));
 #endif
 
     if (auto* tiledBacking = this->tiledBacking()) {

diff --git a/Source/WebCore/rendering/RenderLayerCompositor.cpp b/Source/WebCore/rendering/RenderLayerCompositor.cpp
@@ -2670,6 +2670,10 @@ static FullScreenDescendant isDescendantOfFullScreenLayer(const RenderLayer& lay
     if (!fullScreenRenderer || !fullScreenLayer)
         return FullScreenDescendant::NotApplicable;
 
+    auto backdropRenderer = fullScreenRenderer->backdropRenderer();
+    if (backdropRenderer && backdropRenderer.get() == &layer.renderer())
+        return FullScreenDescendant::Yes;
+
     return layer.isDescendantOf(*fullScreenLayer) ? FullScreenDescendant::Yes : FullScreenDescendant::No;
 }
 #endif

diff --git a/Source/WebCore/rendering/RenderObject.h b/Source/WebCore/rendering/RenderObject.h
@@ -262,10 +262,6 @@ class RenderObject : public CachedImageClient {
     virtual bool isCanvas() const { return false; }
 #if ENABLE(ATTACHMENT_ELEMENT)
     virtual bool isAttachment() const { return false; }
-#endif
-#if ENABLE(FULLSCREEN_API)
-    virtual bool isRenderFullScreen() const { return false; }
-    virtual bool isRenderFullScreenPlaceholder() const { return false; }
 #endif
     virtual bool isRenderGrid() const { return false; }
 
@@ -1159,10 +1155,6 @@ inline bool RenderObject::isAnonymousBlock() const
         && (style().display() == DisplayType::Block || style().display() == DisplayType::Box)
         && style().styleType() == PseudoId::None
         && isRenderBlock()
-#if ENABLE(FULLSCREEN_API)
-        && !isRenderFullScreen()
-        && !isRenderFullScreenPlaceholder()
-#endif
 #if ENABLE(MATHML)
         && !isRenderMathMLBlock()
 #endif