visionOS: Text jumps by subpixel increments when repainting

https://bugs.webkit.org/show_bug.cgi?id=261472 rdar://109372324 Reviewed by Mike Wyrzykowski, Richard Robinson and Dean Jackson. * Source/WebKit/Shared/RemoteLayerTree/CGDisplayListImageBufferBackend.h: * Source/WebKit/Shared/RemoteLayerTree/CGDisplayListImageBufferBackend.mm: (WebKit::GraphicsContextCGDisplayList::GraphicsContextCGDisplayList): (WebKit::CGDisplayListImageBufferBackend::context): * Source/WebKit/Shared/RemoteLayerTree/RemoteLayerBackingStore.h: * Source/WebKit/Shared/RemoteLayerTree/RemoteLayerBackingStore.mm: (WebKit::RemoteLayerBackingStore::paintContents): (WebKit::RemoteLayerBackingStore::drawInContext): (WebKit::RemoteLayerBackingStoreProperties::applyBackingStoreToLayer): Now that it is possible to specify the resolution at which a dynamic content scaling display list is recorded, plumb the backing store scale to that mechanism, and remove all of our workarounds from the days when it was only recorded at 1x. This fixes a bug where the integer rounding of the backing store size coupled with subpixel CTMs would make text quantization cause glyphs to land at different quantized positions between the 2x tiles and the 1x recorded display list. Canonical link: https://commits.webkit.org/268107@main
WebKit · Sep 19, 2023 · 7eb6ed0 · 7eb6ed0
1 parent e49ec88
commit 7eb6ed0
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Showing 4 changed files with 11 additions and 38 deletions.
diff --git a/Source/WebKit/Shared/RemoteLayerTree/CGDisplayListImageBufferBackend.h b/Source/WebKit/Shared/RemoteLayerTree/CGDisplayListImageBufferBackend.h
@@ -64,7 +64,7 @@ class CGDisplayListImageBufferBackend : public WebCore::ImageBufferCGBackend, pu
     // ImageBufferBackendSharing
     ImageBufferBackendSharing* toBackendSharing() final { return this; }
 
-    mutable std::unique_ptr<WebCore::GraphicsContext> m_context;
+    mutable std::unique_ptr<WebCore::GraphicsContextCG> m_context;
     RetainPtr<id> m_resourceCache;
     WebCore::RenderingMode m_renderingMode;
 };

diff --git a/Source/WebKit/Shared/RemoteLayerTree/CGDisplayListImageBufferBackend.mm b/Source/WebKit/Shared/RemoteLayerTree/CGDisplayListImageBufferBackend.mm
@@ -57,38 +57,14 @@ static CFDictionaryRef makeContextOptions(const CGDisplayListImageBufferBackend:
 
 class GraphicsContextCGDisplayList : public WebCore::GraphicsContextCG {
 public:
-    GraphicsContextCGDisplayList(const CGDisplayListImageBufferBackend::Parameters& parameters, WebCore::RenderingMode renderingMode)
-        : GraphicsContextCG(adoptCF(WKCGCommandsContextCreate(parameters.logicalSize, makeContextOptions(parameters))).autorelease(), GraphicsContextCG::Unknown, renderingMode)
+    GraphicsContextCGDisplayList(const CGDisplayListImageBufferBackend::Parameters& parameters, WebCore::IntSize backendSize, WebCore::RenderingMode renderingMode)
+        : GraphicsContextCG(adoptCF(WKCGCommandsContextCreate(backendSize, makeContextOptions(parameters))).autorelease(), GraphicsContextCG::Unknown, renderingMode)
     {
-        m_immutableBaseTransform.scale(parameters.resolutionScale);
-        m_inverseImmutableBaseTransform = *m_immutableBaseTransform.inverse();
-        m_resolutionScale = parameters.resolutionScale;
-    }
-
-    void setCTM(const WebCore::AffineTransform& transform) final
-    {
-        GraphicsContextCG::setCTM(m_inverseImmutableBaseTransform * transform);
-    }
-
-    WebCore::AffineTransform getCTM(IncludeDeviceScale includeDeviceScale) const final
-    {
-        return m_immutableBaseTransform * GraphicsContextCG::getCTM(includeDeviceScale);
-    }
-
-    std::optional<std::pair<float, float>> scaleForRoundingToDevicePixels() const final
-    {
-        auto scale = WebCore::GraphicsContextCG::scaleForRoundingToDevicePixels().value_or(std::make_pair<float>(1, 1));
-        return { { scale.first * m_resolutionScale, scale.second * m_resolutionScale } };
     }
 
     bool canUseShadowBlur() const final { return false; }
 
     bool needsCachedNativeImageInvalidationWorkaround(WebCore::RenderingMode) override { return true; }
-
-private:
-    WebCore::AffineTransform m_immutableBaseTransform;
-    WebCore::AffineTransform m_inverseImmutableBaseTransform;
-    float m_resolutionScale;
 };
 
 WTF_MAKE_ISO_ALLOCATED_IMPL(CGDisplayListImageBufferBackend);
@@ -152,8 +128,10 @@ void setCTM(const WebCore::AffineTransform& transform) final
 
 WebCore::GraphicsContext& CGDisplayListImageBufferBackend::context()
 {
-    if (!m_context)
-        m_context = makeUnique<GraphicsContextCGDisplayList>(m_parameters, m_renderingMode);
+    if (!m_context) {
+        m_context = makeUnique<GraphicsContextCGDisplayList>(m_parameters, backendSize(), m_renderingMode);
+        applyBaseTransform(*m_context);
+    }
     return *m_context;
 }
 

diff --git a/Source/WebKit/Shared/RemoteLayerTree/RemoteLayerBackingStore.h b/Source/WebKit/Shared/RemoteLayerTree/RemoteLayerBackingStore.h
@@ -182,7 +182,7 @@ class RemoteLayerBackingStore : public CanMakeWeakPtr<RemoteLayerBackingStore> {
 private:
     RemoteLayerBackingStoreCollection* backingStoreCollection() const;
 
-    void drawInContext(WebCore::GraphicsContext&, WTF::Function<void()>&& additionalContextSetupCallback = nullptr);
+    void drawInContext(WebCore::GraphicsContext&);
 
     struct Buffer {
         RefPtr<WebCore::ImageBuffer> imageBuffer;

diff --git a/Source/WebKit/Shared/RemoteLayerTree/RemoteLayerBackingStore.mm b/Source/WebKit/Shared/RemoteLayerTree/RemoteLayerBackingStore.mm
@@ -570,10 +570,7 @@ static bool hasValue(const ImageBufferBackendHandle& backendHandle)
         auto& displayListContext = m_displayListBuffer->context();
 
         BifurcatedGraphicsContext context(m_frontBuffer.imageBuffer->context(), displayListContext);
-        drawInContext(context, [&] {
-            displayListContext.scale(FloatSize(1, -1));
-            displayListContext.translate(0, -m_parameters.size.height());
-        });
+        drawInContext(context);
         return;
     }
 #endif
@@ -582,16 +579,13 @@ static bool hasValue(const ImageBufferBackendHandle& backendHandle)
     drawInContext(context);
 }
 
-void RemoteLayerBackingStore::drawInContext(GraphicsContext& context, WTF::Function<void()>&& additionalContextSetupCallback)
+void RemoteLayerBackingStore::drawInContext(GraphicsContext& context)
 {
     auto markFrontBufferNotCleared = makeScopeExit([&]() {
         m_frontBuffer.isCleared = false;
     });
     GraphicsContextStateSaver stateSaver(context);
 
-    if (additionalContextSetupCallback)
-        additionalContextSetupCallback();
-
     // If we have less than webLayerMaxRectsToPaint rects to paint and they cover less
     // than webLayerWastedSpaceThreshold of the total dirty area, we'll repaint each rect separately.
     // Otherwise, repaint the entire bounding box of the dirty region.
@@ -770,6 +764,7 @@ static bool hasValue(const ImageBufferBackendHandle& backendHandle)
         if (!replayCGDisplayListsIntoBackingStore) {
             [layer setValue:@1 forKeyPath:WKCGDisplayListEnabledKey];
             [layer setValue:@1 forKeyPath:WKCGDisplayListBifurcationEnabledKey];
+            [layer setValue:@(layer.contentsScale) forKeyPath:@"separatedOptions.bifurcationScale"];
         } else
             layer.opaque = m_isOpaque;
         [(WKCompositingLayer *)layer _setWKContents:contents.get() withDisplayList:WTFMove(std::get<CGDisplayList>(*m_displayListBufferHandle)) replayForTesting:replayCGDisplayListsIntoBackingStore];