Changeset 238379 in webkit

Timestamp:

Nov 19, 2018 1:22:51 PM (5 years ago)

Author:

commit-queue@webkit.org

Message:

[cairo] BackingStore::incorporateUpdate should use CompositeCopy to support drawsBackground=false in general Cairo ports
​https://bugs.webkit.org/show_bug.cgi?id=191577

Patch by Tomoki Imai <Tomoki Imai> on 2018-11-19
Reviewed by Carlos Garcia Campos.

We should use CompositeCopy operator to update bitmap to overwrite existing bitmap even if source contains
transparent parts. It enables ports which uses Cairo to set drawsBackground to false.
GTK ports has custom background extension, and in such case, we need to use CompositeSourceOver to retain
custom background.

• UIProcess/cairo/BackingStoreCairo.cpp:

(WebKit::BackingStore::incorporateUpdate): Use CompositeCopy operator to update bitmap.

Location:

trunk/Source/WebKit

Files:

• ChangeLog (modified) (1 diff)
• UIProcess/cairo/BackingStoreCairo.cpp (modified) (2 diffs)

trunk/Source/WebKit/ChangeLog

@@ +1 @@
+2018-11-19  Tomoki Imai  <Tomoki.Imai@sony.com>
+
+        [cairo] BackingStore::incorporateUpdate should use CompositeCopy to support drawsBackground=false in general Cairo ports
+        https://bugs.webkit.org/show_bug.cgi?id=191577
+
+        Reviewed by Carlos Garcia Campos.
+
+        We should use CompositeCopy operator to update bitmap to overwrite existing bitmap even if source contains
+        transparent parts. It enables ports which uses Cairo to set drawsBackground to false.
+        GTK ports has custom background extension, and in such case, we need to use CompositeSourceOver to retain
+        custom background.
+
+        * UIProcess/cairo/BackingStoreCairo.cpp:
+        (WebKit::BackingStore::incorporateUpdate): Use CompositeCopy operator to update bitmap.
+
 2018-11-19  Joseph Pecoraro  <pecoraro@apple.com>
 

trunk/Source/WebKit/UIProcess/cairo/BackingStoreCairo.cpp

@@ -90 +90 @@
     RefPtr<cairo_t> cairoContext = adoptRef(cairo_create(m_backend->surface()));
     GraphicsContext graphicsContext(GraphicsContextImplCairo::createFactory(cairoContext.get()));
+
+    // When m_webPageProxy.drawsBackground() is false, bitmap contains transparent parts as a background of the webpage.
+    // For such case, bitmap must be drawn using CompositeCopy to overwrite the existing surface.
+    graphicsContext.setCompositeOperation(WebCore::CompositeCopy);
+
     for (const auto& updateRect : updateInfo.updateRects) {
         IntRect srcRect = updateRect;
@@ -96 +101 @@
         if (!m_webPageProxy.drawsBackground()) {
             const WebCore::Color color = m_webPageProxy.backgroundColor();
-            if (!color.isOpaque())
-                graphicsContext.clearRect(srcRect);
-            if (color.isVisible())
+            if (color.isVisible()) {
+                // When the application sets the background color through m_webPageProxy.backgroundColor(), we update the surface in 2 steps.
+                //   1. Fill the surface by m_webPageProxy.backgroundColor().
+                //   2. Composite webpage's bitmap which has a transparent background.
+                // In step 1, we use CompositeCopy as m_webPageProxy.backgroundColor() may not be opaque.
+                // On the other hand, in step 2, bitmap should be composited by CompositeSourceOver
+                // because it should be blended with m_webPageProxy.backgroundColor().
                 graphicsContext.fillRect(srcRect, color);
+                graphicsContext.setCompositeOperation(WebCore::CompositeSourceOver);
+                bitmap->paint(graphicsContext, deviceScaleFactor(), updateRect.location(), srcRect);
+                graphicsContext.setCompositeOperation(WebCore::CompositeCopy);
+                continue;
+            }
         }
 #endif