[1249] Fix body background rendering

magomez · magomez · commit aa8b54b5804b · 2024-01-23T14:11:25.000+01:00
diff --git a/Source/WebCore/rendering/RenderBox.cpp b/Source/WebCore/rendering/RenderBox.cpp
@@ -1655,6 +1655,11 @@ void RenderBox::paintBoxDecorations(PaintInfo& paintInfo, const LayoutPoint& pai
 bool RenderBox::paintsOwnBackground() const
 {
     if (isBody()) {
+        // If the body element is composited, then it needs to paint its own background, otherwise it won't be
+        // painted at all. See https://bugs.webkit.org/show_bug.cgi?id=266478.
+        if (isComposited())
+            return true;
+
         // The <body> only paints its background if the root element has defined a background independent of the body,
         // or if the <body>'s parent is not the document element's renderer (e.g. inside SVG foreignObject).
         auto documentElementRenderer = document().documentElement()->renderer();
@@ -2041,22 +2046,14 @@ bool RenderBox::repaintLayerRectsForImage(WrappedImagePtr image, const FillLayer
         if (layer->image() && image == layer->image()->data() && (layer->image()->isLoaded() || layer->image()->canRender(this, style().effectiveZoom()))) {
             // Now that we know this image is being used, compute the renderer and the rect if we haven't already.
             bool drawingRootBackground = drawingBackground && (isDocumentElementRenderer() || (isBody() && !document().documentElement()->renderer()->hasBackground()));
-            if (!layerRenderer) {
-                if (drawingRootBackground) {
-                    layerRenderer = &view();
 
-                    LayoutUnit rw = downcast<RenderView>(*layerRenderer).frameView().contentsWidth();
-                    LayoutUnit rh = downcast<RenderView>(*layerRenderer).frameView().contentsHeight();
+            // There are 2 cases here that need explanation when we're drawing the root background.
+            // * If this is the DocumentElementRenderer, then we use it as renderer.
+            // * If this is the body element, its background image can be painted by itself (if paintsOwnBackground is false) or
+            //   by the DocumentElementRenderer. In both cases setting this instance as the renderer does the appropriate job.
+            layerRenderer = this;
+            rendererRect = borderBoxRect();
 
-                    rendererRect = LayoutRect(-layerRenderer->marginLeft(),
-                        -layerRenderer->marginTop(),
-                        std::max(layerRenderer->width() + layerRenderer->horizontalMarginExtent() + layerRenderer->borderLeft() + layerRenderer->borderRight(), rw),
-                        std::max(layerRenderer->height() + layerRenderer->verticalMarginExtent() + layerRenderer->borderTop() + layerRenderer->borderBottom(), rh));
-                } else {
-                    layerRenderer = this;
-                    rendererRect = borderBoxRect();
-                }
-            }
             // FIXME: Figure out how to pass absolute position to calculateBackgroundImageGeometry (for pixel snapping)
             BackgroundImageGeometry geometry = layerRenderer->calculateBackgroundImageGeometry(nullptr, *layer, LayoutPoint(), rendererRect);
             if (geometry.hasNonLocalGeometry()) {
