Compute correct repaint rect for decorated RenderSVGRoots

Source/core/rendering/svg/RenderSVGRoot.cpp

Index: Source/core/rendering/svg/RenderSVGRoot.cpp
diff --git a/Source/core/rendering/svg/RenderSVGRoot.cpp b/Source/core/rendering/svg/RenderSVGRoot.cpp
index f63f5f9a8c9583b583577bff16721aabd575d66e..91d6ceea364bf586ea2b95d8e242102229e37fd6 100644
--- a/Source/core/rendering/svg/RenderSVGRoot.cpp
+++ b/Source/core/rendering/svg/RenderSVGRoot.cpp
@@ -29,6 +29,7 @@
 #include "core/rendering/HitTestResult.h"
 #include "core/rendering/LayoutRectRecorder.h"
 #include "core/rendering/LayoutRepainter.h"
+#include "core/rendering/RenderLayer.h"
 #include "core/rendering/RenderPart.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/svg/RenderSVGResourceContainer.h"
@@ -221,10 +222,12 @@ void RenderSVGRoot::layout()
         m_needsBoundariesOrTransformUpdate = false;
     }
 
+    m_overflow.clear();

[f(malita), 2014/04/02 20:45:48]

Not the fault of this CL I think, but poking at this in subclasses smells.

[fs, 2014/04/03 07:58:59]

Yes, this pattern seemed to be used in a few places (clear()+addVisual...).

+    addVisualEffectOverflow();
     updateLayerTransform();
+    invalidateBackgroundObscurationStatus();
 
     repainter.repaintAfterLayout();
-
     clearNeedsLayout();
 }
 
@@ -353,9 +356,53 @@ const AffineTransform& RenderSVGRoot::localToParentTransform() const
     return m_localToParentTransform;
 }
 
+bool RenderSVGRoot::needToRepaintBorderBox() const
+{
+    // Check if the box has any overflow defined (includes outline and
+    // box-shadow for instance.)
+    if (hasRenderOverflow())
+        return true;
+    // If it's the document root, then include the border-box in the repaint
+    // rect if it's got a background or a border specified. The reason for not
+    // using the flag in this case is because said flag is unconditionally set
+    // to 'true' for the document root.
+    if (isRoot())
+        return calculateHasBoxDecorations();
+    // Otherwise, consider all box decorations.
+    return hasBoxDecorations();
+}
+
 LayoutRect RenderSVGRoot::clippedOverflowRectForRepaint(const RenderLayerModelObject* repaintContainer) const
 {
-    return SVGRenderSupport::clippedOverflowRectForRepaint(this, repaintContainer);
+    // This is an open-coded aggregate of SVGRenderSupport::clippedOverflowRectForRepaint,
+    // RenderSVGRoot::computeFloatRectForRepaint and RenderReplaced::clippedOverflowRectForRepaint.
+    // The reason for this is to optimize/minimize the repaint rect when the box is not "decorated"
+    // (does not have background/border/etc.)
+
+    // Return early for any cases where we don't actually paint.
+    if (style()->visibility() != VISIBLE && !enclosingLayer()->hasVisibleContent())
+        return LayoutRect();
+
+    // Compute the repaint rect of the content of the SVG in the border-box coordinate space.
+    FloatRect contentRepaintRect = repaintRectInLocalCoordinates();
+    contentRepaintRect = m_localToBorderBoxTransform.mapRect(contentRepaintRect);
+
+    // Apply initial viewport clip - not affected by overflow settings
+    contentRepaintRect.intersect(pixelSnappedBorderBoxRect());
+
+    LayoutRect repaintRect = enclosingLayoutRect(contentRepaintRect);
+    // If the box is decorated, extend it to include the border-box.
+    if (needToRepaintBorderBox()) {
+        // The selectionRect can project outside of the overflowRect, so take their union
+        // for repainting to avoid selection painting glitches.
+        LayoutRect decoratedRepaintRect = unionRect(localSelectionRect(false), visualOverflowRect());
+        repaintRect.unite(decoratedRepaintRect);
+    }
+
+    // Compute the repaint rect in the parent coordinate space.
+    LayoutRect rect = enclosingIntRect(repaintRect);
+    RenderReplaced::computeRectForRepaint(repaintContainer, rect);
+    return rect;
 }
 
 void RenderSVGRoot::computeFloatRectForRepaint(const RenderLayerModelObject* repaintContainer, FloatRect& repaintRect, bool fixed) const
@@ -392,7 +439,6 @@ void RenderSVGRoot::updateCachedBoundaries()
 {
     SVGRenderSupport::computeContainerBoundingBoxes(this, m_objectBoundingBox, m_objectBoundingBoxValid, m_strokeBoundingBox, m_repaintBoundingBox);
     SVGRenderSupport::intersectRepaintRectWithResources(this, m_repaintBoundingBox);
-    m_repaintBoundingBox.inflate(borderAndPaddingWidth().toFloat());
 }
 
 bool RenderSVGRoot::nodeAtPoint(const HitTestRequest& request, HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction hitTestAction)