Use LayoutRect during addFocusRingRects to avoid loss of precision

Source/core/rendering/RenderObject.cpp

Index: Source/core/rendering/RenderObject.cpp
diff --git a/Source/core/rendering/RenderObject.cpp b/Source/core/rendering/RenderObject.cpp
index cb6890fc7fbb2181ff07bf906bad36f7c4adef6c..a757a63d4503595a0988d8222a9d19d1f3644a25 100644
--- a/Source/core/rendering/RenderObject.cpp
+++ b/Source/core/rendering/RenderObject.cpp
@@ -1217,12 +1217,16 @@ void RenderObject::drawSolidBoxSide(GraphicsContext* graphicsContext, int x1, in
 
 void RenderObject::paintFocusRing(PaintInfo& paintInfo, const LayoutPoint& paintOffset, RenderStyle* style)
 {
-    Vector<IntRect> focusRingRects;
+    Vector<LayoutRect> focusRingRects;
     addFocusRingRects(focusRingRects, paintOffset, paintInfo.paintContainer());
-    if (style->outlineStyleIsAuto())
-        paintInfo.context->drawFocusRing(focusRingRects, style->outlineWidth(), style->outlineOffset(), resolveColor(style, CSSPropertyOutlineColor));
-    else
-        addPDFURLRect(paintInfo.context, unionRect(focusRingRects));
+    if (style->outlineStyleIsAuto()) {
+        Vector<IntRect> focusRingIntRects;
+        for (size_t i = 0; i < focusRingRects.size(); ++i)
+            focusRingIntRects.append(pixelSnappedIntRect(focusRingRects[i]));

[Julien - ping for review, 2014/08/20 22:12:31]

We talked about this O(N) loop and while it shouldn't be terrible in the common
(N should be 1 most of the time), there is no guarantee that it is.

Nit: Ideally we would want to avoid it (or at least remove the nested one to
compensate).

[Xianzhu, 2014/09/04 00:29:12]

Previously the computation of the loop was distributed in addFocusRingRects().
Considering the layered path combines rects, the new N <= the old N, so the
total computation won't increase.

+        paintInfo.context->drawFocusRing(focusRingIntRects, style->outlineWidth(), style->outlineOffset(), resolveColor(style, CSSPropertyOutlineColor));
+        return;
+    }
+    addPDFURLRect(paintInfo.context, unionRect(focusRingRects));
 }
 
 void RenderObject::addPDFURLRect(GraphicsContext* context, const LayoutRect& rect)
@@ -1314,7 +1318,7 @@ void RenderObject::paintOutline(PaintInfo& paintInfo, const LayoutRect& paintRec
         graphicsContext->endLayer();
 }
 
-void RenderObject::addChildFocusRingRects(Vector<IntRect>& rects, const LayoutPoint& additionalOffset, const RenderLayerModelObject* paintContainer) const
+void RenderObject::addChildFocusRingRects(Vector<LayoutRect>& rects, const LayoutPoint& additionalOffset, const RenderLayerModelObject* paintContainer) const
 {
     for (RenderObject* current = slowFirstChild(); current; current = current->nextSibling()) {
         if (current->isText() || current->isListMarker())
@@ -1323,16 +1327,16 @@ void RenderObject::addChildFocusRingRects(Vector<IntRect>& rects, const LayoutPo
         if (current->isBox()) {
             RenderBox* box = toRenderBox(current);
             if (box->hasLayer()) {
-                Vector<IntRect> layerFocusRingRects;
+                Vector<LayoutRect> layerFocusRingRects;
                 box->addFocusRingRects(layerFocusRingRects, LayoutPoint(), box);
                 for (size_t i = 0; i < layerFocusRingRects.size(); ++i) {
-                    FloatQuad quadInBox = box->localToContainerQuad(FloatRect(layerFocusRingRects[i]), paintContainer);
-                    rects.append(pixelSnappedIntRect(LayoutRect(quadInBox.boundingBox())));
+                    FloatQuad quadInBox = box->localToContainerQuad(FloatQuad(layerFocusRingRects[i]), paintContainer);
+                    LayoutRect rect = LayoutRect(quadInBox.boundingBox());
+                    if (!rect.isEmpty())
+                        rects.append(rect);
                 }
             } else {
-                FloatPoint pos(additionalOffset);
-                pos.move(box->locationOffset()); // FIXME: Snap offsets? crbug.com/350474
-                box->addFocusRingRects(rects, flooredIntPoint(pos), paintContainer);
+                box->addFocusRingRects(rects, additionalOffset + box->locationOffset(), paintContainer);
             }
         } else {
             current->addFocusRingRects(rects, additionalOffset, paintContainer);
@@ -1383,7 +1387,7 @@ IntRect RenderObject::absoluteBoundingBoxRectIgnoringTransforms() const
 
 void RenderObject::absoluteFocusRingQuads(Vector<FloatQuad>& quads)
 {
-    Vector<IntRect> rects;
+    Vector<LayoutRect> rects;
     const RenderLayerModelObject* container = containerForPaintInvalidation();
     addFocusRingRects(rects, LayoutPoint(localToContainerPoint(FloatPoint(), container)), container);
     size_t count = rects.size();