Support subpixel values for text-shadow and box-shadow

Source/core/rendering/RenderBoxModelObject.cpp

Index: Source/core/rendering/RenderBoxModelObject.cpp
diff --git a/Source/core/rendering/RenderBoxModelObject.cpp b/Source/core/rendering/RenderBoxModelObject.cpp
index d8f3ee81977f8fffa40309594d1719aabfa14186..aacee56026715b5fb1d85eed465c14374c59066b 100644
--- a/Source/core/rendering/RenderBoxModelObject.cpp
+++ b/Source/core/rendering/RenderBoxModelObject.cpp
@@ -2482,9 +2482,9 @@ void RenderBoxModelObject::paintBoxShadow(const PaintInfo& info, const LayoutRec
         if (shadow.style() != shadowStyle)
             continue;
 
-        IntSize shadowOffset(shadow.x(), shadow.y());
-        int shadowBlur = shadow.blur();
-        int shadowSpread = shadow.spread();
+        LayoutSize shadowOffset(shadow.x(), shadow.y());
+        LayoutUnit shadowBlur = shadow.blur();
+        LayoutUnit shadowSpread = shadow.spread();
 
         if (shadowOffset.isZero() && !shadowBlur && !shadowSpread)
             continue;
@@ -2492,12 +2492,12 @@ void RenderBoxModelObject::paintBoxShadow(const PaintInfo& info, const LayoutRec
         const Color& shadowColor = resolveColor(shadow.color());
 
         if (shadow.style() == Normal) {
-            RoundedRect fillRect = border;
+            FloatRect fillRect = border.rect();
             fillRect.inflate(shadowSpread);
             if (fillRect.isEmpty())
                 continue;
 
-            IntRect shadowRect(border.rect());
+            LayoutRect shadowRect(border.rect());
             shadowRect.inflate(shadowBlur + shadowSpread);
             shadowRect.move(shadowOffset);
 
@@ -2518,6 +2518,8 @@ void RenderBoxModelObject::paintBoxShadow(const PaintInfo& info, const LayoutRec
                         context->clipOutRoundedRect(rectToClipOut);
                     }
                 } else {
+                    // This IntRect is correct even with fractional shadows, because it is used for the rectangle
+                    // of the box itself, which is always pixel-aligned.
                     IntRect rectToClipOut = border.rect();
 
                     // If the box is opaque, it is unnecessary to clip it out. However, doing so saves time
@@ -2545,20 +2547,25 @@ void RenderBoxModelObject::paintBoxShadow(const PaintInfo& info, const LayoutRec
             context->setDrawLooper(drawLooper);
 
             if (hasBorderRadius) {
-                RoundedRect influenceRect(shadowRect, border.radii());
+                // XXX is this IntRect conversion correct?

[eae, 2013/11/27 23:45:27]

Why not use pixelSnappedIntRect instead?

[cbiesinger, 2013/12/18 02:09:12]

Good idea, thanks.

+                RoundedRect influenceRect(IntRect(shadowRect.pixelSnappedLocation(), shadowRect.pixelSnappedSize()), border.radii());
                 influenceRect.expandRadii(2 * shadowBlur + shadowSpread);
                 if (allCornersClippedOut(influenceRect, info.rect))
-                    context->fillRect(fillRect.rect(), Color::black);
+                    context->fillRect(fillRect, Color::black);
                 else {
-                    fillRect.expandRadii(shadowSpread);
-                    if (!fillRect.isRenderable())
-                        fillRect.adjustRadii();
-                    context->fillRoundedRect(fillRect, Color::black);
+                    RoundedRect roundedFillRect = border;
+                    roundedFillRect.inflate(shadowSpread);
+
+                    roundedFillRect.expandRadii(shadowSpread);
+                    if (!roundedFillRect.isRenderable())
+                        roundedFillRect.adjustRadii();
+                    context->fillRoundedRect(roundedFillRect, Color::black);
                 }
             } else {
-                context->fillRect(fillRect.rect(), Color::black);
+                context->fillRect(fillRect, Color::black);
             }
         } else {
+            // inset shadow

[eae, 2013/11/27 23:45:27]

Update comment to be more descriptive or remove it.

[cbiesinger, 2013/12/18 02:09:12]

Done.

             GraphicsContext::Edges clippedEdges = GraphicsContext::NoEdge;
             if (!includeLogicalLeftEdge) {
                 if (isHorizontal)
@@ -2572,7 +2579,8 @@ void RenderBoxModelObject::paintBoxShadow(const PaintInfo& info, const LayoutRec
                 else
                     clippedEdges |= GraphicsContext::BottomEdge;
             }
-            context->drawInnerShadow(border, shadowColor, shadowOffset, shadowBlur, shadowSpread, clippedEdges);
+            // TODO: support non-integer shadows
+            context->drawInnerShadow(border, shadowColor, IntSize(shadowOffset.width(), shadowOffset.height()), shadowBlur, shadowSpread, clippedEdges);

[eae, 2013/11/27 23:45:27]

do you want to floor or round the offset here? Use flooredIntSize or
roundedIntSize to be explicit.

[cbiesinger, 2013/12/18 02:09:12]

Ah, thanks - done. Switched to floored because that's what we used to do.

         }
     }
 }