Bug 1227216. Part 2: Fallback to blur destination rect if a large sha…

…dow offset occurs. r=mstange

gfx/thebes/gfxBlur.cpp

@@ -919,6 +919,8 @@ gfxAlphaBoxBlur::GetInsetBlur(IntMargin& aExtendDestBy,
                               const RectCornerRadii& aInnerClipRadii,
                               const Color& aShadowColor,
                               const bool& aHasBorderRadius,
+                              const Point aShadowOffset,
+                              bool& aMovedOffset,
                               gfxContext* aDestinationCtx)
 {
   if (!gBlurCache) {
@@ -933,14 +935,27 @@ gfxAlphaBoxBlur::GetInsetBlur(IntMargin& aExtendDestBy,
                                 aShadowClipRect, aHasBorderRadius,
                                 aInnerClipRadii);
 
+  // If we have a shadow offset larger than the min rect,
+  // there's no clean way we can properly create a min rect with the offset
+  // in the correct place and still render correctly.  In those cases,
+  // fallback to just rendering the dest rect as is.
+  bool useDestRect = (std::abs(aShadowOffset.x) > aSlice.left) ||
+                     (std::abs(aShadowOffset.y) > aSlice.top);
+  aMovedOffset = false;
+  if (useDestRect) {
+    aDestinationRect.ToIntRect(&outerRect);
+    aShadowClipRect.ToIntRect(&innerRect);
+    aMovedOffset = true;
+  }
+
   DrawTarget* destDrawTarget = aDestinationCtx->GetDrawTarget();
   BlurCacheData* cached =
       gBlurCache->LookupInsetBoxShadow(outerRect.Size(), innerRect.Size(),
                                        aBlurRadius, aSpreadRadius,
                                        &aInnerClipRadii, aShadowColor,
                                        aHasBorderRadius,
                                        destDrawTarget->GetBackendType());
-  if (cached) {
+  if (cached && !useDestRect) {
     aExtendDestBy = cached->mExtendDest;
     // Need to extend it twice: once for the outer rect and once for the inner rect.
     aSlice += aExtendDestBy;
@@ -985,14 +1000,22 @@ gfxAlphaBoxBlur::GetInsetBlur(IntMargin& aExtendDestBy,
 
   IntRect blurRect(topLeft, minInsetBlur->GetSize());
   aExtendDestBy = blurRect - outerRect;
-  aSlice += aExtendDestBy;
-  aSlice += aExtendDestBy;
 
-  CacheInsetBlur(outerRect.Size(), innerRect.Size(),
+  if (useDestRect) {
+    // Since we're just going to paint the actual rect to the destination
+    aSlice.SizeTo(0, 0, 0, 0);
+  } else {
+    aSlice += aExtendDestBy;
+    aSlice += aExtendDestBy;
+
+    CacheInsetBlur(outerRect.Size(), innerRect.Size(),
                  aBlurRadius, aSpreadRadius,
                  &aInnerClipRadii, aShadowColor,
                  aHasBorderRadius, destDrawTarget->GetBackendType(),
                  aExtendDestBy, minInsetBlur);
+
+  }
+
   return minInsetBlur.forget();
 }
 
@@ -1027,11 +1050,13 @@ gfxAlphaBoxBlur::BlurInsetBox(gfxContext* aDestinationCtx,
 
   IntMargin extendDest;
   IntMargin slice;
+  bool didMoveOffset;
   RefPtr<SourceSurface> minInsetBlur = GetInsetBlur(extendDest, slice,
                                                     aDestinationRect, aShadowClipRect,
                                                     aBlurRadius, aSpreadRadius,
                                                     aInnerClipRadii, aShadowColor,
-                                                    aHasBorderRadius, aDestinationCtx);
+                                                    aHasBorderRadius, aShadowOffset,
+                                                    didMoveOffset, aDestinationCtx);
   if (!minInsetBlur) {
     return;
   }
@@ -1041,7 +1066,9 @@ gfxAlphaBoxBlur::BlurInsetBox(gfxContext* aDestinationCtx,
   srcInner.Deflate(Margin(slice));
 
   Rect dstOuter(aDestinationRect);
-  dstOuter.MoveBy(aShadowOffset);
+  if (!didMoveOffset) {
+    dstOuter.MoveBy(aShadowOffset);
+  }
   dstOuter.Inflate(Margin(extendDest));
   Rect dstInner = dstOuter;
   dstInner.Deflate(Margin(slice));

gfx/thebes/gfxBlur.h

@@ -174,6 +174,8 @@ class gfxAlphaBoxBlur
                  const RectCornerRadii& aInnerClipRadii,
                  const mozilla::gfx::Color& aShadowColor,
                  const bool& aHasBorderRadius,
+                 const mozilla::gfx::Point aShadowOffset,
+                 bool& aMovedOffset,
                  gfxContext* aDestinationCtx);
 
     /**

layout/reftests/box-shadow/boxshadow-large-offset-ref.html

@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html>
+<style>
+.top {
+  background-color: red;
+  width: 800px;
+  height: 400px;
+}
+
+.bottom {
+  background-color: #fec;
+  width: 800px;
+  height: 400px;
+}
+
+.leftCut {
+  position: absolute;
+  margin-left: 0px;
+  margin-top: 0px;
+  width: 10px;
+  height: 800px;
+  background-color: black;
+}
+
+.rightCut {
+  position: absolute;
+  margin-left: 790px;
+  margin-top: 0px;
+  width: 10px;
+  height: 800px;
+  background-color: black;
+}
+
+.centerCut {
+  position: absolute;
+  margin-top: 395px;
+  width: 800px;
+  height: 20px;
+  background-color: black;
+}
+</style>
+
+<body>
+<div class="leftCut"></div>
+<div class="rightCut"></div>
+<div class="centerCut"></div>
+<div class="top"></div>
+<div class="bottom"></div>
+</body>
+</html>

layout/reftests/box-shadow/boxshadow-large-offset.html

@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html>
+<style>
+.test {
+  background-color: #fec;
+  display: inline-block;
+  width: 800px;
+  height: 800px;
+}
+
+.second {
+  box-shadow: inset 0 400px 1px 0px red;
+}
+
+.leftCut {
+  position: absolute;
+  margin-left: 0px;
+  margin-top: 0px;
+  width: 10px;
+  height: 800px;
+  background-color: black;
+}
+
+.rightCut {
+  position: absolute;
+  margin-left: 790px;
+  margin-top: 0px;
+  width: 10px;
+  height: 800px;
+  background-color: black;
+}
+
+.centerCut {
+  position: absolute;
+  margin-top: 395px;
+  width: 800px;
+  height: 20px;
+  background-color: black;
+}
+
+</style>
+
+<body>
+<div class="leftCut"></div>
+<div class="rightCut"></div>
+<div class="centerCut"></div>
+<div class="test second"></div>
+</body>
+</html>

layout/reftests/box-shadow/reftest.list

@@ -38,3 +38,4 @@ fuzzy-if(winWidget,5,30) == fieldset-inset.html fieldset-inset-ref.html # minor
 == 1178575.html 1178575-ref.html
 == 1178575-2.html 1178575-2-ref.html
 fuzzy(159,2) fails-if(!d2d) == 1212823-1.html 1212823-1-ref.html
+== boxshadow-large-offset.html boxshadow-large-offset-ref.html