Bug 1227327 - Use regular background image display items for painting button backgrounds. r=mattwoodrow

This has multiple benefits:
 - It makes DLBI detection of background-position changes work for buttons.
 - It makes background-attachment: fixed work for button backgrounds.
 - It allows the willPaintBorder optimization to be used for button background
   drawing, which reduces the background clip to not overlap with opaque borders.

The willPaintBorder optimization requires a change to the reftest 611574-2.html.
This reftest compares backgrounds to inset box shadows. Box shadows those don't
have a willPaintBorder optimization, so we'd get different results due to the
borders - inset box shadows will bleed through the rounded corner anti-aliasing
of the border, backgrounds won't any more. So we just turn off button borders
and cover the outer edges of the borders with an outline in that reftest.

MozReview-Commit-ID: Lvx2p5szjw7
***
Cover the antialiasing in 611574-2.html with a black outline.

MozReview-Commit-ID: IHC3B7Eq72j

--HG--
extra : rebase_source : e2c625e25ebce052948dc39de6f9af91d4987315

layout/forms/nsButtonFrameRenderer.cpp

@@ -112,19 +112,18 @@ nsDisplayButtonBoxShadowOuter::Paint(nsDisplayListBuilder* aBuilder,
                                       buttonRect, mVisibleRect);
 }
 
-class nsDisplayButtonBorderBackground : public nsDisplayItem {
+class nsDisplayButtonBorder : public nsDisplayItem {
 public:
-  nsDisplayButtonBorderBackground(nsDisplayListBuilder* aBuilder,
+  nsDisplayButtonBorder(nsDisplayListBuilder* aBuilder,
                                   nsButtonFrameRenderer* aRenderer)
     : nsDisplayItem(aBuilder, aRenderer->GetFrame()), mBFR(aRenderer) {
-    MOZ_COUNT_CTOR(nsDisplayButtonBorderBackground);
+    MOZ_COUNT_CTOR(nsDisplayButtonBorder);
   }
 #ifdef NS_BUILD_REFCNT_LOGGING
-  virtual ~nsDisplayButtonBorderBackground() {
-    MOZ_COUNT_DTOR(nsDisplayButtonBorderBackground);
+  virtual ~nsDisplayButtonBorder() {
+    MOZ_COUNT_DTOR(nsDisplayButtonBorder);
   }
 #endif
-  
   virtual void HitTest(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
                        HitTestState* aState,
                        nsTArray<nsIFrame*> *aOutFrames) override {
@@ -144,13 +143,13 @@ private:
 };
 
 nsDisplayItemGeometry*
-nsDisplayButtonBorderBackground::AllocateGeometry(nsDisplayListBuilder* aBuilder)
+nsDisplayButtonBorder::AllocateGeometry(nsDisplayListBuilder* aBuilder)
 {
   return new nsDisplayItemGenericImageGeometry(this, aBuilder);
 }
 
 void
-nsDisplayButtonBorderBackground::ComputeInvalidationRegion(
+nsDisplayButtonBorder::ComputeInvalidationRegion(
   nsDisplayListBuilder* aBuilder,
   const nsDisplayItemGeometry* aGeometry,
   nsRegion *aInvalidRegion)
@@ -167,7 +166,7 @@ nsDisplayButtonBorderBackground::ComputeInvalidationRegion(
   nsDisplayItem::ComputeInvalidationRegion(aBuilder, aGeometry, aInvalidRegion);
 }
 
-void nsDisplayButtonBorderBackground::Paint(nsDisplayListBuilder* aBuilder,
+void nsDisplayButtonBorder::Paint(nsDisplayListBuilder* aBuilder,
                                   nsRenderingContext* aCtx)
 {
   NS_ASSERTION(mFrame, "No frame?");
@@ -176,13 +175,13 @@ void nsDisplayButtonBorderBackground::Paint(nsDisplayListBuilder* aBuilder,
 
   // draw the border and background inside the focus and outline borders
   DrawResult result =
-    mBFR->PaintBorderAndBackground(aBuilder, pc, *aCtx, mVisibleRect, r);
+    mBFR->PaintBorder(aBuilder, pc, *aCtx, mVisibleRect, r);
 
   nsDisplayItemGenericImageGeometry::UpdateDrawResult(this, result);
 }
 
 nsRect
-nsDisplayButtonBorderBackground::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) {
+nsDisplayButtonBorder::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) {
   *aSnap = false;
   return aBuilder->IsForEventDelivery() ? nsRect(ToReferenceFrame(), mFrame->GetSize())
           : mFrame->GetVisualOverflowRectRelativeToSelf() + ToReferenceFrame();
@@ -264,10 +263,14 @@ nsButtonFrameRenderer::DisplayButton(nsDisplayListBuilder* aBuilder,
       nsDisplayButtonBoxShadowOuter(aBuilder, this));
   }
 
-  // Almost all buttons draw some kind of background so there's not much
-  // point in checking whether we should create this item.
+  nsRect buttonRect;
+  GetButtonRect(mFrame->GetRectRelativeToSelf(), buttonRect);
+
+  nsDisplayBackgroundImage::AppendBackgroundItemsToTop(
+    aBuilder, mFrame, buttonRect, aBackground);
+
   aBackground->AppendNewToTop(new (aBuilder)
-    nsDisplayButtonBorderBackground(aBuilder, this));
+    nsDisplayButtonBorder(aBuilder, this));
 
   // Only display focus rings if we actually have them. Since at most one
   // button would normally display a focus ring, most buttons won't have them.
@@ -325,9 +328,8 @@ nsButtonFrameRenderer::PaintOutlineAndFocusBorders(
   return result;
 }
 
-
 DrawResult
-nsButtonFrameRenderer::PaintBorderAndBackground(
+nsButtonFrameRenderer::PaintBorder(
   nsDisplayListBuilder* aBuilder,
   nsPresContext* aPresContext,
   nsRenderingContext& aRenderingContext,
@@ -340,19 +342,14 @@ nsButtonFrameRenderer::PaintBorderAndBackground(
 
   nsStyleContext* context = mFrame->StyleContext();
 
-  uint32_t bgFlags = aBuilder->GetBackgroundPaintFlags();
   PaintBorderFlags borderFlags = aBuilder->ShouldSyncDecodeImages()
                                ? PaintBorderFlags::SYNC_DECODE_IMAGES
                                : PaintBorderFlags();
 
-  DrawResult result =
-    nsCSSRendering::PaintBackground(aPresContext, aRenderingContext, mFrame,
-                                    aDirtyRect, buttonRect, bgFlags);
-
   nsCSSRendering::PaintBoxShadowInner(aPresContext, aRenderingContext,
                                       mFrame, buttonRect);
 
-  result &=
+  DrawResult result =
     nsCSSRendering::PaintBorder(aPresContext, aRenderingContext, mFrame,
                                 aDirtyRect, buttonRect, context, borderFlags);
 

layout/forms/nsButtonFrameRenderer.h

@@ -45,7 +45,7 @@ public:
                                          const nsRect& aDirtyRect,
                                          const nsRect& aRect);
 
-  DrawResult PaintBorderAndBackground(nsDisplayListBuilder* aBuilder,
+  DrawResult PaintBorder(nsDisplayListBuilder* aBuilder,
                          nsPresContext* aPresContext,
                          nsRenderingContext& aRenderingContext,
                          const nsRect& aDirtyRect,

layout/reftests/box-shadow/611574-2-ref.html

@@ -2,6 +2,7 @@
 <html>
 <head><style>
 button,span,fieldset { border-radius: 7px 3px;  background-color: #0F0; }
+button { border: none; outline: 3px solid black; -moz-outline-radius: 7px 3px; outline-offset: -2px; }
 </style></head>
 <body style="margin:30px">
 <div style="-moz-column-count:3">

layout/reftests/box-shadow/611574-2.html

@@ -2,6 +2,7 @@
 <html>
 <head><style>
 button,span,fieldset { border-radius: 7px 3px;  background-color: #0F0; }
+button { border: none; outline: 3px solid black; -moz-outline-radius: 7px 3px; outline-offset: -2px; }
 </style></head>
 <body style="margin:30px">
 <div style="-moz-column-count:3">