Bug 1360246 - Clean up WebRenderTextLayer::RenderLayer. r=nical

This uses the StackingContextHelper and typed helper functions in
WebRenderLayer to simplify WebRenderTextLayer::RenderLayer. It also
removes the implicit assumption in WebRenderTextLayer that the parent
layer pushed a stacking context, which is an assumption we will
probably break in the future.

MozReview-Commit-ID: CARoGVQd56i

gfx/layers/wr/StackingContextHelper.cpp

@@ -60,5 +60,11 @@ StackingContextHelper::ToRelativeWrRect(const LayerRect& aRect) const
   return wr::ToWrRect(aRect - mOrigin);
 }
 
+WrPoint
+StackingContextHelper::ToRelativeWrPoint(const LayerPoint& aPoint) const
+{
+  return wr::ToWrPoint(aPoint - mOrigin);
+}
+
 } // namespace layers
 } // namespace mozilla

gfx/layers/wr/StackingContextHelper.h

@@ -53,6 +53,8 @@ public:
   // things that are pushed inside the stacking context need to be relative
   // to the stacking context.
   WrRect ToRelativeWrRect(const LayerRect& aRect) const;
+  // Same but for points
+  WrPoint ToRelativeWrPoint(const LayerPoint& aPoint) const;
 
 private:
   wr::DisplayListBuilder* mBuilder;

gfx/layers/wr/WebRenderBridgeChild.cpp

@@ -10,6 +10,7 @@
 #include "mozilla/layers/CompositableClient.h"
 #include "mozilla/layers/CompositorBridgeChild.h"
 #include "mozilla/layers/ImageDataSerializer.h"
+#include "mozilla/layers/StackingContextHelper.h"
 #include "mozilla/layers/PTextureChild.h"
 #include "mozilla/webrender/WebRenderAPI.h"
 
@@ -178,8 +179,8 @@ WriteFontFileData(const uint8_t* aData, uint32_t aLength, uint32_t aIndex,
 
 void
 WebRenderBridgeChild::PushGlyphs(wr::DisplayListBuilder& aBuilder, const nsTArray<GlyphArray>& aGlyphs,
-                                 gfx::ScaledFont* aFont, const LayerPoint& aOffset, const gfx::Rect& aBounds,
-                                 const gfx::Rect& aClip)
+                                 gfx::ScaledFont* aFont, const StackingContextHelper& aSc,
+                                 const LayerRect& aBounds, const LayerRect& aClip)
 {
   MOZ_ASSERT(aFont);
   MOZ_ASSERT(!aGlyphs.IsEmpty());
@@ -187,7 +188,7 @@ WebRenderBridgeChild::PushGlyphs(wr::DisplayListBuilder& aBuilder, const nsTArra
   WrFontKey key = GetFontKeyForScaledFont(aFont);
   MOZ_ASSERT(key.mNamespace && key.mHandle);
 
-  WrClipRegion clipRegion = aBuilder.BuildClipRegion(wr::ToWrRect(aClip));
+  WrClipRegion clipRegion = aBuilder.BuildClipRegion(aSc.ToRelativeWrRect(aClip));
 
   for (size_t i = 0; i < aGlyphs.Length(); i++) {
     GlyphArray glyph_array = aGlyphs[i];
@@ -198,10 +199,10 @@ WebRenderBridgeChild::PushGlyphs(wr::DisplayListBuilder& aBuilder, const nsTArra
 
     for (size_t j = 0; j < glyphs.Length(); j++) {
       wr_glyph_instances[j].index = glyphs[j].mIndex;
-      wr_glyph_instances[j].point.x = glyphs[j].mPosition.x - aOffset.x;
-      wr_glyph_instances[j].point.y = glyphs[j].mPosition.y - aOffset.y;
+      wr_glyph_instances[j].point = aSc.ToRelativeWrPoint(
+              LayerPoint::FromUnknownPoint(glyphs[j].mPosition));
     }
-    aBuilder.PushText(wr::ToWrRect(aBounds),
+    aBuilder.PushText(aSc.ToRelativeWrRect(aBounds),
                       clipRegion,
                       glyph_array.color().value(),
                       key,

gfx/layers/wr/WebRenderBridgeChild.h

@@ -24,6 +24,7 @@ namespace layers {
 
 class CompositableClient;
 class CompositorBridgeChild;
+class StackingContextHelper;
 class TextureForwarder;
 
 class UnscaledFontHashKey : public PLDHashEntryHdr
@@ -92,8 +93,8 @@ public:
   }
 
   void PushGlyphs(wr::DisplayListBuilder& aBuilder, const nsTArray<GlyphArray>& aGlyphs,
-                  gfx::ScaledFont* aFont, const LayerPoint& aOffset, const gfx::Rect& aBounds,
-                  const gfx::Rect& aClip);
+                  gfx::ScaledFont* aFont, const StackingContextHelper& aSc,
+                  const LayerRect& aBounds, const LayerRect& aClip);
 
   wr::FontKey GetFontKeyForScaledFont(gfx::ScaledFont* aScaledFont);
 

gfx/layers/wr/WebRenderLayer.cpp

@@ -64,12 +64,6 @@ WebRenderLayer::RelativeToParent(const LayoutDeviceRect& aRect)
       aRect, PixelCastJustification::WebRenderHasUnitResolution));
 }
 
-LayerPoint
-WebRenderLayer::GetOffsetToParent()
-{
-  return ParentBounds().TopLeft();
-}
-
 gfx::Rect
 WebRenderLayer::TransformedVisibleBoundsRelativeToParent()
 {

gfx/layers/wr/WebRenderLayer.h

@@ -50,7 +50,6 @@ public:
 
   LayerRect RelativeToParent(const LayerRect& aRect);
   LayerRect RelativeToParent(const LayoutDeviceRect& aRect);
-  LayerPoint GetOffsetToParent();
 
   LayerRect Bounds();
   LayerRect BoundsForStackingContext();

gfx/layers/wr/WebRenderTextLayer.cpp

@@ -25,24 +25,21 @@ WebRenderTextLayer::RenderLayer(wr::DisplayListBuilder& aBuilder,
         return;
     }
 
-    gfx::Rect rect = GetTransform().TransformBounds(IntRectToRect(mBounds))
-        - ParentBounds().ToUnknownRect().TopLeft();
-    gfx::Rect clip;
-    if (GetClipRect().isSome()) {
-      clip = IntRectToRect(GetClipRect().ref().ToUnknownRect())
-          - ParentBounds().ToUnknownRect().TopLeft();
-    } else {
-      clip = rect;
-    }
+    LayerRect rect = LayerRect::FromUnknownRect(
+        // I am not 100% sure this is correct, but it probably is. Because:
+        // the bounds are in layer space, and when gecko composites layers it
+        // applies the transform to the layer before compositing. However with
+        // WebRender compositing, we don't pass the transform on this layer to
+        // WR, so WR has no way of knowing about the transformed bounds unless
+        // we apply it here. The glyphs that we push to WR should already be
+        // taking the transform into account.
+        GetTransform().TransformBounds(IntRectToRect(mBounds))
+    );
+    DumpLayerInfo("TextLayer", rect);
 
-    if (gfxPrefs::LayersDump()) {
-        printf_stderr("TextLayer %p using rect=%s, clip=%s\n",
-                      this->GetLayer(),
-                      Stringify(rect).c_str(),
-                      Stringify(clip).c_str());
-    }
+    LayerRect clipRect = ClipRect().valueOr(rect);
 
-    WrBridge()->PushGlyphs(aBuilder, mGlyphs, mFont, GetOffsetToParent(), rect, clip);
+    WrBridge()->PushGlyphs(aBuilder, mGlyphs, mFont, aSc, rect, clipRect);
 }
 
 } // namespace layers

layout/generic/nsBulletFrame.cpp

@@ -30,6 +30,7 @@
 #include "nsCounterManager.h"
 #include "nsBidiUtils.h"
 #include "CounterStyleManager.h"
+#include "UnitTransforms.h"
 
 #include "imgIContainer.h"
 #include "ImageLayers.h"
@@ -504,12 +505,12 @@ BulletRenderer::CreateWebRenderCommandsForText(nsDisplayItem* aItem,
   nsDisplayListBuilder* builder = layer->GetDisplayListBuilder();
   const int32_t appUnitsPerDevPixel = aItem->Frame()->PresContext()->AppUnitsPerDevPixel();
   bool dummy;
-  LayoutDeviceRect destRect = LayoutDeviceRect::FromAppUnits(
-      aItem->GetBounds(builder, &dummy), appUnitsPerDevPixel);
-  gfx::Rect destRectTransformed = aLayer->RelativeToParent(destRect).ToUnknownRect();
+  LayerRect destRect = ViewAs<LayerPixel>(
+      LayoutDeviceRect::FromAppUnits(
+          aItem->GetBounds(builder, &dummy), appUnitsPerDevPixel),
+      PixelCastJustification::WebRenderHasUnitResolution);
 
-  layer->WrBridge()->PushGlyphs(aBuilder, mGlyphs, mFont, aLayer->GetOffsetToParent(),
-                                destRectTransformed, destRectTransformed);
+  layer->WrBridge()->PushGlyphs(aBuilder, mGlyphs, mFont, aSc, destRect, destRect);
 }
 
 class nsDisplayBullet final : public nsDisplayItem {