Bug 1275694 - Use the local visible region to decide when to cull a layer in CalculateScissorRect(). r=kats

We still take care not to cull a layer if we need to draw a checkerboarding
background for it.

MozReview-Commit-ID: 3EuXEFB2wF9

--HG--
extra : rebase_source : 88e20d9c56be0e09056b7fc3d3e72addee1b1af4
extra : source : 1b8e6e22a983754ef967fe81c1d184a4a966d828

gfx/layers/Layers.cpp

@@ -799,15 +799,13 @@ Layer::CalculateScissorRect(const RenderTargetIntRect& aCurrentScissorRect)
     return currentClip;
   }
 
-  if (GetVisibleRegion().IsEmpty()) {
+  if (GetLocalVisibleRegion().IsEmpty() &&
+      !(AsLayerComposite() && AsLayerComposite()->NeedToDrawCheckerboarding())) {
     // When our visible region is empty, our parent may not have created the
     // intermediate surface that we would require for correct clipping; however,
     // this does not matter since we are invisible.
-    // Note that we do not use GetLocalVisibleRegion(), because that can be
-    // empty for a layer whose rendered contents have been async-scrolled
-    // completely offscreen, but for which we still need to draw a
-    // checkerboarding backround color, and calculating an empty scissor rect
-    // for such a layer would prevent that (see bug 1247452 comment 10).
+    // Make sure we still compute a clip rect if we want to draw checkboarding
+    // for this layer, since we want to do this even if the layer is invisible.
     return RenderTargetIntRect(currentClip.TopLeft(), RenderTargetIntSize(0, 0));
   }
 

gfx/layers/composite/ContainerLayerComposite.cpp

@@ -53,24 +53,6 @@ namespace layers {
 
 using namespace gfx;
 
-static bool
-LayerHasCheckerboardingAPZC(Layer* aLayer, Color* aOutColor)
-{
-  for (LayerMetricsWrapper i(aLayer, LayerMetricsWrapper::StartAt::BOTTOM); i; i = i.GetParent()) {
-    if (!i.Metrics().IsScrollable()) {
-      continue;
-    }
-    if (i.GetApzc() && i.GetApzc()->IsCurrentlyCheckerboarding()) {
-      if (aOutColor) {
-        *aOutColor = i.Metadata().GetBackgroundColor();
-      }
-      return true;
-    }
-    break;
-  }
-  return false;
-}
-
 static void DrawLayerInfo(const RenderTargetIntRect& aClipRect,
                           LayerManagerComposite* aManager,
                           Layer* aLayer)
@@ -357,15 +339,6 @@ ContainerRenderVR(ContainerT* aContainer,
   DUMP("<<< ContainerRenderVR [%p]\n", aContainer);
 }
 
-static bool
-NeedToDrawCheckerboardingForLayer(Layer* aLayer, Color* aOutCheckerboardingColor)
-{
-  return (aLayer->Manager()->AsyncPanZoomEnabled() &&
-         aLayer->GetContentFlags() & Layer::CONTENT_OPAQUE) &&
-         aLayer->IsOpaqueForVisibility() &&
-         LayerHasCheckerboardingAPZC(aLayer, aOutCheckerboardingColor);
-}
-
 /* all of the prepared data that we need in RenderLayer() */
 struct PreparedData
 {
@@ -412,7 +385,7 @@ ContainerPrepare(ContainerT* aContainer,
     // may be null which is not allowed.
     if (!layerToRender->GetLayer()->AsContainerLayer()) {
       if (!layerToRender->GetLayer()->IsVisible() &&
-          !NeedToDrawCheckerboardingForLayer(layerToRender->GetLayer(), nullptr)) {
+          !layerToRender->NeedToDrawCheckerboarding(nullptr)) {
         CULLING_LOG("Sublayer %p has no effective visible region\n", layerToRender->GetLayer());
         continue;
       }
@@ -635,7 +608,7 @@ RenderLayers(ContainerT* aContainer,
     }
 
     Color color;
-    if (NeedToDrawCheckerboardingForLayer(layer, &color)) {
+    if (layerToRender->NeedToDrawCheckerboarding(&color)) {
       if (gfxPrefs::APZHighlightCheckerboardedAreas()) {
         color = Color(255 / 255.f, 188 / 255.f, 217 / 255.f, 1.f); // "Cotton Candy"
       }
@@ -967,7 +940,6 @@ RefLayerComposite::Prepare(const RenderTargetIntRect& aClipRect)
   ContainerPrepare(this, mCompositeManager, aClipRect);
 }
 
-
 void
 RefLayerComposite::CleanupResources()
 {

gfx/layers/composite/LayerManagerComposite.cpp

@@ -22,6 +22,7 @@
 #include "TiledContentHost.h"
 #include "Units.h"                      // for ScreenIntRect
 #include "UnitTransforms.h"             // for ViewAs
+#include "apz/src/AsyncPanZoomController.h"  // for AsyncPanZoomController
 #include "gfxPrefs.h"                   // for gfxPrefs
 #ifdef XP_MACOSX
 #include "gfxPlatformMac.h"
@@ -1603,6 +1604,35 @@ LayerComposite::HasStaleCompositor() const
   return mCompositeManager->GetCompositor() != mCompositor;
 }
 
+static bool
+LayerHasCheckerboardingAPZC(Layer* aLayer, Color* aOutColor)
+{
+  bool answer = false;
+  for (LayerMetricsWrapper i(aLayer, LayerMetricsWrapper::StartAt::BOTTOM); i; i = i.GetParent()) {
+    if (!i.Metrics().IsScrollable()) {
+      continue;
+    }
+    if (i.GetApzc() && i.GetApzc()->IsCurrentlyCheckerboarding()) {
+      if (aOutColor) {
+        *aOutColor = i.Metadata().GetBackgroundColor();
+      }
+      answer = true;
+      break;
+    }
+    break;
+  }
+  return answer;
+}
+
+bool
+LayerComposite::NeedToDrawCheckerboarding(gfx::Color* aOutCheckerboardingColor)
+{
+  return GetLayer()->Manager()->AsyncPanZoomEnabled() &&
+         (GetLayer()->GetContentFlags() & Layer::CONTENT_OPAQUE) &&
+         GetLayer()->IsOpaqueForVisibility() &&
+         LayerHasCheckerboardingAPZC(GetLayer(), aOutCheckerboardingColor);
+}
+
 #ifndef MOZ_HAVE_PLATFORM_SPECIFIC_LAYER_BUFFERS
 
 /*static*/ bool

gfx/layers/composite/LayerManagerComposite.h

@@ -560,6 +560,12 @@ public:
    */
   virtual nsIntRegion GetFullyRenderedRegion();
 
+  /**
+   * Return true if a checkerboarding background color needs to be drawn
+   * for this layer.
+   */
+  bool NeedToDrawCheckerboarding(gfx::Color* aOutCheckerboardingColor = nullptr);
+
 protected:
   gfx::Matrix4x4 mShadowTransform;
   LayerIntRegion mShadowVisibleRegion;