Bug 1405465 - Handle WR paint codepath with no frame r=kats

gfx/layers/wr/WebRenderLayerManager.cpp

@@ -240,16 +240,15 @@ WebRenderLayerManager::EndTransaction(DrawPaintedLayerCallback aCallback,
 void
 WebRenderLayerManager::EndTransactionWithoutLayer(nsDisplayList* aDisplayList,
                                                   nsDisplayListBuilder* aDisplayListBuilder,
-                                                  const nsTArray<wr::WrFilterOp>& aFilters)
+                                                  const nsTArray<wr::WrFilterOp>& aFilters,
+                                                  WebRenderBackgroundData* aBackground)
 {
-  MOZ_ASSERT(aDisplayList && aDisplayListBuilder);
-
   AUTO_PROFILER_TRACING("Paint", "RenderLayers");
 
 #if DUMP_LISTS
   // Useful for debugging, it dumps the display list *before* we try to build
   // WR commands from it
-  if (XRE_IsContentProcess()) nsFrame::PrintDisplayList(aDisplayListBuilder, *aDisplayList);
+  if (XRE_IsContentProcess() && aDisplayList) nsFrame::PrintDisplayList(aDisplayListBuilder, *aDisplayList);
 #endif
 
 #ifdef XP_WIN
@@ -266,7 +265,9 @@ WebRenderLayerManager::EndTransactionWithoutLayer(nsDisplayList* aDisplayList,
   wr::DisplayListBuilder builder(WrBridge()->GetPipeline(), contentSize, mLastDisplayListSize);
   wr::IpcResourceUpdateQueue resourceUpdates(WrBridge());
 
-  { // Record the time spent "layerizing". WR doesn't actually layerize but
+  if (aDisplayList) {
+    MOZ_ASSERT(aDisplayListBuilder && !aBackground);
+    // Record the time spent "layerizing". WR doesn't actually layerize but
     // generating the WR display list is the closest equivalent
     PaintTelemetry::AutoRecord record(PaintTelemetry::Metric::Layerization);
 
@@ -277,6 +278,10 @@ WebRenderLayerManager::EndTransactionWithoutLayer(nsDisplayList* aDisplayList,
                                                     mScrollData,
                                                     contentSize,
                                                     aFilters);
+  } else {
+    // ViewToPaint does not have frame yet, then render only background clolor.
+    MOZ_ASSERT(!aDisplayListBuilder && aBackground);
+    aBackground->AddWebRenderCommands(builder);
   }
 
   DiscardCompositorAnimations();

gfx/layers/wr/WebRenderLayerManager.h

@@ -71,7 +71,8 @@ public:
   virtual bool EndEmptyTransaction(EndTransactionFlags aFlags = END_DEFAULT) override;
   void EndTransactionWithoutLayer(nsDisplayList* aDisplayList,
                                   nsDisplayListBuilder* aDisplayListBuilder,
-                                  const nsTArray<wr::WrFilterOp>& aFilters = nsTArray<wr::WrFilterOp>());
+                                  const nsTArray<wr::WrFilterOp>& aFilters = nsTArray<wr::WrFilterOp>(),
+                                  WebRenderBackgroundData* aBackground = nullptr);
   virtual void EndTransaction(DrawPaintedLayerCallback aCallback,
                               void* aCallbackData,
                               EndTransactionFlags aFlags = END_DEFAULT) override;

gfx/layers/wr/WebRenderUserData.cpp

@@ -20,6 +20,15 @@
 namespace mozilla {
 namespace layers {
 
+void
+WebRenderBackgroundData::AddWebRenderCommands(wr::DisplayListBuilder& aBuilder)
+{
+  aBuilder.PushRect(mBounds,
+                    mBounds,
+                    true,
+                    mColor);
+}
+
 /* static */ bool
 WebRenderUserData::SupportsAsyncUpdate(nsIFrame* aFrame)
 {

gfx/layers/wr/WebRenderUserData.h

@@ -37,6 +37,19 @@ class WebRenderFallbackData;
 class WebRenderLayerManager;
 class WebRenderGroupData;
 
+class WebRenderBackgroundData
+{
+public:
+  WebRenderBackgroundData(wr::LayoutRect aBounds, wr::ColorF aColor)
+    : mBounds(aBounds)
+    , mColor(aColor)
+  { }
+  void AddWebRenderCommands(wr::DisplayListBuilder& aBuilder);
+protected:
+  wr::LayoutRect mBounds;
+  wr::ColorF mColor;
+};
+
 class WebRenderUserData
 {
 public:

layout/base/PresShell.cpp

@@ -176,6 +176,8 @@
 #include "nsLayoutStylesheetCache.h"
 #include "mozilla/layers/InputAPZContext.h"
 #include "mozilla/layers/FocusTarget.h"
+#include "mozilla/layers/WebRenderLayerManager.h"
+#include "mozilla/layers/WebRenderUserData.h"
 #include "mozilla/ServoBindings.h"
 #include "mozilla/ServoStyleSet.h"
 #include "mozilla/StyleSheet.h"
@@ -6319,7 +6321,15 @@ PresShell::Paint(nsView*         aViewToPaint,
   }
 
   if (layerManager->GetBackendType() == layers::LayersBackend::LAYERS_WR) {
-    // TODO: bug 1405465 - create a WR display list which simulates the color layer below.
+    nsPresContext* pc = GetPresContext();
+    LayoutDeviceRect bounds =
+      LayoutDeviceRect::FromAppUnits(pc->GetVisibleArea(), pc->AppUnitsPerDevPixel());
+    bgcolor = NS_ComposeColors(bgcolor, mCanvasBackgroundColor);
+    WebRenderBackgroundData data(wr::ToLayoutRect(bounds), wr::ToColorF(ToDeviceColor(bgcolor)));
+    nsTArray<wr::WrFilterOp> wrFilters;
+
+    MaybeSetupTransactionIdAllocator(layerManager, presContext);
+    layerManager->AsWebRenderLayerManager()->EndTransactionWithoutLayer(nullptr, nullptr, wrFilters, &data);
     return;
   }