From a80e13e6fe121b2450b551e76a1d582748ed53d4 Mon Sep 17 00:00:00 2001
From: James Willcox <snorp@snorp.net>
Date: Fri, 28 Aug 2015 11:20:05 -0500
Subject: [PATCH] Bug 1182665 - Add gfxPlatform::CanUseDoubleBufferedContent()
 r=nical

---
 gfx/layers/client/ContentClient.cpp | 22 +---------------------
 gfx/thebes/gfxPlatform.cpp          | 28 ++++++++++++++++++++++++++++
 gfx/thebes/gfxPlatform.h            |  5 +++++
 3 files changed, 34 insertions(+), 21 deletions(-)

diff --git a/gfx/layers/client/ContentClient.cpp b/gfx/layers/client/ContentClient.cpp
index 1efa41da06af..4d02a90e0faa 100644
--- a/gfx/layers/client/ContentClient.cpp
+++ b/gfx/layers/client/ContentClient.cpp
@@ -69,27 +69,7 @@ ContentClient::CreateContentClient(CompositableForwarder* aForwarder)
     return nullptr;
   }
 
-  bool useDoubleBuffering = false;
-
-#ifdef XP_WIN
-  if (backend == LayersBackend::LAYERS_D3D11) {
-    useDoubleBuffering = !!gfxWindowsPlatform::GetPlatform()->GetD3D10Device();
-  } else
-#endif
-#ifdef MOZ_WIDGET_GTK
-  // We can't use double buffering when using image content with
-  // Xrender support on Linux, as ContentHostDoubleBuffered is not
-  // suited for direct uploads to the server.
-  if (!gfxPlatformGtk::GetPlatform()->UseImageOffscreenSurfaces() ||
-      !gfxPlatformGtk::GetPlatform()->UseXRender())
-#endif
-  {
-    useDoubleBuffering = (LayerManagerComposite::SupportsDirectTexturing() &&
-                         backend != LayersBackend::LAYERS_D3D9) ||
-                         backend == LayersBackend::LAYERS_BASIC;
-  }
-
-  if (useDoubleBuffering || PR_GetEnv("MOZ_FORCE_DOUBLE_BUFFERING")) {
+  if (gfxPlatform::GetPlatform()->CanUseDoubleBufferedContent(backend)) {
     return MakeAndAddRef<ContentClientDoubleBuffered>(aForwarder);
   }
   return MakeAndAddRef<ContentClientSingleBuffered>(aForwarder);
diff --git a/gfx/thebes/gfxPlatform.cpp b/gfx/thebes/gfxPlatform.cpp
index 698b488fb21e..9fbb056decdd 100644
--- a/gfx/thebes/gfxPlatform.cpp
+++ b/gfx/thebes/gfxPlatform.cpp
@@ -9,6 +9,7 @@
 #include "mozilla/layers/ImageBridgeChild.h"
 #include "mozilla/layers/SharedBufferManagerChild.h"
 #include "mozilla/layers/ISurfaceAllocator.h"     // for GfxMemoryImageReporter
+#include "mozilla/layers/LayerManagerComposite.h"
 
 #include "mozilla/Logging.h"
 #include "mozilla/Services.h"
@@ -2301,6 +2302,33 @@ gfxPlatform::DisableBufferRotation()
   sBufferRotationCheckPref = false;
 }
 
+bool
+gfxPlatform::CanUseDoubleBufferedContent(LayersBackend aBackend) const
+{
+  bool useDoubleBuffering = false;
+
+#ifdef XP_WIN
+  if (aBackend == LayersBackend::LAYERS_D3D11) {
+    useDoubleBuffering = !!gfxWindowsPlatform::GetPlatform()->GetD3D10Device();
+  } else
+#endif
+#ifdef MOZ_WIDGET_GTK
+  // We can't use double buffering when using image content with
+  // Xrender support on Linux, as ContentHostDoubleBuffered is not
+  // suited for direct uploads to the server.
+  if (!gfxPlatformGtk::GetPlatform()->UseImageOffscreenSurfaces() ||
+      !gfxPlatformGtk::GetPlatform()->UseXRender())
+#endif
+  {
+    useDoubleBuffering = (LayerManagerComposite::SupportsDirectTexturing() &&
+                         aBackend != LayersBackend::LAYERS_D3D9) ||
+                         aBackend == LayersBackend::LAYERS_BASIC;
+  }
+
+  return useDoubleBuffering || PR_GetEnv("MOZ_FORCE_DOUBLE_BUFFERING");
+}
+
+
 already_AddRefed<ScaledFont>
 gfxPlatform::GetScaledFontForFontWithCairoSkia(DrawTarget* aTarget, gfxFont* aFont)
 {
diff --git a/gfx/thebes/gfxPlatform.h b/gfx/thebes/gfxPlatform.h
index 9e3e9415e6f3..156b50ed56ca 100644
--- a/gfx/thebes/gfxPlatform.h
+++ b/gfx/thebes/gfxPlatform.h
@@ -496,6 +496,11 @@ public:
     static bool BufferRotationEnabled();
     static void DisableBufferRotation();
 
+    /**
+     * Check to see if we should use double buffered content client
+     */
+    bool CanUseDoubleBufferedContent(mozilla::layers::LayersBackend aBackend) const;
+
     /**
      * Are we going to try color management?
      */