Bug 1155649 - XFlush at the end of frames when OMTC is enabled on Linux. r=jrmuizel

gfx/layers/ipc/ShadowLayers.cpp

@@ -538,6 +538,13 @@ ShadowLayerForwarder::EndTransaction(InfallibleTArray<EditReply>* aReplies,
     return true;
   }
 
+  if (!mTxn->mPaints.empty()) {
+    // With some platforms, telling the drawing backend that there will be no more
+    // drawing for this frame helps with preventing command queues from spanning
+    // across multiple frames.
+    gfxPlatform::GetPlatform()->FlushContentDrawing();
+  }
+
   MOZ_LAYERS_LOG(("[LayersForwarder] destroying buffers..."));
 
   MOZ_LAYERS_LOG(("[LayersForwarder] building transaction..."));

gfx/thebes/gfxPlatform.h

@@ -630,6 +630,7 @@ public:
       return false;
     }
 
+    virtual void FlushContentDrawing() {}
 protected:
     gfxPlatform();
     virtual ~gfxPlatform();

gfx/thebes/gfxPlatformGtk.cpp

@@ -30,6 +30,7 @@
 #include "gfxXlibSurface.h"
 #include "cairo-xlib.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/X11Util.h"
 
 /* Undefine the Status from Xlib since it will conflict with system headers on OSX */
 #if defined(__APPLE__) && defined(Status)
@@ -81,6 +82,14 @@ gfxPlatformGtk::~gfxPlatformGtk()
     gfxPangoFontGroup::Shutdown();
 }
 
+void
+gfxPlatformGtk::FlushContentDrawing()
+{
+    if (UseXRender()) {
+        XFlush(DefaultXDisplay());
+    }
+}
+
 already_AddRefed<gfxASurface>
 gfxPlatformGtk::CreateOffscreenSurface(const IntSize& size,
                                        gfxContentType contentType)

gfx/thebes/gfxPlatformGtk.h

@@ -75,6 +75,11 @@ public:
     virtual bool IsFontFormatSupported(nsIURI *aFontURI,
                                          uint32_t aFormatFlags) override;
 
+    /**
+     * Calls XFlush if xrender is enabled.
+     */
+    virtual void FlushContentDrawing() override;
+
 #if (MOZ_WIDGET_GTK == 2)
     static void SetGdkDrawable(cairo_surface_t *target,
                                GdkDrawable *drawable);