Bug 1251984 - allow gfx.xrender.enabled pref to work for compositing even if content backend is not Cairo. r=jrmuizel

gfx/thebes/gfxPlatformGtk.cpp

@@ -350,13 +350,8 @@ gfxPlatformGtk::GetDPIScale()
 bool
 gfxPlatformGtk::UseImageOffscreenSurfaces()
 {
-    // We want to turn on image offscreen surfaces ONLY for GTK3 builds since
-    // GTK2 theme rendering still requires xlib surfaces.
-#if (MOZ_WIDGET_GTK == 3)
-    return gfxPrefs::UseImageOffscreenSurfaces();
-#else
-    return false;
-#endif
+    return GetDefaultContentBackend() != mozilla::gfx::BackendType::CAIRO ||
+           gfxPrefs::UseImageOffscreenSurfaces();
 }
 
 gfxImageFormat

gfx/thebes/gfxPlatformGtk.h

@@ -100,10 +100,6 @@ public:
 
     bool UseXRender() {
 #if defined(MOZ_X11)
-        if (GetDefaultContentBackend() != mozilla::gfx::BackendType::NONE &&
-            GetDefaultContentBackend() != mozilla::gfx::BackendType::CAIRO)
-            return false;
-
         return sUseXRender;
 #else
         return false;

gfx/thebes/gfxXlibNativeRenderer.cpp

@@ -537,11 +537,7 @@ gfxXlibNativeRenderer::Draw(gfxContext* ctx, IntSize size,
     gfxPoint deviceTranslation = gfxPoint(dtTransform._31, dtTransform._32);
     cairo_t* cairo = static_cast<cairo_t*>
         (drawTarget->GetNativeSurface(NativeSurfaceType::CAIRO_CONTEXT));
-    if (!cairo) {
-        return;
-    }
-
-    cairo_surface_t* cairoTarget = cairo_get_group_target(cairo);
+    cairo_surface_t* cairoTarget = cairo ? cairo_get_group_target(cairo) : nullptr;
     cairo_surface_t* tempXlibSurface =
         CreateTempXlibSurface(cairoTarget, drawTarget, size,
                               canDrawOverBackground, flags, screen, visual,

widget/gtk/nsWindow.cpp

@@ -6496,6 +6496,9 @@ nsWindow::GetDrawTarget(const LayoutDeviceIntRegion& aRegion, BufferMode* aBuffe
 
 #ifdef MOZ_X11
 #  ifdef MOZ_HAVE_SHMIMAGE
+#    ifdef MOZ_WIDGET_GTK
+  if (!gfxPlatformGtk::GetPlatform()->UseXRender())
+#    endif
   if (nsShmImage::UseShm()) {
     mBackShmImage.swap(mFrontShmImage);
     if (!mBackShmImage) {

widget/nsShmImage.cpp

@@ -5,13 +5,11 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "nsShmImage.h"
-#ifdef MOZ_WIDGET_GTK
-#include "gfxPlatformGtk.h"
-#endif
 
 #ifdef MOZ_HAVE_SHMIMAGE
 #include "mozilla/X11Util.h"
 #include "mozilla/ipc/SharedMemory.h"
+#include "gfxPlatform.h"
 #include "nsPrintfCString.h"
 #include "nsTArray.h"
 
@@ -51,11 +49,7 @@ nsShmImage::~nsShmImage()
 static bool gShmAvailable = true;
 bool nsShmImage::UseShm()
 {
-#ifdef MOZ_WIDGET_GTK
-  return (gShmAvailable && !gfxPlatformGtk::GetPlatform()->UseXRender());
-#else
   return gShmAvailable;
-#endif
 }
 
 static int gShmError = 0;
@@ -154,7 +148,7 @@ nsShmImage::InitExtension()
   }
 
   if (pixmaps && XShmPixmapFormat(mDisplay) == ZPixmap) {
-    gShmPixmapAtom = XInternAtom(mDisplay, "_MOZ_SHM_PIXMAP", 0);
+    gShmPixmapAtom = XInternAtom(mDisplay, "_MOZ_SHM_PIXMAP", False);
   }
 
   return true;