Bug 1333122 - Remove gfxPrefs::WebRenderEnabled() to avoid it being used inappopriately; do WR and APZ decision-making during compositor creation. r=dvander?

MozReview-Commit-ID: Fkv6G35BcFw

gfx/thebes/gfxPlatform.cpp

@@ -2464,12 +2464,6 @@ gfxPlatform::AsyncPanZoomEnabled()
   if (!BrowserTabsRemoteAutostart()) {
     return false;
   }
-#ifdef MOZ_ENABLE_WEBRENDER
-  // For webrender hacking we have a special pref to disable APZ even with e10s
-  if (gfxPrefs::WebRenderEnabled() && !gfxPrefs::APZAllowWithWebRender()) {
-    return false;
-  }
-#endif // MOZ_ENABLE_WEBRENDER
 #endif
 #ifdef MOZ_WIDGET_ANDROID
   return true;

gfx/thebes/gfxPrefs.h

@@ -425,13 +425,6 @@ private:
   // Use vsync events generated by hardware
   DECL_GFX_PREF(Once, "gfx.work-around-driver-bugs",           WorkAroundDriverBugs, bool, true);
   DECL_GFX_PREF(Once, "gfx.screen-mirroring.enabled",          ScreenMirroringEnabled, bool, false);
-#ifdef MOZ_ENABLE_WEBRENDER
-  DECL_GFX_PREF(Once, "gfx.webrender.enabled",                 WebRenderEnabled, bool, false);
-#else
-public:
-  static bool WebRenderEnabled() { return false; }
-private:
-#endif
 
   DECL_GFX_PREF(Live, "gl.ignore-dx-interop2-blacklist",       IgnoreDXInterop2Blacklist, bool, false);
   DECL_GFX_PREF(Live, "gl.msaa-level",                         MSAALevel, uint32_t, 2);

widget/nsBaseWidget.cpp

@@ -1298,7 +1298,18 @@ void nsBaseWidget::CreateCompositor(int aWidth, int aHeight)
 
   CreateCompositorVsyncDispatcher();
 
-  CompositorOptions options(UseAPZ(), gfxPrefs::WebRenderEnabled());
+  // For now we decide whether or not to enable WR on this widget by the current
+  // value of the pref (this is the only place in the code allowed to check the
+  // value of the pref). We might want to change this eventually and drop the
+  // pref entirely.
+  bool enableWR = Preferences::GetBool("gfx.webrender.enabled", false);
+  bool enableAPZ = UseAPZ();
+  if (enableWR && !gfxPrefs::APZAllowWithWebRender()) {
+    // Disable APZ on widgets using WebRender, since it doesn't work yet. Allow
+    // it on non-WR widgets or if the pref forces it on.
+    enableAPZ = false;
+  }
+  CompositorOptions options(enableAPZ, enableWR);
 
   RefPtr<LayerManager> lm;
   if (options.UseWebRender()) {