Don't initialize gfxPrefs with libpref in the GPU process. (bug 1280822 part 1, r=milan)

gfx/thebes/gfxPrefs.cpp

@@ -8,6 +8,7 @@
 #include "mozilla/Preferences.h"
 #include "MainThreadUtils.h"
 #include "mozilla/gfx/Preferences.h"
+#include "nsXULAppAPI.h"
 
 using namespace mozilla;
 
@@ -51,6 +52,13 @@ gfxPrefs::SingletonExists()
 
 gfxPrefs::gfxPrefs()
 {
+  // UI, content, and plugin processes use XPCOM and should have prefs
+  // ready by the time we initialize gfxPrefs.
+  MOZ_ASSERT_IF(XRE_IsContentProcess() ||
+                XRE_IsParentProcess() ||
+                XRE_GetProcessType() == GeckoProcessType_Plugin,
+                Preferences::IsServiceAvailable());
+
   gfxPrefs::AssertMainThread();
   mMoz2DPrefAccess = new PreferenceAccessImpl;
   mozilla::gfx::PreferenceAccess::SetAccess(mMoz2DPrefAccess);
@@ -72,10 +80,20 @@ void gfxPrefs::AssertMainThread()
   MOZ_ASSERT(NS_IsMainThread(), "this code must be run on the main thread");
 }
 
+// On lightweight processes such as for GMP and GPU, XPCOM is not initialized,
+// and therefore we don't have access to Preferences. When XPCOM is not
+// available we rely on manual synchronization of gfxPrefs values over IPC.
+/* static */ bool
+gfxPrefs::IsPrefsServiceAvailable()
+{
+  return Preferences::IsServiceAvailable();
+}
+
 void gfxPrefs::PrefAddVarCache(bool* aVariable,
                                const char* aPref,
                                bool aDefault)
 {
+  MOZ_ASSERT(IsPrefsServiceAvailable());
   Preferences::AddBoolVarCache(aVariable, aPref, aDefault);
 }
 
@@ -83,6 +101,7 @@ void gfxPrefs::PrefAddVarCache(int32_t* aVariable,
                                const char* aPref,
                                int32_t aDefault)
 {
+  MOZ_ASSERT(IsPrefsServiceAvailable());
   Preferences::AddIntVarCache(aVariable, aPref, aDefault);
 }
 
@@ -90,6 +109,7 @@ void gfxPrefs::PrefAddVarCache(uint32_t* aVariable,
                                const char* aPref,
                                uint32_t aDefault)
 {
+  MOZ_ASSERT(IsPrefsServiceAvailable());
   Preferences::AddUintVarCache(aVariable, aPref, aDefault);
 }
 
@@ -97,46 +117,55 @@ void gfxPrefs::PrefAddVarCache(float* aVariable,
                                const char* aPref,
                                float aDefault)
 {
+  MOZ_ASSERT(IsPrefsServiceAvailable());
   Preferences::AddFloatVarCache(aVariable, aPref, aDefault);
 }
 
 bool gfxPrefs::PrefGet(const char* aPref, bool aDefault)
 {
+  MOZ_ASSERT(IsPrefsServiceAvailable());
   return Preferences::GetBool(aPref, aDefault);
 }
 
 int32_t gfxPrefs::PrefGet(const char* aPref, int32_t aDefault)
 {
+  MOZ_ASSERT(IsPrefsServiceAvailable());
   return Preferences::GetInt(aPref, aDefault);
 }
 
 uint32_t gfxPrefs::PrefGet(const char* aPref, uint32_t aDefault)
 {
+  MOZ_ASSERT(IsPrefsServiceAvailable());
   return Preferences::GetUint(aPref, aDefault);
 }
 
 float gfxPrefs::PrefGet(const char* aPref, float aDefault)
 {
+  MOZ_ASSERT(IsPrefsServiceAvailable());
   return Preferences::GetFloat(aPref, aDefault);
 }
 
 void gfxPrefs::PrefSet(const char* aPref, bool aValue)
 {
+  MOZ_ASSERT(IsPrefsServiceAvailable());
   Preferences::SetBool(aPref, aValue);
 }
 
 void gfxPrefs::PrefSet(const char* aPref, int32_t aValue)
 {
+  MOZ_ASSERT(IsPrefsServiceAvailable());
   Preferences::SetInt(aPref, aValue);
 }
 
 void gfxPrefs::PrefSet(const char* aPref, uint32_t aValue)
 {
+  MOZ_ASSERT(IsPrefsServiceAvailable());
   Preferences::SetUint(aPref, aValue);
 }
 
 void gfxPrefs::PrefSet(const char* aPref, float aValue)
 {
+  MOZ_ASSERT(IsPrefsServiceAvailable());
   Preferences::SetFloat(aPref, aValue);
 }
 

gfx/thebes/gfxPrefs.h

@@ -84,26 +84,30 @@ private:
   };
 
   // Since we cannot use const char*, use a function that returns it.
-  template <UpdatePolicy Update, class T, T Default(void), const char* Pref(void)>
+  template <UpdatePolicy Update, class T, T Default(void), const char* Prefname(void)>
   class PrefTemplate
   {
   public:
     PrefTemplate()
     : mValue(Default())
     {
-      Register(Update, Pref());
+      // If not using the Preferences service, values are synced over IPC, so
+      // there's no need to register us as a Preferences observer.
+      if (IsPrefsServiceAvailable()) {
+        Register(Update, Prefname());
+      }
     }
     void Register(UpdatePolicy aUpdate, const char* aPreference)
     {
       AssertMainThread();
-      switch(aUpdate) {
+      switch (aUpdate) {
         case UpdatePolicy::Skip:
           break;
         case UpdatePolicy::Once:
           mValue = PrefGet(aPreference, mValue);
           break;
         case UpdatePolicy::Live:
-          PrefAddVarCache(&mValue,aPreference, mValue);
+          PrefAddVarCache(&mValue, aPreference, mValue);
           break;
         default:
           MOZ_CRASH("Incomplete switch");
@@ -493,6 +497,7 @@ private:
   static bool sInstanceHasBeenDestroyed;
 
 private:
+  static bool IsPrefsServiceAvailable();
   // Creating these to avoid having to include Preferences.h in the .h
   static void PrefAddVarCache(bool*, const char*, bool);
   static void PrefAddVarCache(int32_t*, const char*, int32_t);

modules/libpref/Preferences.cpp

@@ -433,6 +433,13 @@ Preferences::GetInstanceForService()
   return sPreferences;
 }
 
+// static
+bool
+Preferences::IsServiceAvailable()
+{
+  return !!sPreferences;
+}
+
 // static
 bool
 Preferences::InitStaticMembers()

modules/libpref/Preferences.h

@@ -51,6 +51,11 @@ public:
 
   nsresult Init();
 
+  /**
+   * Returns true if the Preferences service is available, false otherwise.
+   */
+  static bool IsServiceAvailable();
+
   /**
    * Reset loaded user prefs then read them
    */