Bug 1517205 - Make nsWaylandDisplay() global, r=lsalzman

Lazilly create nsWaylandDisplay objects and remove them at Firefox quit.

nsWaylandDisplay objects should stay as global objects and don't be created/released.
The creation/removal wastes resources on server side as the wl_registry objects at nsWaylandDisplay has to be stored at server
side and can't be removed until firefox ends [1] anyway.

Also the removed nsWaylandDisplay causes crashes when display
topology changes due to the global nature of the wl_registry.

[1] https://wayland.freedesktop.org/docs/html/apa.html#protocol-spec-wl_registry

Differential Revision: https://phabricator.services.mozilla.com/D26673

--HG--
extra : moz-landing-system : lando

widget/gtk/WindowSurfaceWayland.cpp

@@ -413,16 +413,6 @@ WindowSurfaceWayland::~WindowSurfaceWayland() {
       delete mBackupBuffer[i];
     }
   }
-
-  if (!mIsMainThread) {
-    // We can be destroyed from main thread even though we was created/used
-    // in compositor thread. We have to unref/delete WaylandDisplay in
-    // compositor thread then and we can't use MessageLoop::current() here.
-    mDisplayThreadMessageLoop->PostTask(NewRunnableFunction(
-        "WaylandDisplayRelease", &WaylandDisplayRelease, mWaylandDisplay));
-  } else {
-    WaylandDisplayRelease(mWaylandDisplay);
-  }
 }
 
 WindowBackBuffer* WindowSurfaceWayland::GetWaylandBufferToDraw(int aWidth,

widget/gtk/mozcontainer.cpp

@@ -610,7 +610,6 @@ struct wl_surface *moz_container_get_wl_surface(MozContainer *container) {
 
     wl_surface_commit(container->surface);
     wl_display_flush(waylandDisplay->GetDisplay());
-    WaylandDisplayRelease(waylandDisplay);
   }
 
   LOGWAYLAND(("%s [%p] created surface %p\n", __FUNCTION__, (void *)container,

widget/gtk/nsClipboardWayland.cpp

@@ -639,7 +639,6 @@ static gboolean offer_hash_remove(gpointer wl_offer, gpointer aDataOffer,
 nsRetrievalContextWayland::~nsRetrievalContextWayland(void) {
   g_hash_table_foreach_remove(mActiveOffers, offer_hash_remove, nullptr);
   g_hash_table_destroy(mActiveOffers);
-  WaylandDisplayRelease(mDisplay);
 }
 
 GdkAtom *nsRetrievalContextWayland::GetTargets(int32_t aWhichClipboard,

widget/gtk/nsWaylandDisplay.cpp

@@ -21,6 +21,13 @@ namespace widget {
 static nsWaylandDisplay *gWaylandDisplays[MAX_DISPLAY_CONNECTIONS];
 static StaticMutex gWaylandDisplaysMutex;
 
+static void ReleaseDisplaysAtExit() {
+  for (int i = 0; i < MAX_DISPLAY_CONNECTIONS; i++) {
+    delete gWaylandDisplays[i];
+    gWaylandDisplays[i] = nullptr;
+  }
+}
+
 // Each thread which is using wayland connection (wl_display) has to operate
 // its own wl_event_queue. Main Firefox thread wl_event_queue is handled
 // by Gtk main loop, other threads/wl_event_queue has to be handled by us.
@@ -31,19 +38,24 @@ static StaticMutex gWaylandDisplaysMutex;
 static void WaylandDisplayLoop(wl_display *aDisplay);
 
 // Get WaylandDisplay for given wl_display and actual calling thread.
-static nsWaylandDisplay *WaylandDisplayGetLocked(wl_display *aDisplay,
+static nsWaylandDisplay *WaylandDisplayGetLocked(GdkDisplay *aGdkDisplay,
                                                  const StaticMutexAutoLock &) {
+  // Available as of GTK 3.8+
+  static auto sGdkWaylandDisplayGetWlDisplay = (wl_display * (*)(GdkDisplay *))
+      dlsym(RTLD_DEFAULT, "gdk_wayland_display_get_wl_display");
+  wl_display *waylandDisplay = sGdkWaylandDisplayGetWlDisplay(aGdkDisplay);
+
+  // Search existing display connections for wl_display:thread combination.
   for (auto &display : gWaylandDisplays) {
-    if (display && display->Matches(aDisplay)) {
-      NS_ADDREF(display);
+    if (display && display->Matches(waylandDisplay)) {
       return display;
     }
   }
 
   for (auto &display : gWaylandDisplays) {
     if (display == nullptr) {
-      display = new nsWaylandDisplay(aDisplay);
-      NS_ADDREF(display);
+      display = new nsWaylandDisplay(waylandDisplay);
+      atexit(ReleaseDisplaysAtExit);
       return display;
     }
   }
@@ -57,34 +69,8 @@ nsWaylandDisplay *WaylandDisplayGet(GdkDisplay *aGdkDisplay) {
     aGdkDisplay = gdk_display_get_default();
   }
 
-  // Available as of GTK 3.8+
-  static auto sGdkWaylandDisplayGetWlDisplay = (wl_display * (*)(GdkDisplay *))
-      dlsym(RTLD_DEFAULT, "gdk_wayland_display_get_wl_display");
-
-  wl_display *display = sGdkWaylandDisplayGetWlDisplay(aGdkDisplay);
-
   StaticMutexAutoLock lock(gWaylandDisplaysMutex);
-  return WaylandDisplayGetLocked(display, lock);
-}
-
-static bool WaylandDisplayReleaseLocked(nsWaylandDisplay *aDisplay,
-                                        const StaticMutexAutoLock &) {
-  for (auto &display : gWaylandDisplays) {
-    if (display == aDisplay) {
-      int rc = display->Release();
-      if (rc == 0) {
-        display = nullptr;
-      }
-      return true;
-    }
-  }
-  MOZ_ASSERT(false, "Missing nsWaylandDisplay for this thread!");
-  return false;
-}
-
-void WaylandDisplayRelease(nsWaylandDisplay *aDisplay) {
-  StaticMutexAutoLock lock(gWaylandDisplaysMutex);
-  WaylandDisplayReleaseLocked(aDisplay, lock);
+  return WaylandDisplayGetLocked(aGdkDisplay, lock);
 }
 
 static void WaylandDisplayLoopLocked(wl_display *aDisplay,
@@ -130,6 +116,8 @@ static void global_registry_handler(void *data, wl_registry *registry,
                                     uint32_t id, const char *interface,
                                     uint32_t version) {
   auto display = reinterpret_cast<nsWaylandDisplay *>(data);
+  if (!display)
+    return;
 
   if (strcmp(interface, "wl_shm") == 0) {
     auto shm = static_cast<wl_shm *>(
@@ -180,9 +168,7 @@ bool nsWaylandDisplay::Matches(wl_display *aDisplay) {
   return mThreadId == PR_GetCurrentThread() && aDisplay == mDisplay;
 }
 
-NS_IMPL_ISUPPORTS(nsWaylandDisplay, nsISupports);
-
-nsWaylandDisplay::nsWaylandDisplay(wl_display *aDisplay)
+nsWaylandDisplay::nsWaylandDisplay(wl_display* aDisplay)
     : mThreadId(PR_GetCurrentThread()),
       mDisplay(aDisplay),
       mEventQueue(nullptr),
@@ -190,9 +176,10 @@ nsWaylandDisplay::nsWaylandDisplay(wl_display *aDisplay)
       mSubcompositor(nullptr),
       mSeat(nullptr),
       mShm(nullptr),
-      mPrimarySelectionDeviceManager(nullptr) {
-  wl_registry *registry = wl_display_get_registry(mDisplay);
-  wl_registry_add_listener(registry, &registry_listener, this);
+      mPrimarySelectionDeviceManager(nullptr),
+      mRegistry(nullptr) {
+  mRegistry = wl_display_get_registry(mDisplay);
+  wl_registry_add_listener(mRegistry, &registry_listener, this);
 
   if (NS_IsMainThread()) {
     // Use default event queue in main thread operated by Gtk+.
@@ -203,17 +190,19 @@ nsWaylandDisplay::nsWaylandDisplay(wl_display *aDisplay)
     mEventQueue = wl_display_create_queue(mDisplay);
     MessageLoop::current()->PostTask(NewRunnableFunction(
         "WaylandDisplayLoop", &WaylandDisplayLoop, mDisplay));
-    wl_proxy_set_queue((struct wl_proxy *)registry, mEventQueue);
+    wl_proxy_set_queue((struct wl_proxy *)mRegistry, mEventQueue);
     wl_display_roundtrip_queue(mDisplay, mEventQueue);
     wl_display_roundtrip_queue(mDisplay, mEventQueue);
   }
 }
 
 nsWaylandDisplay::~nsWaylandDisplay() {
-  MOZ_ASSERT(mThreadId == PR_GetCurrentThread());
   // Owned by Gtk+, we don't need to release
   mDisplay = nullptr;
 
+  wl_registry_destroy(mRegistry);
+  mRegistry = nullptr;
+
   if (mEventQueue) {
     wl_event_queue_destroy(mEventQueue);
     mEventQueue = nullptr;

widget/gtk/nsWaylandDisplay.h

@@ -20,11 +20,10 @@ namespace widget {
 
 // Our general connection to Wayland display server,
 // holds our display connection and runs event loop.
-class nsWaylandDisplay : public nsISupports {
-  NS_DECL_THREADSAFE_ISUPPORTS
-
+class nsWaylandDisplay {
  public:
   explicit nsWaylandDisplay(wl_display* aDisplay);
+  virtual ~nsWaylandDisplay();
 
   bool DisplayLoop();
   bool Matches(wl_display* aDisplay);
@@ -41,7 +40,6 @@ class nsWaylandDisplay : public nsISupports {
     return mPrimarySelectionDeviceManager;
   };
 
- public:
   void SetShm(wl_shm* aShm);
   void SetSubcompositor(wl_subcompositor* aSubcompositor);
   void SetDataDeviceManager(wl_data_device_manager* aDataDeviceManager);
@@ -49,9 +47,7 @@ class nsWaylandDisplay : public nsISupports {
   void SetPrimarySelectionDeviceManager(
       gtk_primary_selection_device_manager* aPrimarySelectionDeviceManager);
 
- private:
-  virtual ~nsWaylandDisplay();
-
+private:
   PRThread* mThreadId;
   wl_display* mDisplay;
   wl_event_queue* mEventQueue;
@@ -60,10 +56,10 @@ class nsWaylandDisplay : public nsISupports {
   wl_seat* mSeat;
   wl_shm* mShm;
   gtk_primary_selection_device_manager* mPrimarySelectionDeviceManager;
+  wl_registry *mRegistry;
 };
 
 nsWaylandDisplay* WaylandDisplayGet(GdkDisplay* aGdkDisplay = nullptr);
-void WaylandDisplayRelease(nsWaylandDisplay* aDisplay);
 
 }  // namespace widget
 }  // namespace mozilla