bug 921565 - look for WM_DEVICECHANGE in Windows gamepad backend and rescan for devices. r=jimm

hal/windows/WindowsGamepad.cpp

@@ -232,7 +232,6 @@ public:
     mTimer = do_CreateInstance("@mozilla.org/timer;1", &rv);
     nsCOMPtr<nsIObserverService> observerService =
       mozilla::services::GetObserverService();
-    observerService->AddObserver(this, "devices-changed", false);
     observerService->AddObserver(this,
                                  NS_XPCOM_WILL_SHUTDOWN_OBSERVER_ID,
                                  false);
@@ -245,7 +244,6 @@ public:
     if (mObserving) {
       nsCOMPtr<nsIObserverService> observerService =
         mozilla::services::GetObserverService();
-      observerService->RemoveObserver(this, "devices-changed");
       observerService->RemoveObserver(this, NS_XPCOM_WILL_SHUTDOWN_OBSERVER_ID);
       mObserving = false;
     }
@@ -255,6 +253,15 @@ public:
     Stop();
   }
 
+  void SetDeviceChangeTimer() {
+    // set stable timer, since we will get multiple devices-changed
+    // notifications at once
+    if (mTimer) {
+      mTimer->Cancel();
+      mTimer->Init(this, kDevicesChangedStableDelay, nsITimer::TYPE_ONE_SHOT);
+    }
+  }
+
 private:
   // Gamepad service owns us, we just hold a reference back to it.
   WindowsGamepadService& mSvc;
@@ -277,7 +284,11 @@ public:
     }
   }
 
-  void DevicesChanged();
+  enum DeviceChangeType {
+    DeviceChangeNotification,
+    DeviceChangeStable
+  };
+  void DevicesChanged(DeviceChangeType type);
   void Startup();
   void Shutdown();
 
@@ -589,8 +600,12 @@ WindowsGamepadService::CleanupGamepad(Gamepad& gamepad) {
 }
 
 void
-WindowsGamepadService::DevicesChanged() {
-  SetEvent(mThreadRescanEvent);
+WindowsGamepadService::DevicesChanged(DeviceChangeType type) {
+  if (type == DeviceChangeNotification) {
+    mObserver->SetDeviceChangeTimer();
+  } else if (type == DeviceChangeStable) {
+    SetEvent(mThreadRescanEvent);
+  }
 }
 
 NS_IMETHODIMP
@@ -598,27 +613,39 @@ Observer::Observe(nsISupports* aSubject,
                   const char* aTopic,
                   const PRUnichar* aData) {
   if (strcmp(aTopic, "timer-callback") == 0) {
-    mSvc.DevicesChanged();
+    mSvc.DevicesChanged(WindowsGamepadService::DeviceChangeStable);
   } else if (strcmp(aTopic, NS_XPCOM_WILL_SHUTDOWN_OBSERVER_ID) == 0) {
     Stop();
-  } else if (strcmp(aTopic, "devices-changed")) {
-    // set stable timer, since we will get multiple devices-changed
-    // notifications at once
-    if (mTimer) {
-      mTimer->Cancel();
-      mTimer->Init(this, kDevicesChangedStableDelay, nsITimer::TYPE_ONE_SHOT);
-    }
   }
   return NS_OK;
 }
 
+WindowsGamepadService* gService = nullptr;
+HWND sHWnd = nullptr;
+
+static
+LRESULT CALLBACK
+GamepadWindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
+  const unsigned int DBT_DEVICEARRIVAL        = 0x8000;
+  const unsigned int DBT_DEVICEREMOVECOMPLETE = 0x8004;
+  const unsigned int DBT_DEVNODES_CHANGED     = 0x7;
+
+  if (msg == WM_DEVICECHANGE &&
+      (wParam == DBT_DEVICEARRIVAL ||
+       wParam == DBT_DEVICEREMOVECOMPLETE ||
+       wParam == DBT_DEVNODES_CHANGED)) {
+    if (gService) {
+      gService->DevicesChanged(WindowsGamepadService::DeviceChangeNotification);
+    }
+  }
+  return DefWindowProc(hwnd, msg, wParam, lParam);
+}
+
 } // namespace
 
 namespace mozilla {
 namespace hal_impl {
 
-WindowsGamepadService* gService = nullptr;
-
 void StartMonitoringGamepadStatus()
 {
   if (gService)
@@ -626,6 +653,23 @@ void StartMonitoringGamepadStatus()
 
   gService = new WindowsGamepadService();
   gService->Startup();
+
+  if (sHWnd == nullptr) {
+    WNDCLASSW wc;
+    HMODULE hSelf = GetModuleHandle(nullptr);
+
+    if (!GetClassInfoW(hSelf, L"MozillaGamepadClass", &wc)) {
+      ZeroMemory(&wc, sizeof(WNDCLASSW));
+      wc.hInstance = hSelf;
+      wc.lpfnWndProc = GamepadWindowProc;
+      wc.lpszClassName = L"MozillaGamepadClass";
+      RegisterClassW(&wc);
+    }
+
+    sHWnd = CreateWindowW(L"MozillaGamepadClass", L"Gamepad Watcher",
+                          0, 0, 0, 0, 0,
+                          nullptr, nullptr, hSelf, nullptr);
+  }
 }
 
 void StopMonitoringGamepadStatus()
@@ -633,6 +677,11 @@ void StopMonitoringGamepadStatus()
   if (!gService)
     return;
 
+  if (sHWnd) {
+    DestroyWindow(sHWnd);
+    sHWnd = nullptr;
+  }
+
   gService->Shutdown();
   delete gService;
   gService = nullptr;