Bug 1671490 - Mark the GPU process as being in the foreground whenever the parent process is in the foreground to make their priorities (and priority boosts) match, r=bas.

Differential Revision: https://phabricator.services.mozilla.com/D161065

gfx/ipc/GPUProcessManager.cpp

@@ -466,6 +466,11 @@ void GPUProcessManager::OnProcessLaunchComplete(GPUProcessHost* aHost) {
 
   mGPUChild = mProcess->GetActor();
   mProcessToken = mProcess->GetProcessToken();
+#if defined(XP_WIN)
+  if (mAppInForeground) {
+    SetProcessIsForeground();
+  }
+#endif
 
   ipc::Endpoint<PVsyncBridgeParent> vsyncParent;
   ipc::Endpoint<PVsyncBridgeChild> vsyncChild;
@@ -824,7 +829,11 @@ void GPUProcessManager::HandleProcessLost() {
   // Except on Android if the app is in the background, where we want to wait
   // until the app is in the foreground again.
   if (gfxConfig::IsEnabled(Feature::GPU_PROCESS)) {
+#ifdef MOZ_WIDGET_ANDROID
     if (mAppInForeground) {
+#else
+    {
+#endif
       Unused << LaunchGPUProcess();
     }
   } else {
@@ -1393,6 +1402,57 @@ RefPtr<MemoryReportingProcess> GPUProcessManager::GetProcessMemoryReporter() {
   return new GPUMemoryReporter();
 }
 
+void GPUProcessManager::SetAppInForeground(bool aInForeground) {
+  if (mAppInForeground == aInForeground) {
+    return;
+  }
+
+  mAppInForeground = aInForeground;
+#if defined(XP_WIN)
+  SetProcessIsForeground();
+#endif
+}
+
+#if defined(XP_WIN)
+void GPUProcessManager::SetProcessIsForeground() {
+  NTSTATUS WINAPI NtSetInformationProcess(
+      IN HANDLE process_handle, IN ULONG info_class,
+      IN PVOID process_information, IN ULONG information_length);
+  constexpr unsigned int NtProcessInformationForeground = 25;
+
+  static bool alreadyInitialized = false;
+  static decltype(NtSetInformationProcess)* setInformationProcess = nullptr;
+  if (!alreadyInitialized) {
+    alreadyInitialized = true;
+    nsModuleHandle module(LoadLibrary(L"ntdll.dll"));
+    if (module) {
+      setInformationProcess =
+          (decltype(NtSetInformationProcess)*)GetProcAddress(
+              module, "NtSetInformationProcess");
+    }
+  }
+  if (MOZ_UNLIKELY(!setInformationProcess)) {
+    return;
+  }
+
+  unsigned pid = GPUProcessPid();
+  if (pid <= 0) {
+    return;
+  }
+  // Using the handle from mProcess->GetChildProcessHandle() fails;
+  // the PROCESS_SET_INFORMATION permission is probably missing.
+  nsAutoHandle processHandle(
+      ::OpenProcess(PROCESS_SET_INFORMATION, FALSE, pid));
+  if (!processHandle) {
+    return;
+  }
+
+  BOOLEAN foreground = mAppInForeground;
+  setInformationProcess(processHandle, NtProcessInformationForeground,
+                        (PVOID)&foreground, sizeof(foreground));
+}
+#endif
+
 RefPtr<PGPUChild::TestTriggerMetricsPromise>
 GPUProcessManager::TestTriggerMetrics() {
   if (!NS_WARN_IF(!mGPUChild)) {

gfx/ipc/GPUProcessManager.h

@@ -199,6 +199,10 @@ class GPUProcessManager final : public GPUProcessHost::Listener {
   // Returns the process host
   GPUProcessHost* Process() { return mProcess; }
 
+  // Sets the value of mAppInForeground, and (on Windows) adjusts the priority
+  // of the GPU process accordingly.
+  void SetAppInForeground(bool aInForeground);
+
   /*
    * ** Test-only Method **
    *
@@ -285,6 +289,10 @@ class GPUProcessManager final : public GPUProcessHost::Listener {
   void EnsureImageBridgeChild();
   void EnsureVRManager();
 
+#if defined(XP_WIN)
+  void SetProcessIsForeground();
+#endif
+
 #if defined(MOZ_WIDGET_ANDROID)
   already_AddRefed<UiCompositorControllerChild> CreateUiCompositorController(
       nsBaseWidget* aWidget, const LayersId aId);

widget/windows/nsWindow.cpp

@@ -6194,6 +6194,10 @@ bool nsWindow::ProcessMessageInternal(UINT msg, WPARAM& wParam, LPARAM& lParam,
       }
     } break;
 
+    case WM_ACTIVATEAPP: {
+      GPUProcessManager::Get()->SetAppInForeground(wParam);
+    } break;
+
     case WM_MOUSEACTIVATE:
       // A popup with a parent owner should not be activated when clicked but
       // should still allow the mouse event to be fired, so the return value