1 files changed, 121 insertions, 0 deletions
diff --git a/widget/windows/WidgetTraceEvent.cpp b/widget/windows/WidgetTraceEvent.cpp
new file mode 100644
index 0000000000..15bb4d720c
--- /dev/null
+++ b/widget/windows/WidgetTraceEvent.cpp
@@ -0,0 +1,121 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Windows widget support for event loop instrumentation.
+ * See toolkit/xre/EventTracer.cpp for more details.
+ */
+
+#include <stdio.h>
+#include <windows.h>
+
+#include "mozilla/RefPtr.h"
+#include "mozilla/WidgetTraceEvent.h"
+#include "nsAppShellCID.h"
+#include "nsComponentManagerUtils.h"
+#include "nsCOMPtr.h"
+#include "nsIAppShellService.h"
+#include "nsIBaseWindow.h"
+#include "nsIDocShell.h"
+#include "nsISupportsImpl.h"
+#include "nsIWidget.h"
+#include "nsIAppWindow.h"
+#include "nsServiceManagerUtils.h"
+#include "nsThreadUtils.h"
+#include "nsWindowDefs.h"
+
+namespace {
+
+// Used for signaling the background thread from the main thread.
+HANDLE sEventHandle = nullptr;
+
+// We need a runnable in order to find the hidden window on the main
+// thread.
+class HWNDGetter : public mozilla::Runnable {
+ public:
+  HWNDGetter() : Runnable("HWNDGetter"), hidden_window_hwnd(nullptr) {}
+
+  HWND hidden_window_hwnd;
+
+  NS_IMETHOD Run() override {
+    // Jump through some hoops to locate the hidden window.
+    nsCOMPtr<nsIAppShellService> appShell(
+        do_GetService(NS_APPSHELLSERVICE_CONTRACTID));
+    nsCOMPtr<nsIAppWindow> hiddenWindow;
+
+    nsresult rv = appShell->GetHiddenWindow(getter_AddRefs(hiddenWindow));
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+
+    nsCOMPtr<nsIDocShell> docShell;
+    rv = hiddenWindow->GetDocShell(getter_AddRefs(docShell));
+    if (NS_FAILED(rv) || !docShell) {
+      return rv;
+    }
+
+    nsCOMPtr<nsIBaseWindow> baseWindow(do_QueryInterface(docShell));
+
+    if (!baseWindow) return NS_ERROR_FAILURE;
+
+    nsCOMPtr<nsIWidget> widget;
+    baseWindow->GetMainWidget(getter_AddRefs(widget));
+
+    if (!widget) return NS_ERROR_FAILURE;
+
+    hidden_window_hwnd = (HWND)widget->GetNativeData(NS_NATIVE_WINDOW);
+
+    return NS_OK;
+  }
+};
+
+HWND GetHiddenWindowHWND() {
+  // Need to dispatch this to the main thread because plenty of
+  // the things it wants to access are main-thread-only.
+  RefPtr<HWNDGetter> getter = new HWNDGetter();
+  NS_DispatchAndSpinEventLoopUntilComplete(
+      "GetHiddenWindowHWND"_ns, mozilla::GetMainThreadSerialEventTarget(),
+      do_AddRef(getter));
+  return getter->hidden_window_hwnd;
+}
+
+}  // namespace
+
+namespace mozilla {
+
+bool InitWidgetTracing() {
+  sEventHandle = CreateEventW(nullptr, FALSE, FALSE, nullptr);
+  return sEventHandle != nullptr;
+}
+
+void CleanUpWidgetTracing() {
+  CloseHandle(sEventHandle);
+  sEventHandle = nullptr;
+}
+
+// This function is called from the main (UI) thread.
+void SignalTracerThread() {
+  if (sEventHandle != nullptr) SetEvent(sEventHandle);
+}
+
+// This function is called from the background tracer thread.
+bool FireAndWaitForTracerEvent() {
+  MOZ_ASSERT(sEventHandle, "Tracing not initialized!");
+
+  // First, try to find the hidden window.
+  static HWND hidden_window = nullptr;
+  if (hidden_window == nullptr) {
+    hidden_window = GetHiddenWindowHWND();
+  }
+
+  if (hidden_window == nullptr) return false;
+
+  // Post the tracer message into the hidden window's message queue,
+  // and then block until it's processed.
+  PostMessage(hidden_window, MOZ_WM_TRACE, 0, 0);
+  WaitForSingleObject(sEventHandle, INFINITE);
+  return true;
+}
+
+}  // namespace mozilla