Bug 627084 - Add an app shell native event starvation timeout for cases where our native event pump messages get dropped by 3rd party code. r=roc

widget/src/windows/nsAppShell.cpp

@@ -54,6 +54,9 @@
 const PRUnichar* kAppShellEventId = L"nsAppShell:EventID";
 const PRUnichar* kTaskbarButtonEventId = L"TaskbarButtonCreated";
 
+// The maximum time we allow before forcing a native event callback
+#define NATIVE_EVENT_STARVATION_LIMIT mozilla::TimeDuration::FromSeconds(1)
+
 static UINT sMsgId;
 
 #if MOZ_WINSDK_TARGETVER >= MOZ_NTDDI_WIN7
@@ -135,6 +138,8 @@ nsAppShell::Init()
   LSPAnnotate();
 #endif
 
+  mLastNativeEventScheduled = TimeStamp::Now();
+
   if (!sMsgId)
     sMsgId = RegisterWindowMessageW(kAppShellEventId);
 
@@ -306,6 +311,9 @@ nsAppShell::ScheduleNativeEventCallback()
 {
   // Post a message to the hidden message window
   NS_ADDREF_THIS(); // will be released when the event is processed
+  // Time stamp this event so we can detect cases where the event gets
+  // dropping in sub classes / modal loops we do not control. 
+  mLastNativeEventScheduled = TimeStamp::Now();
   ::PostMessage(mEventWnd, sMsgId, 0, reinterpret_cast<LPARAM>(this));
 }
 
@@ -348,5 +356,12 @@ nsAppShell::ProcessNextNativeEvent(PRBool mayWait)
   if (mNativeCallbackPending && mEventloopNestingLevel == 1)
     DoProcessMoreGeckoEvents();
 
+  // Check for starved native callbacks. If we haven't processed one
+  // of these events in NATIVE_EVENT_STARVATION_LIMIT, fire one off.
+  if ((TimeStamp::Now() - mLastNativeEventScheduled) >
+      NATIVE_EVENT_STARVATION_LIMIT) {
+    ScheduleNativeEventCallback();
+  }
+  
   return gotMessage;
 }

widget/src/windows/nsAppShell.h

@@ -40,6 +40,7 @@
 
 #include "nsBaseAppShell.h"
 #include <windows.h>
+#include "mozilla/TimeStamp.h"
 
 /**
  * Native Win32 Application shell wrapper
@@ -51,6 +52,7 @@ public:
     mEventWnd(NULL),
     mNativeCallbackPending(PR_FALSE)
   {}
+  typedef mozilla::TimeStamp TimeStamp;
 
   nsresult Init();
   void DoProcessMoreGeckoEvents();
@@ -72,6 +74,7 @@ protected:
 protected:
   HWND mEventWnd;
   PRBool mNativeCallbackPending;
+  TimeStamp mLastNativeEventScheduled;
 };
 
 #endif // nsAppShell_h__