Bug 1152353: Repost printer properties completion messages after nsAppShell::ProcessNextNativeEvent. r=jimm

widget/windows/nsAppShell.cpp

@@ -25,6 +25,12 @@
 #include "nsComponentManagerUtils.h"
 #include "nsITimer.h"
 
+// These are two messages that the code in winspool.drv on Windows 7 explicitly
+// waits for while it is pumping other Windows messages, during display of the
+// Printer Properties dialog.
+#define MOZ_WM_PRINTER_PROPERTIES_COMPLETION 0x5b7a
+#define MOZ_WM_PRINTER_PROPERTIES_FAILURE 0x5b7f
+
 using namespace mozilla;
 using namespace mozilla::widget;
 
@@ -372,6 +378,15 @@ nsAppShell::ProcessNextNativeEvent(bool mayWait)
           continue;  // the message is consumed.
         }
 
+        // Store Printer Properties messages for reposting, because they are not
+        // processed by a window procedure, but are explicitly waited for in the
+        // winspool.drv code that will be further up the stack.
+        if (msg.message == MOZ_WM_PRINTER_PROPERTIES_COMPLETION ||
+            msg.message == MOZ_WM_PRINTER_PROPERTIES_FAILURE) {
+          mMsgsToRepost.push_back(msg);
+          continue;
+        }
+
         ::TranslateMessage(&msg);
         ::DispatchMessageW(&msg);
       }
@@ -407,3 +422,16 @@ nsAppShell::ProcessNextNativeEvent(bool mayWait)
 
   return gotMessage;
 }
+
+nsresult
+nsAppShell::AfterProcessNextEvent(nsIThreadInternal* /* unused */,
+                                  bool /* unused */)
+{
+  if (!mMsgsToRepost.empty()) {
+    for (MSG msg : mMsgsToRepost) {
+      ::PostMessageW(msg.hwnd, msg.message, msg.wParam, msg.lParam);
+    }
+    mMsgsToRepost.clear();
+  }
+  return NS_OK;
+}

widget/windows/nsAppShell.h

@@ -8,6 +8,7 @@
 
 #include "nsBaseAppShell.h"
 #include <windows.h>
+#include <vector>
 #include "mozilla/TimeStamp.h"
 #include "mozilla/Mutex.h"
 
@@ -34,6 +35,9 @@ public:
 
   static UINT GetTaskbarButtonCreatedMessage();
 
+  NS_IMETHOD AfterProcessNextEvent(nsIThreadInternal* thread,
+                                   bool eventWasProcessed) final;
+
 protected:
   NS_IMETHOD Run();
   NS_IMETHOD Exit();
@@ -49,6 +53,7 @@ protected:
 
   Mutex mLastNativeEventScheduledMutex;
   TimeStamp mLastNativeEventScheduled;
+  std::vector<MSG> mMsgsToRepost;
 };
 
 #endif // nsAppShell_h__