Bug 544945, part 2: Periodically unblock the parent to allow it to process events while the plugin subprocess is in a nested event loop. r=karlt

--HG--
extra : rebase_source : bf9a2df9d7d6b420fb93d11dc5abaeb4be1214db

dom/plugins/PPluginModule.ipdl

@@ -93,6 +93,12 @@ parent:
   rpc NPN_GetValue_WithBoolReturn(NPNVariable aVariable)
     returns (NPError aError,
              bool aBoolVal);
+
+  // Wake up and process a few native events.  Periodically called by
+  // Gtk-specific code upon detecting that the plugin process has
+  // entered a nested event loop.  If the browser doesn't process
+  // native events, then "livelock" and some other glitches can occur.
+  rpc ProcessSomeEvents();
 };
 
 } // namespace plugins

dom/plugins/PluginModuleChild.cpp

@@ -290,7 +290,7 @@ PluginModuleChild::ProcessBrowserEvents(gpointer data)
 
     PluginModuleChild* pmc = static_cast<PluginModuleChild*>(data);
 
-    PLUGIN_LOG_DEBUG(("FIXME/bug 544945: rpc-call to browser to process a few events"));
+    pmc->CallProcessSomeEvents();
 
     return TRUE;
 }

dom/plugins/PluginModuleParent.cpp

@@ -45,6 +45,7 @@
 #include "nsContentUtils.h"
 #include "nsCRT.h"
 #include "nsNPAPIPlugin.h"
+#include "nsThreadUtils.h"
 
 using base::KillProcess;
 
@@ -837,3 +838,35 @@ PluginModuleParent::AnswerNPN_GetValue_WithBoolReturn(const NPNVariable& aVariab
     *aBoolVal = boolVal ? true : false;
     return true;
 }
+
+#if !defined(MOZ_WIDGET_GTK2)
+bool
+PluginModuleParent::AnswerProcessSomeEvents()
+{
+    NS_RUNTIMEABORT("unreached");
+    return false;
+}
+
+#else
+static const int kMaxChancesToProcessEvents = 20;
+
+bool
+PluginModuleParent::AnswerProcessSomeEvents()
+{
+    PLUGIN_LOG_DEBUG(("Spinning mini nested loop ..."));
+
+    // XXX it would seem sensical to make the condition be
+    // |NS_HasPendingEvents() && i < kMaxEventsToProcess|.  The
+    // problem is, the native appshell is just an observer of our
+    // nsThread, and processes native events as a side effect of
+    // nsThread::ProcessNextEvent().  Since native events are the ones
+    // we really care about here, we need to go straight to
+    // NS_ProcessNextEvent().
+    for (int i = 0; i < kMaxChancesToProcessEvents; ++i)
+        NS_ProcessNextEvent(nsnull, PR_FALSE);
+
+    PLUGIN_LOG_DEBUG(("... quitting mini nested loop"));
+
+    return true;
+}
+#endif

dom/plugins/PluginModuleParent.h

@@ -154,6 +154,9 @@ protected:
                                       NPError* aError,
                                       bool* aBoolVal);
 
+    NS_OVERRIDE
+    virtual bool AnswerProcessSomeEvents();
+
     static PluginInstanceParent* InstCast(NPP instance);
     static BrowserStreamParent* StreamCast(NPP instance, NPStream* s);