Comment 65 for bug 91334

Hi, I don't think this issue is caused by bug #469538.

However, I looked briefly at XEMBED (through GtkPlug / GtkSocket) while debugging a problem for nspluginwrapper. It turns out Firefox never destroys the plugin window cleanly, and its not really its fault. First, Firefox never propagates NPP_SetWindow(NPP, (NPWindow){ .window = NULL }); down to the plugin. Then, DoStopPlugin() will generally delay destroy of the page window, not the plugin window. That window is destroyed at the Gdk level (through a simple g_object_unref() IIRC). However, in the best cases, that "toplevel" window destruction will trigger the destruction of the GtkSocket, but not the underlying X window.

Something important to note: GtkPlug / GtkSocket work differently depending on whether the other GtkPlug is in-process or out of process. In out-of-process case, destroying a window will destroy all subsequent windows in the hierarchy, including the plugins X windows and windows in the other process. However, in the in-process case, the X window (exposed to the plugin) is never destroyed. Nada, no call to XDestroyWindow() with that XID.

AFAIK, this is a problem for Flash that doesn't expect someone else destroying its plugin window from behind its back. It currently works in Firefox because the plugin XID is never destroyed for the lifetime of the program. However, when run through nspluginwrapper, and since I tried to respect the NPAPI specs and destroying the windows around NPP_Destroy(), it fails.

I will probably open another bug entry for this specific issue, though this is not really Firefox's fault (rather Gtk2). However, Firefox could have been cool and send NPP_SetWindow() with a NULL NPWindow::window, as mentioned in the specs. Though, Flash (even version 10) doesn't handle that case either anyway. So, we are left with a possible Gtk2 bug.

Note: I workarounded the issue at the nspluginwrapper level by forbidding propagation of WM_DELETE_EVENT (that the GtkSocket sends) + other tricks.

I am not sure I was clear enough as I was typing this away from the actual Firefox sources, but rather dumped what I had in memory. ;-)