From 7f59cefafb1cd733cf527fb935b2cd32418fcbe2 Mon Sep 17 00:00:00 2001
From: Matthew Waters <matthew@centricular.com>
Date: Thu, 26 Mar 2020 13:51:24 +1100
Subject: [PATCH] glcontext/cocoa: handle sending one message during shutdown

gst_gl_window_quit() will attempt to send a message but will be called
from GstGLContext's finalize handler and so the weak ref that backs
gst_gl_window_get_context will return NULL as it has already been
cleared.  We need that context in send_message_async to decide whether
to run the provided callback immediately or queue in GCD
---
 gst-libs/gst/gl/cocoa/gstglwindow_cocoa.m | 37 +++++++++++++++++++++--
 1 file changed, 34 insertions(+), 3 deletions(-)

diff --git a/gst-libs/gst/gl/cocoa/gstglwindow_cocoa.m b/gst-libs/gst/gl/cocoa/gstglwindow_cocoa.m
index f70001ee3d..0997b8d539 100644
--- a/gst-libs/gst/gl/cocoa/gstglwindow_cocoa.m
+++ b/gst-libs/gst/gl/cocoa/gstglwindow_cocoa.m
@@ -69,6 +69,7 @@ static void gst_gl_window_cocoa_finalize (GObject * object);
 
 static gboolean gst_gl_window_cocoa_open (GstGLWindow *window, GError **err);
 static void gst_gl_window_cocoa_close (GstGLWindow *window);
+static void gst_gl_window_cocoa_quit (GstGLWindow *window);
 static guintptr gst_gl_window_cocoa_get_window_handle (GstGLWindow * window);
 static void gst_gl_window_cocoa_set_window_handle (GstGLWindow * window,
     guintptr handle);
@@ -96,6 +97,9 @@ struct _GstGLWindowCocoaPrivate
   int view_ready;
 
   gpointer gl_queue;
+
+  gboolean shutting_down;
+  GstGLContext *last_context;
 };
 
 #define DEBUG_INIT \
@@ -114,6 +118,7 @@ gst_gl_window_cocoa_class_init (GstGLWindowCocoaClass * klass)
 
   window_class->open = GST_DEBUG_FUNCPTR (gst_gl_window_cocoa_open);
   window_class->close = GST_DEBUG_FUNCPTR (gst_gl_window_cocoa_close);
+  window_class->quit = GST_DEBUG_FUNCPTR (gst_gl_window_cocoa_quit);
   window_class->get_window_handle =
       GST_DEBUG_FUNCPTR (gst_gl_window_cocoa_get_window_handle);
   window_class->set_window_handle =
@@ -468,7 +473,8 @@ gst_gl_window_cocoa_send_message_async (GstGLWindow * window,
 {
   GstGLWindowCocoa *window_cocoa = (GstGLWindowCocoa *) window;
   GstGLContext *context = gst_gl_window_get_context (window);
-  GThread *thread = gst_gl_context_get_thread (context);
+  GstGLContext *unref_context = NULL;
+  GThread *thread = NULL;
   GstGLWindowCocoaPrivate *priv = window_cocoa->priv;
 #if OS_OBJECT_USE_OBJC
   dispatch_queue_t gl_queue = (__bridge dispatch_queue_t)priv->gl_queue;
@@ -476,16 +482,31 @@ gst_gl_window_cocoa_send_message_async (GstGLWindow * window,
   dispatch_queue_t gl_queue = (dispatch_queue_t)priv->gl_queue;
 #endif
 
+  if (context)
+    window_cocoa->priv->last_context = unref_context = context;
+
+  /* we may not have a context if we are shutting down */
+  if (!context && window_cocoa->priv->shutting_down) {
+    context = window_cocoa->priv->last_context;
+    window_cocoa->priv->shutting_down = FALSE;
+  }
+
+  g_return_if_fail (context != NULL);
+
+  thread = gst_gl_context_get_thread (context);
+
   if (thread == g_thread_self()) {
     /* this case happens for nested calls happening from inside the GCD queue */
     callback (data);
     if (destroy)
       destroy (data);
-    gst_object_unref (context);
+    if (unref_context)
+      gst_object_unref (unref_context);
   } else {
     dispatch_async (gl_queue, ^{
       gst_gl_context_activate (context, TRUE);
-      gst_object_unref (context);
+      if (unref_context)
+        gst_object_unref (unref_context);
       callback (data);
       if (destroy)
         destroy (data);
@@ -495,6 +516,16 @@ gst_gl_window_cocoa_send_message_async (GstGLWindow * window,
     g_thread_unref (thread);
 }
 
+static void
+gst_gl_window_cocoa_quit (GstGLWindow * window)
+{
+  GstGLWindowCocoa *window_cocoa = (GstGLWindowCocoa *) window;
+
+  window_cocoa->priv->shutting_down = TRUE;
+
+  GST_GL_WINDOW_CLASS (parent_class)->quit (window);
+}
+
 struct SetRenderRectangle
 {
  GstGLWindowCocoa *window_cocoa;