From deefedd002a91dcb66351cee6f3f92b5f62bcac7 Mon Sep 17 00:00:00 2001
From: Damian Hobson-Garcia <dhobsong@igel.co.jp>
Date: Wed, 22 Jul 2020 16:32:37 +0900
Subject: [PATCH] waylandsink: Update stale GstBuffer references in wayland
 buffer cache

"waylandsink: use GstMemory instead of GstBuffer for cache lookup"
changes the cache key to GstMemory, but the cached data still needs
a pointer to the GstBuffer to control the buffer lifecycle.
If the GstMemory used as the cache key moves from one GstBuffer to
another, the pointer in the cached data will be out-of-date.

Update the current GstBuffer pointer for each frame so that it always
represents the currently in use (from attach to release) GstBuffer
for each wl_buffer.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1473>
---
 ext/wayland/wlbuffer.c | 34 +++++++++++++++++++---------------
 ext/wayland/wlbuffer.h |  3 ++-
 2 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/ext/wayland/wlbuffer.c b/ext/wayland/wlbuffer.c
index 9b2a03f4cd..0739bdaf2c 100644
--- a/ext/wayland/wlbuffer.c
+++ b/ext/wayland/wlbuffer.c
@@ -95,8 +95,7 @@ gst_wl_buffer_dispose (GObject * gobject)
    * block and in the end the display will increase the refcount
    * of this GstWlBuffer, so it will not be finalized */
   if (self->display) {
-    GstMemory *mem0 = gst_buffer_peek_memory (self->gstbuffer, 0);
-    gst_wl_display_unregister_buffer (self->display, mem0);
+    gst_wl_display_unregister_buffer (self->display, self->gstmem);
   }
 
   G_OBJECT_CLASS (gst_wl_buffer_parent_class)->dispose (gobject);
@@ -133,13 +132,15 @@ static void
 buffer_release (void *data, struct wl_buffer *wl_buffer)
 {
   GstWlBuffer *self = data;
+  GstBuffer *buf = self->current_gstbuffer;
 
-  GST_LOG_OBJECT (self, "wl_buffer::release (GstBuffer: %p)", self->gstbuffer);
+  GST_LOG_OBJECT (self, "wl_buffer::release (GstBuffer: %p)", buf);
 
   self->used_by_compositor = FALSE;
+  self->current_gstbuffer = NULL;
 
   /* unref should be last, because it may end up destroying the GstWlBuffer */
-  gst_buffer_unref (self->gstbuffer);
+  gst_buffer_unref (buf);
 }
 
 static const struct wl_buffer_listener buffer_listener = {
@@ -163,19 +164,18 @@ gst_buffer_add_wl_buffer (GstBuffer * gstbuffer, struct wl_buffer *wlbuffer,
     GstWlDisplay * display)
 {
   GstWlBuffer *self;
-  GstMemory *mem0;
 
   self = g_object_new (GST_TYPE_WL_BUFFER, NULL);
-  self->gstbuffer = gstbuffer;
+  self->current_gstbuffer = gstbuffer;
   self->wlbuffer = wlbuffer;
   self->display = display;
+  self->gstmem = gst_buffer_peek_memory (gstbuffer, 0);
 
-  mem0 = gst_buffer_peek_memory (gstbuffer, 0);
-  gst_wl_display_register_buffer (self->display, mem0, self);
+  gst_wl_display_register_buffer (self->display, self->gstmem, self);
 
   wl_buffer_add_listener (self->wlbuffer, &buffer_listener, self);
 
-  gst_mini_object_weak_ref (GST_MINI_OBJECT (mem0),
+  gst_mini_object_weak_ref (GST_MINI_OBJECT (self->gstmem),
       (GstMiniObjectNotify) gstmemory_disposed, self);
 
 
@@ -186,7 +186,10 @@ GstWlBuffer *
 gst_buffer_get_wl_buffer (GstWlDisplay * display, GstBuffer * gstbuffer)
 {
   GstMemory *mem0 = gst_buffer_peek_memory (gstbuffer, 0);
-  return gst_wl_display_lookup_buffer (display, mem0);
+  GstWlBuffer *wlbuf = gst_wl_display_lookup_buffer (display, mem0);
+  if (wlbuf)
+    wlbuf->current_gstbuffer = gstbuffer;
+  return wlbuf;
 }
 
 void
@@ -198,9 +201,9 @@ gst_wl_buffer_force_release_and_unref (GstBuffer * buf, GstWlBuffer * self)
    * at the same time from the event loop thread */
   if (self->used_by_compositor) {
     GST_DEBUG_OBJECT (self, "forcing wl_buffer::release (GstBuffer: %p)",
-        self->gstbuffer);
+        self->current_gstbuffer);
     self->used_by_compositor = FALSE;
-    gst_buffer_unref (self->gstbuffer);
+    gst_buffer_unref (self->current_gstbuffer);
   }
 
   /* Finalize this GstWlBuffer early.
@@ -214,7 +217,7 @@ gst_wl_buffer_force_release_and_unref (GstBuffer * buf, GstWlBuffer * self)
   wl_buffer_destroy (self->wlbuffer);
   self->wlbuffer = NULL;
   self->display = NULL;
-  self->gstbuffer = NULL;
+  self->current_gstbuffer = NULL;
 
   /* remove the reference that the caller (GstWlDisplay) owns */
   g_object_unref (self);
@@ -224,7 +227,8 @@ void
 gst_wl_buffer_attach (GstWlBuffer * self, struct wl_surface *surface)
 {
   if (self->used_by_compositor) {
-    GST_DEBUG_OBJECT (self, "buffer used by compositor %p", self->gstbuffer);
+    GST_DEBUG_OBJECT (self, "buffer used by compositor %p",
+        self->current_gstbuffer);
     return;
   }
 
@@ -233,6 +237,6 @@ gst_wl_buffer_attach (GstWlBuffer * self, struct wl_surface *surface)
   /* Add a reference to the buffer. This represents the fact that
    * the compositor is using the buffer and it should not return
    * back to the pool and be re-used until the compositor releases it. */
-  gst_buffer_ref (self->gstbuffer);
+  gst_buffer_ref (self->current_gstbuffer);
   self->used_by_compositor = TRUE;
 }
diff --git a/ext/wayland/wlbuffer.h b/ext/wayland/wlbuffer.h
index 5bd25168c8..95433f21d7 100644
--- a/ext/wayland/wlbuffer.h
+++ b/ext/wayland/wlbuffer.h
@@ -40,7 +40,8 @@ struct _GstWlBuffer
   GObject parent_instance;
 
   struct wl_buffer * wlbuffer;
-  GstBuffer *gstbuffer;
+  GstBuffer *current_gstbuffer;
+  GstMemory *gstmem;
 
   GstWlDisplay *display;