[gtk/cherry-pick-b63c4d67] wayland: Fix memleaks when rendering with Cairo

[Benjamin Otte <otte src gnome org>]

commit eda758ecf0cbfd897590ec972f0b9ab644f472df
Author: Benjamin Otte <otte redhat com>
Date:   Tue Mar 9 18:52:59 2021 +0000

    wayland: Fix memleaks when rendering with Cairo
    
    We were leaking buffers. This wasn't caught by valgrind and friends
    because it was shared memory (with the compositor), but top(1) would
    instantly see memory consumption of the app and the shell go through the
    roof.
    
    
    (cherry picked from commit 0a9d075b47a06c342ab3fee84c230ba768f05257)

 gdk/wayland/gdkcairocontext-wayland.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
---
diff --git a/gdk/wayland/gdkcairocontext-wayland.c b/gdk/wayland/gdkcairocontext-wayland.c
index fcc547ecf6..819daa140e 100644
--- a/gdk/wayland/gdkcairocontext-wayland.c
+++ b/gdk/wayland/gdkcairocontext-wayland.c
@@ -109,6 +109,8 @@ gdk_wayland_cairo_context_buffer_release (void             *_data,
 
   /* Get rid of all the extra ones */
   gdk_wayland_cairo_context_remove_surface (self, cairo_surface);
+  /* Release the reference the compositor held to this surface */
+  cairo_surface_destroy (cairo_surface);
 }
 
 static const struct wl_buffer_listener buffer_listener = {
@@ -194,7 +196,7 @@ gdk_wayland_cairo_context_end_frame (GdkDrawContext *draw_context,
 static void
 gdk_wayland_cairo_context_clear_all_cairo_surfaces (GdkWaylandCairoContext *self)
 {
-  self->cached_surface = NULL;
+  g_clear_pointer (&self->cached_surface, cairo_surface_destroy);
   while (self->surfaces)
     gdk_wayland_cairo_context_remove_surface (self, self->surfaces->data);
 }
@@ -221,6 +223,8 @@ gdk_wayland_cairo_context_dispose (GObject *object)
   GdkWaylandCairoContext *self = GDK_WAYLAND_CAIRO_CONTEXT (object);
 
   gdk_wayland_cairo_context_clear_all_cairo_surfaces (self);
+  g_assert (self->cached_surface == NULL);
+  g_assert (self->paint_surface == NULL);
 
   G_OBJECT_CLASS (gdk_wayland_cairo_context_parent_class)->dispose (object);
 }