ui/gtk-gl-area: implement GL context destruction

The counterpart function for gd_gl_area_create_context() is
currently empty. Implement the gd_gl_area_destroy_context()
function to avoid GL context leaks.

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-Id: <20220605085131.7711-1-vr_qemu@t-online.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

ui/gtk-gl-area.c

@@ -201,7 +201,13 @@ QEMUGLContext gd_gl_area_create_context(DisplayGLCtx *dgc,
 
 void gd_gl_area_destroy_context(DisplayGLCtx *dgc, QEMUGLContext ctx)
 {
-    /* FIXME */
+    GdkGLContext *current_ctx = gdk_gl_context_get_current();
+
+    trace_gd_gl_area_destroy_context(ctx, current_ctx);
+    if (ctx == current_ctx) {
+        gdk_gl_context_clear_current();
+    }
+    g_clear_object(&ctx);
 }
 
 void gd_gl_area_scanout_texture(DisplayChangeListener *dcl,

ui/trace-events

@@ -26,6 +26,7 @@ gd_key_event(const char *tab, int gdk_keycode, int qkeycode, const char *action)
 gd_grab(const char *tab, const char *device, const char *reason) "tab=%s, dev=%s, reason=%s"
 gd_ungrab(const char *tab, const char *device) "tab=%s, dev=%s"
 gd_keymap_windowing(const char *name) "backend=%s"
+gd_gl_area_destroy_context(void *ctx, void *current_ctx) "ctx=%p, current_ctx=%p"
 
 # vnc-auth-sasl.c
 # vnc-auth-vencrypt.c