src/xvba_videx_{x11,glx}: add debugging code

Assert if prerequisites are not met.

src/xvba_video.c

@@ -554,16 +554,23 @@ xvba_DestroySurfaces(
 
 #if USE_GLX
         if (obj_surface->gl_surface) {
+            /* NOTE: multiple VASurfaces can point to the same GLX Surface
+             * therefor only unref the surface here. The GLX Surface will
+             * be destroyed automatically when the refcount reaches 0. */
             glx_surface_unref(driver_data, obj_surface->gl_surface);
             obj_surface->gl_surface = NULL;
         }
 #endif
 
         for (j = 0; j < obj_surface->output_surfaces_count; j++) {
+            /* NOTE: multiple VASurfaces can point to the same output surface
+             * therefor only unref the surface here. The output surface will
+             * be destroyed automatically when the refcount reaches 0. */
             output_surface_unref(driver_data, obj_surface->output_surfaces[j]);
             obj_surface->output_surfaces[j] = NULL;
         }
         free(obj_surface->output_surfaces);
+        obj_surface->output_surfaces = NULL;
         obj_surface->output_surfaces_count = 0;
         obj_surface->output_surfaces_count_max = 0;
 

src/xvba_video_glx.c

@@ -633,6 +633,8 @@ destroy_glx_surface(
     if (!obj_glx_surface)
         return;
 
+    ASSERT(obj_glx_surface->refcount == 0);
+
     if (obj_glx_surface->texture) {
         gl_destroy_texture(&obj_glx_surface->texture, obj_glx_surface->target);
         obj_glx_surface->texture = 0;
@@ -1106,6 +1108,7 @@ transfer_surface_native(
             obj_glx_surface->evergreen_params_count = n_params;
 
             if (shader_fp && shader_fp_length) {
+                ASSERT(obj_glx_surface->evergreen_shader == NULL);
                 obj_glx_surface->evergreen_shader = gl_create_shader_object(
                     shader_fp,
                     shader_fp_length

src/xvba_video_x11.c

@@ -58,6 +58,8 @@ output_surface_destroy(
     object_output_p     obj_output
 )
 {
+    ASSERT(obj_output->refcount == 0);
+
 #if USE_GLX
     if (obj_output->glx) {
         glx_output_surface_destroy(driver_data, obj_output->glx);