osd: refactor how mp_ass_render_frame() is called

Instead of passing an explicit cache to the function, the res parameter
is used. Also, instead of replacing its contents, sub bitmaps are now
appended to it (all assuming the format doesn't actually change).

This is preparation for the following commits.

1 files changed, 1 insertions, 1 deletions

diff --git a/sub/osd_state.h b/sub/osd_state.h
index 30f04d8449..9ef8458f0d 100644
--- a/sub/osd_state.h
+++ b/sub/osd_state.h
@@ -37,7 +37,7 @@ struct osd_object {
     struct mp_osd_res vo_res;
 
     // Internally used by osd_libass.c
-    struct sub_bitmap *parts_cache;
+    struct sub_bitmaps parts_cache;
     struct ass_track *osd_track;
     struct ass_renderer *osd_render;
     struct ass_library *osd_ass_library;