draw_bmp: add a function to return a single-texture OSD overlay

Maybe this is useful for some of the lesser VOs. It's preferable over
bad ad-hoc solutions based on the more complex sub_bitmap data
structures (as observed e.g. in vo_vaapi.c), and does not use that much
more code since draw_bmp already created such an overlay internally.

But I still wanted something that avoids having to upload/render a full
screen-sized overlay if for example there's only a tiny subtitle line on
the bottom of the screen. So the new API can return a list of modified
pixels (for upload) and non-transparent pixels (for display). The way
these pixel rectangles are computed is a bit dumb and returns dumb
results, but it should be usable, and the implementation can change.

1 files changed, 4 insertions, 1 deletions

diff --git a/sub/osd.c b/sub/osd.c
index 52b69461ff..d6f284c398 100644
--- a/sub/osd.c
+++ b/sub/osd.c
@@ -425,9 +425,12 @@ void osd_draw_on_image_p(struct osd_state *osd, struct mp_osd_res res,
     // Need to lock for the dumb osd->draw_cache thing.
     pthread_mutex_lock(&osd->lock);
 
+    if (!osd->draw_cache)
+        osd->draw_cache = mp_draw_sub_alloc(osd);
+
     stats_time_start(osd->stats, "draw-bmp");
 
-    if (!mp_draw_sub_bitmaps(&osd->draw_cache, dest, list))
+    if (!mp_draw_sub_bitmaps(osd->draw_cache, dest, list))
         MP_WARN(osd, "Failed rendering OSD.\n");
     talloc_steal(osd, osd->draw_cache);