command: extend osd-overlay command with bounds reporting

This is more or less a minimal hack to make _some_ text measurement
functionality available to scripts. Since libass does not support such a
thing, this simply uses the bounding box of the rendered text.

This is far from ideal. Problems include:
- using a bitmap bounding box
- additional memory waste and/or flushing caches
- dependency on window size
- odd small deviations with different window sizes (run osd-test.lua and
  resize the window after each timer update; the bounding boxes aren't
  adjusted in an overly useful way)
- inability to query the size _after_ actual rendering

But I guess it's a start. Since I'm aware that it's crap, add a threat
to the manpage that this may be changed/removed again. For now, I'm
interested whether anyone will have use for it in its current form, as
it's an often requested feature.

1 files changed, 2 insertions, 0 deletions

diff --git a/sub/ass_mp.h b/sub/ass_mp.h
index 4ebb7f39a6..f4488bf8c7 100644
--- a/sub/ass_mp.h
+++ b/sub/ass_mp.h
@@ -55,5 +55,7 @@ struct mp_ass_packer *mp_ass_packer_alloc(void *ta_parent);
 void mp_ass_packer_pack(struct mp_ass_packer *p, ASS_Image **image_lists,
                         int num_image_lists, bool changed,
                         int preferred_osd_format, struct sub_bitmaps *out);
+void mp_ass_get_bb(ASS_Image *image_list, ASS_Track *track,
+                   struct mp_osd_res *res, double *out_rc);
 
 #endif                          /* MPLAYER_ASS_MP_H */