osd, lua: manage multiple ASS overlays set with set_osd_ass() calls

Until now, there was only 1 global ASS overlay that could be set by all
scripts. This was often perceived as bug when multiple scripts tried to
set their own ASS overlay.

This was kind of hard to solve because the script could set its own ASS
PlayResX/Y, which makes it impossible to share a single ASS_Renderer for
multiple scripts. The OSC unfortunately makes use of this feature (and
unfortunately can't be fixed because it's a POS), so we're stuck with
this complication.

Implement the worst-case solution and fix this by creating separate ASS
track and renderer objects for each script that wants to set an ASS
overlay.

The z-order is decided by the order the scripts set their text first.
This is essentially random, unless you do it at script init, and you
pass scripts in a specific order. Script initialization is currently
serialized (as a feature), so the first loaded script gets lowest
Z-order.

The Lua script API interestingly remains the same. (And also will remain
undocumented, unsupported, and potentially volatile.)

1 files changed, 5 insertions, 0 deletions

diff --git a/sub/osd_dummy.c b/sub/osd_dummy.c
index 1982870248..061f6446c3 100644
--- a/sub/osd_dummy.c
+++ b/sub/osd_dummy.c
@@ -26,3 +26,8 @@ void osd_object_get_bitmaps(struct osd_state *osd, struct osd_object *obj,
 {
     *out_imgs = (struct sub_bitmaps) {0};
 }
+
+void osd_set_external(struct osd_state *osd, char *id, int res_x, int res_y,
+                      char *text)
+{
+}