sub/osd: add osd-shaper and set it to simple by default

This is a change in default for libass with harfbuzz enabled, previously
it would choose the best available shaper.

Harfbuzz isn't really needed for mpv's OSD and it comes with a
significant performance penalty, so use simple instead

DOCS/interface-changes/osd-cache-opts.txt

@@ -3,3 +3,4 @@ add `--osd-glyph-limit`
 add `--osd-bitmap-max-size`
 add `--sub-glyph-limit`
 add `--sub-bitmap-max-size`
+add `--osd-shaper`

DOCS/man/options.rst

@@ -4814,6 +4814,10 @@ OSD
     Set the delay for automatic pruning of events from memory in libass.
     Disabled by default. See also ``--sub-ass-prune-delay``.
 
+``--osd-shaper=<simple|complex>``
+    Set the text layout engine used by libass for the OSD. Default: simple.
+    See also ``--sub-shaper``
+
 Screenshot
 ----------
 

options/options.c

@@ -414,6 +414,7 @@ const struct m_sub_options mp_osd_render_sub_opts = {
         {"osd-prune-delay", OPT_DOUBLE(osd_ass_prune_delay), M_RANGE(-1.0, 10000.0)},
         {"osd-glyph-limit", OPT_INT(osd_glyph_limit)},
         {"osd-bitmap-max-size", OPT_INT(osd_bitmap_max_size)},
+        {"osd-shaper", OPT_CHOICE(osd_shaper, {"simple", 0}, {"complex", 1})},
         {0}
     },
     .size = sizeof(OPT_BASE_STRUCT),

options/options.h

@@ -151,6 +151,7 @@ struct mp_osd_render_opts {
     double osd_ass_prune_delay;
     int osd_glyph_limit;
     int osd_bitmap_max_size;
+    int osd_shaper;
 };
 
 typedef struct MPOpts {

sub/osd_libass.c

@@ -128,6 +128,7 @@ static void create_ass_track(struct osd_state *osd, struct osd_object *obj,
     track->WrapStyle = 1; // end-of-line wrapping instead of smart wrapping
     track->Kerning = true;
     track->ScaledBorderAndShadow = true;
+    ass_set_shaper(ass->render, opts->osd_shaper);
 #if LIBASS_VERSION >= 0x01600010
     ass_track_set_feature(track, ASS_FEATURE_WRAP_UNICODE, 1);
 #endif