sub: add --ass-style-override=force option

(The old "force" choice of that option is renamed to "force-default".)

This allows overriding native ASS script subtitle styles with the style
provided by the --sub-text-* options (like --sub-text-font etc.). This
is disabled by default, and needs to be explicitly enabled with the
--ass-style-override=force option and input property.

This uses in fact exactly the same options (--sub-text-*) and semantics
as the ones used to configure unstyled text subtitles.

It's recommended to combine this with this in the mpv config file:

ass-force-style="ScaledBorderAndShadow=1"   # work around dumb libass behavior

Also, adding a key binding to toggle this behavior should be added,
because overriding can easily break:

L cycle ass-style-override

This would cycle override behavior on Shift+L and allows quickly
disabling/enabling style overrides.

Note: ASS should be considered a vector format rather than a subtitle
format. There is no easy or reliable way to determine whether the style
of a given subtitle event can be changed without destroying visuals or
not. This patch relies on a simple heuristic, which often works and
often breaks.

1 files changed, 9 insertions, 0 deletions

diff --git a/sub/ass_mp.c b/sub/ass_mp.c
index 9ff8b03ede..d417912826 100644
--- a/sub/ass_mp.c
+++ b/sub/ass_mp.c
@@ -139,6 +139,7 @@ void mp_ass_configure(ASS_Renderer *priv, struct MPOpts *opts,
     float set_line_spacing = 0;
     float set_font_scale = 1;
     int set_hinting = 0;
+    int set_force_override = 0;
     if (opts->ass_style_override) {
         set_use_margins = opts->ass_use_margins;
 #if LIBASS_VERSION >= 0x01010000
@@ -147,6 +148,7 @@ void mp_ass_configure(ASS_Renderer *priv, struct MPOpts *opts,
         set_line_spacing = opts->ass_line_spacing;
         set_font_scale = opts->sub_scale;
         set_hinting = opts->ass_hinting;
+        set_force_override = opts->ass_style_override == 3;
     }
 
     ass_set_use_margins(priv, set_use_margins);
@@ -156,6 +158,13 @@ void mp_ass_configure(ASS_Renderer *priv, struct MPOpts *opts,
 #if LIBASS_VERSION >= 0x01000000
     ass_set_shaper(priv, opts->ass_shaper);
 #endif
+#if LIBASS_VERSION >= 0x01103000
+    ass_set_selective_style_override_enabled(priv, set_force_override);
+    ASS_Style style = {0};
+    mp_ass_set_style(&style, 288, opts->sub_text_style);
+    ass_set_selective_style_override(priv, &style);
+    free(style.FontName);
+#endif
     ass_set_font_scale(priv, set_font_scale);
     ass_set_hinting(priv, set_hinting);
     ass_set_line_spacing(priv, set_line_spacing);