sd_ass: add a very simple and evil way to override ASS subtitle styles

--ass-style-override=force now attempts to override the 'Default' style.
May or may not work. In some situations it will work, but also mess up
seemingly unrelated things like signs typeset with ASS.

3 files changed, 38 insertions, 6 deletions

diff --git a/DOCS/man/en/options.rst b/DOCS/man/en/options.rst
index 6461750062..fc8b778ac8 100644
--- a/DOCS/man/en/options.rst
+++ b/DOCS/man/en/options.rst
@@ -176,13 +176,18 @@ OPTIONS
 
         Using this option may lead to incorrect subtitle rendering.
 
-``--ass-style-override=<yes|no>``
+``--ass-style-override=<yes|no|force>``
     Control whether user style overrides should be applied.
 
-    :yes: Apply all the ``--ass-*`` style override options. Changing the default
-          for any of these options can lead to incorrect subtitle rendering
-          (default).
-    :no:  Render subtitles as forced by subtitle scripts.
+    :yes:   Apply all the ``--ass-*`` style override options. Changing the default
+            for any of these options can lead to incorrect subtitle rendering
+            (default).
+    :no:    Render subtitles as forced by subtitle scripts.
+    :force: Like ``yes``, but also override the style named ``Default`` to
+            make it look like the like text subtitle style implied by the
+            ``--sub-text-...`` option. This won't always work, because the
+            dialogue style doesn't necessary use this name, and it might break
+            other advanced uses of the ASS format.
 
 ``--ass-use-margins``
     Enables placing toptitles and subtitles in black borders when they are
diff --git a/options/options.c b/options/options.c
index 835ff21f9f..30564ba018 100644
--- a/options/options.c
+++ b/options/options.c
@@ -449,7 +449,7 @@ const m_option_t mp_opts[] = {
     OPT_CHOICE("ass-shaper", ass_shaper, 0,
                ({"simple", 0}, {"complex", 1})),
     OPT_CHOICE("ass-style-override", ass_style_override, 0,
-               ({"no", 0}, {"yes", 1})),
+               ({"no", 0}, {"yes", 1}, {"force", 2})),
     OPT_FLAG("osd-bar", osd_bar_visible, 0),
     OPT_FLOATRANGE("osd-bar-align-x", osd_bar_align_x, 0, -1.0, +1.0),
     OPT_FLOATRANGE("osd-bar-align-y", osd_bar_align_y, 0, -1.0, +1.0),
diff --git a/sub/sd_ass.c b/sub/sd_ass.c
index 8b6f1f1554..e4428516b9 100644
--- a/sub/sd_ass.c
+++ b/sub/sd_ass.c
@@ -128,6 +128,16 @@ static void decode(struct sd *sd, struct demux_packet *packet)
     event->Text = strdup(text);
 }
 
+static ASS_Style *find_style(ASS_Track *track, const char *name)
+{
+    for (int n = track->n_styles - 1; n >= 0; n--) {
+        const char *style_name = track->styles[n].Name;
+        if (style_name && strcasecmp(style_name, name) == 0)
+            return &track->styles[n];
+    }
+    return NULL;
+}
+
 static void get_bitmaps(struct sd *sd, struct mp_osd_res dim, double pts,
                         struct sub_bitmaps *res)
 {
@@ -137,6 +147,18 @@ static void get_bitmaps(struct sd *sd, struct mp_osd_res dim, double pts,
     if (pts == MP_NOPTS_VALUE || !sd->ass_renderer)
         return;
 
+    ASS_Style prev_default_style;
+    ASS_Style *default_style = NULL;
+    if (opts->ass_style_override == 2) {
+        default_style = find_style(ctx->ass_track, "Default");
+        if (default_style) {
+            prev_default_style = *default_style;
+            default_style->FontName = NULL; // don't free this
+            mp_ass_set_style(default_style, ctx->ass_track->PlayResY,
+                             opts->sub_text_style);
+        }
+    }
+
     ASS_Renderer *renderer = sd->ass_renderer;
     double scale = dim.display_par;
     if (!ctx->is_converted && (!opts->ass_style_override ||
@@ -166,6 +188,11 @@ static void get_bitmaps(struct sd *sd, struct mp_osd_res dim, double pts,
 
     if (!ctx->is_converted)
         mangle_colors(sd, res);
+
+    if (default_style) {
+        free(default_style->FontName);
+        *default_style = prev_default_style;
+    }
 }
 
 struct buf {