options: slight cleanup of --sub-ass-style-override

List of changes:

1. Rename `signfs` to `scale`, to better match what it actually does
   (force --sub-scale to apply to ASS subtitles), and fix the blatantly
   wrong documentation (it actually specifically does *not* apply to
   signs)

2. Rename `--sub-ass-style-override` to `--sub-ass-override` to help
   reduce confusion between it and `--sub-ass-force-style`, as well as
   pointing out that it doesn't necessarily actually override styles.
   (The new `scale` option, for example, only sets
   ASS_OVERRIDE_BIT_FONT_SIZE, but not ASS_OVERRIDE_BIT_STYLE)

3. Mention that `--sub-ass-override` is generally sort of smart about
   only overriding dialog, not signs.

DOCS/interface-changes.rst

@@ -25,6 +25,8 @@ Interface changes
     - introduce --replaygain... options, which replace the same functionality
       provided by the deprecated --af=volume:replaygain... mechanism.
     - drop the internal "mp-rawvideo" codec (used by --demuxer=rawvideo)
+    - rename --sub-ass-style-override to --sub-ass-override, and rename the
+      `--sub-ass-override=signfs` setting to `--sub-ass-override=scale`.
  --- mpv 0.25.0 ---
     - remove opengl-cb dxva2 dummy hwdec interop
       (see git "vo_opengl: remove dxva2 dummy hwdec backend")

DOCS/man/options.rst

@@ -1481,7 +1481,7 @@ Subtitles
     Changing styling and position does not work with all subtitles. Image-based
     subtitles (DVD, Bluray/PGS, DVB) cannot changed for fundamental reasons.
     Subtitles in ASS format are normally not changed intentionally, but
-    overriding them can be controlled with ``--sub-ass-style-override``.
+    overriding them can be controlled with ``--sub-ass-override``.
 
     Previously some options working on text subtitles were called
     ``--sub-text-*``, they are now named ``--sub-*``, and those specifically
@@ -1558,8 +1558,8 @@ Subtitles
     scales with the approximate window size, while the other option disables
     this scaling.
 
-    Affects plain text subtitles only (or ASS if ``--sub-ass-style-override`` is
+    Affects plain text subtitles only (or ASS if ``--sub-ass-override`` is set
-    set high enough).
+    high enough).
 
 ``--sub-ass-scale-with-window=<yes|no>``
     Like ``--sub-scale-with-window``, but affects subtitles in ASS format only.
@@ -1638,16 +1638,19 @@ Subtitles
 
         Using this option may lead to incorrect subtitle rendering.
 
-``--sub-ass-style-override=<yes|no|force|signfs|strip>``
+``--sub-ass-override=<yes|no|force|scale|strip>``
-    Control whether user style overrides should be applied.
+    Control whether user style overrides should be applied. Note that all of
+    these overrides try to be somewhat smart about figuring out whether or not
+    a subtitle is considered a "sign".
 
-    :yes:   Apply all the ``--sub-ass-*`` style override options. Changing the default
+    :no:    Render subtitles as specified by the subtitle scripts, without
-            for any of these options can lead to incorrect subtitle rendering
+            overrides.
-            (default).
+    :yes:   Apply all the ``--sub-ass-*`` style override options. Changing the
-    :signfs: like ``yes``, but apply ``--sub-scale`` only to signs
+            default for any of these options can lead to incorrect subtitle
-    :no:    Render subtitles as forced by subtitle scripts.
+            rendering (default).
-    :force: Try to force the font style as defined by the ``--sub-*``
+    :force: Like ``yes``, but also force all ``--sub-*`` options. Can break
-            options. Can break rendering easily.
+            rendering easily.
+    :scale: Like ``yes``, but also apply ``--sub-scale``.
     :strip: Radically strip all ASS tags and styles from the subtitle. This
             is equivalent to the old ``--no-ass`` / ``--no-sub-ass`` options.
 
@@ -1660,7 +1663,7 @@ Subtitles
 ``--sub-use-margins``
     Enables placing toptitles and subtitles in black borders when they are
     available, if the subtitles are in a plain text format  (or ASS if
-    ``--sub-ass-style-override`` is set high enough).
+    ``--sub-ass-override`` is set high enough).
 
     Default: yes.
 
@@ -1715,7 +1718,7 @@ Subtitles
 
     Choosing anything other than ``no`` will make the subtitle color depend on
     the video color space, and it's for example in theory not possible to reuse
-    a subtitle script with another video file. The ``--sub-ass-style-override``
+    a subtitle script with another video file. The ``--sub-ass-override``
     option doesn't affect how this option is interpreted.
 
 ``--stretch-dvd-subs=<yes|no>``
@@ -1755,9 +1758,9 @@ Subtitles
 
     .. note::
 
-        This has been deprecated by ``--sub-ass-style-override=strip``. You also
+        This has been deprecated by ``--sub-ass-override=strip``. You also
         may need ``--embeddedfonts=no`` to get the same behavior. Also,
-        using ``--sub-ass-style-override=force`` should give better results
+        using ``--sub-ass-override=style`` should give better results
         without breaking subtitles too much.
 
     If ``--no-sub-ass`` is specified, all tags and style declarations are
@@ -2000,7 +2003,7 @@ Subtitles
 
 ``--sub-ass-justify=<yes|no>``
     Applies justification as defined by ``--sub-justify`` on ASS subtitles
-    if ``--sub-ass-style-override`` is not set to ``no``.
+    if ``--sub-ass-override`` is not set to ``no``.
     Default: ``no``.
 
 ``--sub-shadow-color=<color>``

options/options.c

@@ -511,8 +511,8 @@ const m_option_t mp_opts[] = {
     OPT_CHOICE("sub-ass-shaper", ass_shaper, UPDATE_OSD,
                ({"simple", 0}, {"complex", 1})),
     OPT_FLAG("sub-ass-justify", ass_justify, 0),
-    OPT_CHOICE("sub-ass-style-override", ass_style_override, UPDATE_OSD,
+    OPT_CHOICE("sub-ass-override", ass_style_override, UPDATE_OSD,
-               ({"no", 0}, {"yes", 1}, {"force", 3}, {"signfs", 4}, {"strip", 5})),
+               ({"no", 0}, {"yes", 1}, {"force", 3}, {"scale", 4}, {"strip", 5})),
     OPT_FLAG("sub-scale-by-window", sub_scale_by_window, UPDATE_OSD),
     OPT_FLAG("sub-scale-with-window", sub_scale_with_window, UPDATE_OSD),
     OPT_FLAG("sub-ass-scale-with-window", ass_scale_with_window, UPDATE_OSD),
@@ -844,6 +844,7 @@ const m_option_t mp_opts[] = {
     OPT_REPLACED("ass-shaper", "sub-ass-shaper"),
     OPT_REPLACED("ass-style-override", "sub-ass-style-override"),
     OPT_REPLACED("ass-scale-with-window", "sub-ass-scale-with-window"),
+    OPT_REPLACED("sub-ass-style-override", "sub-ass-override"),
     OPT_REMOVED("fs-black-out-screens", NULL),
     OPT_REPLACED_MSG("loop", "loop-playlist", "--loop will be changed to map to"
         " --loop-file in future releases."),

sub/sd_ass.c

@@ -313,7 +313,7 @@ static void configure_ass(struct sd *sd, struct mp_osd_res *dim,
     bool set_scale_by_window = true;
     bool total_override = false;
     // With forced overrides, apply the --sub-* specific options
-    if (converted || opts->ass_style_override == 3) {
+    if (converted || opts->ass_style_override == 3) { // 'force'
         set_scale_with_window = opts->sub_scale_with_window;
         set_use_margins = opts->sub_use_margins;
         set_scale_by_window = opts->sub_scale_by_window;
@@ -343,7 +343,7 @@ static void configure_ass(struct sd *sd, struct mp_osd_res *dim,
     int set_force_flags = 0;
     if (total_override)
         set_force_flags |= ASS_OVERRIDE_BIT_STYLE | ASS_OVERRIDE_BIT_FONT_SIZE;
-    if (opts->ass_style_override == 4)
+    if (opts->ass_style_override == 4) // 'scale'
         set_force_flags |= ASS_OVERRIDE_BIT_FONT_SIZE;
 #if LIBASS_VERSION >= 0x01201001
     if (converted)