select.lua: add select-secondary-subtitle-line

Requested in https://github.com/mpv-player/mpv/pull/17730#issuecomment-4321224996

DOCS/man/mpv.rst

@@ -338,6 +338,9 @@ g-e
 g-l
     Select a subtitle line to seek to.
 
+g-L
+    Select a secondary subtitle line to seek to.
+
 g-d
     Select an audio device.
 

etc/input.conf

@@ -191,6 +191,7 @@
 #g-c script-binding select/select-chapter
 #g-e script-binding select/select-edition
 #g-l script-binding select/select-subtitle-line
+#g-L script-binding select/select-secondary-subtitle-line
 #g-d script-binding select/select-audio-device
 #g-h script-binding select/select-watch-history
 #g-w script-binding select/select-watch-later

etc/menu.conf

@@ -107,6 +107,8 @@ P&layback
 		Increase &delay		add secondary-sub-delay  0.1
 		Decrease d&elay		add secondary-sub-delay -0.1
 
+		&Lines	script-binding select/select-secondary-subtitle-line	disabled=not secondary_sid or p["current-tracks/sub2/codec"] == "dvb_subtitle" or p["current-tracks/sub2/codec"] == "dvd_subtitle" or p["current-tracks/sub2/codec"] == "hdmv_pgs_subtitle"
+
 &Window
 	&Fullscreen		cycle fullscreen	checked=fullscreen
 	&Border			cycle border		checked=border

player/lua/select.lua

@@ -284,8 +284,8 @@ mp.add_key_binding(nil, "select-edition", function ()
     })
 end)
 
-mp.add_key_binding(nil, "select-subtitle-line", function ()
-    local lines = mp.get_property_native("sub-lines")
+local function select_subtitle_line(secondary)
+    local lines = mp.get_property_native(secondary .. "sub-lines")
 
     if not lines then
         show_warning("Subtitle lines could not be retrieved.")
@@ -294,7 +294,7 @@ mp.add_key_binding(nil, "select-subtitle-line", function ()
 
     local items = {}
     local default_item
-    local delay = mp.get_property_native("sub-delay")
+    local delay = mp.get_property_native(secondary .. "sub-delay")
     local time_pos = mp.get_property_native("time-pos") - delay
     local duration = mp.get_property_native("duration", math.huge)
 
@@ -320,6 +320,13 @@ mp.add_key_binding(nil, "select-subtitle-line", function ()
             mp.commandv("seek", lines[i].start + delay, "absolute")
         end,
     })
+end
+
+mp.add_key_binding(nil, "select-subtitle-line", function ()
+    select_subtitle_line("")
+end)
+mp.add_key_binding(nil, "select-secondary-subtitle-line", function ()
+    select_subtitle_line("secondary-")
 end)
 
 local function format_audio_device(device)