Show chapter names on hover

mordenx.lua

@@ -45,6 +45,7 @@ local user_opts = {
     visibility = 'auto',        -- only used at init to set visibility_mode(...)
     windowcontrols = 'auto',    -- whether to show window controls
     language = 'eng',		-- eng=English, chs=Chinese
+    chapter_fmt = "Chapter: %s", -- chapter print format for seekbar-hover. "no" to disable
 }
 
 -- Localization
@@ -138,6 +139,7 @@ local state = {
     osd = mp.create_osd_overlay('ass-events'),
     lastvisibility = user_opts.visibility,	-- save last visibility on pause if showonpause
     fulltime = user_opts.timems,
+    chapter_list = {},                      -- sorted by time
 }
 
 local window_control_box_width = 138
@@ -550,8 +552,36 @@ end
 --
 -- Element Rendering
 --
+
+-- returns nil or a chapter element from the native property chapter-list
+function get_chapter(possec)
+    local cl = state.chapter_list  -- sorted, get latest before possec, if any
+
+    for n=#cl,1,-1 do
+        if possec >= cl[n].time then
+            return cl[n]
+        end
+    end
+end
+
 function render_elements(master_ass)
 
+    -- when the slider is dragged or hovered and we have a target chapter name
+    -- then we use it instead of the normal title. we calculate it before the
+    -- render iterations because the title may be rendered before the slider.
+    state.forced_title = nil
+    local se, ae = state.slider_element, elements[state.active_element]
+    if user_opts.chapter_fmt ~= "no" and se and (ae == se or (not ae and mouse_hit(se))) then
+        local dur = mp.get_property_number("duration", 0)
+        if dur > 0 then
+            local possec = get_slider_value(se) * dur / 100 -- of mouse pos
+            local ch = get_chapter(possec)
+            if ch and ch.title and ch.title ~= "" then
+                state.forced_title = string.format(user_opts.chapter_fmt, ch.title)
+            end
+        end
+    end
+
     for n=1, #elements do
         local element = elements[n]
         local style_ass = assdraw.ass_new()
@@ -1115,6 +1145,7 @@ function update_options(list)
     validate_user_opts()
     request_tick()
     visibility_mode(user_opts.visibility, true)
+    update_duration_watch()
     request_init()
 end
 
@@ -1322,7 +1353,8 @@ function osc_init()
     -- title
     ne = new_element('title', 'button')
     ne.content = function ()
-		local title = mp.command_native({'expand-text', user_opts.title})
+        local title = state.forced_title or
+                      mp.command_native({"expand-text", user_opts.title})
         if state.paused then
 			title = title:gsub('\\n', ' '):gsub('\\$', ''):gsub('{','\\{')
 		else
@@ -1336,6 +1368,7 @@ function osc_init()
     ne = new_element('seekbar', 'slider')
 
     ne.enabled = not (mp.get_property('percent-pos') == nil)
+    state.slider_element = ne.enabled and ne or nil  -- used for forced_title
     ne.slider.markerF = function ()
         local duration = mp.get_property_number('duration', nil)
         if not (duration == nil) then
@@ -1930,12 +1963,42 @@ function enable_osc(enable)
     end
 end
 
+-- duration is observed for the sole purpose of updating chapter markers
+-- positions. live streams with chapters are very rare, and the update is also
+-- expensive (with request_init), so it's only observed when we have chapters
+-- and the user didn't disable the livemarkers option (update_duration_watch).
+function on_duration() request_init() end
+
+local duration_watched = false
+function update_duration_watch()
+    local want_watch = user_opts.livemarkers and
+                       (mp.get_property_number("chapters", 0) or 0) > 0 and
+                       true or false  -- ensure it's a boolean
+
+    if (want_watch ~= duration_watched) then
+        if want_watch then
+            mp.observe_property("duration", nil, on_duration)
+        else
+            mp.unobserve_property(on_duration)
+        end
+        duration_watched = want_watch
+    end
+end
+
 validate_user_opts()
+update_duration_watch()
 
 mp.register_event('shutdown', shutdown)
 mp.register_event('start-file', request_init)
 mp.observe_property('track-list', nil, request_init)
 mp.observe_property('playlist', nil, request_init)
+mp.observe_property("chapter-list", "native", function(_, list)
+    list = list or {}  -- safety, shouldn't return nil
+    table.sort(list, function(a, b) return a.time < b.time end)
+    state.chapter_list = list
+    update_duration_watch()
+    request_init()
+end)
 
 mp.register_script_message('osc-message', show_message)
 mp.register_script_message('osc-chapterlist', function(dur)