stats: add toggling of stats

You can now either show the stats once or toggle their display. Both are
using different key bindings which are additionally configurable now.

Please bear in mind that "toggling" means "redraw every x seconds for x
seconds". Therefore, this approach is prone to problems especially when
something else is printing text to the OSD as well as every of these
calls will overwrite each other. This is currently a limitation of mpv.

Fixes #18

player/lua/stats.lua

@@ -13,8 +13,13 @@ local options = require 'mp.options'
 
 -- Options
 local o = {
-    ass_formatting = true,
+    -- Default key bindings
+    key_oneshot = "i",
+    key_toggle = "I",
+
     duration = 3,
+    redraw_delay = 2,           -- acts as duration in the toggling case
+    ass_formatting = true,
     debug = false,
 
     -- Text style
@@ -50,7 +55,7 @@ local o = {
 options.read_options(o)
 
 
-function main()
+function main(duration)
     local stats = {
         header = "",
         file = "",
@@ -77,7 +82,7 @@ function main()
     add_video(stats)
     add_audio(stats)
 
-    mp.osd_message(join_stats(stats), o.duration)
+    mp.osd_message(join_stats(stats), duration or o.duration)
 end
 
 
@@ -280,4 +285,24 @@ function b(t)
     return o.b1 .. t .. o.b0
 end
 
-mp.add_key_binding("i", mp.get_script_name(), main, {repeatable=true})
+
+local timer = mp.add_periodic_timer(o.redraw_delay - 0.1, function() main(o.redraw_delay) end)
+timer:kill()
+
+function periodic_main()
+    if timer:is_enabled() then
+        timer:kill()
+        mp.osd_message("", 0)
+    else
+        timer:resume()
+        main(o.redraw_delay)
+    end
+end
+
+
+mp.add_key_binding(o.key_oneshot, "display_stats", main, {repeatable=true})
+if pcall(function() timer:is_enabled() end) then
+    mp.add_key_binding(o.key_toggle, "display_stats_toggle", periodic_main, {repeatable=false})
+else
+    print("To use continious display of stats please upgrade mpv")
+end