Use a fix scrubber range on the playing screen

this ensure that the amount the scrubber moves for each tick of the
input remains consistent, even when tracks have very different durations

lua/playing.lua

@@ -123,7 +123,10 @@ return screen:new {
     }
 
     scrubber:onevent(lvgl.EVENT.RELEASED, function()
-      playback.position:set(scrubber:value())
+      local track = playback.track:get()
+      if not track then return end
+      if not track.duration then return end
+      playback.position:set(scrubber:value() / 100 * track.duration)
     end)
 
     local controls = self.root:Object {
@@ -202,7 +205,10 @@ return screen:new {
           text = format_time(pos)
         }
         if not scrubber:is_dragged() then
-          scrubber:set { value = pos }
+          local track = playback.track:get()
+          if not track then return end
+          if not track.duration then return end
+          scrubber:set { value = pos / track.duration * 100 }
         end
       end),
       playback.track:bind(function(track)
@@ -212,9 +218,6 @@ return screen:new {
         }
         title:set { text = track.title }
         artist:set { text = track.artist }
-        scrubber:set {
-          range = { min = 0, max = track.duration }
-        }
       end),
       queue.position:bind(function(pos)
         if not pos then return end