lua: add example to rebuild the status line

This can be used to easily extent the status line for one's own needs.

I'm not experienced with lua so a few things could probably be done a
better way.

DOCS/lua_examples/status-line.lua

@@ -0,0 +1,69 @@
+-- Rebuild the status line as a lua script
+-- Be aware that this will require more cpu power!
+
+-- Add a string to the status line
+function atsl(s)
+    newStatus = newStatus .. s
+end
+
+function update_status_line()
+    -- Reset the status line
+    newStatus = ""
+
+    if mp.get_property_bool("pause") then
+        atsl("(Paused) ")
+    elseif mp.get_property_bool("paused-for-cache") then
+        atsl("(Buffering) ")
+    end
+
+    if mp.get_property("vid") ~= "no" then
+        atsl("A")
+    end
+    if mp.get_property("aid") ~= "no" then
+        atsl("V")
+    end
+
+    atsl(": ")
+
+    atsl(mp.get_property_osd("time-pos"))
+
+    atsl(" / ");
+    atsl(mp.get_property_osd("length"));
+
+    atsl(" (")
+    atsl(mp.get_property_osd("percent-pos", -1))
+    atsl("%)")
+
+    local r = mp.get_property_number("speed", -1)   
+    if r ~= 1 then
+        atsl(string.format(" x%4.2f", r))
+    end
+
+    r = mp.get_property_number("avsync", nil)
+    if r ~= nil then
+        atsl(string.format(" A-V: %7.3f", r))
+    end
+
+    r = mp.get_property("total-avsync-change", 0)
+    if math.abs(r) > 0.05 then
+        atsl(string.format(" ct:%7.3f", r))
+    end
+
+    r = mp.get_property_number("drop-frame-count", -1)
+    if r > 0 then
+        atsl(" Late: ")
+        atsl(r)
+    end
+    
+    r = mp.get_property_number("cache", 0)
+    if r > 0 then
+        atsl(string.format(" Cache: %d%% ", r))
+    end
+
+    -- Set the new status line
+    mp.set_property("options/status-msg", newStatus)
+end
+
+-- Register the event
+mp.register_event("tick", update_status_line)
+