diff --git a/system/formspecs/set_position.lua b/system/formspecs/set_position.lua
index 63062fc..59ba0e9 100644
--- a/system/formspecs/set_position.lua
+++ b/system/formspecs/set_position.lua
@@ -2,6 +2,13 @@ local m = mtimer
 local S = m.translator
 
 
+-- Image width and height for setting the screenshot in position and do the
+-- button calculations
+local i_width = 10
+local i_height = 6
+
+
+-- Position names for the current position information  string
 local p_names = {
     ['t'] = S('top'),
     ['m'] = S('middle'),
@@ -12,31 +19,40 @@ local p_names = {
 }
 
 
+-- Return parsed position button
+--
+-- This function shows a button on the given position that sets the position
+-- of the GUI element accordingly. The `position` is one of the following.
+--
+--   tl, tc, tr = top left, center, right
+--   ml, mc, mr = middle left, center, right
+--   bl, bc, br = bottom left, center right
+--
+-- @param top The position of the button from the top
+-- @param left The position of the button from the left
+-- @param position GUI element position to set with this button
+local b_define = function(top, left, position)
+    return ('image_button[+l,+t;+w,+h;+i;pos_+p;d;;false]'):gsub('%+%w', {
+        ['+l'] = (left - 1) * (i_width / 3),
+        ['+t'] = (top - 1) * (i_height / 3),
+        ['+w'] = i_width / 3,
+        ['+h'] = i_height / 3,
+        ['+i'] = 'mtimer_transparent.png',
+        ['+p'] = position,
+    })
+end
+
+
 mtimer.dialog.set_position = function (player_name)
     local player = minetest.get_player_by_name(player_name)
     local howto = S('Click the position you want to place the timer at.')
+    local image = 'mtimer_positions_orientation.png'
 
     -- Get current position name
     local p_value = player:get_meta():get_string(m.meta.position.key)
     local p_name = p_names[p_value:sub(1,1)]..' '..p_names[p_value:sub(2,2)]
     local p_info = S('Current position: @1', p_name)
 
-    -- Set up image
-    local image = 'mtimer_positions_orientation.png'
-    local i_width = 10
-    local i_height = 6
-
-    -- Return the parsed button
-    local b_define = function(t, l, p)
-        return ('image_button[+l,+t;+w,+h;+i;pos_+p;d;;false]'):gsub('%+%w', {
-            ['+l'] = (l - 1) * (i_width / 3),
-            ['+t'] = (t - 1) * (i_height / 3),
-            ['+w'] = i_width / 3,
-            ['+h'] = i_height / 3,
-            ['+i'] = 'mtimer_transparent.png',
-            ['+p'] = p,
-        })
-    end
 
     mtimer.show_formspec('mtimer:set_position', {
         title = S('Position'),