Darktable Lua script slider change

Software darktable
,
1

Hi,
I’ve created a module with LUA script but I can’t figure out, how can I call a function when a slider widget changed by a user?
I’ve tried with clicked_callback and changed_callback but in this way the scipt failed to load.

local cropSlider = dt.new_widget("slider")
{
  label = _("Max crop select"), 
  soft_min = 0,      -- The soft minimum value for the slider, the slider can't go beyond this point
  soft_max = 10,     -- The soft maximum value for the slider, the slider can't go beyond this point
  hard_min = 0,       -- The hard minimum value for the slider, the user can't manually enter a value beyond this point
  hard_max = 100,    -- The hard maximum value for the slider, the user can't manually enter a value beyond this point
  value = 1,          -- The current value of the slider
  changed_callback = function (this)
			-- do something
  end
}

thank you

2 
local function do_something()
  dt.print("did something")
end
local cropSlider = dt.new_widget("slider")
{
  label = _("Max crop select"), 
  soft_min = 0,      -- The soft minimum value for the slider, the slider can't go beyond this point
  soft_max = 10,     -- The soft maximum value for the slider, the slider can't go beyond this point
  hard_min = 0,       -- The hard minimum value for the slider, the user can't manually enter a value beyond this point
  hard_max = 100,    -- The hard maximum value for the slider, the user can't manually enter a value beyond this point
  value = 1,          -- The current value of the slider
  changed_callback = function (this)
			-- do something
    do_something()
  end
}
3

unfortunatelly failed to load :confused:

4

attach the whole script and I’ll look at it.