Getting the animated object in `custom_exec_cb`

Micropython
#1

Hi,

I try to use a custom_exec_cb like below and it works well:

  a1.set_custom_exec_cb(lambda a, v: btn1.set_x(v))

But the goal would be to get the animated object from a in the lambda function. I’ve tried this

  a1.set_custom_exec_cb(lambda a, v: lv.obj_t(a.var).set_x(v))

and got:

AttributeError: no such attribute

So could you help me with how to cast a.var to lv.obj_t?

#2

lv_anim_set_custom_exec_cb is defined like this:

static inline void lv_anim_set_custom_exec_cb(lv_anim_t * a, lv_anim_custom_exec_cb_t exec_cb)
{
    a->var     = a;
    a->exec_cb = (lv_anim_exec_xcb_t)exec_cb;
}

var is passed as the first argument of exec_cb so you can obtain lv_anim_t from var, but not the btn itself.
This needs to be defined like this in order to register the Micropython callback on user_data, and to access it when the callback is called.

Could you explain why your goal is to obtain btn1 from a? You can always access it from the lambda directly.

#3

Ah, really. I should have figured it out.

That’s correct. Seemingly I live too much n the C world :slight_smile:

In case anyone needs it, here is an example:


def my_anim(target):
  anim = lv.anim_t()
  anim.init()
  anim.set_time(1000)
  anim.set_var(target)
  anim.set_values(0, 100)
  anim.set_custom_exec_cb(lambda a, v: target.set_x(v))
  lv.anim_t.start(anim)

my_anim(btn)

Thank you for your help!