Accessing object parameters

Micropython
#1

Hi all,

Is there any way to access the internal parameters of widgets, in python there are no private variables and get/set methods are generally hidden.

The one I particular I am looking to access is the step variable in the spin box widget, normally in python I would expect to be able simply use val =spinbox.step or at least val=spinbox._step but while there is a set_step function I can’t find a get_stem one.

Thanks for the help

#2

Hi @minyiky!
Currently it’s not possible to access the widget internal state in Micropython.
If some internal variable is interesting - there should be an accessor function (set/get function) to access that variable.
In case of “step”, only lv_spinbox_set_step was defined in the C API.

I can suggest one of the following:

  • Add a new lv_spinbox_get_step function to the C API. Once you add this C function and rebuild lv_micropython it will become available in Python. You can open a PR in LVGL GitHub repo to add this.
  • Create a Python class that inherits from spinbox and implements this function. Keep the step state as part of the new Python class and use the new class instead of spinbox
#3

Hi @amigron

Thanks for the detailed response, just to confirm for adjusting the c api are you referring to the main lvgl repo, when looking for functions I did manage to find the set step function in the spin box there so I assume that is the place to add it?

Thanks

#4

Yes.
Just edit lv_spinbox.h and add lv_spinbox_get_step there, preferably as static inline function so it would have zero impact on the C footprint when not in use.

#5

@amirgon

Thank you for the help with this, and I am going to appologise in advance for my lack of knowledge.

I can see how I would set up a get function in the .c and .h file but I am very inexperienced when it comes to c and so not sure how I would add this as an inilne funtion, and specifically in the header.

This is what I have so far:

In lv_spinbox.c

/**
 * Get the spinbox step value (user has to convert to float according to its digit format)
 * @param spinbox pointer to spinbox
 * @return value integer step value of the spinbox
 */
int32_t lv_spinbox_get_step(lv_obj_t * spinbox)
{
    LV_ASSERT_OBJ(spinbox, LV_OBJX_NAME);

    lv_spinbox_ext_t * ext = lv_obj_get_ext_attr(spinbox);

    return ext->step;
}

In lv_spinbox.h

/**
 * Get the spinbox step value (user has to convert to float according to its digit format)
 * @param spinbox pointer to spinbox
 * @return value integer step value of the spinbox
 */
int32_t lv_spinbox_get_step(lv_obj_t * spinbox);
#6

For an inline function, the definition in the .c file should be unnecessary. Put this in the .h file (with the comment above):

static inline int32_t lv_spinbox_get_step(lv_obj_t * spinbox)
{
    LV_ASSERT_OBJ(spinbox, LV_OBJX_NAME);

    lv_spinbox_ext_t * ext = lv_obj_get_ext_attr(spinbox);

    return ext->step;
}
#7

Thanks for the point in the wirte direction, I have now added it and put inh a pull request but one of the checks has failed but I’m not sure why.

Thanks