Dropdown dynamic options [Enhancement]

Feature request
1

Most of my drop down lists are created dynamically, and it does not make sense to allocate static memory for the storage of the options. I have to guess the maximum size of the options and have a list sitting in memory for each drop down, even it is it not currently used. I could handle dynamic memory allocation outside the lv functions but that would just be duplication.

I propose adding functionality to the dropdown list to allow dynamical option storage in a similar way that label uses the static_txt flag.

The first step will be to add another function to set the options with a string which is stored in allocated memory:

void lv_dropdown_set_options(lv_obj_t * ddlist, const char * options);
void lv_dropdown_set_options_dynamic(lv_obj_t * ddlist, const char * options);

The first decision is whether we should follow the convention of the label and default to dynamic storage or keep the current default of static storage

void lv_dropdown_set_options(lv_obj_t * ddlist, const char * options);
void lv_dropdown_set_static_options(lv_obj_t * ddlist, const char * options);

Then the next logical thing would be to add a function which adds another option to the list. That would simplify the loop I use to create the options string. Not that efficient, since it would realloc for even added option, but I don’t think that is a big concern.

void lv_dropdown_add_option(lv_obj_t * ddlist, const char * option);

Also this would not work for static option lists, so depending on the previous decision the function might be

void lv_dropdown_add_option_dynamic(lv_obj_t * ddlist, const char * option);

My preference is to default to dynamic storage.

Any comments?

2

Done with the default set to dynamic. The only other change is that the drop down options default to Option1\nOption2\Option3, which needed to be removed for lv_dropdown_add_option().

void lv_dropdown_set_options(lv_obj_t * ddlist, const char * options);
void lv_dropdown_set_static_options(lv_obj_t * ddlist, const char * options);
void lv_dropdown_add_option(lv_obj_t * ddlist, const char * option, int pos);

Untested with bidi text.

3

The API looks good! Can you send a pull request?

1 Like
4

Ok. Someone else will have to look at the bidi handling because I cannot test that.

5

I would love to test it out also!

6

It should be merged soon otherwise this fork has the code

7

The PR is merged so I mark this topic as solved.

Thank you for the update!

8

It looks good! It would be great to have a lv_dropdown_remove_option function as well.

Hmm, also when changing the options, it should trigger a redraw of the dropdown.

I am using a button for testing, when the button is clicked, the options are changed. The options aren’t redrawn until I click on the dropdown list itself.

static void btn_event_handler(lv_obj_t * obj, lv_event_t event)
{
if(event == LV_EVENT_PRESSED) {
    printf("Clicked\n");
    lv_dropdown_set_options(ddlist, "Click0\nClick1\n");
    lv_dropdown_set_selected(ddlist, 0);
}
else if(event == LV_EVENT_RELEASED) {
    printf("Released\n");
    lv_dropdown_set_options(ddlist, "Release0\nRelease1\n");
    lv_dropdown_set_selected(ddlist, 1);
}
else if(event == LV_EVENT_VALUE_CHANGED) {
    printf("Toggled\n");

}
}

EDIT: I added lv_obj_invalidate(ddlist); to the functions for add_option and set_options so it redraws.

9

I agree. A Pull request would be welcome if you have time for it.

Thank you, I’ve added the invalidation