How to add an outline for a selected object in a dropdown?

How-to
1

I’m using LVGL v8.2. I have a dropdown list that is navigated using an encoder. I want the selected/highlighted option to have an outline instead of a gray background, but I’ve tried a combination of setting background colors and opacity for both the dropdown and dropdown list (dropdown list modified in the associated event callback) with no success. I tracked down this line in the LVGL code, which draws the shaded box I want to remove. Commenting out lv_draw_rect(draw_ctx, &sel_rect, &rect_area); works, but I want to accomplish it without modifying upstream code and with a border/outline replacing it.

EDIT: I misunderstood the selected_highlight option. Setting it to false successfully removes the highlight box, but I’m still not sure how to add a border to the selected item.

2

Adding this code to the dropdown’s event callback worked after re-enabling selected_highlight:

static void event_cb(lv_event_t *e) {
    lv_event_code_t code = lv_event_get_code(e);
    lv_obj_t* list = lv_dropdown_get_list(menu); // TODO get list based on input param
   
    if (code == LV_EVENT_READY)
    {
        if (list != NULL)
        {
          lv_obj_set_style_bg_color(list, lv_color_white(), LV_PART_SELECTED | LV_STATE_CHECKED);
          lv_obj_set_style_border_color(list,lv_color_black(), LV_PART_SELECTED | LV_STATE_CHECKED);
          lv_obj_set_style_border_width(list, 2, LV_PART_SELECTED | LV_STATE_CHECKED);
        }
    }
}