lvgl/examples/scroll/lv_example_scroll_properties.c

#include "../lv_examples.h"
#if LV_BUILD_EXAMPLES && LV_USE_FLEX && LV_USE_SWITCH

static lv_obj_t * list;

static void flag_switch_cb(lv_event_t * e)
{
    lv_obj_t * sw = lv_event_get_target_obj(e);
    lv_obj_flag_t flag = (lv_obj_flag_t)(lv_uintptr_t)lv_event_get_user_data(e);
    lv_obj_set_flag(list, flag, lv_obj_has_state(sw, LV_STATE_CHECKED));
}

static void add_flag_row(lv_obj_t * parent, const char * title, lv_obj_flag_t flag)
{
    lv_obj_t * row = lv_obj_create(parent);
    lv_obj_remove_style_all(row);
    lv_obj_set_size(row, lv_pct(100), LV_SIZE_CONTENT);
    lv_obj_set_flex_flow(row, LV_FLEX_FLOW_ROW);
    lv_obj_set_flex_align(row, LV_FLEX_ALIGN_START, LV_FLEX_ALIGN_CENTER, LV_FLEX_ALIGN_CENTER);

    lv_obj_t * label = lv_label_create(row);
    lv_label_set_text(label, title);
    lv_obj_set_flex_grow(label, 1);

    lv_obj_t * sw = lv_switch_create(row);
    lv_obj_add_state(sw, LV_STATE_CHECKED);          /* flags start enabled */
    lv_obj_add_flag(list, flag);
    lv_obj_add_event_cb(sw, flag_switch_cb, LV_EVENT_VALUE_CHANGED, (void *)(lv_uintptr_t)flag);
}

/**
 * @title Toggling scroll behaviour flags
 * @brief Switch SCROLLABLE, SCROLL_CHAIN, SCROLL_ELASTIC and SCROLL_MOMENTUM on live.
 *
 * These four flags change how a Widget reacts to scrolling but only show
 * their effect through interaction, so one example covers them together.
 * A scrollable list sits above four switches; each switch adds or removes
 * its flag on the list with `lv_obj_set_flag`, so the change can be felt
 * immediately by dragging the list.
 */
void lv_example_scroll_properties(void)
{
    lv_obj_t * panel = lv_obj_create(lv_screen_active());
    lv_obj_set_size(panel, 300, 220);
    lv_obj_center(panel);
    lv_obj_set_flex_flow(panel, LV_FLEX_FLOW_COLUMN);

    list = lv_obj_create(panel);
    lv_obj_set_size(list, lv_pct(100), 110);
    lv_obj_set_flex_flow(list, LV_FLEX_FLOW_COLUMN);
    for(uint32_t i = 1; i <= 8; i++) {
        lv_obj_t * btn = lv_button_create(list);
        lv_obj_set_width(btn, lv_pct(100));
        lv_obj_t * label = lv_label_create(btn);
        lv_label_set_text_fmt(label, "Item %" LV_PRIu32, i);
        lv_obj_center(label);
    }

    add_flag_row(panel, "Scrollable", LV_OBJ_FLAG_SCROLLABLE);
    add_flag_row(panel, "Scroll chain", LV_OBJ_FLAG_SCROLL_CHAIN);
    add_flag_row(panel, "Elastic scroll", LV_OBJ_FLAG_SCROLL_ELASTIC);
    add_flag_row(panel, "Scroll momentum", LV_OBJ_FLAG_SCROLL_MOMENTUM);
}

#endif