lvgl/examples/grad/lv_example_grad_4.c

#include "../lv_examples.h"
#if LV_BUILD_EXAMPLES && LV_USE_LABEL

#if LV_USE_DRAW_SW_COMPLEX_GRADIENTS

static void position_bullet(lv_event_t * e, lv_point_t * p)
{
    lv_indev_t * indev = (lv_indev_t *) lv_event_get_param(e);
    lv_indev_get_point(indev, p);

    lv_obj_t * bullet = lv_event_get_target_obj(e);
    lv_obj_t * parent = lv_obj_get_parent(bullet);

    p->x -= lv_obj_get_x(parent);
    p->y -= lv_obj_get_y(parent);

    int32_t w = lv_obj_get_width(parent);
    int32_t h = lv_obj_get_height(parent);
    lv_obj_set_pos(bullet, LV_CLAMP(5, p->x, w - 20), LV_CLAMP(5, p->y, h - 20));
}

static void start_event_cb(lv_event_t * e)
{
    lv_style_t * style = (lv_style_t *) lv_event_get_user_data(e);
    lv_style_value_t v;
    lv_style_get_prop(style, LV_STYLE_BG_GRAD, &v);
    lv_grad_dsc_t * dsc = (lv_grad_dsc_t *)v.ptr;

    lv_point_t p;
    position_bullet(e, &p);

    lv_obj_t * bullet = lv_event_get_target_obj(e);
    lv_obj_t * parent = lv_obj_get_parent(bullet);
    p.x -= lv_obj_get_width(parent) / 2;
    p.y -= lv_obj_get_height(parent) / 2;

    dsc->params.conical.start_angle = lv_atan2(p.y, p.x);
    lv_obj_invalidate(parent);
}

static void end_event_cb(lv_event_t * e)
{
    lv_style_t * style = (lv_style_t *) lv_event_get_user_data(e);
    lv_style_value_t v;
    lv_style_get_prop(style, LV_STYLE_BG_GRAD, &v);
    lv_grad_dsc_t * dsc = (lv_grad_dsc_t *)v.ptr;

    lv_point_t p;
    position_bullet(e, &p);

    lv_obj_t * bullet = lv_event_get_target_obj(e);
    lv_obj_t * parent = lv_obj_get_parent(bullet);
    p.x -= lv_obj_get_width(parent) / 2;
    p.y -= lv_obj_get_height(parent) / 2;

    dsc->params.conical.end_angle = lv_atan2(p.y, p.x);
    lv_obj_invalidate(parent);
}

/**
 * @title Conical gradient with draggable angles
 * @brief Drag two bullets to set the start and end angles of a conical gradient.
 *
 * A centered 80% by 80% object carries a two-stop conical gradient built
 * with `lv_grad_init_stops` and `lv_grad_conical_init` centered at 50% by
 * 50% sweeping from 0 to 180 degrees with `LV_GRAD_EXTEND_PAD`. Two small
 * buttons act as angle handles; their `LV_EVENT_PRESSING` callbacks read
 * the pointer, reposition the handle, and recompute
 * `dsc->params.conical.start_angle` or `dsc->params.conical.end_angle`
 * with `lv_atan2` relative to the parent center before invalidating it.
 * When `LV_USE_DRAW_SW_COMPLEX_GRADIENTS` is disabled, the example
 * instead shows a single label noting the dependency.
 */
void lv_example_grad_4(void)
{
    static const lv_color_t grad_colors[2] = {
        LV_COLOR_MAKE(0xff, 0x00, 0x00),
        LV_COLOR_MAKE(0x00, 0xff, 0x00),
    };

    static const lv_opa_t grad_opa[2] = {
        LV_OPA_100,
        LV_OPA_0,
    };

    static lv_style_t style;
    lv_style_init(&style);

    /*First define a color gradient. In this example we use a purple to black color map.*/
    static lv_grad_dsc_t grad;

    lv_grad_init_stops(&grad, grad_colors, grad_opa, NULL, sizeof(grad_colors) / sizeof(lv_color_t));

    lv_grad_conical_init(&grad, lv_pct(50), lv_pct(50), 0, 180, LV_GRAD_EXTEND_PAD);

    /*Set gradient as background*/
    lv_style_set_bg_grad(&style, &grad);
    lv_style_set_border_width(&style, 2);
    lv_style_set_pad_all(&style, 0);
    lv_style_set_radius(&style, 12);

    /*Create an object with the new style*/
    lv_obj_t * obj = lv_obj_create(lv_screen_active());
    lv_obj_add_style(obj, &style, 0);
    lv_obj_set_size(obj, lv_pct(80), lv_pct(80));
    lv_obj_center(obj);

    lv_obj_t * start = lv_button_create(obj);
    lv_obj_set_size(start, 15, 15);
    lv_obj_set_style_bg_color(start, lv_color_hex(0x0000ff), 0);
    lv_obj_add_event_cb(start, start_event_cb, LV_EVENT_PRESSING, &style);
    lv_obj_set_ext_click_area(start, 5);
    lv_obj_set_pos(start, lv_pct(80), lv_pct(50));

    lv_obj_t * end = lv_button_create(obj);
    lv_obj_set_size(end, 15, 15);
    lv_obj_set_style_bg_color(end, lv_color_hex(0x00ffff), 0);
    lv_obj_add_event_cb(end, end_event_cb, LV_EVENT_PRESSING, &style);
    lv_obj_set_ext_click_area(end, 5);
    lv_obj_set_pos(end, lv_pct(20), lv_pct(50));
}

#else

void lv_example_grad_4(void)
{
    lv_obj_t * label = lv_label_create(lv_screen_active());
    lv_label_set_text(label, "LV_USE_DRAW_SW_COMPLEX_GRADIENTS needs to be enabled");
    lv_obj_center(label);
}

#endif /*LV_USE_DRAW_SW_COMPLEX_GRADIENTS*/

#endif