The chart with the faded area line cannot display the value pop-up when pressing a point?

[TridentTD]

LVGL version

v9.1.1

What happened?

When using lv_example_chart_3,
it can display pop-up values when a point is pressed,
https://github.com/lvgl/lvgl/blob/master/examples/widgets/chart/lv_example_chart_3.c

And when using lv_example_chart_5,
it can create a faded area line.
https://github.com/lvgl/lvgl/blob/master/examples/widgets/chart/lv_example_chart_5.c

However, when combining them together,
the graph with the faded area line fails to display the values correctly when touched.

I wish to create the chart with the faded area line
with the value pop-up when pressing a point.

How to solve the issue ?

How to reproduce?

static void pupup_value_pressed_point(lv_event_t * e);
static void faded_line_chart_designed(lv_event_t * e);

void lv_example_chart_3_with_5(void)
{
  /*Create a chart*/
  lv_obj_t * chart;
  chart = lv_chart_create(lv_screen_active());
  lv_obj_set_size(chart, 200, 150);
  lv_obj_center(chart);

  /* popup value */
  lv_obj_add_event_cb(chart, pupup_value_pressed_point, LV_EVENT_ALL, NULL);

  /* gradient line chart */
  lv_obj_add_flag(chart, LV_OBJ_FLAG_SEND_DRAW_TASK_EVENTS);
  lv_obj_add_event_cb(chart, faded_line_chart_designed, LV_EVENT_DRAW_TASK_ADDED, NULL);

  lv_obj_refresh_ext_draw_size(chart);

  /*Zoom in a little in X*/
  //    lv_chart_set_scale_x(chart, 800);

  /*Add two data series*/
  lv_chart_series_t * ser1 = lv_chart_add_series(chart, lv_palette_main(LV_PALETTE_RED), LV_CHART_AXIS_PRIMARY_Y);
  lv_chart_series_t * ser2 = lv_chart_add_series(chart, lv_palette_main(LV_PALETTE_GREEN), LV_CHART_AXIS_PRIMARY_Y);
  uint32_t i;
  for(i = 0; i < 10; i++) {
    lv_chart_set_next_value(chart, ser1, lv_rand(60, 90));
    lv_chart_set_next_value(chart, ser2, lv_rand(10, 40));
  }
}


void pupup_value_pressed_point(lv_event_t * e)
{
  lv_event_code_t code = lv_event_get_code(e);
  lv_obj_t * chart = (lv_obj_t *) lv_event_get_target(e);

  if(code == LV_EVENT_VALUE_CHANGED) {
    lv_obj_invalidate(chart);
  }
  if(code == LV_EVENT_REFR_EXT_DRAW_SIZE) {
    int32_t * s = (int32_t *)lv_event_get_param(e);
    *s = LV_MAX(*s, 20);
  }
  else if(code == LV_EVENT_DRAW_POST_END) {
    int32_t id = lv_chart_get_pressed_point(chart);
    if(id == LV_CHART_POINT_NONE) return;

    LV_LOG_USER("Selected point %d", (int)id);

    lv_chart_series_t * ser = lv_chart_get_series_next(chart, NULL);
    while(ser) {
      lv_point_t p;
      lv_chart_get_point_pos_by_id(chart, ser, id, &p);

      int32_t * y_array = lv_chart_get_y_array(chart, ser);
      int32_t value = y_array[id];

      char buf[16];
      lv_snprintf(buf, sizeof(buf), LV_SYMBOL_DUMMY"$%d", value);

      lv_draw_rect_dsc_t draw_rect_dsc;
      lv_draw_rect_dsc_init(&draw_rect_dsc);
      draw_rect_dsc.bg_color = lv_color_black();
      draw_rect_dsc.bg_opa = LV_OPA_50;
      draw_rect_dsc.radius = 3;
      draw_rect_dsc.bg_image_src = buf;
      draw_rect_dsc.bg_image_recolor = lv_color_white();
      draw_rect_dsc.bg_image_symbol_font = &prasanmit_20;

      lv_area_t a;
      a.x1 = chart->coords.x1 + p.x - 20;
      a.x2 = chart->coords.x1 + p.x + 20;
      a.y1 = chart->coords.y1 + p.y - 30;
      a.y2 = chart->coords.y1 + p.y - 10;

      lv_layer_t * layer = lv_event_get_layer(e);
      lv_draw_rect(layer, &draw_rect_dsc, &a);

      ser = lv_chart_get_series_next(chart, ser);
    }
  }
  else if(code == LV_EVENT_RELEASED) {
    lv_obj_invalidate(chart);
  }
}

void faded_line_chart_designed(lv_event_t * e)
{
  lv_draw_task_t * draw_task = lv_event_get_draw_task(e);
  lv_draw_dsc_base_t * base_dsc = (lv_draw_dsc_base_t *)draw_task->draw_dsc;

  if(base_dsc->part == LV_PART_ITEMS && draw_task->type == LV_DRAW_TASK_TYPE_LINE) {
    lv_obj_t * obj = (lv_obj_t *)lv_event_get_target(e);

    lv_draw_task_t * draw_task = lv_event_get_draw_task(e);
    lv_draw_dsc_base_t * base_dsc = (lv_draw_dsc_base_t *)draw_task->draw_dsc;

    const lv_chart_series_t * ser = lv_chart_get_series_next(obj, NULL);
    for(int i = 0; i < base_dsc->id1; i++) {
      ser = lv_chart_get_series_next(obj, ser);
    }
    if(ser == NULL) return;

    /*Draw a triangle below the line witch some opacity gradient*/
    lv_draw_line_dsc_t * draw_line_dsc = (lv_draw_line_dsc_t *)draw_task->draw_dsc;
    lv_draw_triangle_dsc_t tri_dsc;

    lv_draw_triangle_dsc_init(&tri_dsc);
    tri_dsc.p[0].x = draw_line_dsc->p1.x;
    tri_dsc.p[0].y = draw_line_dsc->p1.y;
    tri_dsc.p[1].x = draw_line_dsc->p2.x;
    tri_dsc.p[1].y = draw_line_dsc->p2.y;
    tri_dsc.p[2].x = draw_line_dsc->p1.y < draw_line_dsc->p2.y ? draw_line_dsc->p1.x : draw_line_dsc->p2.x;
    tri_dsc.p[2].y = LV_MAX(draw_line_dsc->p1.y, draw_line_dsc->p2.y);
    tri_dsc.bg_grad.dir = LV_GRAD_DIR_VER;

    int32_t full_h = lv_obj_get_height(obj);
    int32_t fract_uppter = (int32_t)(LV_MIN(draw_line_dsc->p1.y, draw_line_dsc->p2.y) - obj->coords.y1) * 255 / full_h;
    int32_t fract_lower = (int32_t)(LV_MAX(draw_line_dsc->p1.y, draw_line_dsc->p2.y) - obj->coords.y1) * 255 / full_h;
    tri_dsc.bg_grad.stops[0].color = ser->color;
    tri_dsc.bg_grad.stops[0].opa = 255 - fract_uppter;
    tri_dsc.bg_grad.stops[0].frac = 0;
    tri_dsc.bg_grad.stops[1].color = ser->color;
    tri_dsc.bg_grad.stops[1].opa = 255 - fract_lower;
    tri_dsc.bg_grad.stops[1].frac = 255;

    lv_draw_triangle(base_dsc->layer, &tri_dsc);

    /*Draw rectangle below the triangle*/
    lv_draw_rect_dsc_t rect_dsc;
    lv_draw_rect_dsc_init(&rect_dsc);
    rect_dsc.bg_grad.dir = LV_GRAD_DIR_VER;
    rect_dsc.bg_grad.stops[0].color = ser->color;
    rect_dsc.bg_grad.stops[0].frac = 0;
    rect_dsc.bg_grad.stops[0].opa = 255 - fract_lower;
    rect_dsc.bg_grad.stops[1].color = ser->color;
    rect_dsc.bg_grad.stops[1].frac = 255;
    rect_dsc.bg_grad.stops[1].opa = 0;

    lv_area_t rect_area;
    rect_area.x1 = (int32_t)draw_line_dsc->p1.x;
    rect_area.x2 = (int32_t)draw_line_dsc->p2.x - 1;
    rect_area.y1 = (int32_t)LV_MAX(draw_line_dsc->p1.y, draw_line_dsc->p2.y) - 1;
    rect_area.y2 = (int32_t)obj->coords.y2;
    lv_draw_rect(base_dsc->layer, &rect_dsc, &rect_area);
  }
}

[kisvegabor]

Most probably the issue is that buf is local and if multiple draw_tasks are executed in the event LVGL adds them to a list, and when the rectangle will be drawn later, buf will be already lost.

I suggest using a rectangle drawing followed by a label drawing and set draw_label_dsc->text_local = 1 to make LVGL store a copy of the buffer.

(lv_example_chart_3 should be update too. )

[TridentTD]

@kisvegabor

Thank you very much.
It's OK, now!

[kisvegabor]

Great! May I ask if you have time to update lv_example_chart_3()?

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