LVGL add lv.draw_label_dsc and lv_bar.get_indic_area

[s-hadinger]

Description:

Add missing definition to make the example https://docs.lvgl.io/master/examples.html#custom-drawer-to-show-the-current-value work.

Here is the code:

#https://docs.lvgl.io/master/examples.html#custom-drawer-to-show-the-current-value
#- start LVGL and init environment -#
lv.start()

hres = lv.get_hor_res()       # should be 320
vres = lv.get_ver_res()       # should be 240

scr = lv.scr_act()            # default screan object
f20 = lv.montserrat_font(20)  # load embedded Montserrat 20

bar = lv.bar(scr)
bar.set_size(200,20)
bar.center()

def bar_event(obj, event)
  import introspect
  print(f"{obj=} {event=} {event.get_code()=} {event.get_layer()=}")
  var label_dsc = lv.draw_label_dsc()
  lv.draw_label_dsc_init(label_dsc)
  label_dsc.font = f20._p

  var buf = str(obj.get_value())
  var txt_size = lv.point()
  lv.text_get_size(txt_size, buf, f20, label_dsc.letter_space, label_dsc.line_space, lv.COORD_MAX, label_dsc.flag)

  var txt_area = lv.area()
  txt_area.x1 = 0
  txt_area.x2 = txt_size.x - 1
  txt_area.y1 = 0
  txt_area.y2 = txt_size.y - 1

  label_dsc.text = introspect.toptr(buf)
  label_dsc.text_local = true

  var indic_area = obj.get_indic_area()
  if (lv.area_get_width(indic_area) > txt_size.x + 20)
    lv.area_align(indic_area, txt_area, lv.ALIGN_RIGHT_MID, -10, 0)
    label_dsc.color = lv.COLOR_WHITE
  else
    lv.area_align(indic_area, txt_area, lv.ALIGN_OUT_RIGHT_MID, 10, 0)
    label_dsc.color = lv.COLOR_WHITE
  end

  var layer = event.get_layer()
  lv.draw_label(layer, label_dsc, txt_area)

end

bar.add_event_cb(bar_event, lv.EVENT_DRAW_MAIN_END, 0)

bar.set_value(20, lv.ANIM_OFF)

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.6
• The code change is tested and works with Tasmota core ESP32 V.2.0.14
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass