Arc (lv_arc)¶

Overview¶

The Arc consists of a background and a foreground arc. The foreground (indicator) can be touch-adjusted.

Parts and Styles¶

LV_PART_MAIN Draws a background using the typical background style properties and an arc using the arc style properties. The arc's size and position will respect the padding style properties.
LV_PART_INDICATOR Draws another arc using the arc style properties. Its padding values are interpreted relative to the background arc.
LV_PART_KNOB Draws a handle on the end of the indicator using all background properties and padding values. With zero padding the knob size is the same as the indicator's width. Larger padding makes it larger, smaller padding makes it smaller.

Usage¶

Value and range¶

A new value can be set using lv_arc_set_value(arc, new_value). The value is interpreted in a range (minimum and maximum values) which can be modified with lv_arc_set_range(arc, min, max). The default range is 0..100.

The indicator arc is drawn on the main part's arc. This if the value is set to maximum the indicator arc will cover the entire "background" arc. To set the start and end angle of the background arc use the lv_arc_set_bg_angles(arc, start_angle, end_angle) functions or lv_arc_set_bg_start/end_angle(arc, angle).

Zero degrees is at the middle right (3 o'clock) of the object and the degrees are increasing in clockwise direction. The angles should be in the [0;360] range.

Rotation¶

An offset to the 0 degree position can be added with lv_arc_set_rotation(arc, deg).

Mode¶

The arc can be one of the following modes:

LV_ARC_MODE_NORMAL The indicator arc is drawn from the minimum value to the current.
LV_ARC_MODE_REVERSE The indicator arc is drawn counter-clockwise from the maximum value to the current.
LV_ARC_MODE_SYMMETRICAL The indicator arc is drawn from the middle point to the current value.

The mode can be set by lv_arc_set_mode(arc, LV_ARC_MODE_...) and used only if the angle is set by lv_arc_set_value() or the arc is adjusted by finger.

Change rate¶

If the arc is pressed the current value will set with a limited speed according to the set change rate. The change rate is defined in degree/second unit and can be set with lv_arc_set_change_rage(arc, rate)

Setting the indicator manually¶

It's also possible to set the angles of the indicator arc directly with lv_arc_set_angles(arc, start_angle, end_angle) function or lv_arc_set_start/end_angle(arc, start_angle). In this case the set "value" and "mode" are ignored.

In other words, the angle and value settings are independent. You should exclusively use one or the other. Mixing the two might result in unintended behavior.

To make the arc non-adjustable, remove the style of the knob and make the object non-clickable:

lv_obj_remove_style(arc, NULL, LV_PART_KNOB);
lv_obj_clear_flag(arc, LV_OBJ_FLAG_CLICKABLE);

Advanced hit test¶

If the LV_OBJ_FLAG_ADV_HITTEST flag is enabled the arc can be clicked through in the middle. Clicks are recognized only on the ring of the background arc. lv_obj_set_ext_click_size() makes the sensitive area larger inside and outside with the given number of pixels.

Events¶

LV_EVENT_VALUE_CHANGED sent when the arc is pressed/dragged to set a new value.
LV_EVENT_DRAW_PART_BEGIN and LV_EVENT_DRAW_PART_END are sent with the following types:
- LV_ARC_DRAW_PART_BACKGROUND The background arc.
  - part: LV_PART_MAIN
  - p1: center of the arc
  - radius: radius of the arc
  - arc_dsc
- LV_ARC_DRAW_PART_FOREGROUND The foreground arc.
  - part: LV_PART_INDICATOR
  - p1: center of the arc
  - radius: radius of the arc
  - arc_dsc
- LV_ARC_DRAW_PART_KNOB The knob
  - part: LV_PART_KNOB
  - draw_area: the area of the knob
  - rect_dsc:

See the events of the Base object too.

Learn more about Events.

Keys¶

LV_KEY_RIGHT/UP Increases the value by one.
LV_KEY_LEFT/DOWN Decreases the value by one.

Learn more about Keys.

Example¶

Simple Arc¶

A simple example to demonstrate the use of an arc.

#include "../../lv_examples.h"

#if LV_USE_ARC && LV_BUILD_EXAMPLES

void lv_example_arc_1(void)
{
  /*Create an Arc*/
  lv_obj_t * arc = lv_arc_create(lv_scr_act());
  lv_obj_set_size(arc, 150, 150);
  lv_arc_set_rotation(arc, 135);
  lv_arc_set_bg_angles(arc, 0, 270);
  lv_arc_set_value(arc, 40);
  lv_obj_center(arc);
}

#endif

# Create an Arc
arc = lv.arc(lv.scr_act())
arc.set_end_angle(200)
arc.set_size(150, 150)
arc.center()

Loader with Arc¶

#include "../../lv_examples.h"

#if LV_USE_ARC && LV_BUILD_EXAMPLES

static void set_angle(void * obj, int32_t v)
{
    lv_arc_set_value(obj, v);
}

/**
 * Create an arc which acts as a loader.
 */
void lv_example_arc_2(void)
{
  /*Create an Arc*/
  lv_obj_t * arc = lv_arc_create(lv_scr_act());
  lv_arc_set_rotation(arc, 270);
  lv_arc_set_bg_angles(arc, 0, 360);
  lv_obj_remove_style(arc, NULL, LV_PART_KNOB);   /*Be sure the knob is not displayed*/
  lv_obj_clear_flag(arc, LV_OBJ_FLAG_CLICKABLE);  /*To not allow adjusting by click*/
  lv_obj_center(arc);

  lv_anim_t a;
  lv_anim_init(&a);
  lv_anim_set_var(&a, arc);
  lv_anim_set_exec_cb(&a, set_angle);
  lv_anim_set_time(&a, 1000);
  lv_anim_set_repeat_count(&a, LV_ANIM_REPEAT_INFINITE);    /*Just for the demo*/
  lv_anim_set_repeat_delay(&a, 500);
  lv_anim_set_values(&a, 0, 100);
  lv_anim_start(&a);



}

#endif

#
# An `lv_timer` to call periodically to set the angles of the arc
#
class ArcLoader():
    def __init__(self):
        self.a = 270
        
    def arc_loader_cb(self,tim,arc):
        # print(tim,arc)
        self.a += 5

        arc.set_end_angle(self.a)

        if self.a >= 270 + 360:
            tim._del()


#
# Create an arc which acts as a loader.
#

# Create an Arc
arc = lv.arc(lv.scr_act())
arc.set_bg_angles(0, 360)
arc.set_angles(270, 270)
arc.center()

# create the loader
arc_loader = ArcLoader()

# Create an `lv_timer` to update the arc.

timer = lv.timer_create_basic()
timer.set_period(20)
timer.set_cb(lambda src: arc_loader.arc_loader_cb(timer,arc))
  

API¶

Typedefs

typedef uint8_t lv_arc_mode_t¶

Enums

enum [anonymous]¶

Values:

enumerator LV_ARC_MODE_NORMAL¶

enumerator LV_ARC_MODE_SYMMETRICAL¶

enumerator LV_ARC_MODE_REVERSE¶

enum lv_arc_draw_part_type_t¶

type field in lv_obj_draw_part_dsc_t if class_p = lv_arc_class Used in LV_EVENT_DRAW_PART_BEGIN and LV_EVENT_DRAW_PART_END

Values:

enumerator LV_ARC_DRAW_PART_BACKGROUND¶: The background arc

enumerator LV_ARC_DRAW_PART_FOREGROUND¶: The foreground arc

enumerator LV_ARC_DRAW_PART_KNOB¶: The knob

Functions

lv_obj_t *lv_arc_create(lv_obj_t *parent)¶

Create an arc object

Parameters: parent -- pointer to an object, it will be the parent of the new arc
Returns: pointer to the created arc

void lv_arc_set_start_angle(lv_obj_t *arc, uint16_t start)¶

Set the start angle of an arc. 0 deg: right, 90 bottom, etc.

Parameters

arc -- pointer to an arc object
start -- the start angle

void lv_arc_set_end_angle(lv_obj_t *arc, uint16_t end)¶

Set the end angle of an arc. 0 deg: right, 90 bottom, etc.

Parameters

arc -- pointer to an arc object
end -- the end angle

void lv_arc_set_angles(lv_obj_t *arc, uint16_t start, uint16_t end)¶

Set the start and end angles

Parameters

arc -- pointer to an arc object
start -- the start angle
end -- the end angle

void lv_arc_set_bg_start_angle(lv_obj_t *arc, uint16_t start)¶

Set the start angle of an arc background. 0 deg: right, 90 bottom, etc.

Parameters

arc -- pointer to an arc object
start -- the start angle

void lv_arc_set_bg_end_angle(lv_obj_t *arc, uint16_t end)¶

Set the start angle of an arc background. 0 deg: right, 90 bottom etc.

Parameters

arc -- pointer to an arc object
end -- the end angle

void lv_arc_set_bg_angles(lv_obj_t *arc, uint16_t start, uint16_t end)¶

Set the start and end angles of the arc background

Parameters

arc -- pointer to an arc object
start -- the start angle
end -- the end angle

void lv_arc_set_rotation(lv_obj_t *arc, uint16_t rotation)¶

Set the rotation for the whole arc

Parameters

arc -- pointer to an arc object
rotation -- rotation angle

void lv_arc_set_mode(lv_obj_t *arc, lv_arc_mode_t type)¶

Set the type of arc.

Parameters

arc -- pointer to arc object
mode -- arc's mode

void lv_arc_set_value(lv_obj_t *arc, int16_t value)¶

Set a new value on the arc

Parameters

arc -- pointer to an arc object
value -- new value

void lv_arc_set_range(lv_obj_t *arc, int16_t min, int16_t max)¶

Set minimum and the maximum values of an arc

Parameters

arc -- pointer to the arc object
min -- minimum value
max -- maximum value

void lv_arc_set_change_rate(lv_obj_t *arc, uint16_t rate)¶

Set a change rate to limit the speed how fast the arc should reach the pressed point.

Parameters

arc -- pointer to an arc object
rate -- the change rate

uint16_t lv_arc_get_angle_start(lv_obj_t *obj)¶

Get the start angle of an arc.

Parameters: arc -- pointer to an arc object
Returns: the start angle [0..360]

uint16_t lv_arc_get_angle_end(lv_obj_t *obj)¶

Get the end angle of an arc.

Parameters: arc -- pointer to an arc object
Returns: the end angle [0..360]

uint16_t lv_arc_get_bg_angle_start(lv_obj_t *obj)¶

Get the start angle of an arc background.

Parameters: arc -- pointer to an arc object
Returns: the start angle [0..360]

uint16_t lv_arc_get_bg_angle_end(lv_obj_t *obj)¶

Get the end angle of an arc background.

Parameters: arc -- pointer to an arc object
Returns: the end angle [0..360]

int16_t lv_arc_get_value(const lv_obj_t *obj)¶

Get the value of an arc

Parameters: arc -- pointer to an arc object
Returns: the value of the arc

int16_t lv_arc_get_min_value(const lv_obj_t *obj)¶

Get the minimum value of an arc

Parameters: arc -- pointer to an arc object
Returns: the minimum value of the arc

int16_t lv_arc_get_max_value(const lv_obj_t *obj)¶

Get the maximum value of an arc

Parameters: arc -- pointer to an arc object
Returns: the maximum value of the arc

lv_arc_mode_t lv_arc_get_mode(const lv_obj_t *obj)¶

Get whether the arc is type or not.

Parameters: arc -- pointer to an arc object
Returns: arc's mode

Variables

const lv_obj_class_t lv_arc_class¶

struct lv_arc_t¶

Public Members

lv_obj_t obj¶

uint16_t rotation¶

uint16_t indic_angle_start¶

uint16_t indic_angle_end¶

uint16_t bg_angle_start¶

uint16_t bg_angle_end¶

int16_t value¶

int16_t min_value¶

int16_t max_value¶

uint16_t dragging¶

uint16_t type¶

uint16_t min_close¶

uint16_t chg_rate¶

uint32_t last_tick¶

int16_t last_angle¶