lvgl/docs/widgets/arc.md

.. include:: /header.rst 
:github_url: |github_link_base|/widgets/arc.md

Arc (lv_arc)

Overview

The Arc are consists of a background and a foreground arc. Both can have start and end angles and thickness.

Parts and Styles

The Arc's main part is called LV_ARC_PART_MAIN. It draws a background using the typical background style properties and an arc using the line style properties. The arc's size and position will respect the padding style properties.

LV_ARC_PART_INDIC is virtual part and it draws an other arc using the line style properties. It's padding values are interpreted relative to the background arc. The radius of the indicator arc will be modified according to the greatest padding value.

LV_ARC_PART_KNOB is virtual part and it draws on the end of the arc indicator. It uses 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

Angles

To set the angles of the background, use the lv_arc_set_bg_angles(arc, start_angle, end_angle) function or lv_arc_set_bg_start/end_angle(arc, start_angle). Zero degree is at the middle right (3 o'clock) of the object and the degrees are increasing in a clockwise direction. The angles should be in [0;360] range.

Similarly, lv_arc_set_angles(arc, start_angle, end_angle) function or lv_arc_set_start/end_angle(arc, start_angle) sets the angles of the indicator arc.

Rotation

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

Range and values

Besides setting angles manually the arc can have a range and a value. To set the range use lv_arc_set_range(arc, min, max) and to set a value use lv_arc_set_value(arc, value). Using range and value the angle of the indicator will be mapped between background angles.

Note that, settings angles and values are independent. You should use either value and angle settings. Mixing the two might result unintended behavior.

Type

The arc can have the different "types". They are set with lv_arc_set_type. The following types exist:

• LV_ARC_TYPE_NORMAL indicator arc drawn clockwise (min to current)
• LV_ARC_TYPE_REVERSE indicator arc drawn counter clockwise (max to current)
• LV_ARC_TYPE_SYMMETRIC indicator arc drawn from the middle point to the current value.

Events

Besides the Generic events the following Special events are sent by the arcs:

• LV_EVENT_VALUE_CHANGED sent when the arc is pressed/dragged to set a new value.

Learn more about Events.

Keys

No Keys are processed by the object type.

Learn more about Keys.

Example

.. include:: /lv_examples/src/lv_ex_widgets/lv_ex_arc/index.rst

API

.. doxygenfile:: lv_arc.h
  :project: lvgl