The Arc consists of a background and a foreground arc. The foreground (indicator) can be touch-adjusted.
- :cpp
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. - :cpp
LV_PART_INDICATOR
Draws another arc using the arc style properties. Its padding values are interpreted relative to the background arc. - :cpp
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.
A new value can be set using :cpplv_arc_set_value(arc, new_value)
. The value is interpreted in a range (minimum and maximum values) which can be modified with :cpplv_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 :cpplv_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.
An offset to the 0 degree position can be added with :cpplv_arc_set_rotation(arc, deg)
.
The arc can be one of the following modes:
- :cpp
LV_ARC_MODE_NORMAL
The indicator arc is drawn from the minimum value to the current. - :cpp
LV_ARC_MODE_REVERSE
The indicator arc is drawn counter-clockwise from the maximum value to the current. - :cpp
LV_ARC_MODE_SYMMETRICAL
The indicator arc is drawn from the middle point to the current value.
The mode can be set by :cpplv_arc_set_mode(arc, LV_ARC_MODE_...)
and used only if the angle is set by :cpplv_arc_set_value
or the arc is adjusted by finger.
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 :cpplv_arc_set_change_rage(arc, rate)
Changing the knob offset allows the location of the knob to be moved relative to the end of the arc The knob offset can be set by :cpplv_arc_set_knob_offset(arc, offset_angle)
, will only be visible if :cppLV_PART_KNOB
is visible
It's also possible to set the angles of the indicator arc directly with :cpplv_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_remove_flag(arc, LV_OBJ_FLAG_CLICKABLE);
If the :cppLV_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. :cpplv_obj_set_ext_click_size
makes the sensitive area larger inside and outside with the given number of pixels.
Another object can be positioned according to the current position of the arc in order to follow the arc's current value (angle). To do this use :cpplv_arc_align_obj_to_angle(arc, obj_to_align, radius_offset)
.
Similarly :cpplv_arc_rotate_obj_to_angle(arc, obj_to_rotate, radius_offset)
can be used to rotate the object to the current value of the arc.
It's a typical use case to call these functions in the VALUE_CHANGED
event of the arc.
- :cpp
LV_EVENT_VALUE_CHANGED
sent when the arc is pressed/dragged to set a new value. - :cpp
LV_EVENT_DRAW_PART_BEGIN
and :cppLV_EVENT_DRAW_PART_END
are sent with the following types:- :cpp
LV_ARC_DRAW_PART_BACKGROUND
The background arc.part
: :cppLV_PART_MAIN
p1
: center of the arcradius
: radius of the arcarc_dsc
- :cpp
LV_ARC_DRAW_PART_FOREGROUND
The foreground arc.part
: :cppLV_PART_INDICATOR
p1
: center of the arcradius
: radius of the arcarc_dsc
- LV_ARC_DRAW_PART_KNOB The knob
part
: :cppLV_PART_KNOB
draw_area
: the area of the knobrect_dsc
:
- :cpp
See the events of the Base object <lv_obj>
too.
Learn more about events
.
LV_KEY_RIGHT/UP
Increases the value by one.LV_KEY_LEFT/DOWN
Decreases the value by one.
Learn more about indev_keys
.