Arc Label (lv_arclabel)

Display text along an arc — useful for gauges, dials, and other curved layouts.

Overview

The Arc Label displays text along an arc. Useful for gauges, dials, and any layout where the text needs to follow a curved path. You can set the text, direction, radius, alignment, and color.

Styling

• LV_PART_MAIN covers both the arc path and the text drawn along it. Use the typical text and background style properties to change the look.

Text Management

• Text can be set using lv_arclabel_set_text(arclabel, "Your text").
• For formatted text, use lv_arclabel_set_text_fmt(arclabel, "Formatted %s", "text").
• Static text can be set with lv_arclabel_set_text_static(arclabel, static_text), which avoids dynamic memory allocation.

Angle Configuration

• Set the starting angle of the arc with lv_arclabel_set_angle_start(arclabel, angle).
• Define the arc size (angular span) using lv_arclabel_set_angle_size(arclabel, size).
• Angles are measured in degrees, starting from the positive x-axis (3 o'clock position) and increasing clockwise.

Direction

Specify the text direction along the arc using lv_arclabel_set_dir(arclabel, LV_ARCLABEL_DIR_CLOCKWISE) or lv_arclabel_set_dir(arclabel, LV_ARCLABEL_DIR_COUNTERCLOCKWISE).

• LV_ARCLABEL_DIR_CLOCKWISE Text flows in a clockwise direction along the arc.
• LV_ARCLABEL_DIR_COUNTERCLOCKWISE Text flows in a counter-clockwise direction along the arc.

Alignment

Adjust vertical text alignment with lv_arclabel_set_text_vertical_align(arclabel, LV_ARCLABEL_TEXT_ALIGN_CENTER). Set horizontal alignment using lv_arclabel_set_text_horizontal_align(arclabel, LV_ARCLABEL_TEXT_ALIGN_CENTER).

Both vertical and horizontal use the same logic.

• LV_ARCLABEL_TEXT_ALIGN_DEFAULT Uses the default alignment.
• LV_ARCLABEL_TEXT_ALIGN_LEADING Aligns text to the leading edge of the arc.
• LV_ARCLABEL_TEXT_ALIGN_CENTER Centers text along the arc.
• LV_ARCLABEL_TEXT_ALIGN_TRAILING Aligns text to the trailing edge of the arc.

Radius and Center Offset

• Set the radius of the arc with lv_arclabel_set_radius(arclabel, radius).
• Adjust the center offset of the arc using lv_arclabel_set_center_offset_x(arclabel, x) and lv_arclabel_set_center_offset_y(arclabel, y).

Color and Recoloring

Enable text recoloring with lv_arclabel_set_recolor(arclabel, true). This allows parts of the text to be colored differently using color commands embedded in the text string.

Interactive Behavior

Arc Label is not clickable by default. Add the LV_OBJ_FLAG_CLICKABLE flag if you want it to receive input events.

Events

No special events. The widget inherits the events common to all widgets.

Keys

No special keys. Add the widget to a group if you need keypad input.

Example

Simple Arc Label