Line (lv_line)

Overview

The Line object is capable of drawing straight lines between a set of points.

Parts and Styles

  • LV_PART_MAIN uses all the typical background properties and line style properties.

Usage

Set points

The points have to be stored in an lv_point_t array and passed to the object by the lv_line_set_points(lines, point_array, point_cnt) function.

Auto-size

By default the Line's width and height are set to LV_SIZE_CONTENT. This means it will automatically set its size to fit all the points. If the size is set explicitly, parts on the line may not be visible.

Invert y

By default, the y == 0 point is in the top of the object. It might be conter-intuitive in some cases so the y coordinates can be inverted with lv_line_set_y_invert(line, true). In this case, y == 0 will be the bottom of the object. y invert is disabled by default.

Events

Only the Generic events are sent by the object type.

Learn more about Events.

Keys

No Keys are processed by the object type.

Learn more about Keys.

Example

Simple Line

Click to try in the MicroPython simulator!
#include "../../lv_examples.h"
#if LV_USE_LINE && LV_BUILD_EXAMPLES

void lv_example_line_1(void)
{
    /*Create an array for the points of the line*/
    static lv_point_t line_points[] = { {5, 5}, {70, 70}, {120, 10}, {180, 60}, {240, 10} };

    /*Create style*/
    static lv_style_t style_line;
    lv_style_init(&style_line);
    lv_style_set_line_width(&style_line, 8);
    lv_style_set_line_color(&style_line, lv_palette_main(LV_PALETTE_BLUE));
    lv_style_set_line_rounded(&style_line, true);

    /*Create a line and apply the new style*/
    lv_obj_t * line1;
    line1 = lv_line_create(lv_scr_act());
    lv_line_set_points(line1, line_points, 5);     /*Set the points*/
    lv_obj_add_style(line1, &style_line, 0);
    lv_obj_center(line1);
}

#endif

MicroPython code     view on GitHub

# Create an array for the points of the line
line_points = [ {"x":5, "y":5}, 
                {"x":70, "y":70}, 
                {"x":120, "y":10}, 
                {"x":180, "y":60}, 
                {"x":240, "y":10}]

# Create style
style_line = lv.style_t()
style_line.init()
style_line.set_line_width(8)
style_line.set_line_color(lv.palette_main(lv.PALETTE.BLUE))
style_line.set_line_rounded(True)

# Create a line and apply the new style
line1 = lv.line(lv.scr_act())
line1.set_points(line_points, 5)     # Set the points
line1.add_style(style_line, 0)
line1.center()


API

Functions

lv_obj_t *lv_line_create(lv_obj_t *parent)

Create a line objects

Parameters

par -- pointer to an object, it will be the parent of the new line

Returns

pointer to the created line

void lv_line_set_points(lv_obj_t *obj, const lv_point_t points[], uint16_t point_num)

Set an array of points. The line object will connect these points.

Parameters
  • obj -- pointer to a line object

  • points -- an array of points. Only the address is saved, so the array needs to be alive while the line exists

  • point_num -- number of points in 'point_a'

void lv_line_set_y_invert(lv_obj_t *obj, bool en)

Enable (or disable) the y coordinate inversion. If enabled then y will be subtracted from the height of the object, therefore the y = 0 coordinate will be on the bottom.

Parameters
  • obj -- pointer to a line object

  • en -- true: enable the y inversion, false:disable the y inversion

bool lv_line_get_y_invert(const lv_obj_t *obj)

Get the y inversion attribute

Parameters

obj -- pointer to a line object

Returns

true: y inversion is enabled, false: disabled

Variables

const lv_obj_class_t lv_line_class
struct lv_line_t

Public Members

lv_obj_t obj
const lv_point_t *point_array

Pointer to an array with the points of the line

uint16_t point_num

Number of points in 'point_array'

uint8_t y_inv

1: y == 0 will be on the bottom