imgui-rs/imgui-examples/examples/test_drawing_channels_split.rs

mod support;

const WHITE: [f32; 4] = [1.0, 1.0, 1.0, 1.0];
const RED: [f32; 4] = [1.0, 0.0, 0.0, 1.0];

fn main() {
    support::simple_init(file!(), move |_, ui| {
        let draw_list = ui.get_window_draw_list();
        // Will draw channel 0 first, then channel 1, whatever the order of
        // the calls in the code.
        //
        // Here, we draw a red line on channel 1 then a white circle on
        // channel 0. As a result, the red line will always appear on top of
        // the white circle.
        draw_list.channels_split(2, |channels| {
            const RADIUS: f32 = 100.0;
            let canvas_pos = ui.cursor_screen_pos();
            channels.set_current(1);
            draw_list
                .add_line(
                    canvas_pos,
                    [canvas_pos[0] + RADIUS, canvas_pos[1] + RADIUS],
                    RED,
                )
                .thickness(5.0)
                .build();

            channels.set_current(0);
            let center = [canvas_pos[0] + RADIUS, canvas_pos[1] + RADIUS];
            draw_list
                .add_circle(center, RADIUS, WHITE)
                .thickness(10.0)
                .num_segments(50)
                .build();
        });
    });
}