draw_projection.rs

use notan::draw::*;
use notan::math::{vec2, vec3, Mat4, Vec2};
use notan::prelude::*;

// This is the size of our content, no matter the size
// of the window our content will always keep this aspect ratio
const WORK_SIZE: Vec2 = vec2(800.0, 600.0);

#[notan_main]
fn main() -> Result<(), String> {
    let win_config = WindowConfig::default().set_resizable(true);

    notan::init()
        .add_config(win_config)
        .add_config(DrawConfig) // Simple way to add the draw extension
        .draw(draw)
        .build()
}

fn draw(gfx: &mut Graphics) {
    let (width, height) = gfx.size();
    let win_size = vec2(width as f32, height as f32);

    // get the projection that will fit and center our content in the screen
    let (projection, _) = calc_projection(win_size, WORK_SIZE);

    let mut draw = gfx.create_draw();
    draw.clear(Color::BLACK);

    // We set our projection here
    // Anything draw below will keep the aspect ratio
    draw.set_projection(Some(projection));

    // Our resolution bounds
    draw.rect((0.0, 0.0), WORK_SIZE.into())
        .color(Color::ORANGE)
        .stroke(10.0);

    draw.triangle((400.0, 100.0), (100.0, 500.0), (700.0, 500.0));

    // draw to screen
    gfx.render(&draw);
}

// This returns a projection that keeps the aspect ratio while scaling
// and fitting the content in our window
// It also returns the ratio in case we need it to calculate positions
// or manually scale something
fn calc_projection(win_size: Vec2, work_size: Vec2) -> (Mat4, f32) {
    let ratio = (win_size.x / work_size.x).min(win_size.y / work_size.y);

    let projection = Mat4::orthographic_rh_gl(0.0, win_size.x, win_size.y, 0.0, -1.0, 1.0);
    let scale = Mat4::from_scale(vec3(ratio, ratio, 1.0));
    let position = vec3(
        (win_size.x - work_size.x * ratio) * 0.5,
        (win_size.y - work_size.y * ratio) * 0.5,
        1.0,
    );
    let translation = Mat4::from_translation(position);
    (projection * translation * scale, ratio)
}