wenaglia/src/sys/drawing.rs

use crate::consts;
use crate::components::{self,Position,Sprite};
use crate::game::MyGame;

use ggez::{
    Context,
    graphics,
    graphics::spritebatch::SpriteBatch,
};
use specs::RunNow;

/// The `Draw` system is parameterized by which phase we want to draw
/// in.
pub struct Draw<'t, Phase> {
    pub ctx: &'t mut Context,
    pub sprites: &'t mut SpriteBatch,
    pub _phase: Phase,
}

impl<'a, 't, Phase : specs::Component> specs::System<'a> for Draw<'t, Phase> {
    type SystemData = (
        specs::ReadStorage<'a, Position>,
        specs::ReadStorage<'a, Sprite>,
        specs::ReadStorage<'a, Phase>,
    );

    fn run(&mut self, (positions, sprites, phase): Self::SystemData) {
        use specs::Join;

        for (pos, spr, _) in (&positions, &sprites, &phase).join() {
            let param = graphics::DrawParam {
                src: spr.to_rect(),
                dest: pos.to_point(),
                scale: ggez::nalgebra::Point2::new(consts::SCALE, consts::SCALE),
                ..Default::default()
            };
            self.sprites.add(param);
            graphics::draw(
                self.ctx,
                self.sprites,
                ggez::nalgebra::Point2::new(0.0, 0.0),
                0.0).unwrap();
            self.sprites.clear();
        }
    }
}


pub fn systems(game: &mut MyGame, ctx: &mut Context) -> ggez::GameResult<()> {
    graphics::set_background_color(ctx, graphics::BLACK);
    graphics::clear(ctx);

    Draw {
        ctx,
        sprites: &mut game.sprites,
        _phase: components::Background,
    }.run_now(&game.world.res);
    Draw {
        ctx,
        sprites: &mut game.sprites,
        _phase: components::Foreground,
    }.run_now(&game.world.res);
    Draw {
        ctx,
        sprites: &mut game.sprites,
        _phase: components::Decoration,
    }.run_now(&game.world.res);

    graphics::draw(
        ctx,
        &game.sprites,
        ggez::nalgebra::Point2::new(0.0, 0.0),
        0.0
    )?;
    game.sprites.clear();
    graphics::present(ctx);
    Ok(())
}