Slow rect render with ggez

gistfile1.txt

extern crate ggez;

use std::io;
use std::time::Instant;

use ggez::{event, graphics, Context, GameResult};

struct GameState;

impl event::EventHandler for GameState {
    fn update(&mut self, _ctx: &mut Context) -> GameResult<()> {
        Ok(())
    }

    fn draw(&mut self, ctx: &mut Context) -> GameResult<()> {
        let start = Instant::now();

        graphics::clear(ctx);
        for x in 0..50 {
            for y in 0..50 {
                let rect = graphics::Rect::new_i32(x*10, y*10, x*10+10, y*10+10);
                graphics::set_color(ctx, [(x as f32) / 500.0, 0.0, (y as f32) / 500.0, 1.0].into())?;
                graphics::rectangle(ctx, graphics::DrawMode::Fill, rect)?;
            }
        }
        graphics::present(ctx);

        println!("Drawing took: {}ms", start.elapsed().subsec_millis());
        Ok(())
    }
}

fn main() -> io::Result<()> {
    let ctx = &mut ggez::ContextBuilder::new("hello", "Hello!!")
        .window_setup(ggez::conf::WindowSetup::default().title("Hello!"))
        .window_mode(ggez::conf::WindowMode::default().dimensions(500, 500))
        .build()
        .expect("Failed to build ggez context");

    graphics::set_background_color(ctx, [0.0, 0.0, 0.0, 1.0].into());

    let state = &mut GameState{};

    match event::run(ctx, state) {
        Err(e) => println!("Error encountered running game: {}", e),
        Ok(_) => println!("Game exited cleanly!"),
    }

    Ok(())
}