Add non-blocking update function

[SakiiCode]

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PR description

Resolves #70

[rfuest]

Thanks for the PR.

I would prefer to implement this in another way, without requiring two variants of the update method. There is already a way to change the target FPS via Window::set_max_fps and MultiWindow::set_max_fps and the option to disable the FPS limit should be accessible in a similar way. I would suggest to add disable_fps_limit methods to Window and MultiWindow, which set the fps_limiter field to None.

[SakiiCode]

I wanted to avoid having an is_none() check in every update cycle, but did not find a better way to do it.

What if the check is in fps_limiter.sleep() like this:

    fn sleep(&mut self) {
        if self.max_fps == 0 {
            return;
        }
        let sleep_duration = (self.frame_start + self.desired_loop_duration())
            .saturating_duration_since(Instant::now());
        thread::sleep(sleep_duration);

        self.frame_start = Instant::now();
    }

This way the Window functions do not need any modification and the fps limit can be adjusted flexibly

[rfuest]

I wanted to avoid having an is_none() check in every update cycle, but did not find a better way to do it.

Why do you want to avoid this? This doesn't seem bad to me:

    pub fn update<C>(&mut self, display: &SimulatorDisplay<C>)
    where
        C: PixelColor + Into<Rgb888> + From<Rgb888>,
    {
        ...

        if let Some(fps_limiter) = self.fps_limiter.as_mut() {
            fps_limiter.sleep();
        }
    }

Using max_fps == 0 as a special value would work and is something I would use in a C program, but in Rust it's better to use an enum for the special value.

[SakiiCode]

if let Some(fps_limiter) = self.fps_limiter.as_mut() {
       fps_limiter.sleep();
}

It is not possible to later restore the FpsLimiter if needed

Using max_fps == 0 as a special value would work and is something I would use in a C program, but in Rust it's better to use an enum for the special value.

Then it should be Option<NonNull<u32>>

[rfuest]

It is not possible to later restore the FpsLimiter if needed

Why not? Calling set_max_fps can restore the fps limiter.

Then it should be Option<NonNull>

Inside the FpsLimiter or as the parameter to set_max_fps? The second would be a breaking change of the API.

[SakiiCode]

Okay updated the PR, please check if it is good

[rfuest]

Not really what I was thinking, because it still uses 0 as a special value in set_max_fps. But I'm OK with merging this, when you change the documentation of the set_max_fps methods to mention that 0 has a special meaning.

[SakiiCode]

Ok done

[rfuest]

LGTM