Minimal Pixels example isn't working

help
1

Hi,
I've been trying to re-do the pixels "minimal" example, except I tried to make it much more minimal. I think I over-minimalized it since it's just showing a black screen on my device (Pop!_OS 21.04). Any help would be appreciated. Here's my code:

use winit::event::{Event, WindowEvent};
use winit::event_loop::ControlFlow;

fn draw(frame: &mut [u8]) {
    for pixel in frame {
        *pixel = 255;
    }
}

fn main() {
    let event_loop = winit::event_loop::EventLoop::new();
    let window = {
        let size = winit::dpi::LogicalSize::new(320.0, 240.0);
        winit::window::WindowBuilder::new()
            .with_title("Pixels Test")
            .with_inner_size(size)
            .with_min_inner_size(size)
            .build(&event_loop)
            .unwrap()
    };
        
    let mut pixels = {
        let window_size = window.inner_size();
        let surface_texture = pixels::SurfaceTexture::new(window_size.width, window_size.height, &window);
        pixels::Pixels::new(window_size.width, window_size.height, surface_texture).unwrap()
    };

    draw(pixels.get_frame());

    event_loop.run(move |event, _, control_flow| {
        *control_flow = ControlFlow::Poll;

        match event {
            Event::WindowEvent {
                event: WindowEvent::CloseRequested,
                ..
            } => *control_flow = ControlFlow::Exit,
            Event::RedrawRequested(_) => {
                if pixels.render().is_err() {
                    *control_flow = ControlFlow::Exit;
                }
            },
            _ => {}
        };

        window.request_redraw();
    });
}

Thanks!

Edit: I wanted to note that the screen isn't frozen; I can quit out of it perfectly fine. It's just showing a black screen.

2

I get a white window on my linux box. If I change the

*pixel = 255;
into
*pixel = 126
the window is grey.

Your code as posted appears to work.
I get a grey square

1 Like
3

Your comment inspired me to do some digging. Pop!_OS has a feature where you can turn off window title bars. Turns out, if this feature is enabled, winit fails to show anything.

Thanks

Edit: Okay, I found an actual solution to this. The problem was that the program didn't properly handle resizing.

Event::WindowEvent{event: e, ..} => match e {
                WindowEvent::CloseRequested => 
                    *control_flow = ControlFlow::Exit,

                WindowEvent::Resized(new_size) => 
                    pixels.resize_surface(new_size.width, new_size.height),

                _ => {}
            },

Adding this to the program makes it work, even if window title bars are off.

4

Oh hey, I didn't see this earlier. (Honestly, I don't check the forum nearly as often as I should.)

That is an interesting issue you have stumbled upon. And this is the first time I've heard of Pop!_OS. I guess I shouldn't be surprised that the bare minimum example behaves uniquely with winit in that environment. I've noticed several instances of similar behavior with it on various platforms.

Anyway, I don't think this would have solved the initial problem, but I noticed that you have a bug in how you are creating your pixel buffer. You are passing the inner window size to Pixels::new(), which is almost certainly wrong. It looks like you want a 320x240 pixel buffer, not whatever the inner window size is. The code as provided creates a pixel buffer whose size depends on the display environment's DPI scaling factor. Pass an explicit size instead.

It's good that you handle resize events, now. The resize_surface method synchronizes the internal renderer and wgpu with the window surface. This is necessary any time the window size changes for any reason.

5

Ah, thanks for the advice!

6

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