support HiDPI fractional scaling

[lcnr]

extracted from #4,

We currently panic in case dpi is not a whole number.

[Moar-Chan]

How is this going? on Manjaro and i can't launch the engine because of this.

[lcnr]

Don't quite know how to test this myself as my computer does not support it.
I am also unsure on what exactly is the expected behavior there.

• round dpi to the nearest integer (doesn't work nicely as we now either have an empty section of the window or part of the image is invisible)
• somehow use anti aliasing (which kind of defeats why I made this).

In case you have the time to both help me test this and tell me about your desired outcome, I might be able to do something here.

[Moar-Chan]

Hmm you could send me some examples and i can send you the results, or maybe add both these things but let the user pick one.

[lcnr]

The easiest way to test this would be clone this repo and remove these three lines:

crow/src/backend/mod.rs

Lines 135 to 137 in 12af842

	} else if dpi.fract().min(1.0 - dpi.fract()) > std::f64::EPSILON {
	bug!("fractional HiDPI scaling is not yet supported: {}", dpi);
	}

You should then be able to run cargo run --example <example name (e.g. rectangles)> --release.

Adding AA will be kind of a mess so I would first like to see if the first approach works.

[Moar-Chan]

This seems fine

[Moar-Chan]

(its running on a 1440p screen)

[lcnr]

hmm, does look ok I guess. What's your DPI? I can replace the bug with a warning for now I guess 🤔

[Moar-Chan]

fractional HiDPI scaling is not yet supported: 1.5 <---
Should that not be the almost worst case as in the furthest from a whole int.

[lcnr]

It is the worst case 😆 It doesn't seem like I have an example that requires the whole screen though.

Will look into this more later 👍

[Moar-Chan]

IDK how github works,
but would it not be better to just do:
if dpi < 0.5 {
bug!("unexpected dpi: {}", dpi);
} else if dpi.fract().min(1.0 - dpi.fract()) > std::f64::EPSILON {
println!("fractional HiDPI scaling is not yet supported. but may work! (dpi: {})", dpi);
}

[Klebestreifen]

I have some data for the devs:

Panic

     Running `target\debug\crowtest.exe`
thread 'main' panicked at 'fractional HiDPI scaling is not yet supported: 1.25

    This might be a bug, consider filing an issue at https://github.com/lcnr/crow/issues/new', C:\Users\rkleb\.cargo\registry\src\github.com-1ecc6299db9ec823\crow-0.7.1\src\backend\mod.rs:136:13
stack backtrace:
   0: std::panicking::begin_panic_handler
             at /rustc/c8dfcfe046a7680554bf4eb612bad840e7631c4b\/library\std\src\panicking.rs:515
   1: std::panicking::begin_panic_fmt
             at /rustc/c8dfcfe046a7680554bf4eb612bad840e7631c4b\/library\std\src\panicking.rs:457
   2: crow::backend::Backend::initialize<tuple$<> >
             at C:\Users\rkleb\.cargo\registry\src\github.com-1ecc6299db9ec823\crow-0.7.1\src\backend\mod.rs:136
   3: crow::Context::new<tuple$<> >
             at C:\Users\rkleb\.cargo\registry\src\github.com-1ecc6299db9ec823\crow-0.7.1\src\context.rs:37
   4: crowtest::main
             at .\src\main.rs:34
   5: core::ops::function::FnOnce::call_once<enum$<core::result::Result<tuple$<>,enum$<crow::error::Error> >, 0, 3, Err> (*)(),tuple$<> >  
             at /rustc/c8dfcfe046a7680554bf4eb612bad840e7631c4b\library\core\src\ops\function.rs:227
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
error: process didn't exit successfully: `target\debug\crowtest.exe` (exit code: 101)

cargo --version --verbose

cargo 1.55.0 (32da73ab1 2021-08-23)
release: 1.55.0
commit-hash: 32da73ab19417aa89686e1d85c1440b72fdf877d
commit-date: 2021-08-23

My Code:

use crow::{
    glutin::{
        event::{Event, WindowEvent},
        event_loop::{ControlFlow, EventLoop},
        window::WindowBuilder,
    },
    Context, 
    DrawConfig,
    Texture,
    NewTextureError,
    image::{
        self,
        ImageFormat,
    }
};
use std::path::Path;
use asefile::AsepriteFile;

trait FromAseprite{
    fn from_ase(ctx: &mut Context, path: &Path) -> Result<Texture, NewTextureError>;
}

impl FromAseprite for Texture{
    fn from_ase(ctx: &mut Context, path: &Path) -> Result<Texture, NewTextureError> {
        let ase = AsepriteFile::read_file(path).unwrap();
        let img = ase.frame(0).image();

        Texture::from_image(ctx, img)
    }
}

fn main() -> Result<(), crow::Error> {
    let event_loop = EventLoop::new();
    let mut ctx = Context::new(WindowBuilder::new(), &event_loop)?;

    let texture = Texture::from_ase(&mut ctx, Path::new("./data/graphics/player.aseprite"))?;

    event_loop.run(
        move |event: Event<()>, _window_target: _, control_flow: &mut ControlFlow| match event {
            Event::WindowEvent {
                event: WindowEvent::CloseRequested,
                ..
            } => *control_flow = ControlFlow::Exit,
            Event::MainEventsCleared => ctx.window().request_redraw(),
            Event::RedrawRequested(_) => {
                let mut surface = ctx.surface();
                ctx.clear_color(&mut surface, (0.4, 0.4, 0.8, 1.0));
                ctx.draw(&mut surface, &texture, (100, 150), &DrawConfig::default());
                ctx.present(surface).unwrap();
            }
            _ => (),
        },
    )
}

[lcnr]

forgot to actually publish a new version of this crate, published version 0.7.2 now