Colour doesn't appear to work correctly with circle functions

[Guddler]

I have been trying to use filled_circle from gfx::primitives. I am not sure if iI'm doing something wrong, but if I try to draw 4 circles, two red and two black. One each using the predefined colours and one each using RGBA values the results are not as expected. I haven't included all the boiler plate code but I can provide a full example if needed.

At first sight it seems that the endianness of the colour is reversed but I don't think it is as simple as that because I ran my same code on a Big Endian PowrPC system and got different results again!

The below code and comment is from MacOS

// Renders a red circle
let _= canvas.filled_circle(200, 200, 75, Color::RED);
// Does not render - or more accurately, renders but is invisible due to alpha of 0
let _= canvas.filled_circle(600, 200, 75, Color::BLACK);
// Renders correctly - but is potentially ambiguous
let _= canvas.filled_circle(200, 400, 75, Color::RGBA(255, 0, 0, 255)); 
// Renders correctly, but clearly the RGBA values are reversed to what I assume they should be
let _ = canvas.filled_circle(600, 400, 75, Color::RGBA(255, 0, 0, 0));

Am I missing something fundamental here?

[EDIT]

Just to follow up here, the only way I can get the correct colours on either of my systems is by reversing the bytes as per the following. This works correctly on both big endian system and little endian system, so not sure if this is a bug or I'm missing a step:

let c = Color::BLUE;
let _= canvas.filled_circle(200, 200, 75, Color::RGBA(c.a, c.b, c.g, c.r));

[stice2446]

Facing the same issue here, and it's not just for circle functions but also for filled_polygon etc. and expect the same wherever gfx submodule's ToColor is used.

Unlike the example above, the workaround to simply assume ABGR format is sending a close but still erroneous colour to the filled_polygon functions. I was able to make it work by doing this before calling the library functions:

        // Use an arbitrary pixel format (RGBA8888 here) to convert the colour to a u32 in the native, then force it to 
        // to big-endian, then back to a colour before sending it to the filled_circle or filled_polygon fns provided
    pub fn gfx_lib_color_correction(color: Color) -> Color {
        let conversion_pixel_format = PixelFormat::try_from(PixelFormatEnum::RGBA8888).unwrap();
        let color_as_be_u32 = color.to_u32(&conversion_pixel_format).to_be();

        Color::from_u32(&conversion_pixel_format, color_as_be_u32)
    }

I suspect the issue is in this line here: https://github.com/Rust-SDL2/rust-sdl2/blob/master/src/sdl2/gfx/primitives.rs#L20

/// generic Color type
pub trait ToColor {
    fn as_rgba(&self) -> (u8, u8, u8, u8);

    #[inline]
    fn as_u32(&self) -> u32 {
        let (r, g, b, a) = self.as_rgba();
        u32::from_be_bytes([r, g, b, a]) // <-----------------------
    }
}

Is it correct that as_u32 is using u32::from_be_bytes if rust-sdl2's Color struct implements the trait, since Color doesn't have anything to do with the pixel format in bytes yet? I'm not familiar with the required public API and how the underlying gfx C code actually works though, so please let me know if I'm simply using this wrong.

Found an old issue that might be related: #1470

[antonilol]

Can you take a look at #1522