Consider splitting up top screen into two types?

[Ian Chamberlain]

As I've been trying to work on rust3ds/citro3d-rs#4, it occurred to me that it might make sense for us to break out the top-left and top-right screen into their own structs. Currently, it's a bit challenging to write code that's generic for both screens, since you can't get the raw frame buffer, so you have to write something like:

impl Thing {
    pub fn new_top(screen: TopScreen, side: Side);
    pub fn new_bottom(screen: BottomScreen);
}

I was thinking, maybe we could separate the top screen into two types, and add frame buffer helpers to Screen instead, like:

pub trait Screen {
    /// Returns the libctru value for the Screen kind
    fn as_raw(&self) -> ctru_sys::gfxScreen_t;

    /// Returns the raw frame buffer for rendering to the Screen
    fn get_raw_framebuffer(&mut self) -> RawFrameBuffer;
}

This way, it would be a bit easier to have separate ownership of the top-left and top-right screens, in case e.g. you wanted to have separate render targets:

let top_left = render::Target::new(gfx.top_left_screen.borrow_mut());
let top_right = render::Target::new(gfx.top_right_screen.borrow_mut());

For simplicity, maybe we could also have a helper struct/method in case you want to render to both sides, although I don't think it could implement Screen so it may have limited uses. Perhaps a helper like that would be more useful in render code than in gfx itself.

I think this implementation would be more consistent with e.g. the CAM implementation in #65 and would make it a bit easier to write generic code against screens. @Meziu @AzureMarker what are your thoughts?

[Meziu]

That makes sense. They have different framebuffers and work in a parallel way. The only issue would be when rendering in wide mode, since both sides are used as one (i believe). For everything else it should be pretty straightforward.

[Mark Drobnak]

Sounds good, my only concern is about how code using both sides like Console will look. Do you have an example of what creating a top screen console would look like with this change?