[Fix] Quads of different background types not ordered

[bungoboingo]

So caught up in the elation of lerping, I completely forgot to order quads of different background types 🤦

This will fix any issues with using quads of different background types on top of one another.

I made a separate order field of the layer::Quads struct to consolidate quads for rendering, similar to how we're doing it with triangle meshes already.

[hecrj]

I have some ideas to improve layering overall in the backlog.

For now, having gradients always be on top of solid seems consistent with the way other primitives work for a specific layer. I don't think we should introduce ordering (primitive layering) at a layer level.

[bungoboingo]

This is just for grouping quads together to be rendered actually in order of when they're supposed to be. Right now you can't put a container with a solid background over a container with a gradient background or else the solid will be rendered over since we're rendering all solids & then all gradients. I'm not sure where else to put ordering besides at the layer level since that's where they're being grouped, unless we want to introduce like a depth value or something to primitives.

Current master:

Fixed:

fn view(&self) -> Element<'_, Self::Message, Renderer<Self::Theme>> {
        let small_center_box = container(":-)")
            .center_x().center_y()
            .height(100)
            .width(100)
            .style(theme::Container::Custom(Box::new(SolidBackgroundStyle)));

        let center_box = container(small_center_box)
            .center_x()
            .center_y()
            .height(300)
            .width(300)
            .style(theme::Container::Custom(Box::new(SolidBackgroundStyle)));

        container(center_box)
            .width(Length::Fill)
            .height(Length::Fill)
            .center_x()
            .center_y()
            .style(theme::Container::Custom(Box::new(GradientBackgroundStyle)))
            .into()
    }

[hecrj]

Yeah, I know. This is layering at the primitive level. Just pointing out that it shouldn't be a problem soon.

But I forgot the fact that gradients can be used as backgrounds now... So we should definitely fix this before that exploration lands.

I guess I'm not happy with how the implementation details of the quad module are leaking into our layering logic. Any kind of index logic should be opaque.

We should move the Quads struct to the quad module, rename it to Layer, make it completely opaque, and expose methods that the layer module can use. That way we keep all the limitations of the quad pipeline in the quad module, and we can guarantee that the indices are only generated in a single place.

[bungoboingo]

Adjusted in 10a68ac 👍

[hecrj]

Awesome!

Moved some code around to avoid the quad pipeline details from leaking into layer by removing layer::quad altogether! We should probably do the same thing with the other layer submodules; but no need to do that here.

Also simplified some minor things! Hopefully I didn't break anything.

Let's merge! 🚢

[hecrj]

Found the right way to keep solid and gradient details also private!

[bungoboingo]

Looks good, we can move the other layer submodule code into its respective pipeline implementation files later.