The ResizeHandler mentioned by changelog doesn't really exist yet

[RybekU]

Describe the bug
The ResizeHandler module, which got introduced to help maintaining the same aspect ratio when the screen size changes isn't added as a module. It's not a simple case of just adding the module as it's not finished yet in the current form.

To Reproduce
Try to use ResizeHandler, really

Environment and versions:

• Environment: any
• Rust compiler version: any
• Quicksilver version: latest development branch

[RybekU]

Also, as a sidenote, the current interface it's only function has is

pub fn projection(&self, size: Vector) -> Transform

It seems to not be able to provide functionality for every single enum variant.
Some options would require using Graphics::set_viewport and not only Graphics::set_projection (which the current interface is implying).
I would like to hear an opinion of someone more experienced with this style of API first or maybe a new function interface proposition before I can prepare a pull request.

[RybekU]

A heads up that I just basically have a copy-pasted/ported version of it from the previous quicksilver.
https://github.com/RybekU/Slimeu/blob/master/src/engine/resize_strategy.rs
It however doesn't set a projection (and i frankly have no idea how it can be achieved with just a projection, i find the Rectangle useful in the future to for example draw something that fills the space and looks nicely), but a Rectangle that should be used to make a new viewport (you can't make viewport from Rectangle so the actual usage is quite ugly, or at least couldn't back when I tried).
Usage example here: https://github.com/RybekU/Slimeu/blob/master/src/events.rs#L24.

If @ryanisaacg you are fine with how it works I could PR it once I have time to move my project to the current master alongside some minimalistic usage example.

[ryanisaacg]

I do think it should be possible to implement this solely with set_projection and without touching the viewport; once I've sat down and worked through some of the linear algebra I'll be a bit more confident in that.