Export the needed parts of Winit or add better utilities for centering a window.

[CalinZBaenen]

What problem does this solve or what need does it fill?

The problem this proposition intents to solve is making the task of centering a window easier.
It intents to remove the need to have dependencies for both bevy and winit.

What solution would you like?

There's multiple ways to o about this.
First, the way I would not like to see, by re-exporting the required parts of winit to center a window: winit::dpi::(::PhysicalPosition) and winit::event_loop(::EventLoop).

Second, the solution I'd like to see implemented, WindowDescriptor.position when set to None should say that the window should be centered, then Bevy can take care of everything behind the scenes.
This also allows all windows to be centered by default.

What alternative(s) have you considered?

The alternative I'm using is to have dependencies for both winit and bevy in my Cargo.toml file:

[[bin]]
name = "bevytest"
path = "./src/main.rs"

[package]
edition = "2021"
version = "0.1.0"
name = "bevy_test"

[profile.dev]
opt-level = 1

[profile.dev.package."*"]
opt-level = 3

[dependencies]
winit = { version = "0.26.0", default-features = false }
bevy = { version="0.7" }

However, this seems inconvenient.

Additional Context

I believe centering the window could be delegated to WindowDescriptor.position = None or a center() method on a Window.
Check out the current solution for centering a window in a Discord-thread on the Bevy Discord guild.

[alice-i-cecile]

This is an excellent write-up, thanks! I agree with your analysis, and would like this to be simple. We get this question pretty regularly!

[CalinZBaenen]

@alice-i-cecile Thank you for the compliment. I feel honored to have gotten the "Good-First-Issue" tag, even for as little as its worth.

[CalinZBaenen]

I just had an afterthought, and this may or may not be a good idea, but it would be cool to control the window's visibility in a WindowDescriptor as a visibility property, this would theoretically allow you to center the window perfectly accounting for the border without anyone seeing, then you can unhide the window once it's in place.

[alice-i-cecile]

Ideally we reuse our standard visibility component for that, by making windows entities in #4530 :)

[bjorn3]

Second, the solution I'd like to see implemented, WindowDescriptor.position when set to None should say that the window should be centered

I think that should use the default position assigned by the window manager, not use a centered position.

[CalinZBaenen]

@bjorn3 Then how would one make the window centered using a WindowDescriptor? Would you suggest a centered:bool property?

[bjorn3]

Maybe make position an enum between fixed absolute position, centered and default position?

[LoipesMas]

That's exactly what mockersf suggested in #4999 (and I now implemented)

[bjorn3]

I didn't see PR until after I commented.