Moved UI widgets to a bevy_widget crate

[Pietrek14]

Objective

Fixes #7190.

Solution

• Added a new bevy_widget crate to Bevy
• Moved the widgets to the new crate
• Created a seperate category for widget-related examples

---

Changelog

• Added
  • A bevy_widget crate
  • WidgetPlugin
• Moved
  • Widgets to bevy_widget crate
  • Widget-related examples to a dedicated directory

Migration Guide

• Widget imports now have to reference the widget module instead of ui
• If you don't use the default features and want to have widgets available, you will have to enable the bevy_widget feature flag
• If you don't use the default plugins and want to have widgets available, you will have to add a WidgetPlugin to your app

[alice-i-cecile]

Can you add forbid(unsafe_code) and warn(missing_docs) crate level rules please?

Once that's in, we should add basic doc strings.

[Pietrek14]

The only thing with missing docs is QueuedText. It's only used as a Local for text_system, so should we even keep it public?

[alice-i-cecile]

We should probably keep text_system public, so we need to keep the Local type public or Rust will complain.

[alice-i-cecile]

Marked as Controversial since this adds a new crate, but it seems like there's pretty clear consensus on splitting apart the code like this.

[alice-i-cecile]

Feedback on structure:

1. I think that the widget bundles belong in the same file as the logic for that widget.
2. I don't think that the widget module is useful since we're in a dedicated crate for widgets. We can just make each widget a top level module.

[alice-i-cecile]

LGTM now :) I trust that you'll get basic docs for QueuedText working.

[github-actions]

You added a new feature but didn't add a description for it. Please update the root Cargo.toml file.

[github-actions]

You added a new feature but didn't add a description for it. Please update the root Cargo.toml file.

[github-actions]

You added a new feature but didn't add a description for it. Please update the root Cargo.toml file.

[github-actions]

You added a new feature but didn't add a description for it. Please update the root Cargo.toml file.

[Pietrek14]

I don't mean to rush anything, but how long may it take for this PR to reach Cart's attention? There are merge conflicts to resolve every time any change is made to the bevy_ui crate, which is pretty often. I'm going to try to keep this up-to-date as much as I can, but I'm travelling to Portugal in the second half of April and I won't be able to take care of it. I'm not planning on abandoning this PR, but I just want to know if it will be reviewed by then.

[mockersf]

Disclaimer: I'm not Cart

I think it's too early to do this, and I haven't seen either in this PR or in the issue it fixes a good enough justification for the change. This is just a code organisation changes that doesn't improve anything or unlock anything, as such it's very low priority

[github-actions]

You added a new example but didn't update the readme. Please run cargo run -p build-templated-pages -- update examples to update it, and commit the file change.

[github-actions]

You added a new example but didn't update the readme. Please run cargo run -p build-templated-pages -- update examples to update it, and commit the file change.

[bas-ie]

Backlog cleanup: closing due to inactivity. We've already split out a number of crates, so I guess there's nothing to stop us doing this later but probably easier to begin again after 0.15.

[alice-i-cecile]

I still think we should do something like this, but yeah, this requires consensus and broad maintainer buy-in :(

[bas-ie]

I hovered over the button, but figured someone would yell if they really wanted it kept!