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# Objective Add specialized UI transform `Component`s and fix some related problems: * Animating UI elements by modifying the `Transform` component of UI nodes doesn't work very well because `ui_layout_system` overwrites the translations each frame. The `overflow_debug` example uses a horrible hack where it copies the transform into the position that'll likely cause a panic if any users naively copy it. * Picking ignores rotation and scaling and assumes UI nodes are always axis aligned. * The clipping geometry stored in `CalculatedClip` is wrong for rotated and scaled elements. * Transform propagation is unnecessary for the UI, the transforms can be updated during layout updates. * The UI internals use both object-centered and top-left-corner-based coordinates systems for UI nodes. Depending on the context you have to add or subtract the half-size sometimes before transforming between coordinate spaces. We should just use one system consistantly so that the transform can always be directly applied. * `Transform` doesn't support responsive coordinates. ## Solution * Unrequire `Transform` from `Node`. * New components `UiTransform`, `UiGlobalTransform`: - `Node` requires `UiTransform`, `UiTransform` requires `UiGlobalTransform` - `UiTransform` is a 2d-only equivalent of `Transform` with a translation in `Val`s. - `UiGlobalTransform` newtypes `Affine2` and is updated in `ui_layout_system`. * New helper functions on `ComputedNode` for mapping between viewport and local node space. * The cursor position is transformed to local node space during picking so that it respects rotations and scalings. * To check if the cursor hovers a node recursively walk up the tree to the root checking if any of the ancestor nodes clip the point at the cursor. If the point is clipped the interaction is ignored. * Use object-centered coordinates for UI nodes. * `RelativeCursorPosition`'s coordinates are now object-centered with (0,0) at the the center of the node and the corners at (±0.5, ±0.5). * Replaced the `normalized_visible_node_rect: Rect` field of `RelativeCursorPosition` with `cursor_over: bool`, which is set to true when the cursor is over an unclipped point on the node. The visible area of the node is not necessarily a rectangle, so the previous implementation didn't work. This should fix all the logical bugs with non-axis aligned interactions and clipping. Rendering still needs changes but they are far outside the scope of this PR. Tried and abandoned two other approaches: * New `transform` field on `Node`, require `GlobalTransform` on `Node`, and unrequire `Transform` on `Node`. Unrequiring `Transform` opts out of transform propagation so there is then no conflict with updating the `GlobalTransform` in `ui_layout_system`. This was a nice change in its simplicity but potentially confusing for users I think, all the `GlobalTransform` docs mention `Transform` and having special rules for how it's updated just for the UI is unpleasently surprising. * New `transform` field on `Node`. Unrequire `Transform` on `Node`. New `transform: Affine2` field on `ComputedNode`. This was okay but I think most users want a separate specialized UI transform components. The fat `ComputedNode` doesn't work well with change detection. Fixes #18929, #18930 ## Testing There is an example you can look at: ``` cargo run --example ui_transform ``` Sometimes in the example if you press the rotate button couple of times the first glyph from the top label disappears , I'm not sure what's causing it yet but I don't think it's related to this PR. ## Migration Guide New specialized 2D UI transform components `UiTransform` and `UiGlobalTransform`. `UiTransform` is a 2d-only equivalent of `Transform` with a translation in `Val`s. `UiGlobalTransform` newtypes `Affine2` and is updated in `ui_layout_system`. `Node` now requires `UiTransform` instead of `Transform`. `UiTransform` requires `UiGlobalTransform`. In previous versions of Bevy `ui_layout_system` would overwrite UI node's `Transform::translation` each frame. `UiTransform`s aren't overwritten and there is no longer any need for systems that cache and rewrite the transform for translated UI elements. `RelativeCursorPosition`'s coordinates are now object-centered with (0,0) at the the center of the node and the corners at (±0.5, ±0.5). Its `normalized_visible_node_rect` field has been removed and replaced with a new `cursor_over: bool` field which is set to true when the cursor is hovering an unclipped area of the UI node. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> |
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What is Bevy?
Bevy is a refreshingly simple data-driven game engine built in Rust. It is free and open-source forever!
WARNING
Bevy is still in the early stages of development. Important features are missing. Documentation is sparse. A new version of Bevy containing breaking changes to the API is released approximately once every 3 months. We provide migration guides, but we can't guarantee migrations will always be easy. Use only if you are willing to work in this environment.
MSRV: Bevy relies heavily on improvements in the Rust language and compiler. As a result, the Minimum Supported Rust Version (MSRV) is generally close to "the latest stable release" of Rust.
Design Goals
- Capable: Offer a complete 2D and 3D feature set
- Simple: Easy for newbies to pick up, but infinitely flexible for power users
- Data Focused: Data-oriented architecture using the Entity Component System paradigm
- Modular: Use only what you need. Replace what you don't like
- Fast: App logic should run quickly, and when possible, in parallel
- Productive: Changes should compile quickly ... waiting isn't fun
About
- Features: A quick overview of Bevy's features.
- News: A development blog that covers our progress, plans and shiny new features.
Docs
- Quick Start Guide: Bevy's official Quick Start Guide. The best place to start learning Bevy.
- Bevy Rust API Docs: Bevy's Rust API docs, which are automatically generated from the doc comments in this repo.
- Official Examples: Bevy's dedicated, runnable examples, which are great for digging into specific concepts.
- Community-Made Learning Resources: More tutorials, documentation, and examples made by the Bevy community.
Community
Before contributing or participating in discussions with the community, you should familiarize yourself with our Code of Conduct.
- Discord: Bevy's official discord server.
- Reddit: Bevy's official subreddit.
- GitHub Discussions: The best place for questions about Bevy, answered right here!
- Bevy Assets: A collection of awesome Bevy projects, tools, plugins and learning materials.
Contributing
If you'd like to help build Bevy, check out the Contributor's Guide. For simple problems, feel free to open an issue or PR and tackle it yourself!
For more complex architecture decisions and experimental mad science, please open an RFC (Request For Comments) so we can brainstorm together effectively!
Getting Started
We recommend checking out the Quick Start Guide for a brief introduction.
Follow the Setup guide to ensure your development environment is set up correctly. Once set up, you can quickly try out the examples by cloning this repo and running the following commands:
# Switch to the correct version (latest release, default is main development branch)
git checkout latest
# Runs the "breakout" example
cargo run --example breakout
To draw a window with standard functionality enabled, use:
use bevy::prelude::*;
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.run();
}
Fast Compiles
Bevy can be built just fine using default configuration on stable Rust. However for really fast iterative compiles, you should enable the "fast compiles" setup by following the instructions here.
Bevy Cargo Features
This list outlines the different cargo features supported by Bevy. These allow you to customize the Bevy feature set for your use-case.
Thanks
Bevy is the result of the hard work of many people. A huge thanks to all Bevy contributors, the many open source projects that have come before us, the Rust gamedev ecosystem, and the many libraries we build on.
A huge thanks to Bevy's generous sponsors. Bevy will always be free and open source, but it isn't free to make. Please consider sponsoring our work if you like what we're building.
This project is tested with BrowserStack.
License
Bevy is free, open source and permissively licensed! Except where noted (below and/or in individual files), all code in this repository is dual-licensed under either:
- MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
at your option. This means you can select the license you prefer! This dual-licensing approach is the de-facto standard in the Rust ecosystem and there are very good reasons to include both.
Some of the engine's code carries additional copyright notices and license terms due to their external origins.
These are generally BSD-like, but exact details vary by crate:
If the README of a crate contains a 'License' header (or similar), the additional copyright notices and license terms applicable to that crate will be listed.
The above licensing requirement still applies to contributions to those crates, and sections of those crates will carry those license terms.
The license field of each crate will also reflect this.
For example, bevy_mikktspace has code under the Zlib license (as well as a copyright notice when choosing the MIT license).
The assets included in this repository (for our examples) typically fall under different open licenses. These will not be included in your game (unless copied in by you), and they are not distributed in the published bevy crates. See CREDITS.md for the details of the licenses of those files.
Your contributions
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.