bevy/examples/ui
Viktor Gustavsson f86ee32576
Add UI GhostNode (#15341)
# Objective

- Fixes #14826 
- For context, see #15238

## Solution
Add a `GhostNode` component to `bevy_ui` and update all the relevant
systems to use it to traverse for UI children.

- [x] `ghost_hierarchy` module
  - [x] Add `GhostNode`
- [x] Add `UiRootNodes` system param for iterating (ghost-aware) UI root
nodes
- [x] Add `UiChildren` system param for iterating (ghost-aware) UI
children
- [x] Update `layout::ui_layout_system`
  - [x] Use ghost-aware root nodes for camera updates
  - [x] Update and remove children in taffy
    - [x] Initial spawn
    - [x] Detect changes on nested UI children
- [x] Use ghost-aware children traversal in
`update_uinode_geometry_recursive`
- [x] Update the rest of the UI systems to use the ghost hierarchy
  - [x] `stack::ui_stack_system`
  - [x] `update::`
    - [x] `update_clipping_system`
    - [x] `update_target_camera_system`
  - [x] `accessibility::calc_name`

## Testing
- [x] Added a new example `ghost_nodes` that can be used as a testbed.
- [x] Added unit tests for _some_ of the traversal utilities in
`ghost_hierarchy`
- [x] Ensure this fulfills the needs for currently known use cases
  - [x] Reactivity libraries (test with `bevy_reactor`)
- [ ] Text spans (mentioned by koe [on
discord](https://discord.com/channels/691052431525675048/1285371432460881991/1285377442998915246))
  
---
## Performance
[See comment
below](https://github.com/bevyengine/bevy/pull/15341#issuecomment-2385456820)

## Migration guide
Any code that previously relied on `Parent`/`Children` to iterate UI
children may now want to use `bevy_ui::UiChildren` to ensure ghost nodes
are skipped, and their first descendant Nodes included.

UI root nodes may now be children of ghost nodes, which means
`Without<Parent>` might not query all root nodes. Use
`bevy_ui::UiRootNodes` where needed to iterate root nodes instead.

## Potential future work
- Benchmarking/optimizations of hierarchies containing lots of ghost
nodes
- Further exploration of UI hierarchies and markers for root nodes/leaf
nodes to create better ergonomics for things like `UiLayer` (world-space
ui)

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: UkoeHB <37489173+UkoeHB@users.noreply.github.com>
2024-10-02 00:24:28 +00:00
..
borders.rs use precomputed border values (#15163) 2024-09-26 23:10:35 +00:00
button.rs Fixing text sizes for examples (#15190) 2024-09-16 23:14:37 +00:00
display_and_visibility.rs Simpler lint fixes: makes ci lints work but disables a lint for now (#15376) 2024-09-24 11:42:59 +00:00
flex_layout.rs Omit font size where it closely matches the default in examples (#13952) 2024-06-20 21:01:28 +00:00
font_atlas_debug.rs Fixing text sizes for examples (#15190) 2024-09-16 23:14:37 +00:00
ghost_nodes.rs Add UI GhostNode (#15341) 2024-10-02 00:24:28 +00:00
grid.rs Fixing text sizes for examples (#15190) 2024-09-16 23:14:37 +00:00
overflow.rs Updates default Text font size to 24px (#13603) 2024-05-31 16:41:27 +00:00
overflow_debug.rs Add core and alloc over std Lints (#15281) 2024-09-27 00:59:59 +00:00
relative_cursor_position.rs Fixing text sizes for examples (#15190) 2024-09-16 23:14:37 +00:00
render_ui_to_texture.rs Migrate meshes and materials to required components (#15524) 2024-10-01 21:33:17 +00:00
scroll.rs Simpler lint fixes: makes ci lints work but disables a lint for now (#15376) 2024-09-24 11:42:59 +00:00
size_constraints.rs Fixing text sizes for examples (#15190) 2024-09-16 23:14:37 +00:00
text.rs Fix floating point math (#15239) 2024-09-16 23:28:12 +00:00
text_debug.rs Rename push children to add children (#15196) 2024-09-16 23:16:04 +00:00
text_wrap_debug.rs Rename BreakLineOn to LineBreak (#15583) 2024-10-01 22:30:50 +00:00
transparency_ui.rs Fixing text sizes for examples (#15190) 2024-09-16 23:14:37 +00:00
ui.rs UI Scrolling (#15291) 2024-09-23 17:17:58 +00:00
ui_material.rs Simpler lint fixes: makes ci lints work but disables a lint for now (#15376) 2024-09-24 11:42:59 +00:00
ui_scaling.rs Fix floating point math (#15239) 2024-09-16 23:28:12 +00:00
ui_texture_atlas.rs Make default behavior for BackgroundColor and BorderColor more intuitive (#14017) 2024-06-25 21:50:41 +00:00
ui_texture_atlas_slice.rs Fixing text sizes for examples (#15190) 2024-09-16 23:14:37 +00:00
ui_texture_slice.rs Fixing text sizes for examples (#15190) 2024-09-16 23:14:37 +00:00
ui_texture_slice_flip_and_tile.rs fix imports in example ui_texture_slice_flip_and_tile (#15064) 2024-09-06 06:00:43 +00:00
viewport_debug.rs Fix green colors becoming darker in various examples (#12328) 2024-03-05 23:42:03 +00:00
window_fallthrough.rs Fixing text sizes for examples (#15190) 2024-09-16 23:14:37 +00:00
z_index.rs Simplified ui_stack_system (#9889) 2024-09-30 18:43:57 +00:00