# Objective
`ui_stack_system` generates a tree of `StackingContexts` which it then
flattens to get the `UiStack`.
But there's no need to construct a new tree. We can query for nodes with
a global `ZIndex`, add those nodes to the root nodes list and then build
the `UiStack` from a walk of the existing layout tree, ignoring any
branches that have a global `Zindex`.
Fixes#9877
## Solution
Split the `ZIndex` enum into two separate components, `ZIndex` and
`GlobalZIndex`
Query for nodes with a `GlobalZIndex`, add those nodes to the root nodes
list and then build the `UiStack` from a walk of the existing layout
tree, filtering branches by `Without<GlobalZIndex>` so we don't revisit
nodes.
```
cargo run --profile stress-test --features trace_tracy --example many_buttons
```
<img width="672" alt="ui-stack-system-walk-split-enum"
src="https://github.com/bevyengine/bevy/assets/27962798/11e357a5-477f-4804-8ada-c4527c009421">
(Yellow is this PR, red is main)
---
## Changelog
`Zindex`
* The `ZIndex` enum has been split into two separate components `ZIndex`
(which replaces `ZIndex::Local`) and `GlobalZIndex` (which replaces
`ZIndex::Global`). An entity can have both a `ZIndex` and
`GlobalZIndex`, in comparisons `ZIndex` breaks ties if two
`GlobalZIndex` values are equal.
`ui_stack_system`
* Instead of generating a tree of `StackingContexts`, query for nodes
with a `GlobalZIndex`, add those nodes to the root nodes list and then
build the `UiStack` from a walk of the existing layout tree, filtering
branches by `Without<GlobalZIndex` so we don't revisit nodes.
## Migration Guide
The `ZIndex` enum has been split into two separate components `ZIndex`
(which replaces `ZIndex::Local`) and `GlobalZIndex` (which replaces
`ZIndex::Global`). An entity can have both a `ZIndex` and
`GlobalZIndex`, in comparisons `ZIndex` breaks ties if two
`GlobalZindex` values are equal.
---------
Co-authored-by: Gabriel Bourgeois <gabriel.bourgeoisv4si@gmail.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: UkoeHB <37489173+UkoeHB@users.noreply.github.com>
# Objective
Fixes#15223
## Solution
Adds an `enabled` flag to the `FpsOverlayConfig` resource with a system
that detects it's change, and adjusts the visibility of the overlay text
entity.
## Testing
I extended the `fps_overlay` example with the option to toggle the
overlay. Run with:
```
cargo run --features="bevy_dev_tools" --example fps_overlay
```
# Objective
The `BuildChildren` and `BuildWorldChildren` traits are mostly
identical, so I decided to try and merge them. I'm not sure of the
history, maybe they were added before GATs existed.
## Solution
- Add an associated type to `BuildChildren` which reflects the prior
differences between the `BuildChildren` and `BuildWorldChildren` traits.
- Add `ChildBuild` trait that is the bounds for
`BuildChildren::Builder`, with impls for `ChildBuilder` and
`WorldChildBuilder`.
- Remove `BuildWorldChildren` trait and replace it with an impl of
`BuildChildren` for `EntityWorldMut`.
## Testing
I ran several of the examples that use entity hierarchies, mainly UI.
---
## Changelog
n/a
## Migration Guide
n/a
# Objective
- Currently the fps_overlay affects any other ui node spawned. This
should not happen
## Solution
- Use position absolute and a ZIndex of `i32::MAX - 32`
- I also modified the example a little bit to center it correctly. It
only worked previously because the overlay was pushing it down. I also
took the opportunity to simplify the text spawning code a little bit.
# Objective
- Part of #12351
- Add fps overlay
## Solution
- Create `FpsOverlayPlugin`
- Allow for configuration through resource `FpsOverlayConfig`
- Allow for configuration during runtime
### Preview on default settings
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
