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# Objective Allow UI elements to be positioned relative to the viewport rather than their parent element. Fixes #9564 ## Solution - New UI marker component `FixedNode`. Requires `Node` and `OverrideClip`. - `FixedNode` entities are treated as UI roots in layout, even if they have a parent. - `FixedNode`s don't inherit their parent's layout, clipping or transform context. - During the taffy layout updates children with `FixedNode` are skipped. - Added a couple of basic helper functions to `UiSurface`, mainly there to make the tests a little less painful. - Added a fairly comprehensive range of new tests, including tests with `GhostNode`s. - In the Taffy layout (stored in `UiSurface`) there is nothing to distinguish `FixedNode`s and root nodes, so they are treated identically during updates. -- The original suggestion was to implement it as a `PositionType::Fixed` variant that could used with `Node`, but I think that would be much more complicated without support from Taffy. Being able to just directly query for and filter out `FixedNode` entities directly makes the implementation much simpler and more efficient. ## Testing Basic example which shows events bubbling up to the parent from the fixed node: ``` cargo run --example fixed_node ``` There are also a number of new tests in the `layout` module. ``` cargo test -p bevy_ui --lib --features ghost_nodes ``` --------- Co-authored-by: François Mockers <francois.mockers@vleue.com>
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497 B
title, authors, pull_requests
| title | authors | pull_requests | ||
|---|---|---|---|---|
| FixedNode |
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FixedNode is a new marker component for Bevy UI.
A UI node entity with the FixedNode component is positioned relative to the target camera's viewport rather than its parent element. FixedNodes don't inherit their parent's layout, clipping or transform context.
In the Taffy layout (stored in UiSurface) there is nothing to distinguish FixedNodes and root nodes, so they are treated identically during updates.