Update `ComputedNode` for scrollbar thumbs in `update_scrollbar_thumb` by ickshonpe · Pull Request #23612 · bevyengine/bevy

ickshonpe · 2026-03-31T22:19:58Z

Objective

Update ComputedNode for scrollbar thumbs in update_scrollbar_thumb to avoid delays and system ambiguities.

Solution

Removed Node from scrollbar thumb node entities.
Renamed CoreScrollbarThumb to ScrollbarThumb.
ScrollbarThumb now requires all the UI components and gains border and border_radius fields.
update_scrollbar_thumb now updates ScrollbarThumb node's UiGlobalTransform and ComputedNode in PostLayout.

Testing

cargo run --example scrollbars

We need a better scrollbars example, added an issue #23622.

…b` requires all the UI components and gains a `border_radius` field. `update_scrollbar_thumb` updates its `UiGlobalTransform` and `ComputedNode` in `PostLayout`.

micttyoid · 2026-04-01T22:01:06Z

Can we have this "after" PostLayout? #23346
This does not have ambiguity with text systems and ComputedNode

kfc35

Now that I understand the logic, this looks fine to me.
Also checked out the branch and the example looks fine.

I think it’s fine to merge with all those requirements from node merged in to ensure correctness, but I will say that I tested the example while removing BackgroundColor, BorderColor, and ScrollPosition, and the example looks fine, so that may be a sign that those are OK to remove.

I think you should probably answer @micttyoid since it still seems there may still be ambiguities by placing update_scrollbar_thumb in PostLayout. After that, this is probably OK to merge?

alice-i-cecile · 2026-04-02T05:03:02Z

Adding to the milestone because this is needed for me to be confident in a solution for #23346. I'll finish this up tomorrow if you're busy :)

viridia · 2026-04-02T05:46:18Z

Can we also rename CoreScrollbarThumb to ScrollbarThumb?

The Core prefix is a hold-over from an earlier design, it was dropped from all the other widgets, but this one got missed because it was developed on a different branch.

ickshonpe · 2026-04-02T08:13:04Z

Can we have this "after" PostLayout? #23346 This does not have ambiguity with text systems and ComputedNode

Just realised this shouldn't be in PostLayout, but after would be wrong too. Since this system does layout for thumb nodes, it should be in layout itself, just ordered after ui_layout_system I think. Same with the new popover system

ickshonpe · 2026-04-02T08:19:53Z

Adding to the milestone because this is needed for me to be confident in a solution for #23346. I'll finish this up tomorrow if you're busy :)

Nope I got it, doesn't need much

…ollThumb`. Added a `border: UiRect` field, which is used to set the thumb's `ComputedNode::border` in `update_scrollbar_thumb`.

ickshonpe · 2026-04-02T09:54:32Z

Can we also rename CoreScrollbarThumb to ScrollbarThumb?

The Core prefix is a hold-over from an earlier design, it was dropped from all the other widgets, but this one got missed because it was developed on a different branch.

Done

…t_system`.

kfc35 · 2026-04-02T14:49:12Z

+                thumb_node.border_radius = border_radius;
+            }
+
+            let resolve_border_val = |val: Val| {


Does this actually need to be two diff lambdas for thumb_physical_size.x and thumb_physical_size.y?

It's iffy, but generally with percentage values both axes are resolved based on the horizontal width.

Co-authored-by: Kevin Chen <chen.kevin.f@gmail.com>

micttyoid · 2026-04-02T20:25:01Z

According to what we did this time, for the future scheduler ordering, it's worth noting that system granularity (without system set) should be fine. We have rigorous ambiguity detection, so we don't suffer much if we need to update anything.

bevyengine#23612) # Objective Update `ComputedNode` for scrollbar thumbs in `update_scrollbar_thumb` to avoid delays and system ambiguities. ## Solution * Removed `Node` from scrollbar thumb node entities. * Renamed `CoreScrollbarThumb` to `ScrollbarThumb`. * `ScrollbarThumb` now requires all the UI components and gains `border` and `border_radius` fields. * `update_scrollbar_thumb` now updates `ScrollbarThumb` node's `UiGlobalTransform` and `ComputedNode` in `PostLayout`. ## Testing ``` cargo run --example scrollbars ``` We need a better scrollbars example, added an issue bevyengine#23622. --------- Co-authored-by: Kevin Chen <chen.kevin.f@gmail.com> Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

Removed Node from scrollbar thumb nodes, instead `CoreScrollbarThum…

c623595

…b` requires all the UI components and gains a `border_radius` field. `update_scrollbar_thumb` updates its `UiGlobalTransform` and `ComputedNode` in `PostLayout`.

alice-i-cecile approved these changes Mar 31, 2026

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alice-i-cecile requested a review from viridia March 31, 2026 22:22

github-project-automation Bot added this to UI Mar 31, 2026

github-project-automation Bot moved this to Needs SME Triage in UI Mar 31, 2026

alice-i-cecile requested a review from kfc35 March 31, 2026 22:23

fixed doc link

02858f3

alice-i-cecile mentioned this pull request Mar 31, 2026

UiWidgetsPlugins and InputDispatchPlugin are now in DefaultPlugins #23346

Merged

viridia reviewed Mar 31, 2026

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Comment thread crates/bevy_ui_widgets/src/scrollbar.rs

alice-i-cecile added S-Waiting-on-Author The author needs to make changes or address concerns before this can be merged and removed S-Needs-Review Needs reviewer attention (from anyone!) to move forward labels Apr 1, 2026

kfc35 reviewed Apr 1, 2026

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Comment thread crates/bevy_ui_widgets/src/scrollbar.rs

kfc35 approved these changes Apr 2, 2026

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Comment thread examples/ui/scroll_and_overflow/scrollbars.rs Outdated

alice-i-cecile added this to the 0.19 milestone Apr 2, 2026

ickshonpe added 2 commits April 2, 2026 09:24

Merge branch 'main' into thumb

bb56003

Removed ContentSize and ScrollPosition requirements from `CoreScr…

6a52804

…ollThumb`. Added a `border: UiRect` field, which is used to set the thumb's `ComputedNode::border` in `update_scrollbar_thumb`.

ickshonpe added 6 commits April 2, 2026 10:43

Updated scrollbars example to give the thumb a border.

99b2900

Made extract_uinode_borders Node query optional

06d9dee

adjust example

44433cd

Added migration guide

cc3a05c

Merge branch 'thumb' of https://github.com/ickshonpe/bevy into thumb

f0f4e92

Renamed CoreScrollbarThumb to ScrollbarThumb

f02dab7

Moved update_scrollbar_thumb to UiSystems::Layout after `ui_layou…

3eaea7c

…t_system`.

kfc35 reviewed Apr 2, 2026

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ickshonpe and others added 4 commits April 2, 2026 16:11

Update crates/bevy_ui_widgets/src/scrollbar.rs

e73ae92

Co-authored-by: Kevin Chen <chen.kevin.f@gmail.com>

Update crates/bevy_ui_widgets/src/scrollbar.rs

f8f09f9

Co-authored-by: Kevin Chen <chen.kevin.f@gmail.com>

Update crates/bevy_ui_widgets/src/scrollbar.rs

8229a6c

Co-authored-by: Kevin Chen <chen.kevin.f@gmail.com>

Update crates/bevy_ui_widgets/src/scrollbar.rs

38cef91

Co-authored-by: Kevin Chen <chen.kevin.f@gmail.com>

alice-i-cecile added S-Ready-For-Final-Review This PR has been approved by the community. It's ready for a maintainer to consider merging it and removed S-Waiting-on-Author The author needs to make changes or address concerns before this can be merged labels Apr 2, 2026

alice-i-cecile enabled auto-merge April 2, 2026 15:15

alice-i-cecile disabled auto-merge April 2, 2026 15:21

alice-i-cecile added 2 commits April 2, 2026 08:29

Newline at end of file

207b87f

Missed doc link rename

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alice-i-cecile enabled auto-merge April 2, 2026 15:30

alice-i-cecile added this pull request to the merge queue Apr 2, 2026

Merged via the queue into bevyengine:main with commit 33dbf93 Apr 2, 2026
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github-project-automation Bot moved this from Needs SME Triage to Done in UI Apr 2, 2026

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ickshonpe commented Mar 31, 2026 •

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