368B of GC is allocated for each UI Document in the scene

Unity: UI Toolkit Framework

Won't Fix

6.2.X

The GC allocs are caused by an editor-only OnGUI() call on UIDocument. This call was used to capture the display size, and have been removed in Unity 6.3. However, we won't backport the change since the allocation only affects the editor (the OnGUI() call is stripped from players).

How to reproduce:

Create and open a new project
Create a new UXML file in the Project tab
Create a new UI Document GameObject in the Hierarchy
Attach the UXML file to the UI Document Component in the Inspector
Open the Analysis → Profiler
Enter Play Mode
Click anywhere on the CPU section in the Profiler
Observe the Profiler

Actual result: 368B are allocated every frame
Expected result: 0B are allocated every frame

Reproducible in: 2023.1.0a15, 6000.2.15f1, 6000.3.0a4
Not reproducible in: 2023.1.0a14, 6000.0.63f1, 6000.3.0f1, 6000.4.0a5, 6000.5.0a2
Fixed in: 6000.3.0a5

Reproduced on: Windows 11 Pro (25H2)
Not reproduced on: No other environment tested

Note: GC.Alloc is called twice for each UI Document:
1. ”GUILayoutUtility.Begin()” - 288B
2. ”GUILayoutGroup..ctor()” - 80B

368B of GC is allocated for each UI Document in the scene

Unity: UI Toolkit Framework

Won't Fix

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Have a workaround or additional info about this issue?

368B of GC is allocated for each UI Document in the scene

Unity: UI Toolkit Framework

Statuses

Won't Fix

Resolution Notes

6.2.XWon't FixThe GC allocs are caused by an editor-only OnGUI() call on UIDocument. This call was used to capture the display size, and have been removed in Unity 6.3. However, we won't backport the change since the allocation only affects the editor (the OnGUI() call is stripped from players).

Description

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