Reproduction steps:
1. Open the attached “AnimationBug.zip” project
2. Open the “SampleScene”
3. Enter the Play mode
4. Hover the mouse over the white rectangle
5. Observe the animation
Expected result: The rectangle transitions to pink with an transition animation
Actual result: The rectangle instantly turns pink
Reproducible with: 2022.3.57f1, 6000.0.36f1, 6000.1.0b4, 6000.2.0a2
Reproducible on: macOS 15.2 (Intel) (User reported), Windows 11
Not reproducible on: No other environment tested
Workaround: Open the test.uxml in UI Builder and select the .test selector. Expand the Background property and edit the Size Width property to any value other than 0. Save the file, and then edit the property back to 0 and save again. The animation transition is then visible when in Play mode even when the value is 0.
Notes:
- The issue reappears every time the Editor is reopened
- Also reproduces in Windows and WebGL builds