[UUM-133526] Material Editor - fix warning from GUILayout

[thomas-tu]

Purpose of this PR

Fix a warning thrown by the GUILayout system due to missing End gui layout calls. We exit the scope of a function early, so we need to make the End calls.

Links

Jira: UUM-133526

[u-pr]

I have reviewed the changes and found one area for improvement regarding the handling of IMGUI layout states when returning early. Overall, the code quality is high.

_{🤖 Helpful? 👍/👎}

[codecov-github-com]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
Editor/EditorCore/MaterialEditor.cs	0.00%	1 Missing ⚠️

@@           Coverage Diff           @@
##           master     #659   +/-   ##
=======================================
  Coverage   36.05%   36.06%           
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  Files         277      277           
  Lines       34909    34911    +2     
=======================================
+ Hits        12588    12589    +1     
- Misses      22321    22322    +1     

Flag	Coverage Δ
probuilder_MacOS_6000.0	34.58% <0.00%> (-0.01%)	⬇️
probuilder_MacOS_6000.3	34.58% <0.00%> (-0.01%)	⬇️
probuilder_MacOS_6000.4	34.57% <0.00%> (-0.01%)	⬇️
probuilder_MacOS_6000.5	34.57% <0.00%> (-0.01%)	⬇️
probuilder_MacOS_6000.6	34.57% <0.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
Editor/EditorCore/MaterialEditor.cs	0.00% <0.00%> (ø)

... and 1 file with indirect coverage changes

[varinotmUnity]

nice

[unity-kristinn]

/test_plan

[u-pr]

Test Plan

• Test plan approved by PR author
• Test execution in progress
• Test execution complete
• Ready for merge

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Summary of Changes & Risk Assessment

Summary of Changes

This PR addresses a GUILayout state corruption warning (GUI Error: Invalid GUILayout state in MaterialEditor view.) in the ProBuilder Material Editor. The fix involves adding GUIUtility.ExitGUI() before an early return in Editor/EditorCore/MaterialEditor.cs, ensuring the IMGUI system correctly terminates the current layout pass after the material list is modified.

Risk Assessment

• High Risk Areas: None identified.
• Medium Risk Areas: None identified.
• Low Risk Areas: Material Editor UI, specifically the material slot management.

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Test Scenarios

Functional Testing

• Verify Fix: Open the ProBuilder Material Editor (Tools > ProBuilder > Editors > Material Editor). Add several material slots, then click the red 'X' button to delete a slot. Verify that no "Invalid GUILayout state" warnings appear in the Console.
• State Consistency: Verify that after deleting a material slot, the list updates correctly in the UI and the remaining materials are preserved.

Regression Testing

• Data Persistence: Ensure that clicking the delete button correctly triggers SaveUserMaterials and that the changes persist after closing and reopening the Material Editor or restarting Unity.
• Button Functionality: Verify that other buttons within the same horizontal group (the material slot selector itself) still function correctly before and after a deletion.

Edge Cases

• Empty List: Verify behavior when deleting the last remaining material slot (if allowed by the UI).
• Rapid Input: Rapidly click the delete button to ensure multiple ExitGUI() calls or rapid list modifications do not cause an editor crash or unexpected UI behavior.

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_{💡 This test plan updates automatically when /test_plan is run on new commits. If you have any feedback, please reach out in #ai-qa}

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