Proof of concept for shader support on UIFrame:
- Add shader and shader_enabled members to UIFrame
- Add initializeTestShader() with hardcoded wave/glow fragment shader
- Add shader_enabled Python property for toggling
- Apply shader when drawing RenderTexture sprite
- Auto-update time uniform for animated effects
Also fixes position corruption when toggling RenderTexture usage:
- Standard rendering path now uses `position` as source of truth
- Prevents box position from staying at (0,0) after texture render
Test files:
- tests/shader_poc_test.py: Visual test of 6 render variants
- tests/shader_toggle_test.py: Regression test for position bug
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
