Merge pull request #50 from brisklib/beta

Fix initialization for AppleClang

Fix matrix tests

Add text subpixel alignment test and corresponding image

Use box blur for image antialiasing

Add tests for matrix-transformed drawing

Fix Knob border radius

Build debug-enabled showcase binaries

Porter-duff compositing

Blending in shader

Skip blur tests on Windows due to WARP bug

2-pass gaussian blur

Layers are always supported

Fix drawImage tests

Compute gradient interpolation in shader