support uniform textures and other compose methods#125
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…ional compose methods
4 tasks
- Add doc comments to Canvas.SetUniformTexture and GLShader.SetUniformTexture describing the sampler binding semantics and the unit index constraint. - Drop unnecessary else after early return in GLShader.SetUniformTexture. - Remove dead commented-out clamp-to-[0,1] snippet from ComposeMultiply. - Revert .gitignore to upstream state (.idea/ belongs in a global ignore). - Add tests/compose_test.go with table-driven cases for ComposeMultiply and ComposeScreen covering opaque, black, white, and transparent inputs.
dusk125
requested changes
Apr 22, 2026
| } | ||
| ct.shader.s.SetUniformAttr(loc, u.Value()) | ||
| } | ||
| gl.ActiveTexture(gl.TEXTURE0) |
Contributor
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Maybe cache the active texture before this loop and restore it here (I'm assuming that that's the intention behind this call)
| } | ||
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| c.shader = NewGLShader(baseCanvasFragmentShader) | ||
| c.shader = NewGLShader(BaseCanvasFragmentShader) |
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Why the change to exporting the base shader?
| case pixel.ComposeMultiply: | ||
| glhf.BlendFunc(glhf.BlendFactor(gl.DST_COLOR), glhf.Zero) | ||
| case pixel.ComposeScreen: | ||
| gl.BlendEquation(gl.FUNC_ADD) |
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Could these be added back down to glhf?
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Changes
Two independent additions to the opengl backend.
Sampler uniforms (
SetUniformTexture)Canvas.SetUniformTexture(name, tex, unit)binds a*glhf.Textureto a namedsampler2Din the canvas's fragment shader. The texture is activated on the given unit and bound each frame during draw.In the shader:
The two default shader constants are now exported (
BaseCanvasVertexShader,BaseCanvasFragmentShader) so custom shaders can extend the defaults without duplicating the source.Compose methods
Two new Porter-Duff composition modes for
canvas.SetComposeMethod:pixel.ComposeMultiply— multiplies source and destination channels. Useful for lighting masks: https://www.slembcke.net/blog/2DLightingTechniques#screen-space-lightmapspixel.ComposeScreen— inverse of multiply; lightens by1-(1-src)*(1-dst).Both modes have software implementations in
Compose()and hardware blend function registrations in the opengl backend. The hardware path uses rawgo-gl/glcalls forBlendEquationandBlendFuncSeparatesince glhf v2.0.0 does not yet expose those wrappers (the companion glhf PR #8 adds them — once that lands these can be simplified).Test plan
go build ./...unchanged.go test ./...— newtests/compose_test.gocoversComposeMultiplyandComposeScreenwith opaque, transparent, black, and white inputs.