Binding programs without drawing anything can result in inconsistent uniform state

[truecolour]

1. Bind a program with a geometry shader.
2. Set the first uniform in the geometry shader to value A.
3. Without rendering anything, bind a different program without a geometry shader.
4. Set the first uniform in the vertex shader to value B.
5. Render something. The results will use value A.

Adding a C3D_UpdateUniforms(GPU_GEOMETRY_SHADER) between steps 2 and 3 fixes the problem.

If I understand the internals correctly, the problem is that the C3D_{FV,IV,Bool}UnifDirty flags don't get cleared when binding a new program.

[fincs]

Without rendering anything

That is the problem. Why are you binding a program, then afterwards binding another one without having rendered anything in the first place? Can't you avoid binding the first program since it's not used for rendering?

[truecolour]

Context: I'm adding particle effects to a game I'm working on. The rendering code configures the shading, etc., binds the program, then loops through all particle sources, sets up buffers and calls DrawArrays. Regular objects get drawn afterwards. If there aren't any particle sources, the graphics get glitchy.

So yes, I can easily avoid binding the program at all. But this is really confusing behaviour. If this is intentional, IMO it should be documented somewhere.