[HOpenGL] GL_BLEND

[Glynn Clements]

Sven Panne wrote:

> Glynn Clements wrote:

> > Does this rely upon the underlying OpenGL implementation/driver
> > supporting glBlendEquation() (i.e. OpenGL 1.3 or 1.2+GL_ARB_imaging)?
> 
> Yes, blendEquation depends on the glBlendEquationEXT extension function.
> If the extension is not supported, an exception with the message
> 
>     unknown OpenGL call glBlendEquationEXT, check for GL_EXT_blend_minmax or GL_EXT_blend_subtract or OpenGL 1.4
> 
> should be thrown, not a segfault. This is a bit mysterious...

That's a bug in the HOpenGL API.

Whilst glBlendEquation() requires GL_ARB_imaging or 1.3, glBlendFunc()
and gl{Enable,Disable}(GL_BLEND) are in OpenGL 1.0. If you want to
"merge" gl{Enable,Disable}(GL_BLEND), it should be merged with
glBlendFunc(), not glBlendEquation().

-- 
Glynn Clements <glynn.clements at virgin.net>