[Lazarus] RE : RE : New widgetset

[Ludo Brands]

> glCreateShader is initialized by Load_GL_version_2_0 (also, 
> higher Load_GL_version_x_x call Load_GL_version_2_0).
> 
> Ludo: Are you sure you have OpenGL 2.1? Some OpenGL 
> implementations unfortunately lie, claiming in 
> glGetString(GL_VERSION) that they support higher version than 
> in reality. You can try adding
> Writeln(Load_GL_version_2_0) into any OpenGL example program, 
> and you will probably see that it answers false. For example, 
> you can add
> Writeln(Load_GL_version_2_0) inside the FPC demo 
> packages/opengl/examples/glutdemo.pp, near the other writelns.
> 

Apparently it is an incomplete 2.1: glBlendEquationSeparate isn't defined
and Load_GL_version_2_0 exits immediately. I checked all others up to
glCreateShader and they are present (nm -D /usr/lib/mesa/libGL.so.1.2).  

I made a local copy of glext.pp and commented the lines that load and check
the address of glBlendEquationSeparate and the example runs now. There is a
message "fragment shader compile failed" though.

The all or nothing approach in Load_GL_version_X_Y (all functions are
present or fail) is simple but has its disadvantages when working with third
party libraries. Fe Synapse uses a more elaborate method of loading
functions at runtime. It defines for every function a wrapper that checks if
the function pointer is assigned and then calls it or raises a meaningfull
exception.   

Ludo