Re: Converting a nim string to a ptr GlChar

[Krux02]

`ptr GlChar` should be compatible with `cstring`. Therefore I would suggest 
that this should work:
    
    
    let vertexShaderSrc = """
    #version 400
    
    in vec3 pos;
    
    void main() {
      gl_Position = vec4(pos, 1.0);
    }
    """
    
    GLuint vertShader = glCreateShader(GL_VERTEX_SHADER)
    var charPtr : ptr GlChar = (ptr GlChar)(cstring(vertexShaderSrc))
    glShaderSource(vertShader, 1, charPtr.addr, nil)
    

if it still doesn't work, use force: `var charPtr : ptr GlChar = cast[ptr 
GlChar](cstring(vertexShaderSrc))`