function as a parameter for another function

Question

I am implementing a class named FilesWorkFlow:

//this function is called by other functions of the class to set openGL data type
//based on GDAL data type
void FilesWorkFlow::setOpenGLDataType(void)
{
    switch (eType)
    {
    case GDT_Byte:
        type = GL_UNSIGNED_BYTE;
        break;
    case GDT_UInt16:
        type = GL_UNSIGNED_SHORT;
        break;
    case GDT_Int16:
        type = GL_SHORT;
        break;
    case GDT_UInt32:
        type = GL_UNSIGNED_INT;
        break;
    case GDT_Int32:
        type = GL_INT;
    }
}


//this function is called by other functions of the class to draw scene
void FilesWorkFlow::RenderScene(void)
{
    GLint iWidth = (GLint)RasterXSize;
    GLint iHeight = (GLint)RasterYSize;
    setOpenGLDataType();
    glClear(GL_COLOR_BUFFER_BIT);
    glRasterPos2i(0,0);
    glDrawPixels(iWidth,iHeight,format,type,pImage);
    glFlush();
}


//this function is called by other functions of the class to setup the 
//rendering state
void FilesWorkFlow::SetupRC(void)
{
    glClearColor(0.0f,0.0f,0.0f,1.0f);
}

void FilesWorkFlow::Show(void)
{
    int argc = 1;
    char **argv;
    argv[0] = "OPENGL";
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_SINGLE);
    glutCreateWindow("Image");
    glutDisplayFunc(RenderScene);
    SetupRC();
    glutMainLoop();
}  

This is part of the class that will be used in a MFC application to render a create a window a render a tiff image on it but at the line glutDisplayFunc(RenderScene) I get the error

argument of type "void (FilesWorkFlow::*)()" is incompatible with parameter of type "void (__cdecl *)()"  

even writing the code as glutDisplayFunc((_cdecl)RenderScene) didn't help. How can I fix this problem and implement this task in a class that will be used in MFC applications?

Answer 1

First to get that misconception out of the way: GLUT is not part of OpenGL and you don't have to use it!

You can't mix GLUT and MFC. Both GLUT and MFC do about the same things:

• Provide a Framework to create Windows and deal with user input
• Manage the application's main event loop

You can't have two different things in the same program try to do the very same thing.

---

Anyway that error you're getting tells you the following:

• glutDisplayFunc expects a plain function pointer as callback
• The thing you pass to glutDisplayFunc is not a function pointer, but a class member pointer, which by itself lacks information about which instance of the class it refers to. The instance must be passed as an additional parameter or be packed up with the member pointer – yet glutDisplayFunc will never be able to work with that.

Or in other words: What you try to do is impossible (without building some wrappers or use some dirty hacks).