I want to draw a Rectangle with color Gradient in GtkGLArea. I know it can be done with Cairo on GtkDrawingArea. But I want to draw it with OpenGL. Can anyone tell me how this can be done?

I want to draw a Rectangle with 4 corner color Gradient in GtkGLArea. I know it can be done with Cairo on GtkDrawingArea. But I want to draw it with OpenGL. Can anyone tell me how this can be done?

I want to draw a Rectangle with 4 corner color Gradient in GtkGLArea. I know it can be done with Cairo on GtkDrawingArea. But I want to draw it with OpenGL. Can anyone tell me how this can be done?