opengl : Running at least 25 windows with different Draw callback

Question

I need to run at least 25 windows concurrently with each window rendering a different game state. I am storing all the 25 game states in the array of type GameState allGameStates[25].

For each of the window, i am currently doing this to register a different draw callback for each of the 25 windows.

 glutCreateWindow(title);
 glutDisplayFunc(allGameStates[i].Draw);

The issue here is that glutDisplayFunc requires a parameter of type function ptr, and i cannot pass in a member function ptr.(i am using GLUT which is in C)

It is not feasible to make the Draw function static as i require the Draw function to render differently accordingly to the other variables in the game state object.

How do i overcome this problem?

Answer 1

According to the documentation for glutDisplayFunc():

Before the callback, the current window is set to the window needing to be redisplayed

This means that inside the display callback, you can call glutGetWindow() to find out which window is being drawn to.

This means that you can use a static member function as the display callback; just have that static member function figure out which window is being drawn to, and map from that window to its particular game state object instance, and then call a non-static member function on that instance.