OpenGL Programming Guide

Chapter 4Display Lists

Managing Display Lists and Their Indices

So far, we've used an arbitrary positive integer as a display-list index. This could be dangerous in practice because you might accidentally choose an index that's already in use, thereby overwriting an existing display list. To avoid accidental deletions, use glGenLists() to generate an unused index and glIsList() to determine whether a specific index is in use. You can explicitly delete a specific display list or a range of lists with glDeleteLists(). GLuint glGenLists(GLsizei range);

Allocates range number of contiguous, previously unallocated display-list indices. The integer returned is the index that marks the beginning of a contiguous block of empty display-list indices. The returned indices are all marked as empty and used, so subsequent calls to glGenLists() don't return these indices until they're deleted. Zero is returned if the requested number of indices isn't available, or if range is zero.

GLboolean glIsList(GLuint list);

Returns TRUE if list is already used for a display list and FALSE otherwise.

In the following example, a single index is requested, and if it proves to be available, it's used to create a new display list:

listIndex=glGenLists(1);
if(listIndex!=0) {
   glNewList(listIndex,GL_COMPILE);
      ...
   glEndList();
}

The command glDeleteLists() deletes a contiguous group of display lists, thereby making their indices available again. void glDeleteLists(GLuint list, GLsizei range);

Deletes range display lists, starting at the index specified by list. An attempt to delete a list that has never been created is ignored.

OpenGL Programming Guide