| ActiveTcl User Guide |

## Tcl/Tk Documentation > TkLib > FreeXId

### Tcl/Tk Applications | Tcl Commands | Tk Commands | Tcl Library | Tk Library

### NAME

Tk_FreeXId - make X resource identifier available for reuse

### SYNOPSIS

#include <tk.h>
Tk_FreeXId(display, id)

### ARGUMENTS

Display *display (in)
  Display for which id was allocated.
XID id (in)
  Identifier of X resource (window, font, pixmap, cursor, graphics context, or colormap) that is no longer in use.

### DESCRIPTION

The default allocator for resource identifiers provided by Xlib is very simple-minded and does not allow resource identifiers to be re-used. If a long-running application reaches the end of the resource id space, it will generate an X protocol error and crash. Tk replaces the default id allocator with its own allocator, which allows identifiers to be reused. In order for this to work, Tk_FreeXId must be called to tell the allocator about resources that have been freed. Tk automatically calls Tk_FreeXId whenever it frees a resource, so if you use procedures like Tk_GetFont, Tk_GetGC, and Tk_GetPixmap then you need not call Tk_FreeXId. However, if you allocate resources directly from Xlib, for example by calling XCreatePixmap, then you should call Tk_FreeXId when you call the corresponding Xlib free procedure, such as XFreePixmap. If you do not call Tk_FreeXId then the resource identifier will be lost, which could cause problems if the application runs long enough to lose all of the available identifiers.

### KEYWORDS

resource identifier
Copyright © 1995-1997 Roger E. Critchlow Jr. Copyright © 1990 The Regents of the University of California. Copyright © 1994-1996 Sun Microsystems, Inc.