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Tk_GetGC(3)		     Tk	Library	Procedures		   Tk_GetGC(3)

______________________________________________________________________________

NAME
       Tk_GetGC, Tk_FreeGC - maintain database of read-only graphics contexts

SYNOPSIS
       #include	<tk.h>

       GC
       Tk_GetGC(tkwin, valueMask, valuePtr)

       Tk_FreeGC(display, gc)

ARGUMENTS
       Tk_Window tkwin (in)		     Token  for	 window	 in  which the
					     graphics context will be used.

       unsigned	long valueMask (in)	     Mask of  bits  (such  as  GCFore-
					     ground  or	 GCStipple) indicating
					     which  fields  of	*valuePtr  are
					     valid.

       XGCValues *valuePtr (in)		     Pointer  to  structure describing
					     the desired values	for the	graph-
					     ics context.

       Display *display	(in)		     Display  for  which  gc was allo-
					     cated.

       GC gc (in)			     X identifier for graphics context
					     that  is  no longer needed.  Must
					     have been allocated by Tk_GetGC.
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DESCRIPTION
       Tk_GetGC	and Tk_FreeGC manage a collection of graphics  contexts	 being
       used  by	 an application.  The procedures allow graphics	contexts to be
       shared, thereby avoiding	the server overhead that would be incurred  if
       a  separate GC were created for each use.  Tk_GetGC takes arguments de-
       scribing	the desired graphics context and returns an X identifier for a
       GC  that	 fits  the description.	 The graphics context that is returned
       will have default values	in all of the fields not specified  explicitly
       by valueMask and	valuePtr.

       Tk_GetGC	 maintains a database of all the graphics contexts it has cre-
       ated.  Whenever possible, a call	to Tk_GetGC will  return  an  existing
       graphics	 context  rather  than	creating a new one.  This approach can
       substantially reduce server overhead, so	Tk_GetGC should	 generally  be
       used in preference to the Xlib procedure	XCreateGC, which creates a new
       graphics	context	on each	call.

       Since the return	values of Tk_GetGC are shared,	callers	 should	 never
       modify  the graphics contexts returned by Tk_GetGC.  If a graphics con-
       text must be modified dynamically, then it should be created by calling
       XCreateGC instead of Tk_GetGC.

       When a graphics context is no longer needed, Tk_FreeGC should be	called
       to release it.  There should be exactly one call	to Tk_FreeGC for  each
       call to Tk_GetGC.  When a graphics context is no	longer in use anywhere
       (i.e. it	has been freed as many times as	it has been gotten)  Tk_FreeGC
       will release it to the X	server and delete it from the database.

KEYWORDS
       graphics	context

Tk								   Tk_GetGC(3)

NAME | SYNOPSIS | ARGUMENTS | DESCRIPTION | KEYWORDS

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