Tk_GetGC(3tk)						       Tk Library Procedures						     Tk_GetGC(3tk)

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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 GCForeground or GCStipple) indicating which fields of *valuePtr are valid.

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

       Display *display (in)		     Display for which gc was allocated.

       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
       describing  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 created.  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(3tk)