Tk_GetGC

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.

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 context 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