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Tk_GetVisual(3)		     Tk	Library	Procedures	       Tk_GetVisual(3)


       Tk_GetVisual - translate	from string to visual

       #include	<tk.h>

       Visual *
       Tk_GetVisual(interp, tkwin, string, depthPtr, colormapPtr)

       Tcl_Interp *interp (in)		     Interpreter  to use for error re-

       Tk_Window tkwin (in)		     Token for	window	in  which  the
					     visual will be used.

       const char *string (in)		     String  that  identifies  the de-
					     sired  visual.   See  below   for
					     valid formats.

       int *depthPtr (out)		     Depth  of	returned  visual  gets
					     stored here.

       Colormap	*colormapPtr (out)	     If	non-NULL then a	suitable  col-
					     ormap for visual is found and its
					     identifier	is stored here.

       Tk_GetVisual takes a string description of a visual and finds  a	 suit-
       able  X Visual for use in tkwin,	if there is one.  It returns a pointer
       to the X	Visual structure for the visual	and stores the number of  bits
       per  pixel  for	it at *depthPtr.  If string is unrecognizable or if no
       suitable	visual could be	found, then NULL is returned and  Tk_GetVisual
       leaves an error message in interpreter interp's result.	If colormap is
       non-NULL	then Tk_GetVisual also locates an appropriate colormap for use
       with the	result visual and stores its X identifier at *colormapPtr.

       The  string argument specifies the desired visual in one	of the follow-
       ing ways:

       class depth    The string consists of a class name followed by an inte-
		      ger  depth,  with	 any  amount of	white space (including
		      none) in between.	 class selects what sort of visual  is
		      desired  and  must  be  one  of  directcolor, grayscale,
		      greyscale, pseudocolor, staticcolor, staticgray, static-
		      grey,  or	 truecolor,  or	 a unique abbreviation.	 depth
		      specifies	how many bits per pixel	 are  needed  for  the
		      visual.	If possible, Tk_GetVisual will return a	visual
		      with this	depth; if there	is no visual  of  the  desired
		      depth  then  Tk_GetVisual	 looks first for a visual with
		      greater depth, then one with less	depth.

       default	      Use the default visual for tkwin's screen.

       pathName	      Use the visual for the window given by pathName.	 path-
		      Name  must be the	name of	a window on the	same screen as

       number	      Use the visual whose X identifier	is number.

       best ?depth?   Choose the "best possible" visual, using	the  following
		      rules, in	decreasing order of priority:

		      (a)    a	visual	that  has exactly the desired depth is
			     best, followed by a  visual  with	greater	 depth
			     than requested (but as little extra as possible),
			     followed by a visual with	less  depth  than  re-
			     quested (but as great a depth as possible);

		      (b)    if	no depth is specified, then the	deepest	avail-
			     able visual is chosen;

		      (c)    pseudocolor is better than	truecolor  or  direct-
			     color,  which  are	better than staticcolor, which
			     is	better than staticgray or grayscale;

		      (d)    the default visual	for the	screen is better  than
			     any other visual.

       The idea	for Tk_GetVisual, and the first	implementation,	came from Paul

       colormap, screen, visual

Tk				      4.0		       Tk_GetVisual(3)


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