Tk_GetVisual(3Tk)					     Tk_GetVisual(3Tk)

NAME    [Toc]    [Back]

     Tk_GetVisual - translate from string to visual

SYNOPSIS    [Toc]    [Back]

     #include <tk.h>

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

ARGUMENTS    [Toc]    [Back]

     Tcl_Interp	  *interp	 (in)	   Interpreter to use for error
					   reporting.

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

     char	  *string	 (in)	   String that identifies the desired
					   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
					   colormap for	visual is found	and
					   its identifier is stored here.

DESCRIPTION    [Toc]    [Back]

     Tk_GetVisual takes	a string description of	a visual and finds a suitable
     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 interp->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 following
     ways:

     class depth    The	string consists	of a class name	followed by an integer
		    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, staticgrey, 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.



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Tk_GetVisual(3Tk)					     Tk_GetVisual(3Tk)



     default	    Use	the default visual for tkwin's screen.

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

     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 requested (but	as great a depth as possible); (b) if
		    no depth is	specified, then	the deepest available visual
		    is chosen; (c) pseudocolor is better than truecolor	or
		    directcolor, 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.

CREDITS    [Toc]    [Back]

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

KEYWORDS    [Toc]    [Back]

     colormap, screen, visual


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