NAME

       Tk_GetVisual - translate from string to visual

SYNOPSIS

       #include <tk.h>

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

ARGUMENTS

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

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

       const 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

       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.

       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.

       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 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

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

KEYWORDS

       colormap, screen, visual