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.
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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