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Tk_GetVisual(3)                             Tk Library Procedures                            Tk_GetVisual(3)



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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,  stat-icgray, staticgray,
                      icgray,  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  win-dow window
                      dow 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



Tk                                                   4.0                                     Tk_GetVisual(3)