getvisual(3Tk)

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.

     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.

     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