Tk_GetVisual(3)

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

Tk                      Last change: 4.0                        1

Tk_GetVisual(3)       Tk Library Procedures       Tk_GetVisual(3)

                    space (including  none)  in  between.   class
                    selects  what  sort  of visual is desired and
                    must be one of directcolor, grayscale, greys-
                    cale,  pseudocolor,  staticcolor, staticgray,
                    staticgrey, or truecolor, or a unique  abbre-
                    viation.   depth  specifies how many bits per
                    pixel are needed for the visual.   If  possi-
                    ble,  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  path-
                    Name.   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 sta-
                         ticcolor,  which  is  better  than  sta-
                         ticgray 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                      Last change: 4.0                        2