Tk_GetVisual(3) Tk Library Procedures Tk_GetVisual(3)_________________________________________________________________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 identi-
fies 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 suit-
able 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 fol-
lowed by an integer depth, with any amount
of white space (including none) in between.
Tk 4.0 1
Tk_GetVisual(3) Tk Library Procedures Tk_GetVisual(3)
class selects what sort of visual is
desired and must be one of directcolor,
grayscale, greyscale, pseudocolor, static-
color, staticgray, staticgrey, or true-
color, 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 num-
ber.
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 avail-
able visual is chosen; (c) pseudocolor is
better than truecolor or directcolor, which
are better than staticcolor, which is bet-
ter 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 2
