Tk_GetVisual(3) Tk (4.0) 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.
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
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Tk_GetVisual(3) Tk (4.0) Tk_GetVisual(3)
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
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