Tk_GetVisual
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.
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 col-
ormap 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 suit-
able 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 follow-
ing ways:
class depth The string consists of a class name followed by an inte-
ger 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, static-
grey, 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. path-
Name 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 lit-
tle 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 true-
color 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)
