Tk_GetVisual(3Tk)Tk_GetVisual(3Tk)NAMETk_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.
DESCRIPTIONTk_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.
Page 1
Tk_GetVisual(3Tk)Tk_GetVisual(3Tk)
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
Page 2
