DragonFly On-Line Manual Pages
Tk_GetVisual(3) Tk Library Procedures Tk_GetVisual(3)
Tk_GetVisual - translate from string to visual
Tk_GetVisual(interp, tkwin, string, depthPtr, colormapPtr)
Tcl_Interp *interp (in) Interpreter to use for error
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
int *depthPtr (out) Depth of returned visual gets
Colormap *colormapPtr (out) If non-NULL then a suitable
colormap for visual is found and
its identifier is stored here.
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 interpreter interp's 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
The string argument specifies the desired visual in one of the
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.
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
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.
The idea for Tk_GetVisual, and the first implementation, came from Paul
colormap, screen, visual
Tk 4.0 Tk_GetVisual(3)