DOKK / manpages / debian 12 / tk8.6-doc / Tk_GetVisual.3tk.en
Tk_GetVisual(3tk) Tk Library Procedures Tk_GetVisual(3tk) 







Tk_GetVisual - translate from string to visual








#include <tk.h>

Visual *
Tk_GetVisual(interp, tkwin, string, depthPtr, colormapPtr)









  
Tcl_Interp *interp (in)

  
Interpreter to use for error reporting.

  
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 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.
    
    

    

  










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 *colormapPtr.


The string argument specifies the desired visual in one of
    the following ways:



  

  
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.

  

  
Use the default visual for tkwin's screen.

  

  
Use the visual for the window given by pathName. pathName
      must be the name of a window on the same screen as tkwin.

  

  
Use the visual whose X identifier is number.

  

  
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 Mackerras.








colormap, screen, visual







  

    4.0
    Tk