Tk\_GetVisual(3) Tk Library Procedures Tk\_GetVisual(3)

```

```

# [NAME](#NAME)

Tk\_GetVisual - translate from string to visual

# [SYNOPSIS](#SYNOPSIS)

```
#include <tk.h>

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

# [ARGUMENTS](#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.

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.

```
    
```

# [DESCRIPTION](#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 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:

[*class depth*](#class)

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**](#default)

Use the default visual for *tkwin*'s screen.

[*pathName*](#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*](#number)

Use the visual whose X identifier is *number*.

[**best** ?*depth*?](#best)

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](#CREDITS)

The idea for **Tk\_GetVisual**, and the first implementation, came from Paul Mackerras.

# [KEYWORDS](#KEYWORDS)

colormap, screen, visual

4.0 Tk

---

Document: Tk_GetVisual(3) from tk 9.1.0-r0 (Chainguard OS)
Source: https://downloads.sourceforge.net/sourceforge/tcl/tk9.1.0-src.tar.gz