Tk_GetColormap(3) Tk Library Procedures Tk_GetColormap(3)

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NAME

Tk_GetColormap, Tk_PreserveColormap, Tk_FreeColormap - allocate and
free colormaps

SYNOPSIS

#include <tk.h>

Colormap
Tk_GetColormap(interp, tkwin, string)

Tk_PreserveColormap(display, colormap)

Tk_FreeColormap(display, colormap)

ARGUMENTS

Tcl_Interp *interp (in) Interpreter to use for error
reporting.

Tk_Window tkwin (in) Token for window in which colormap
will be used.

const char *string (in) Selects a colormap: either new or
the name of a window with the same
screen and visual as tkwin.

Display *display (in) Display for which colormap was
allocated.

Colormap colormap (in) Colormap to free or preserve; must
have been returned by a previous call
to Tk_GetColormap or Tk_GetVisual.
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DESCRIPTION

These procedures are used to manage colormaps. Tk_GetColormap
returns a colormap suitable for use in tkwin. If its string argument
is new then a new colormap is created; otherwise string must be the
name of another window with the same screen and visual as tkwin, and
the colormap from that window is returned. If string does not make
sense, or if it refers to a window on a different screen from tkwin
or with a different visual than tkwin, then Tk_GetColormap returns
None and leaves an error message in interp's result.

Tk_PreserveColormap increases the internal reference count for a
colormap previously returned by Tk_GetColormap, which allows the
colormap to be stored in several locations without knowing which
order they will be released.

Tk_FreeColormap should be called when a colormap returned by
Tk_GetColormap is no longer needed. Tk maintains a reference count
for each colormap returned by Tk_GetColormap, so there should
eventually be one call to Tk_FreeColormap for each call to
Tk_GetColormap and each call to Tk_PreserveColormap. When a
colormap's reference count becomes zero, Tk releases the X colormap.

Tk_GetVisual and Tk_GetColormap work together, in that a new colormap
created by Tk_GetVisual may later be returned by Tk_GetColormap. The
reference counting mechanism for colormaps includes both procedures,
so callers of Tk_GetVisual must also call Tk_FreeColormap to release
the colormap. If Tk_GetColormap is called with a string value of new
then the resulting colormap will never be returned by Tk_GetVisual;
however, it can be used in other windows by calling Tk_GetColormap
with the original window's name as string.

KEYWORDS

colormap, visual

Tk 4.0 Tk_GetColormap(3)