Tk_GetBitmap

Pixmap
Tk_GetBitmap(interp, tkwin, id)

int
Tk_DefineBitmap(interp, nameId, source, width, height)

Tk_Uid
Tk_NameOfBitmap(display, bitmap)

Tk_SizeOfBitmap(display, bitmap, widthPtr, heightPtr)

Tk_FreeBitmap(display, bitmap)

ARGUMENTS

Tcl_Interp *interp (in)

Interpreter to use for error reporting.

Tk_Window tkwin (in)

Token for window in which the bitmap will be used.

Tk_Uid id (in)

Description of bitmap; see below for possible values.

Tk_Uid *nameId (in)

Name for new bitmap to be defined.

char *source (in)

Data for bitmap, in standard bitmap format.
Must be stored in static memory whose value will never change.

"int" width (in)

Width of bitmap.

"int" height (in)

Height of bitmap.

"int" *widthPtr (out)

Pointer to word to fill in with bitmap's width.

"int" *heightPtr (out)

Pointer to word to fill in with bitmap's height.

Display *display (in)

Display for which bitmap was allocated.

Pixmap bitmap (in)

Identifier for a bitmap allocated by Tk_GetBitmap.

These procedures manage a collection of bitmaps (one-plane pixmaps)
being used by an application. The procedures allow bitmaps to be
re-used efficiently, thereby avoiding server overhead, and also
allow bitmaps to be named with character strings.

Tk_GetBitmap takes as argument a Tk_Uid describing a bitmap.
It returns a Pixmap identifier for a bitmap corresponding to the
description. It re-uses an existing bitmap, if possible, and
creates a new one otherwise. At present, id must have
one of the following forms:

@fileName

FileName must be the name of a file containing a bitmap
description in the standard X11 or X10 format.

name

Name must be the name of a bitmap defined previously with
a call to Tk_DefineBitmap. The following names are pre-defined
by Tk:

error

The international "don't" symbol: a circle with a diagonal line
across it.

gray50

50% gray: a checkerboard pattern where every other bit is on.

gray25

25% gray: a pattern where 25% of the bits are on, consisting of all the
bit positions that can be reached by a chess knight starting at (0,0).

hourglass

An hourglass symbol.

info

A large letter ``i''.

questhead

The silhouette of a human head, with a question mark in it.

question

A large question-mark.

warning

A large exclamation point.

Under normal conditions, Tk_GetBitmap
returns an identifier for the requested bitmap. If an error
occurs in creating the bitmap, such as when id refers
to a non-existent file, then None is returned and an error
message is left in interp->result.

Tk_DefineBitmap associates a name with
in-memory bitmap data so that the name can be used in later
calls to Tk_GetBitmap. The nameId
argument gives a name for the bitmap; it must not previously
have been used in a call to Tk_DefineBitmap.
The arguments source, width, and height
describe the bitmap.
Tk_DefineBitmap normally returns TCL_OK; if an error occurs
(e.g. a bitmap named nameId has already been defined) then
TCL_ERROR is returned and an error message is left in
interp->result.
Note: Tk_DefineBitmap expects the memory pointed to by
source to be static: Tk_DefineBitmap doesn't make
a private copy of this memory, but uses the bytes pointed to
by source later in calls to Tk_GetBitmap.

Typically Tk_DefineBitmap is used by #include-ing a
bitmap file directly into a C program and then referencing
the variables defined by the file.
For example, suppose there exists a file stip.bitmap,
which was created by the bitmap program and contains
a stipple pattern.
The following code uses Tk_DefineBitmap to define a
new bitmap named foo:

Pixmap bitmap;

#include "stip.bitmap"

Tk_DefineBitmap(interp, Tk_GetUid("foo"), stip_bits,

	stip_width, stip_height);

...

bitmap = Tk_GetBitmap(interp, tkwin, Tk_GetUid("foo"));

Pixmap bitmap;

bitmap = Tk_GetBitmap(interp, tkwin, Tk_GetUid("@stip.bitmap"));

Tk_GetBitmap maintains a database of all the bitmaps that are currently in use. Whenever possible, it will return an existing bitmap rather than creating a new one. This approach can substantially reduce server overhead, so Tk_GetBitmap should generally be used in preference to Xlib procedures like XReadBitmapFile.

The bitmaps returned by Tk_GetBitmap are shared, so callers should never modify them. If a bitmap must be modified dynamically, then it should be created by calling Xlib procedures such as XReadBitmapFile or XCreatePixmap directly.

The procedure Tk_NameOfBitmap is roughly the inverse of Tk_GetBitmap. Given an X Pixmap argument, it returns the id that was passed to Tk_GetBitmap when the bitmap was created. Bitmap must have been the return value from a previous call to Tk_GetBitmap.

Tk_SizeOfBitmap returns the dimensions of its bitmap argument in the words pointed to by the widthPtr and heightPtr arguments. As with Tk_NameOfBitmap, bitmap must have been created by Tk_GetBitmap.

When a bitmap returned by Tk_GetBitmap is no longer needed, Tk_FreeBitmap should be called to release it. There should be exactly one call to Tk_FreeBitmap for each call to Tk_GetBitmap. When a bitmap is no longer in use anywhere (i.e. it has been freed as many times as it has been gotten) Tk_FreeBitmap will release it to the X server and delete it from the database.

BUGS