Tk_GetBitmap(3) Tk (8.0) Tk_GetBitmap(3)
_________________________________________________________________
NAME
Tk_GetBitmap, Tk_DefineBitmap, Tk_NameOfBitmap,
Tk_SizeOfBitmap, Tk_FreeBitmap, Tk_GetBitmapFromData -
maintain database of single-plane pixmaps
SYNOPSIS
#include <tk.h>
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.
Page 1 (printed 2/26/99)
Tk_GetBitmap(3) Tk (8.0) Tk_GetBitmap(3)
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.
_________________________________________________________________
DESCRIPTION
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.
gray75 ||
75% gray: a checkerboard |
pattern where three out of |
four bits are on.
gray50 50% gray: a checkerboard
pattern where every other
bit is on.
gray25 ||
25% gray: a checkerboard |
pattern where one out of |
every four bits is on.
Page 2 (printed 2/26/99)
Tk_GetBitmap(3) Tk (8.0) Tk_GetBitmap(3)
gray12 12.5% gray: a pattern where
one-eighth of the bits are
on, consisting of every
fourth pixel in every other
row.
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.
In addition, the following pre-defined
names are available only on the
Macintosh platform:
document A generic document.
stationery Document stationery.
edition The edition symbol.
application Generic application icon.
accessory A desk accessory.
folder Generic folder icon.
pfolder A locked folder.
trash A trash can.
floppy A floppy disk.
ramdisk A floppy disk with chip.
cdrom A cd disk icon.
preferences A folder with prefs symbol.
querydoc A database document icon.
stop A stop sign.
note A face with ballon words.
Page 3 (printed 2/26/99)
Tk_GetBitmap(3) Tk (8.0) Tk_GetBitmap(3)
caution A triangle with an
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"));
This code causes the bitmap file to be read at compile-time
and incorporates the bitmap information into the program's
executable image. The same bitmap file could be read at
run-time using Tk_GetBitmap:
Pixmap bitmap;
bitmap = Tk_GetBitmap(interp, tkwin, Tk_GetUid("@stip.bitmap"));
The second form is a bit more flexible (the file could be
modified after the program has been compiled, or a different
string could be provided to read a different file), but it
is a little slower and requires the bitmap file to exist
separately from the program.
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.
Page 4 (printed 2/26/99)
Tk_GetBitmap(3) Tk (8.0) Tk_GetBitmap(3)
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
In determining whether an existing bitmap can be used to
satisfy a new request, Tk_GetBitmap considers only the
immediate value of its id argument. For example, when a
file name is passed to Tk_GetBitmap, Tk_GetBitmap will
assume it is safe to re-use an existing bitmap created from
the same file name: it will not check to see whether the
file itself has changed, or whether the current directory
has changed, thereby causing the name to refer to a
different file.
KEYWORDS
bitmap, pixmap
Page 5 (printed 2/26/99)
