Tk_GetBitmap(3) Tk Library Procedures 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 bit‐
map 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.
_________________________________________________________________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 bit‐
maps 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 descrip‐
tion. 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 for‐
mat.
name Name must be the name of a bitmap defined previ‐
ously with a call to Tk_DefineBitmap. The follow‐
ing 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.
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.
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 argu‐
ment 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 incor‐
porates 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.
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 cre‐
ated 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
Tk 8.0 Tk_GetBitmap(3)