NAME
Tk_AllocBitmapFromObj, Tk_GetBitmap, Tk_GetBitmapFromObj,
Tk_DefineBitmap, Tk_NameOfBitmap, Tk_SizeOfBitmap,
Tk_FreeBitmapFromObj, Tk_FreeBitmap, Tk_GetBitmapFromData
- maintain database of single-plane pixmaps
SYNOPSIS
#include <tk.h>
Pixmap |
Tk_GetBitmapFromObj(interp, tkwin, objPtr) |
Pixmap |
Tk_GetBitmap(interp, tkwin, info) |
Pixmap |
Tk_GetBitmapFromObj(tkwin, objPtr) |
int
Tk_DefineBitmap(interp, name, source, width, height)
char *
Tk_NameOfBitmap(display, bitmap)
Tk_SizeOfBitmap(display, bitmap, widthPtr, heightPtr)
Tk_FreeBitmapFromObj(tkwin, objPtr) |
Tk_FreeBitmap(display, bitmap)
ARGUMENTS
Tcl_Interp *interp (in) Interpreter to use
for error reporting;
if NULL then no
error message is
left after errors.
Tk_Window tkwin (in) Token for window in
which the bitmap
will be used.
Tcl_Obj *objPtr (in/out) ||
String value |
describes desired |
bitmap; internal rep |
will be modified to |
cache pointer to |
corresponding |
Pixmap. |
CONST |
char *info (in) ||
except description |
of bitmap is passed |
as a string and |
resulting Pixmap |
isn't cached.
CONST char *name (in) Name for new bitmap
to be defined.
char *source (in) Data for bitmap, in
standard bitmap for
mat. 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 allo
cated.
Pixmap bitmap (in) Identifier for a
bitmap allocated by
Tk_AllocBitmapFro
mObj or Tk_Get
Bitmap.
_________________________________________________________________
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_AllocBitmapFromObj returns a Pixmap identifier for a |
bitmap that matches the description in objPtr and is suit |
able for use in tkwin. It re-uses an existing bitmap, if |
possible, and creates a new one otherwise. ObjPtr's value |
must have one of the following forms:
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.
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 Macin
tosh platform:
document A generic document.
stationery Document stationery.
edition The edition symbol.
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 sym
bol.
querydoc A database document icon.
stop A stop sign.
note A face with ballon words.
caution A triangle with an excla
mation point.
Under normal conditions, Tk_AllocBitmapFromObj returns an |
identifier for the requested bitmap. If an error occurs |
in creating the bitmap, such as when objPtr refers to a |
non-existent file, then None is returned and an error mes |
sage is left in interp's result if interp isn't NULL. |
Tk_AllocBitmapFromObj caches information about the return |
value in objPtr, which speeds up future calls to proce |
dures such as Tk_AllocBitmapFromObj and Tk_GetBitmapFro |
mObj. |
Tk_GetBitmap is identical to Tk_AllocBitmapFromObj except |
that the description of the bitmap is specified with a |
string instead of an object. This prevents Tk_GetBitmap |
from caching the return value, so Tk_GetBitmap is less |
efficient than Tk_AllocBitmapFromObj. |
Tk_GetBitmapFromObj returns the token for an existing |
bitmap, given the window and description used to create |
the bitmap. Tk_GetBitmapFromObj doesn't actually create |
the bitmap; the bitmap must already have been created with |
a previous call to Tk_AllocBitmapFromObj or Tk_GetBitmap. |
The return value is cached in objPtr, which speeds up |
future calls to Tk_GetBitmapFromObj with the same objPtr |
and tkwin.
Tk_DefineBitmap associates a name with in-memory bitmap
Tk_AllocBitmapFromObj or 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 argu
ments 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 mem
ory, but uses the bytes pointed to by source later in
calls to Tk_AllocBitmapFromObj or 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, "foo", stip_bits, |
stip_width, stip_height); |
... |
bitmap = Tk_GetBitmap(interp, tkwin, "foo"); |
This code causes the bitmap file to be read at compile-
time and incorporates the bitmap information into the pro
gram's executable image. The same bitmap file could be
read at run-time using Tk_GetBitmap: |
Pixmap bitmap; |
bitmap = Tk_GetBitmap(interp, tkwin, "@stip.bitmap");|
The second form is a bit more flexible (the file could be
modified after the program has been compiled, or a differ
ent 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 maintains a database of all the bitmaps that are cur
rently in use. Whenever possible, it will return an
existing bitmap rather than creating a new one. When a
bitmap is no longer used, Tk will release it automati
cally. This approach can substantially reduce server
overhead, so Tk_AllocBitmapFromObj and Tk_GetBitmap should
generally be used in preference to Xlib procedures like
XReadBitmapFile.
The bitmaps returned by Tk_AllocBitmapFromObj and Tk_Get
Bitmap 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 XReadBitmap
File or XCreatePixmap directly.
Tk_GetBitmap. Given an X Pixmap argument, it returns the
textual description that was passed to Tk_GetBitmap when
the bitmap was created. Bitmap must have been the return
value from a previous call to Tk_AllocBitmapFromObj or
Tk_GetBitmap.
Tk_SizeOfBitmap returns the dimensions of its bitmap argu
ment in the words pointed to by the widthPtr and heightPtr
arguments. As with Tk_NameOfBitmap, bitmap must have been
created by Tk_AllocBitmapFromObj or Tk_GetBitmap.
When a bitmap is no longer needed, Tk_FreeBitmapFromObj or |
Tk_FreeBitmap should be called to release it. For |
Tk_FreeBitmapFromObj the bitmap to release is specified |
with the same information used to create it; for |
Tk_FreeBitmap the bitmap to release is specified with its |
Pixmap token. There should be exactly one call to |
Tk_FreeBitmapFromObj or Tk_FreeBitmap for each call to |
Tk_AllocBitmapFromObj or Tk_GetBitmap.
BUGS
In determining whether an existing bitmap can be used to
satisfy a new request, Tk_AllocBitmapFromObj and Tk_Get
Bitmap consider only the immediate value of the string
description. 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
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