tk_allocbitmapfromobj(3)

NAME

Tk_AllocBitmapFromObj, Tk_GetBitmap, Tk_GetBitmapFromObj,
Tk_DefineBitmap, Tk_NameOfBitmap, Tk_SizeOfBitmap,
Tk_FreeBitmapFromObj, Tk_FreeBitmap - 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)
CONST 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)

Same as objPtr 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.

CONST 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:

@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.

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.

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 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 data so that the name can be used in later calls to
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 compiletime 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
automatically. 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.

The procedure Tk_NameOfBitmap is roughly the inverse of 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 reuse 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

Tk 8.1 Tk_AllocBitmapFromObj(3)