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Tk_AllocBitmapFromObj(3)     Tk Library Procedures    Tk_AllocBitmapFromObj(3)

______________________________________________________________________________

NAME
       Tk_AllocBitmapFromObj,	     Tk_GetBitmap,	  Tk_GetBitmapFromObj,
       Tk_DefineBitmap,	 Tk_NameOfBitmap,  Tk_SizeOfBitmap,  Tk_FreeBitmapFro‐
       mObj, Tk_FreeBitmap - maintain database of single-plane pixmaps

SYNOPSIS
       #include <tk.h>

       Pixmap
       Tk_AllocBitmapFromObj(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 mod‐
					     ified to cache pointer to	corre‐
					     sponding Pixmap.

       const char *info (in)		     Same as objPtr except description
					     of bitmap is passed as  a	string
					     and   resulting   Pixmap  is  not
					     cached.

       const char *name (in)		     Name  for	new   bitmap   to   be
					     defined.

       const void *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_AllocBitmapFromObj    or
					     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_AllocBitmapFromObj returns a Pixmap identifier  for  a  bitmap  that
       matches the description in objPtr and is suitable for use in tkwin.  It
       re-uses an existing bitmap, if possible, and creates a new  one	other‐
       wise.  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 format.

       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 balloon words.

			   caution     A triangle with an exclamation 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 message is left in interp's result if interp is
       not NULL. Tk_AllocBitmapFromObj caches  information  about  the	return
       value  in  objPtr,  which  speeds up future calls to procedures such as
       Tk_AllocBitmapFromObj and Tk_GetBitmapFromObj.

       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
       does  not 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_Get‐
       Bitmap.	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  nor‐
       mally  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  mes‐
       sage  is	 left  in interpreter interp's result.	Note:  Tk_DefineBitmap
       expects the memory pointed to by source to be static:   Tk_DefineBitmap
       does not make a private copy of this memory, 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	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, "@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  maintains  a database of all the bitmaps that are currently in use.
       Whenever possible, it will return an existing bitmap rather than creat‐
       ing  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_GetBitmap  are
       shared, so callers should never modify them.  If a bitmap must be modi‐
       fied 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 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 argument 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_GetBitmap consider only the imme‐
       diate 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 cur‐
       rent directory has changed, thereby causing the name to refer to a dif‐
       ferent file.

KEYWORDS
       bitmap, pixmap

Tk				      8.1	      Tk_AllocBitmapFromObj(3)
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