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Tk_AllocBitmapFromObj(3)                    Tk Library Procedures                   Tk_AllocBitmapFromObj(3)



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NAME
       Tk_AllocBitmapFromObj,  Tk_GetBitmap, Tk_GetBitmapFromObj, Tk_DefineBitmap, Tk_NameOfBitmap, Tk_Size-OfBitmap, Tk_SizeOfBitmap,
       OfBitmap, Tk_FreeBitmapFromObj, 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
                                             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 is not cached.

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

       const 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.

       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.
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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 suitable 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 stan-dard standard
                           dard 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 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 spec-ified specified
       ified  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_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 bit-map bitmap
       map 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 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 incorporates the  bitmap  information
       into  the  program's  executable image.  The same bitmap file could be read at run-time using Tk_Get-Bitmap: Tk_GetBitmap:
       Bitmap:
              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  com-piled, compiled,
       piled,  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 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_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 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 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



Tk                                                   8.1                            Tk_AllocBitmapFromObj(3)