1Tk_AllocBitmapFromObj(3)     Tk Library Procedures    Tk_AllocBitmapFromObj(3)
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5______________________________________________________________________________
6

NAME

8       Tk_AllocBitmapFromObj,    Tk_GetBitmap,   Tk_GetBitmapFromObj,   Tk_De‐
9       fineBitmap,  Tk_NameOfBitmap,  Tk_SizeOfBitmap,   Tk_FreeBitmapFromObj,
10       Tk_FreeBitmap - maintain database of single-plane pixmaps
11

SYNOPSIS

13       #include <tk.h>
14
15       Pixmap
16       Tk_AllocBitmapFromObj(interp, tkwin, objPtr)
17
18       Pixmap
19       Tk_GetBitmap(interp, tkwin, info)
20
21       Pixmap
22       Tk_GetBitmapFromObj(tkwin, objPtr)
23
24       int
25       Tk_DefineBitmap(interp, name, source, width, height)
26
27       const char *
28       Tk_NameOfBitmap(display, bitmap)
29
30       Tk_SizeOfBitmap(display, bitmap, widthPtr, heightPtr)
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32       Tk_FreeBitmapFromObj(tkwin, objPtr)
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34       Tk_FreeBitmap(display, bitmap)
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ARGUMENTS

37       Tcl_Interp *interp (in)               Interpreter  to use for error re‐
38                                             porting; if NULL  then  no  error
39                                             message is left after errors.
40
41       Tk_Window tkwin (in)                  Token  for  window  in  which the
42                                             bitmap will be used.
43
44       Tcl_Obj *objPtr (in/out)              String  value  describes  desired
45                                             bitmap; internal rep will be mod‐
46                                             ified to cache pointer to  corre‐
47                                             sponding Pixmap.
48
49       const char *info (in)                 Same as objPtr except description
50                                             of bitmap is passed as  a  string
51                                             and   resulting   Pixmap  is  not
52                                             cached.
53
54       const char *name (in)                 Name for new  bitmap  to  be  de‐
55                                             fined.
56
57       const void *source (in)               Data for bitmap, in standard bit‐
58                                             map format.  Must  be  stored  in
59                                             static  memory  whose  value will
60                                             never change.
61
62       int width (in)                        Width of bitmap.
63
64       int height (in)                       Height of bitmap.
65
66       int *widthPtr (out)                   Pointer to word to fill  in  with
67                                             bitmap's width.
68
69       int *heightPtr (out)                  Pointer  to  word to fill in with
70                                             bitmap's height.
71
72       Display *display (in)                 Display for which bitmap was  al‐
73                                             located.
74
75       Pixmap bitmap (in)                    Identifier for a bitmap allocated
76                                             by    Tk_AllocBitmapFromObj    or
77                                             Tk_GetBitmap.
78______________________________________________________________________________
79

DESCRIPTION

81       These procedures manage a collection of bitmaps (one-plane pixmaps) be‐
82       ing used by an application.  The procedures allow bitmaps to be re-used
83       efficiently,  thereby  avoiding server overhead, and also allow bitmaps
84       to be named with character strings.
85
86       Tk_AllocBitmapFromObj returns a Pixmap identifier  for  a  bitmap  that
87       matches the description in objPtr and is suitable for use in tkwin.  It
88       re-uses an existing bitmap, if possible, and creates a new  one  other‐
89       wise.  ObjPtr's value must have one of the following forms:
90
91       @fileName           FileName  must  be  the name of a file containing a
92                           bitmap description in the standard X11 format.
93
94       name                Name must be the name of a  bitmap  defined  previ‐
95                           ously  with a call to Tk_DefineBitmap.  The follow‐
96                           ing names are pre-defined by Tk:
97
98                           error       The international  “don't”  symbol:   a
99                                       circle with a diagonal line across it.
100
101                           gray75      75%  gray: a checkerboard pattern where
102                                       three out of four bits are on.
103
104                           gray50      50% gray: a checkerboard pattern  where
105                                       every other bit is on.
106
107                           gray25      25%  gray: a checkerboard pattern where
108                                       one out of every four bits is on.
109
110                           gray12      12.5% gray: a pattern where  one-eighth
111                                       of the bits are on, consisting of every
112                                       fourth pixel in every other row.
113
114                           hourglass   An hourglass symbol.
115
116                           info        A large letter “i”.
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118                           questhead   The silhouette of a human head, with  a
119                                       question mark in it.
120
121                           question    A large question-mark.
122
123                           warning     A large exclamation point.
124
125                           In  addition,  the  following pre-defined names are
126                           available only on the Macintosh platform:
127
128                           document    A generic document.
129
130                           stationery  Document stationery.
131
132                           edition     The edition symbol.
133
134                           application Generic application icon.
135
136                           accessory   A desk accessory.
137
138                           folder      Generic folder icon.
139
140                           pfolder     A locked folder.
141
142                           trash       A trash can.
143
144                           floppy      A floppy disk.
145
146                           ramdisk     A floppy disk with chip.
147
148                           cdrom       A cd disk icon.
149
150                           preferences A folder with prefs symbol.
151
152                           querydoc    A database document icon.
153
154                           stop        A stop sign.
155
156                           note        A face with balloon words.
157
158                           caution     A triangle with an exclamation point.
159
160       Under normal conditions, Tk_AllocBitmapFromObj  returns  an  identifier
161       for  the  requested bitmap.  If an error occurs in creating the bitmap,
162       such as when objPtr refers to a non-existent file,  then  None  is  re‐
163       turned and an error message is left in interp's result if interp is not
164       NULL. Tk_AllocBitmapFromObj caches information about the  return  value
165       in  objPtr,  which  speeds up future calls to procedures such as Tk_Al‐
166       locBitmapFromObj and Tk_GetBitmapFromObj.
167
168       Tk_GetBitmap is identical to Tk_AllocBitmapFromObj except that the  de‐
169       scription  of  the  bitmap is specified with a string instead of an ob‐
170       ject.  This prevents Tk_GetBitmap from caching  the  return  value,  so
171       Tk_GetBitmap is less efficient than Tk_AllocBitmapFromObj.
172
173       Tk_GetBitmapFromObj returns the token for an existing bitmap, given the
174       window and description used to create the bitmap.   Tk_GetBitmapFromObj
175       does  not actually create the bitmap; the bitmap must already have been
176       created with a previous call to Tk_AllocBitmapFromObj or  Tk_GetBitmap.
177       The  return  value is cached in objPtr, which speeds up future calls to
178       Tk_GetBitmapFromObj with the same objPtr and tkwin.
179
180       Tk_DefineBitmap associates a name with in-memory bitmap  data  so  that
181       the name can be used in later calls to Tk_AllocBitmapFromObj or Tk_Get‐
182       Bitmap.  The nameId argument gives a name for the bitmap;  it must  not
183       previously  have been used in a call to Tk_DefineBitmap.  The arguments
184       source, width, and height describe the  bitmap.   Tk_DefineBitmap  nor‐
185       mally  returns  TCL_OK;  if an error occurs (e.g. a bitmap named nameId
186       has already been defined) then TCL_ERROR is returned and an error  mes‐
187       sage  is  left  in interpreter interp's result.  Note:  Tk_DefineBitmap
188       expects the memory pointed to by source to be static:   Tk_DefineBitmap
189       does not make a private copy of this memory, but uses the bytes pointed
190       to by source later in calls to Tk_AllocBitmapFromObj or Tk_GetBitmap.
191
192       Typically Tk_DefineBitmap is used by #include-ing  a  bitmap  file  di‐
193       rectly  into  a C program and then referencing the variables defined by
194       the file.  For example, suppose there exists a file stip.bitmap,  which
195       was  created by the bitmap program and contains a stipple pattern.  The
196       following code uses Tk_DefineBitmap to define a new bitmap named foo:
197              Pixmap bitmap;
198              #include "stip.bitmap"
199              Tk_DefineBitmap(interp, "foo", stip_bits,
200                  stip_width, stip_height);
201              ...
202              bitmap = Tk_GetBitmap(interp, tkwin, "foo");
203       This code causes the bitmap file to be read at compile-time and  incor‐
204       porates  the  bitmap  information  into the program's executable image.
205       The same bitmap file could be read at run-time using Tk_GetBitmap:
206              Pixmap bitmap;
207              bitmap = Tk_GetBitmap(interp, tkwin, "@stip.bitmap");
208       The second form is a bit more flexible (the file could be modified  af‐
209       ter  the program has been compiled, or a different string could be pro‐
210       vided to read a different file), but it is a little slower and requires
211       the bitmap file to exist separately from the program.
212
213       Tk  maintains  a database of all the bitmaps that are currently in use.
214       Whenever possible, it will return an existing bitmap rather than creat‐
215       ing a new one.  When a bitmap is no longer used, Tk will release it au‐
216       tomatically.  This approach can substantially reduce  server  overhead,
217       so  Tk_AllocBitmapFromObj  and Tk_GetBitmap should generally be used in
218       preference to Xlib procedures like XReadBitmapFile.
219
220       The bitmaps returned  by  Tk_AllocBitmapFromObj  and  Tk_GetBitmap  are
221       shared, so callers should never modify them.  If a bitmap must be modi‐
222       fied dynamically, then it should be created by calling Xlib  procedures
223       such as XReadBitmapFile or XCreatePixmap directly.
224
225       The  procedure  Tk_NameOfBitmap is roughly the inverse of Tk_GetBitmap.
226       Given an X Pixmap argument, it returns the textual description that was
227       passed  to  Tk_GetBitmap when the bitmap was created.  Bitmap must have
228       been the return value from a previous call to Tk_AllocBitmapFromObj  or
229       Tk_GetBitmap.
230
231       Tk_SizeOfBitmap  returns  the  dimensions of its bitmap argument in the
232       words pointed to by the widthPtr  and  heightPtr  arguments.   As  with
233       Tk_NameOfBitmap, bitmap must have been created by Tk_AllocBitmapFromObj
234       or Tk_GetBitmap.
235
236       When  a  bitmap  is   no   longer   needed,   Tk_FreeBitmapFromObj   or
237       Tk_FreeBitmap should be called to release it.  For Tk_FreeBitmapFromObj
238       the bitmap to release is specified with the same  information  used  to
239       create  it;  for  Tk_FreeBitmap the bitmap to release is specified with
240       its  Pixmap   token.    There   should   be   exactly   one   call   to
241       Tk_FreeBitmapFromObj   or   Tk_FreeBitmap   for  each  call  to  Tk_Al‐
242       locBitmapFromObj or Tk_GetBitmap.
243

BUGS

245       In determining whether an existing bitmap can be used to satisfy a  new
246       request, Tk_AllocBitmapFromObj and Tk_GetBitmap consider only the imme‐
247       diate value of the string description.  For example, when a  file  name
248       is  passed  to Tk_GetBitmap, Tk_GetBitmap will assume it is safe to re-
249       use an existing bitmap created from the same file name:   it  will  not
250       check  to  see whether the file itself has changed, or whether the cur‐
251       rent directory has changed, thereby causing the name to refer to a dif‐
252       ferent file.
253

KEYWORDS

255       bitmap, pixmap
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258
259Tk                                    8.1             Tk_AllocBitmapFromObj(3)
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