1Tk_AllocBitmapFromObj(3) Tk Library Procedures Tk_AllocBitmapFromObj(3)
2______________________________________________________________________________
6
8 Tk_AllocBitmapFromObj, Tk_GetBitmap, Tk_GetBitmapFromObj,
9 Tk_DefineBitmap, Tk_NameOfBitmap, Tk_SizeOfBitmap, Tk_FreeBitmapFro‐
10 mObj, Tk_FreeBitmap - maintain database of single-plane pixmaps
11
13 #include <tk.h>
14 Pixmap
16 Tk_AllocBitmapFromObj(interp, tkwin, objPtr)
17 Pixmap
19 Tk_GetBitmap(interp, tkwin, info)
20 Pixmap
22 Tk_GetBitmapFromObj(tkwin, objPtr)
23 int
25 Tk_DefineBitmap(interp, name, source, width, height)
26 const char *
28 Tk_NameOfBitmap(display, bitmap)
29 Tk_SizeOfBitmap(display, bitmap, widthPtr, heightPtr)
31 Tk_FreeBitmapFromObj(tkwin, objPtr)
33 Tk_FreeBitmap(display, bitmap)
35
37 Tcl_Interp *interp (in) Interpreter to use for error
38 reporting; if NULL then no error
39 message is left after errors.
40 Tk_Window tkwin (in) Token for window in which the
42 bitmap will be used.
43 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 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 const char *name (in) Name for new bitmap to be
55 defined.
56 const char *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 int width (in) Width of bitmap.
63 int height (in) Height of bitmap.
65 int *widthPtr (out) Pointer to word to fill in with
67 bitmap's width.
68 int *heightPtr (out) Pointer to word to fill in with
70 bitmap's height.
71 Display *display (in) Display for which bitmap was
73 allocated.
74 Pixmap bitmap (in) Identifier for a bitmap allocated
76 by Tk_AllocBitmapFromObj or
77 Tk_GetBitmap.
78_________________________________________________________________
79
82 These procedures manage a collection of bitmaps (one-plane pixmaps)
83 being used by an application. The procedures allow bitmaps to be re-
84 used efficiently, thereby avoiding server overhead, and also allow bit‐
85 maps to be named with character strings.
86 Tk_AllocBitmapFromObj returns a Pixmap identifier for a bitmap that
88 matches the description in objPtr and is suitable for use in tkwin. It
89 re-uses an existing bitmap, if possible, and creates a new one other‐
90 wise. ObjPtr's value must have one of the following forms:
91 @fileName FileName must be the name of a file containing a
93 bitmap description in the standard X11 or X10 for‐
94 mat.
95 name Name must be the name of a bitmap defined previ‐
97 ously with a call to Tk_DefineBitmap. The follow‐
98 ing names are pre-defined by Tk:
99 error The international “don't” symbol: a
101 circle with a diagonal line across it.
102 gray75 75% gray: a checkerboard pattern where
104 three out of four bits are on.
105 gray50 50% gray: a checkerboard pattern where
107 every other bit is on.
108 gray25 25% gray: a checkerboard pattern where
110 one out of every four bits is on.
111 gray12 12.5% gray: a pattern where one-eighth
113 of the bits are on, consisting of every
114 fourth pixel in every other row.
115 hourglass An hourglass symbol.
117 info A large letter “i”.
119 questhead The silhouette of a human head, with a
121 question mark in it.
122 question A large question-mark.
124 warning A large exclamation point.
126 In addition, the following pre-defined names are
128 available only on the Macintosh platform:
129 document A generic document.
131 stationery Document stationery.
133 edition The edition symbol.
135 application Generic application icon.
137 accessory A desk accessory.
139 folder Generic folder icon.
141 pfolder A locked folder.
143 trash A trash can.
145 floppy A floppy disk.
147 ramdisk A floppy disk with chip.
149 cdrom A cd disk icon.
151 preferences A folder with prefs symbol.
153 querydoc A database document icon.
155 stop A stop sign.
157 note A face with balloon words.
159 caution A triangle with an exclamation point.
161 Under normal conditions, Tk_AllocBitmapFromObj returns an identifier
163 for the requested bitmap. If an error occurs in creating the bitmap,
164 such as when objPtr refers to a non-existent file, then None is
165 returned and an error message is left in interp's result if interp is
166 not NULL. Tk_AllocBitmapFromObj caches information about the return
167 value in objPtr, which speeds up future calls to procedures such as
168 Tk_AllocBitmapFromObj and Tk_GetBitmapFromObj.
169 Tk_GetBitmap is identical to Tk_AllocBitmapFromObj except that the
171 description of the bitmap is specified with a string instead of an
172 object. This prevents Tk_GetBitmap from caching the return value, so
173 Tk_GetBitmap is less efficient than Tk_AllocBitmapFromObj.
174 Tk_GetBitmapFromObj returns the token for an existing bitmap, given the
176 window and description used to create the bitmap. Tk_GetBitmapFromObj
177 does not actually create the bitmap; the bitmap must already have been
178 created with a previous call to Tk_AllocBitmapFromObj or Tk_GetBitmap.
179 The return value is cached in objPtr, which speeds up future calls to
180 Tk_GetBitmapFromObj with the same objPtr and tkwin.
181 Tk_DefineBitmap associates a name with in-memory bitmap data so that
183 the name can be used in later calls to Tk_AllocBitmapFromObj or Tk_Get‐
184 Bitmap. The nameId argument gives a name for the bitmap; it must not
185 previously have been used in a call to Tk_DefineBitmap. The arguments
186 source, width, and height describe the bitmap. Tk_DefineBitmap nor‐
187 mally returns TCL_OK; if an error occurs (e.g. a bitmap named nameId
188 has already been defined) then TCL_ERROR is returned and an error mes‐
189 sage is left in interp->result. Note: Tk_DefineBitmap expects the
190 memory pointed to by source to be static: Tk_DefineBitmap does not
191 make a private copy of this memory, but uses the bytes pointed to by
192 source later in calls to Tk_AllocBitmapFromObj or Tk_GetBitmap.
193 Typically Tk_DefineBitmap is used by #include-ing a bitmap file
195 directly into a C program and then referencing the variables defined by
196 the file. For example, suppose there exists a file stip.bitmap, which
197 was created by the bitmap program and contains a stipple pattern. The
198 following code uses Tk_DefineBitmap to define a new bitmap named foo:
199 Pixmap bitmap;
200 #include "stip.bitmap"
201 Tk_DefineBitmap(interp, "foo", stip_bits,
202 stip_width, stip_height);
203 ...
204 bitmap = Tk_GetBitmap(interp, tkwin, "foo");
205 This code causes the bitmap file to be read at compile-time and incor‐
206 porates the bitmap information into the program's executable image.
207 The same bitmap file could be read at run-time using Tk_GetBitmap:
208 Pixmap bitmap;
209 bitmap = Tk_GetBitmap(interp, tkwin, "@stip.bitmap");
210 The second form is a bit more flexible (the file could be modified
211 after the program has been compiled, or a different string could be
212 provided to read a different file), but it is a little slower and
213 requires the bitmap file to exist separately from the program.
214 Tk maintains a database of all the bitmaps that are currently in use.
216 Whenever possible, it will return an existing bitmap rather than creat‐
217 ing a new one. When a bitmap is no longer used, Tk will release it
218 automatically. This approach can substantially reduce server overhead,
219 so Tk_AllocBitmapFromObj and Tk_GetBitmap should generally be used in
220 preference to Xlib procedures like XReadBitmapFile.
221 The bitmaps returned by Tk_AllocBitmapFromObj and Tk_GetBitmap are
223 shared, so callers should never modify them. If a bitmap must be modi‐
224 fied dynamically, then it should be created by calling Xlib procedures
225 such as XReadBitmapFile or XCreatePixmap directly.
226 The procedure Tk_NameOfBitmap is roughly the inverse of Tk_GetBitmap.
228 Given an X Pixmap argument, it returns the textual description that was
229 passed to Tk_GetBitmap when the bitmap was created. Bitmap must have
230 been the return value from a previous call to Tk_AllocBitmapFromObj or
231 Tk_GetBitmap.
232 Tk_SizeOfBitmap returns the dimensions of its bitmap argument in the
234 words pointed to by the widthPtr and heightPtr arguments. As with
235 Tk_NameOfBitmap, bitmap must have been created by Tk_AllocBitmapFromObj
236 or Tk_GetBitmap.
237 When a bitmap is no longer needed, Tk_FreeBitmapFromObj or
239 Tk_FreeBitmap should be called to release it. For Tk_FreeBitmapFromObj
240 the bitmap to release is specified with the same information used to
241 create it; for Tk_FreeBitmap the bitmap to release is specified with
242 its Pixmap token. There should be exactly one call to
243 Tk_FreeBitmapFromObj or Tk_FreeBitmap for each call to
244 Tk_AllocBitmapFromObj or Tk_GetBitmap.
245
248 In determining whether an existing bitmap can be used to satisfy a new
249 request, Tk_AllocBitmapFromObj and Tk_GetBitmap consider only the imme‐
250 diate value of the string description. For example, when a file name
251 is passed to Tk_GetBitmap, Tk_GetBitmap will assume it is safe to re-
252 use an existing bitmap created from the same file name: it will not
253 check to see whether the file itself has changed, or whether the cur‐
254 rent directory has changed, thereby causing the name to refer to a dif‐
255 ferent file.
256
259 bitmap, pixmap
260Tk 8.1 Tk_AllocBitmapFromObj(3)