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) │
45 String value describes desired │
46 bitmap; internal rep will be mod‐ │
47 ified to cache pointer to corre‐ │
48 sponding Pixmap. │
49 CONST char *info (in) │
51 Same as objPtr except description │
52 of bitmap is passed as a string │
53 and resulting Pixmap isn't │
54 cached.
55 CONST char *name (in) Name for new bitmap to be
57 defined.
58 CONST char *source (in) Data for bitmap, in standard bit‐
60 map format. Must be stored in
61 static memory whose value will
62 never change.
63 int width (in) Width of bitmap.
65 int height (in) Height of bitmap.
67 int *widthPtr (out) Pointer to word to fill in with
69 bitmap's width.
70 int *heightPtr (out) Pointer to word to fill in with
72 bitmap's height.
73 Display *display (in) Display for which bitmap was
75 allocated.
76 Pixmap bitmap (in) Identifier for a bitmap allocated
78 by Tk_AllocBitmapFromObj or
79 Tk_GetBitmap.
80_________________________________________________________________
81
84 These procedures manage a collection of bitmaps (one-plane pixmaps)
85 being used by an application. The procedures allow bitmaps to be re-
86 used efficiently, thereby avoiding server overhead, and also allow bit‐
87 maps to be named with character strings.
88 Tk_AllocBitmapFromObj returns a Pixmap identifier for a bitmap that │
90 matches the description in objPtr and is suitable for use in tkwin. It │
91 re-uses an existing bitmap, if possible, and creates a new one other‐ │
92 wise. ObjPtr's value must have one of the following forms:
93 @fileName FileName must be the name of a file containing a
95 bitmap description in the standard X11 or X10 for‐
96 mat.
97 name Name must be the name of a bitmap defined previ‐
99 ously with a call to Tk_DefineBitmap. The follow‐
100 ing names are pre-defined by Tk:
101 error The international "don't" symbol: a
103 circle with a diagonal line across it.
104 gray75 │
106 75% gray: a checkerboard pattern where │
107 three out of four bits are on.
108 gray50 50% gray: a checkerboard pattern where
110 every other bit is on.
111 gray25 │
113 25% gray: a checkerboard pattern where │
114 one out of every four bits is on.
115 gray12 12.5% gray: a pattern where one-eighth
117 of the bits are on, consisting of every
118 fourth pixel in every other row.
119 hourglass An hourglass symbol.
121 info A large letter ``i''.
123 questhead The silhouette of a human head, with a
125 question mark in it.
126 question A large question-mark.
128 warning A large exclamation point.
130 In addition, the following pre-defined names are
132 available only on the Macintosh platform:
133 document A generic document.
135 stationery Document stationery.
137 edition The edition symbol.
139 application Generic application icon.
141 accessory A desk accessory.
143 folder Generic folder icon.
145 pfolder A locked folder.
147 trash A trash can.
149 floppy A floppy disk.
151 ramdisk A floppy disk with chip.
153 cdrom A cd disk icon.
155 preferences A folder with prefs symbol.
157 querydoc A database document icon.
159 stop A stop sign.
161 note A face with ballon words.
163 caution A triangle with an exclamation point.
165 Under normal conditions, Tk_AllocBitmapFromObj returns an identifier │
167 for the requested bitmap. If an error occurs in creating the bitmap, │
168 such as when objPtr refers to a non-existent file, then None is │
169 returned and an error message is left in interp's result if interp │
170 isn't NULL. Tk_AllocBitmapFromObj caches information about the return │
171 value in objPtr, which speeds up future calls to procedures such as │
172 Tk_AllocBitmapFromObj and Tk_GetBitmapFromObj. │
173 Tk_GetBitmap is identical to Tk_AllocBitmapFromObj except that the │
175 description of the bitmap is specified with a string instead of an │
176 object. This prevents Tk_GetBitmap from caching the return value, so │
177 Tk_GetBitmap is less efficient than Tk_AllocBitmapFromObj. │
178 Tk_GetBitmapFromObj returns the token for an existing bitmap, given the │
180 window and description used to create the bitmap. Tk_GetBitmapFromObj │
181 doesn't actually create the bitmap; the bitmap must already have been │
182 created with a previous call to Tk_AllocBitmapFromObj or Tk_GetBitmap. │
183 The return value is cached in objPtr, which speeds up future calls to │
184 Tk_GetBitmapFromObj with the same objPtr and tkwin.
185 Tk_DefineBitmap associates a name with in-memory bitmap data so that
187 the name can be used in later calls to Tk_AllocBitmapFromObj or Tk_Get‐
188 Bitmap. The nameId argument gives a name for the bitmap; it must not
189 previously have been used in a call to Tk_DefineBitmap. The arguments
190 source, width, and height describe the bitmap. Tk_DefineBitmap nor‐
191 mally returns TCL_OK; if an error occurs (e.g. a bitmap named nameId
192 has already been defined) then TCL_ERROR is returned and an error mes‐
193 sage is left in interp->result. Note: Tk_DefineBitmap expects the
194 memory pointed to by source to be static: Tk_DefineBitmap doesn't make
195 a private copy of this memory, but uses the bytes pointed to by source
196 later in calls to Tk_AllocBitmapFromObj or Tk_GetBitmap.
197 Typically Tk_DefineBitmap is used by #include-ing a bitmap file
199 directly into a C program and then referencing the variables defined by
200 the file. For example, suppose there exists a file stip.bitmap, which
201 was created by the bitmap program and contains a stipple pattern. The
202 following code uses Tk_DefineBitmap to define a new bitmap named foo: │
203 Pixmap bitmap; │
204 #include "stip.bitmap" │
205 Tk_DefineBitmap(interp, "foo", stip_bits, │
206 stip_width, stip_height); │
207 ... │
208 bitmap = Tk_GetBitmap(interp, tkwin, "foo"); │
209 This code causes the bitmap file to be read at compile-time and incor‐
210 porates the bitmap information into the program's executable image.
211 The same bitmap file could be read at run-time using Tk_GetBitmap: │
212 Pixmap bitmap; │
213 bitmap = Tk_GetBitmap(interp, tkwin, "@stip.bitmap"); │
214 The second form is a bit more flexible (the file could be modified
215 after the program has been compiled, or a different string could be
216 provided to read a different file), but it is a little slower and
217 requires the bitmap file to exist separately from the program.
218 Tk maintains a database of all the bitmaps that are currently in use.
220 Whenever possible, it will return an existing bitmap rather than creat‐
221 ing a new one. When a bitmap is no longer used, Tk will release it
222 automatically. This approach can substantially reduce server overhead,
223 so Tk_AllocBitmapFromObj and Tk_GetBitmap should generally be used in
224 preference to Xlib procedures like XReadBitmapFile.
225 The bitmaps returned by Tk_AllocBitmapFromObj and Tk_GetBitmap are
227 shared, so callers should never modify them. If a bitmap must be modi‐
228 fied dynamically, then it should be created by calling Xlib procedures
229 such as XReadBitmapFile or XCreatePixmap directly.
230 The procedure Tk_NameOfBitmap is roughly the inverse of Tk_GetBitmap.
232 Given an X Pixmap argument, it returns the textual description that was
233 passed to Tk_GetBitmap when the bitmap was created. Bitmap must have
234 been the return value from a previous call to Tk_AllocBitmapFromObj or
235 Tk_GetBitmap.
236 Tk_SizeOfBitmap returns the dimensions of its bitmap argument in the
238 words pointed to by the widthPtr and heightPtr arguments. As with
239 Tk_NameOfBitmap, bitmap must have been created by Tk_AllocBitmapFromObj
240 or Tk_GetBitmap.
241 When a bitmap is no longer needed, Tk_FreeBitmapFromObj or │
243 Tk_FreeBitmap should be called to release it. For Tk_FreeBitmapFromObj │
244 the bitmap to release is specified with the same information used to │
245 create it; for Tk_FreeBitmap the bitmap to release is specified with │
246 its Pixmap token. There should be exactly one call to │
247 Tk_FreeBitmapFromObj or Tk_FreeBitmap for each call to │
248 Tk_AllocBitmapFromObj or Tk_GetBitmap.
249
252 In determining whether an existing bitmap can be used to satisfy a new
253 request, Tk_AllocBitmapFromObj and Tk_GetBitmap consider only the imme‐
254 diate value of the string description. For example, when a file name
255 is passed to Tk_GetBitmap, Tk_GetBitmap will assume it is safe to re-
256 use an existing bitmap created from the same file name: it will not
257 check to see whether the file itself has changed, or whether the cur‐
258 rent directory has changed, thereby causing the name to refer to a dif‐
259 ferent file.
260
263 bitmap, pixmap
264Tk 8.1 Tk_AllocBitmapFromObj(3)