1Tk_AllocCursorFromObj(3) Tk Library Procedures Tk_AllocCursorFromObj(3)
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6
8 Tk_AllocCursorFromObj, Tk_GetCursor, Tk_GetCursorFromObj, Tk_GetCursor‐
9 FromData, Tk_NameOfCursor, Tk_FreeCursorFromObj, Tk_FreeCursor - main‐
10 tain database of cursors
11
13 #include <tk.h>
14 Tk_Cursor │
16 Tk_AllocCursorFromObj(interp, tkwin, objPtr) │
17 Tk_Cursor │
19 Tk_GetCursor(interp, tkwin, name) │
20 Tk_Cursor │
22 Tk_GetCursorFromObj(tkwin, objPtr) │
23 Tk_Cursor
25 Tk_GetCursorFromData(interp, tkwin, source, mask, width, height, xHot, yHot, fg, bg)
26 CONST char *
28 Tk_NameOfCursor(display, cursor)
29 Tk_FreeCursorFromObj(tkwin, objPtr) │
31 Tk_FreeCursor(display, cursor)
33
35 Tcl_Interp *interp (in) Interpreter to use for error
36 reporting.
37 Tk_Window tkwin (in) Token for window in which the
39 cursor will be used.
40 Tcl_Obj *objPtr (in/out) │
42 Description of cursor; see below │
43 for possible values. Internal │
44 rep will be modified to cache │
45 pointer to corresponding Tk_Cur‐ │
46 sor. │
47 char *name (in) │
49 Same as objPtr except description │
50 of cursor is passed as a string │
51 and resulting Tk_Cursor isn't │
52 cached.
53 CONST char *source (in) Data for cursor cursor, in stan‐
55 dard cursor format.
56 CONST char *mask (in) Data for mask cursor, in standard
58 cursor format.
59 int width (in) Width of source and mask.
61 int height (in) Height of source and mask.
63 int xHot (in) X-location of cursor hot-spot.
65 int yHot (in) Y-location of cursor hot-spot.
67 Tk_Uid fg (in) Textual description of foreground
69 color for cursor.
70 Tk_Uid bg (in) Textual description of background
72 color for cursor.
73 Display *display (in) Display for which cursor was
75 allocated.
76 Tk_Cursor cursor (in) Opaque Tk identifier for cursor.
78 If passed to Tk_FreeCursor, must
79 have been returned by some previ‐
80 ous call to Tk_GetCursor or
81 Tk_GetCursorFromData.
82_________________________________________________________________
83
86 These procedures manage a collection of cursors being used by an appli‐
87 cation. The procedures allow cursors to be re-used efficiently,
88 thereby avoiding server overhead, and also allow cursors to be named
89 with character strings.
90 Tk_AllocCursorFromObj takes as argument an object describing a cursor, │
92 and returns an opaque Tk identifier for a cursor corresponding to the │
93 description. It re-uses an existing cursor if possible and creates a │
94 new one otherwise. Tk_AllocCursorFromObj caches information about the │
95 return value in objPtr, which speeds up future calls to procedures such │
96 as Tk_AllocCursorFromObj and Tk_GetCursorFromObj. If an error occurs in │
97 creating the cursor, such as when objPtr refers to a non-existent file, │
98 then None is returned and an error message will be stored in interp's │
99 result if interp isn't NULL. ObjPtr must contain a standard Tcl list │
100 with one of the following forms:
101 name [fgColor [bgColor]]
103 Name is the name of a cursor in the standard X cursor cursor,
104 i.e., any of the names defined in cursorcursor.h, without the
105 XC_. Some example values are X_cursor, hand2, or left_ptr. Ap‐
106 pendix B of ``The X Window System'' by Scheifler & Gettys has
107 illustrations showing what each of these cursors looks like. If
108 fgColor and bgColor are both specified, they give the foreground
109 and background colors to use for the cursor (any of the forms
110 acceptable to Tk_GetColor may be used). If only fgColor is
111 specified, then there will be no background color: the back‐
112 ground will be transparent. If no colors are specified, then
113 the cursor will use black for its foreground color and white for
114 its background color.
115 The Macintosh version of Tk supports all of the X cursors and
117 will also accept any of the standard Mac cursors including
118 ibeam, crosshair, watch, plus, and arrow. In addition, Tk will
119 load Macintosh cursor resources of the types crsr (color) and
120 CURS (black and white) by the name of the of the resource. The
121 application and all its open dynamic library's resource files
122 will be searched for the named cursor. If there are conflicts
123 color cursors will always be loaded in preference to black and
124 white cursors.
125 @sourceName maskName fgColor bgColor
127 In this form, sourceName and maskName are the names of files
128 describing cursors for the cursor's source bits and mask. Each
129 file must be in standard X11 or X10 cursor format. FgColor and
130 bgColor indicate the colors to use for the cursor, in any of the
131 forms acceptable to Tk_GetColor. This form of the command will
132 not work on Macintosh or Windows computers.
133 @sourceName fgColor
135 This form is similar to the one above, except that the source is
136 used as mask also. This means that the cursor's background is
137 transparent. This form of the command will not work on Macin‐
138 tosh or Windows computers.
139 @sourceName
141 This form only works on Windows, and will load a Windows system
142 cursor (.ani or .cur) from the file specified in sourceName.
143 Tk_GetCursor is identical to Tk_AllocCursorFromObj except that the │
145 description of the cursor is specified with a string instead of an │
146 object. This prevents Tk_GetCursor from caching the return value, so │
147 Tk_GetCursor is less efficient than Tk_AllocCursorFromObj. │
148 Tk_GetCursorFromObj returns the token for an existing cursor, given the │
150 window and description used to create the cursor. Tk_GetCursorFromObj │
151 doesn't actually create the cursor; the cursor must already have been │
152 created with a previous call to Tk_AllocCursorFromObj or Tk_GetCursor. │
153 The return value is cached in objPtr, which speeds up future calls to │
154 Tk_GetCursorFromObj with the same objPtr and tkwin.
155 Tk_GetCursorFromData allows cursors to be created from in-memory
157 descriptions of their source and mask cursors. Source points to stan‐
158 dard cursor data for the cursor's source bits, and mask points to stan‐
159 dard cursor data describing which pixels of source are to be drawn and
160 which are to be considered transparent. Width and height give the
161 dimensions of the cursor, xHot and yHot indicate the location of the
162 cursor's hot-spot (the point that is reported when an event occurs),
163 and fg and bg describe the cursor's foreground and background colors
164 textually (any of the forms suitable for Tk_GetColor may be used).
165 Typically, the arguments to Tk_GetCursorFromData are created by includ‐
166 ing a cursor file directly into the source code for a program, as in
167 the following example:
168 Tk_Cursor cursor;
169 #include "source.cursor"
170 #include "mask.cursor"
171 cursor = Tk_GetCursorFromData(interp, tkwin, source_bits,
172 mask_bits, source_width, source_height, source_x_hot,
173 source_y_hot, Tk_GetUid("red"), Tk_GetUid("blue"));
174 Under normal conditions Tk_GetCursorFromData will return an identifier
176 for the requested cursor. If an error occurs in creating the cursor
177 then None is returned and an error message will be stored in interp's
178 result.
179 Tk_AllocCursorFromObj, Tk_GetCursor, and Tk_GetCursorFromData maintain
181 a database of all the cursors they have created. Whenever possible, a
182 call to Tk_AllocCursorFromObj, Tk_GetCursor, or Tk_GetCursorFromData
183 will return an existing cursor rather than creating a new one. This
184 approach can substantially reduce server overhead, so the Tk procedures
185 should generally be used in preference to Xlib procedures like XCreate‐
186 FontCursor or XCreatePixmapCursor, which create a new cursor on each
187 call. The Tk procedures are also more portable than the lower-level X
188 procedures.
189 The procedure Tk_NameOfCursor is roughly the inverse of Tk_GetCursor.
191 If its cursor argument was created by Tk_GetCursor, then the return
192 value is the name argument that was passed to Tk_GetCursor to create
193 the cursor. If cursor was created by a call to Tk_GetCursorFromData,
194 or by any other mechanism, then the return value is a hexadecimal
195 string giving the X identifier for the cursor. Note: the string
196 returned by Tk_NameOfCursor is only guaranteed to persist until the
197 next call to Tk_NameOfCursor. Also, this call is not portable except
198 for cursors returned by Tk_GetCursor.
199 When a cursor returned by Tk_AllocCursorFromObj, Tk_GetCursor, or │
201 Tk_GetCursorFromData is no longer needed, Tk_FreeCursorFromObj or │
202 Tk_FreeCursor should be called to release it. For Tk_FreeCursorFromObj │
203 the cursor to release is specified with the same information used to │
204 create it; for Tk_FreeCursor the cursor to release is specified with │
205 its Tk_Cursor token. There should be exactly one call to Tk_FreeCursor │
206 for each call to Tk_AllocCursorFromObj, Tk_GetCursor, or Tk_GetCursor‐ │
207 FromData.
208
211 In determining whether an existing cursor can be used to satisfy a new
212 request, Tk_AllocCursorFromObj, Tk_GetCursor, and Tk_GetCursorFromData
213 consider only the immediate values of their arguments. For example,
214 when a file name is passed to Tk_GetCursor, Tk_GetCursor will assume it
215 is safe to re-use an existing cursor created from the same file name:
216 it will not check to see whether the file itself has changed, or
217 whether the current directory has changed, thereby causing the name to
218 refer to a different file. Similarly, Tk_GetCursorFromData assumes
219 that if the same source pointer is used in two different calls, then
220 the pointers refer to the same data; it does not check to see if the
221 actual data values have changed.
222
225 cursor
226Tk 8.1 Tk_AllocCursorFromObj(3)