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) Description of cursor; see below
42 for possible values. Internal
43 rep will be modified to cache
44 pointer to corresponding Tk_Cur‐
45 sor.
46 char *name (in) Same as objPtr except description
48 of cursor is passed as a string
49 and resulting Tk_Cursor is not
50 cached.
51 const char *source (in) Data for cursor cursor, in stan‐
53 dard cursor format.
54 const char *mask (in) Data for mask cursor, in standard
56 cursor format.
57 int width (in) Width of source and mask.
59 int height (in) Height of source and mask.
61 int xHot (in) X-location of cursor hot-spot.
63 int yHot (in) Y-location of cursor hot-spot.
65 Tk_Uid fg (in) Textual description of foreground
67 color for cursor.
68 Tk_Uid bg (in) Textual description of background
70 color for cursor.
71 Display *display (in) Display for which cursor was
73 allocated.
74 Tk_Cursor cursor (in) Opaque Tk identifier for cursor.
76 If passed to Tk_FreeCursor, must
77 have been returned by some previ‐
78 ous call to Tk_GetCursor or
79 Tk_GetCursorFromData.
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81
84 These procedures manage a collection of cursors being used by an appli‐
85 cation. The procedures allow cursors to be re-used efficiently,
86 thereby avoiding server overhead, and also allow cursors to be named
87 with character strings.
88 Tk_AllocCursorFromObj takes as argument an object describing a cursor,
90 and returns an opaque Tk identifier for a cursor corresponding to the
91 description. It re-uses an existing cursor if possible and creates a
92 new one otherwise. Tk_AllocCursorFromObj caches information about the
93 return value in objPtr, which speeds up future calls to procedures such
94 as Tk_AllocCursorFromObj and Tk_GetCursorFromObj. If an error occurs in
95 creating the cursor, such as when objPtr refers to a non-existent file,
96 then None is returned and an error message will be stored in interp's
97 result if interp is not NULL. ObjPtr must contain a standard Tcl list
98 with one of the following forms:
99 name [fgColor [bgColor]]
101 Name is the name of a cursor in the standard X cursor cursor,
102 i.e., any of the names defined in cursorcursor.h, without the
103 XC_. Some example values are X_cursor, hand2, or left_ptr. Ap‐
104 pendix B of “The X Window System” by Scheifler & Gettys has
105 illustrations showing what each of these cursors looks like. If
106 fgColor and bgColor are both specified, they give the foreground
107 and background colors to use for the cursor (any of the forms
108 acceptable to Tk_GetColor may be used). If only fgColor is
109 specified, then there will be no background color: the back‐
110 ground will be transparent. If no colors are specified, then
111 the cursor will use black for its foreground color and white for
112 its background color.
113 The Macintosh version of Tk supports all of the X cursors and
115 will also accept any of the standard Mac cursors including
116 ibeam, crosshair, watch, plus, and arrow. In addition, Tk will
117 load Macintosh cursor resources of the types crsr (color) and
118 CURS (black and white) by the name of the resource. The appli‐
119 cation and all its open dynamic library's resource files will be
120 searched for the named cursor. If there are conflicts color
121 cursors will always be loaded in preference to black and white
122 cursors.
123 @sourceName maskName fgColor bgColor
125 In this form, sourceName and maskName are the names of files
126 describing cursors for the cursor's source bits and mask. Each
127 file must be in standard X11 or X10 cursor format. FgColor and
128 bgColor indicate the colors to use for the cursor, in any of the
129 forms acceptable to Tk_GetColor. This form of the command will
130 not work on Macintosh or Windows computers.
131 @sourceName fgColor
133 This form is similar to the one above, except that the source is
134 used as mask also. This means that the cursor's background is
135 transparent. This form of the command will not work on Macin‐
136 tosh or Windows computers.
137 @sourceName
139 This form only works on Windows, and will load a Windows system
140 cursor (.ani or .cur) from the file specified in sourceName.
141 Tk_GetCursor is identical to Tk_AllocCursorFromObj except that the
143 description of the cursor is specified with a string instead of an
144 object. This prevents Tk_GetCursor from caching the return value, so
145 Tk_GetCursor is less efficient than Tk_AllocCursorFromObj.
146 Tk_GetCursorFromObj returns the token for an existing cursor, given the
148 window and description used to create the cursor. Tk_GetCursorFromObj
149 does not actually create the cursor; the cursor must already have been
150 created with a previous call to Tk_AllocCursorFromObj or Tk_GetCursor.
151 The return value is cached in objPtr, which speeds up future calls to
152 Tk_GetCursorFromObj with the same objPtr and tkwin.
153 Tk_GetCursorFromData allows cursors to be created from in-memory
155 descriptions of their source and mask cursors. Source points to stan‐
156 dard cursor data for the cursor's source bits, and mask points to stan‐
157 dard cursor data describing which pixels of source are to be drawn and
158 which are to be considered transparent. Width and height give the
159 dimensions of the cursor, xHot and yHot indicate the location of the
160 cursor's hot-spot (the point that is reported when an event occurs),
161 and fg and bg describe the cursor's foreground and background colors
162 textually (any of the forms suitable for Tk_GetColor may be used).
163 Typically, the arguments to Tk_GetCursorFromData are created by includ‐
164 ing a cursor file directly into the source code for a program, as in
165 the following example:
166 Tk_Cursor cursor;
167 #include "source.cursor"
168 #include "mask.cursor"
169 cursor = Tk_GetCursorFromData(interp, tkwin, source_bits,
170 mask_bits, source_width, source_height, source_x_hot,
171 source_y_hot, Tk_GetUid("red"), Tk_GetUid("blue"));
172 Under normal conditions Tk_GetCursorFromData will return an identifier
174 for the requested cursor. If an error occurs in creating the cursor
175 then None is returned and an error message will be stored in interp's
176 result.
177 Tk_AllocCursorFromObj, Tk_GetCursor, and Tk_GetCursorFromData maintain
179 a database of all the cursors they have created. Whenever possible, a
180 call to Tk_AllocCursorFromObj, Tk_GetCursor, or Tk_GetCursorFromData
181 will return an existing cursor rather than creating a new one. This
182 approach can substantially reduce server overhead, so the Tk procedures
183 should generally be used in preference to Xlib procedures like XCreate‐
184 FontCursor or XCreatePixmapCursor, which create a new cursor on each
185 call. The Tk procedures are also more portable than the lower-level X
186 procedures.
187 The procedure Tk_NameOfCursor is roughly the inverse of Tk_GetCursor.
189 If its cursor argument was created by Tk_GetCursor, then the return
190 value is the name argument that was passed to Tk_GetCursor to create
191 the cursor. If cursor was created by a call to Tk_GetCursorFromData,
192 or by any other mechanism, then the return value is a hexadecimal
193 string giving the X identifier for the cursor. Note: the string
194 returned by Tk_NameOfCursor is only guaranteed to persist until the
195 next call to Tk_NameOfCursor. Also, this call is not portable except
196 for cursors returned by Tk_GetCursor.
197 When a cursor returned by Tk_AllocCursorFromObj, Tk_GetCursor, or
199 Tk_GetCursorFromData is no longer needed, Tk_FreeCursorFromObj or
200 Tk_FreeCursor should be called to release it. For Tk_FreeCursorFromObj
201 the cursor to release is specified with the same information used to
202 create it; for Tk_FreeCursor the cursor to release is specified with
203 its Tk_Cursor token. There should be exactly one call to Tk_FreeCursor
204 for each call to Tk_AllocCursorFromObj, Tk_GetCursor, or Tk_GetCursor‐
205 FromData.
206
209 In determining whether an existing cursor can be used to satisfy a new
210 request, Tk_AllocCursorFromObj, Tk_GetCursor, and Tk_GetCursorFromData
211 consider only the immediate values of their arguments. For example,
212 when a file name is passed to Tk_GetCursor, Tk_GetCursor will assume it
213 is safe to re-use an existing cursor created from the same file name:
214 it will not check to see whether the file itself has changed, or
215 whether the current directory has changed, thereby causing the name to
216 refer to a different file. Similarly, Tk_GetCursorFromData assumes
217 that if the same source pointer is used in two different calls, then
218 the pointers refer to the same data; it does not check to see if the
219 actual data values have changed.
220
223 cursor
224Tk 8.1 Tk_AllocCursorFromObj(3)