1XGetWindowProperty(3) XLIB FUNCTIONS XGetWindowProperty(3)
2
6 XGetWindowProperty, XListProperties, XChangeProperty, XRotateWindow‐
7 Properties, XDeleteProperty - obtain and change window properties
8
10 int XGetWindowProperty(Display *display, Window w, Atom property, long
11 long_offset, long long_length, Bool delete, Atom req_type, Atom
12 *actual_type_return, int *actual_format_return, unsigned long
13 *nitems_return, unsigned long *bytes_after_return, unsigned char
14 **prop_return);
15 Atom *XListProperties(Display *display, Window w, int *num_prop_re‐
17 turn);
18 int XChangeProperty(Display *display, Window w, Atom property, Atom
20 type, int format, int mode, _Xconst unsigned char *data, int
21 nelements);
22 int XRotateWindowProperties(Display *display, Window w, Atom proper‐
24 ties[], int num_prop, int npositions);
25 int XDeleteProperty(Display *display, Window w, Atom property);
27
29 actual_format_return
30 Returns the actual format of the property.
31 actual_type_return
33 Returns the atom identifier that defines the actual type of
34 the property.
35 bytes_after_return
37 Returns the number of bytes remaining to be read in the prop‐
38 erty if a partial read was performed.
39 data Specifies the property data.
41 delete Specifies a Boolean value that determines whether the prop‐
43 erty is deleted.
44 display Specifies the connection to the X server.
46 format Specifies whether the data should be viewed as a list of
48 8-bit, 16-bit, or 32-bit quantities. Possible values are 8,
49 16, and 32. This information allows the X server to cor‐
50 rectly perform byte-swap operations as necessary. If the
51 format is 16-bit or 32-bit, you must explicitly cast your
52 data pointer to an (unsigned char *) in the call to XChange‐
53 Property.
54 long_length
56 Specifies the length in 32-bit multiples of the data to be
57 retrieved.
58 long_offset
60 Specifies the offset in the specified property (in 32-bit
61 quantities) where the data is to be retrieved.
62 mode Specifies the mode of the operation. You can pass PropMod‐
64 eReplace, PropModePrepend, or PropModeAppend.
65 nelements Specifies the number of elements of the specified data for‐
67 mat.
68 nitems_return
70 Returns the actual number of 8-bit, 16-bit, or 32-bit items
71 stored in the prop_return data.
72 num_prop Specifies the length of the properties array.
74 num_prop_return
76 Returns the length of the properties array.
77 npositions
79 Specifies the rotation amount.
80 prop_return
82 Returns the data in the specified format. If the returned
83 format is 8, the returned data is represented as a char ar‐
84 ray. If the returned format is 16, the returned data is rep‐
85 resented as a array of short int type and should be cast to
86 that type to obtain the elements. If the returned format is
87 32, the property data will be stored as an array of longs
88 (which in a 64-bit application will be 64-bit values that are
89 padded in the upper 4 bytes).
90 property Specifies the property name.
92 properties
94 Specifies the array of properties that are to be rotated.
95 req_type Specifies the atom identifier associated with the property
97 type or AnyPropertyType.
98 type Specifies the type of the property. The X server does not
100 interpret the type but simply passes it back to an applica‐
101 tion that later calls XGetWindowProperty.
102 w Specifies the window whose property you want to obtain,
104 change, rotate or delete.
105
107 The XGetWindowProperty function returns the actual type of the prop‐
108 erty; the actual format of the property; the number of 8-bit, 16-bit,
109 or 32-bit items transferred; the number of bytes remaining to be read
110 in the property; and a pointer to the data actually returned. XGetWin‐
111 dowProperty sets the return arguments as follows:
112 • If the specified property does not exist for the specified window,
114 XGetWindowProperty returns None to actual_type_return and the
115 value zero to actual_format_return and bytes_after_return. The
116 nitems_return argument is empty. In this case, the delete argu‐
117 ment is ignored.
118 • If the specified property exists but its type does not match the
120 specified type, XGetWindowProperty returns the actual property
121 type to actual_type_return, the actual property format (never
122 zero) to actual_format_return, and the property length in bytes
123 (even if the actual_format_return is 16 or 32) to bytes_after_re‐
124 turn. It also ignores the delete argument. The nitems_return ar‐
125 gument is empty.
126 • If the specified property exists and either you assign AnyProper‐
128 tyType to the req_type argument or the specified type matches the
129 actual property type, XGetWindowProperty returns the actual prop‐
130 erty type to actual_type_return and the actual property format
131 (never zero) to actual_format_return. It also returns a value to
132 bytes_after_return and nitems_return, by defining the following
133 values:
134 N = actual length of the stored property in bytes
136 (even if the format is 16 or 32)
137 I = 4 * long_offset
138 T = N - I
139 L = MINIMUM(T, 4 * long_length)
140 A = N - (I + L)
141 The returned value starts at byte index I in the property (index‐
143 ing from zero), and its length in bytes is L. If the value for
144 long_offset causes L to be negative, a BadValue error results.
145 The value of bytes_after_return is A, giving the number of trail‐
146 ing unread bytes in the stored property.
147 If the returned format is 8, the returned data is represented as a char
149 array. If the returned format is 16, the returned data is represented
150 as a short array and should be cast to that type to obtain the ele‐
151 ments. If the returned format is 32, the returned data is represented
152 as a long array and should be cast to that type to obtain the elements.
153 XGetWindowProperty always allocates one extra byte in prop_return (even
155 if the property is zero length) and sets it to zero so that simple
156 properties consisting of characters do not have to be copied into yet
157 another string before use.
158 If delete is True and bytes_after_return is zero, XGetWindowProperty
160 deletes the property from the window and generates a PropertyNotify
161 event on the window.
162 The function returns Success if it executes successfully. To free the
164 resulting data, use XFree.
165 XGetWindowProperty can generate BadAtom, BadValue, and BadWindow er‐
167 rors.
168 The XListProperties function returns a pointer to an array of atom
170 properties that are defined for the specified window or returns NULL if
171 no properties were found. To free the memory allocated by this func‐
172 tion, use XFree.
173 XListProperties can generate a BadWindow error.
175 The XChangeProperty function alters the property for the specified win‐
177 dow and causes the X server to generate a PropertyNotify event on that
178 window. XChangeProperty performs the following:
179 • If mode is PropModeReplace, XChangeProperty discards the previous
181 property value and stores the new data.
182 • If mode is PropModePrepend or PropModeAppend, XChangeProperty in‐
184 serts the specified data before the beginning of the existing data
185 or onto the end of the existing data, respectively. The type and
186 format must match the existing property value, or a BadMatch error
187 results. If the property is undefined, it is treated as defined
188 with the correct type and format with zero-length data.
189 If the specified format is 8, the property data must be a char array.
191 If the specified format is 16, the property data must be a short array.
192 If the specified format is 32, the property data must be a long array.
193 The lifetime of a property is not tied to the storing client. Proper‐
195 ties remain until explicitly deleted, until the window is destroyed, or
196 until the server resets. For a discussion of what happens when the
197 connection to the X server is closed, see section 2.6. The maximum
198 size of a property is server dependent and can vary dynamically depend‐
199 ing on the amount of memory the server has available. (If there is in‐
200 sufficient space, a BadAlloc error results.)
201 XChangeProperty can generate BadAlloc, BadAtom, BadMatch, BadValue, and
203 BadWindow errors.
204 The XRotateWindowProperties function allows you to rotate properties on
206 a window and causes the X server to generate PropertyNotify events. If
207 the property names in the properties array are viewed as being numbered
208 starting from zero and if there are num_prop property names in the
209 list, then the value associated with property name I becomes the value
210 associated with property name (I + npositions) mod N for all I from
211 zero to N - 1. The effect is to rotate the states by npositions places
212 around the virtual ring of property names (right for positive nposi‐
213 tions, left for negative npositions). If npositions mod N is nonzero,
214 the X server generates a PropertyNotify event for each property in the
215 order that they are listed in the array. If an atom occurs more than
216 once in the list or no property with that name is defined for the win‐
217 dow, a BadMatch error results. If a BadAtom or BadMatch error results,
218 no properties are changed.
219 XRotateWindowProperties can generate BadAtom, BadMatch, and BadWindow
221 errors.
222 The XDeleteProperty function deletes the specified property only if the
224 property was defined on the specified window and causes the X server to
225 generate a PropertyNotify event on the window unless the property does
226 not exist.
227 XDeleteProperty can generate BadAtom and BadWindow errors.
229
231 BadAlloc The server failed to allocate the requested resource or
232 server memory.
233 BadAtom A value for an Atom argument does not name a defined Atom.
235 BadValue Some numeric value falls outside the range of values accepted
237 by the request. Unless a specific range is specified for an
238 argument, the full range defined by the argument's type is
239 accepted. Any argument defined as a set of alternatives can
240 generate this error.
241 BadWindow A value for a Window argument does not name a defined Window.
243
245 XFree(3), XInternAtom(3)
246 Xlib - C Language X Interface
247X Version 11 libX11 1.7.3.1 XGetWindowProperty(3)