1xcb_get_property(3) XCB Requests xcb_get_property(3)
2
6 xcb_get_property - Gets a window property
7
9 #include <xcb/xproto.h>
10 Request function
12 xcb_get_property_cookie_t xcb_get_property(xcb_connection_t *conn,
13 uint8_t _delete, xcb_window_t window, xcb_atom_t property,
14 xcb_atom_t type, uint32_t long_offset, uint32_t long_length);
15 Reply datastructure
17 typedef struct xcb_get_property_reply_t {
18 uint8_t response_type;
19 uint8_t format;
20 uint16_t sequence;
21 uint32_t length;
22 xcb_atom_t type;
23 uint32_t bytes_after;
24 uint32_t value_len;
25 uint8_t pad0[12];
26 } xcb_get_property_reply_t;
27 Reply function
29 xcb_get_property_reply_t
30 *xcb_get_property_reply(xcb_connection_t *conn,
31 xcb_get_property_cookie_t cookie, xcb_generic_error_t **e);
32 Reply accessors
34 void *xcb_get_property_value(const xcb_get_property_request_t *reply);
35 int xcb_get_property_value_length(const xcb_get_property_reply_t
37 *reply);
38 xcb_generic_iterator_t xcb_get_property_value_end(const
40 xcb_get_property_reply_t *reply);
41
43 conn The XCB connection to X11.
44 _delete Whether the property should actually be deleted. For deleting
46 a property, the specified type has to match the actual prop‐
47 erty type.
48 window The window whose property you want to get.
50 property The property you want to get (an atom).
52 type The type of the property you want to get (an atom).
54 long_offset
56 Specifies the offset (in 32-bit multiples) in the specified
57 property where the data is to be retrieved.
58 long_length
60 Specifies how many 32-bit multiples of data should be re‐
61 trieved (e.g. if you set long_length to 4, you will receive
62 16 bytes of data).
63
65 response_type
66 The type of this reply, in this case XCB_GET_PROPERTY. This
67 field is also present in the xcb_generic_reply_t and can be
68 used to tell replies apart from each other.
69 sequence The sequence number of the last request processed by the X11
71 server.
72 length The length of the reply, in words (a word is 4 bytes).
74 format Specifies whether the data should be viewed as a list of
76 8-bit, 16-bit, or 32-bit quantities. Possible values are 8,
77 16, and 32. This information allows the X server to correctly
78 perform byte-swap operations as necessary.
79 type The actual type of the property (an atom).
81 bytes_after
83 The number of bytes remaining to be read in the property if a
84 partial read was performed.
85 value_len The length of value. You should use the corresponding acces‐
87 sor instead of this field.
88
90 Gets the specified property from the specified window. Properties are
91 for example the window title (WM_NAME) or its minimum size (WM_NOR‐
92 MAL_HINTS). Protocols such as EWMH also use properties - for example
93 EWMH defines the window title, encoded as UTF-8 string, in the
94 _NET_WM_NAME property.
95 TODO: talk about type
97 TODO: talk about delete
99 TODO: talk about the offset/length thing. what's a valid use case?
101
103 Returns an xcb_get_property_cookie_t. Errors have to be handled when
104 calling the reply function xcb_get_property_reply.
105 If you want to handle errors in the event loop instead, use
107 xcb_get_property_unchecked. See xcb-requests(3) for details.
108
110 xcb_atom_error_t
111 property or type do not refer to a valid atom.
112 xcb_value_error_t
114 The specified long_offset is beyond the actual property
115 length (e.g. the property has a length of 3 bytes and you are
116 setting long_offset to 1, resulting in a byte offset of 4).
117 xcb_window_error_t
119 The specified window does not exist.
120
122 /*
123 * Prints the WM_NAME property of the window.
124 *
125 */
126 void my_example(xcb_connection_t *c, xcb_window_t window) {
127 xcb_get_property_cookie_t cookie;
128 xcb_get_property_reply_t *reply;
129 /* These atoms are predefined in the X11 protocol. */
131 xcb_atom_t property = XCB_ATOM_WM_NAME;
132 xcb_atom_t type = XCB_ATOM_STRING;
133 // TODO: a reasonable long_length for WM_NAME?
135 cookie = xcb_get_property(c, 0, window, property, type, 0, 0);
136 if ((reply = xcb_get_property_reply(c, cookie, NULL))) {
137 int len = xcb_get_property_value_length(reply);
138 if (len == 0) {
139 printf("TODO\n");
140 free(reply);
141 return;
142 }
143 printf("WM_NAME is %.*s\n", len,
144 (char*)xcb_get_property_value(reply));
145 }
146 free(reply);
147 }
148
150 xcb-requests(3), xcb-examples(3), xcb_intern_atom(3), xprop(1)
151
153 Generated from xproto.xml. Contact xcb@lists.freedesktop.org for cor‐
154 rections and improvements.
155X Version 11 libxcb 1.12 xcb_get_property(3)