XLIB FUNCTIONS XGetWindowProperty(3x11)
NAME
XGetWindowProperty, XListProperties, XChangeProperty, XRota-
teWindowProperties, XDeleteProperty - obtain and change win-
dow properties SYNTAXcc [ flag... ] file... -lX11 [ library... ]
int XGetWindowProperty(Display *display, Window w, Atom pro-
perty, long long_offset, long long_length, Bool delete,
Atom req_type, Atom *actual_type_return, int
*actual_format_return, unsigned long *nitems_return,
unsigned long *bytes_after_return, unsigned char
**prop_return);
Atom *XListProperties(Display *display, Window w, int*num_prop_return);
int XChangeProperty(Display *display, Window w, Atom pro-
perty, Atom type, int format, int mode, unsigned char *data, int nelements);int XRotateWindowProperties(Display *display, Window w, Atom
properties[], int num_prop, int npositions);
int XDeleteProperty(Display *display, Window w, Atom pro-
perty); ARGUMENTSactual_format_return
Returns the actual format of the property.actual_type_return
Returns the atom identifier that defines the actual type of the property.bytes_after_return
Returns the number of bytes remaining to be read in the property if a partial read was performed. data Specifies the property data. delete Specifies a Boolean value that determines whether the property is deleted. display Specifies the connection to the X server. format Specifies whether the data should be viewed as alist of 8-bit, 16-bit, or 32-bit quantities. Pos-
sible values are 8, 16, and 32. This informationallows the X server to correctly perform byte-swap
operations as necessary. If the format is 16-bit
X Version 11 Last change: libX11 1.3.5 1 XLIB FUNCTIONS XGetWindowProperty(3x11)or 32-bit, you must explicitly cast your data
pointer to an (unsigned char *) in the call to XChangeProperty.long_length
Specifies the length in 32-bit multiples of the
data to be retrieved.long_offset
Specifies the offset in the specified property (in32-bit quantities) where the data is to be
retrieved. mode Specifies the mode of the operation. You can passPropModeReplace, PropModePrepend, or PropModeAp-
pend. nelements Specifies the number of elements of the specified data format.nitems_return
Returns the actual number of 8-bit, 16-bit, or
32-bit items stored in the prop_return data.
num_prop Specifies the length of the properties array.
num_prop_return
Returns the length of the properties array. npositions Specifies the rotation amount.prop_return
Returns the data in the specified format. If the returned format is 8, the returned data isrepresented as a char array. If the returned for-
mat is 16, the returned data is represented as a array of short int type and should be cast to thattype to obtain the elements. If the returned for-
mat is 32, the property data will be stored as anarray of longs (which in a 64-bit application will
be 64-bit values that are padded in the upper 4
bytes). property Specifies the property name. properties Specifies the array of properties that are to be rotated.req_type Specifies the atom identifier associated with the
property type or AnyPropertyType. X Version 11 Last change: libX11 1.3.5 2 XLIB FUNCTIONS XGetWindowProperty(3x11) type Specifies the type of the property. The X server does not interpret the type but simply passes itback to an application that later calls XGetWin-
dowProperty. w Specifies the window whose property you want to obtain, change, rotate or delete.DESCRIPTION
The XGetWindowProperty function returns the actual type of the property; the actual format of the property; the numberof 8-bit, 16-bit, or 32-bit items transferred; the number of
bytes remaining to be read in the property; and a pointer to the data actually returned. XGetWindowProperty sets the return arguments as follows:+o If the specified property does not exist for the speci-
fied window, XGetWindowProperty returns None toactual_type_return and the value zero to
actual_format_return and bytes_after_return. The
nitems_return argument is empty. In this case, the
delete argument is ignored. +o If the specified property exists but its type does not match the specified type, XGetWindowProperty returnsthe actual property type to actual_type_return, the
actual property format (never zero) toactual_format_return, and the property length in bytes
(even if the actual_format_return is 16 or 32) to
bytes_after_return. It also ignores the delete argu-
ment. The nitems_return argument is empty.
+o If the specified property exists and either you assignAnyPropertyType to the req_type argument or the speci-
fied type matches the actual property type, XGetWin-
dowProperty returns the actual property type toactual_type_return and the actual property format
(never zero) to actual_format_return. It also returns a
value to bytes_after_return and nitems_return, by
defining the following values: N = actual length of the stored property in bytes (even if the format is 16 or 32)I = 4 * long_offset
T = N - I
L = MINIMUM(T, 4 * long_length)
A = N - (I + L)
The returned value starts at byte index I in the pro-
perty (indexing from zero), and its length in bytes isL. If the value for long_offset causes L to be
X Version 11 Last change: libX11 1.3.5 3 XLIB FUNCTIONS XGetWindowProperty(3x11) negative, a BadValue error results. The value ofbytes_after_return is A, giving the number of trailing
unread bytes in the stored property. If the returned format is 8, the returned data is represented as a char array. If the returned format is 16, the returned data is represented as a short array and should be cast to that type to obtain the elements. If the returned format is 32, the returned data is represented as a long array and should be cast to that type to obtain the elements. XGetWindowProperty always allocates one extra byte inprop_return (even if the property is zero length) and sets
it to zero so that simple properties consisting of charac-
ters do not have to be copied into yet another string before use.If delete is True and bytes_after_return is zero, XGetWin-
dowProperty deletes the property from the window and gen-
erates a PropertyNotify event on the window. The function returns Success if it executes successfully. To free the resulting data, use XFree. XGetWindowProperty can generate BadAtom, BadValue, and BadWindow errors. The XListProperties function returns a pointer to an array of atom properties that are defined for the specified window or returns NULL if no properties were found. To free the memory allocated by this function, use XFree. XListProperties can generate a BadWindow error. The XChangeProperty function alters the property for thespecified window and causes the X server to generate a Pro-
pertyNotify event on that window. XChangeProperty performs the following: +o If mode is PropModeReplace, XChangeProperty discards the previous property value and stores the new data. +o If mode is PropModePrepend or PropModeAppend, XChangeProperty inserts the specified data before the beginning of the existing data or onto the end of the existing data, respectively. The type and format must match the existing property value, or a BadMatch error results. If the property is undefined, it is treatedas defined with the correct type and format with zero-
length data. X Version 11 Last change: libX11 1.3.5 4 XLIB FUNCTIONS XGetWindowProperty(3x11) If the specified format is 8, the property data must be a char array. If the specified format is 16, the property data must be a short array. If the specified format is 32, the property data must be a long array. The lifetime of a property is not tied to the storing client. Properties remain until explicitly deleted, until the window is destroyed, or until the server resets. For a discussion of what happens when the connection to the X server is closed, see section 2.6. The maximum size of a property is server dependent and can vary dynamically depending on the amount of memory the server has available. (If there is insufficient space, a BadAlloc error results.) XChangeProperty can generate BadAlloc, BadAtom, BadMatch, BadValue, and BadWindow errors.The XRotateWindowProperties function allows you to rotate
properties on a window and causes the X server to generatePropertyNotify events. If the property names in the proper-
ties array are viewed as being numbered starting from zeroand if there are num_prop property names in the list, then
the value associated with property name I becomes the value associated with property name (I + npositions) mod N for allI from zero to N - 1. The effect is to rotate the states by
npositions places around the virtual ring of property names(right for positive npositions, left for negative nposi-
tions). If npositions mod N is nonzero, the X server gen-
erates a PropertyNotify event for each property in the order that they are listed in the array. If an atom occurs more than once in the list or no property with that name is defined for the window, a BadMatch error results. If a BadAtom or BadMatch error results, no properties are changed.XRotateWindowProperties can generate BadAtom, BadMatch, and
BadWindow errors. The XDeleteProperty function deletes the specified property only if the property was defined on the specified window and causes the X server to generate a PropertyNotify event on the window unless the property does not exist. XDeleteProperty can generate BadAtom and BadWindow errors. DIAGNOSTICS BadAlloc The server failed to allocate the requested resource or server memory. BadAtom A value for an Atom argument does not name a defined Atom. X Version 11 Last change: libX11 1.3.5 5 XLIB FUNCTIONS XGetWindowProperty(3x11) BadValue Some numeric value falls outside the range of values accepted by the request. Unless a specific range is specified for an argument, the full range defined by the argument's type is accepted. Anyargument defined as a set of alternatives can gen-
erate this error. BadWindow A value for a Window argument does not name a defined Window.SEE ALSO
XFree(3x11), XInternAtom(3x11)Xlib - C Language X Interface
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | x11/library/libx11 ||_____________________________|_____________________________|
| Interface Stability | Committed ||_____________________________|_____________________________|
| MT-Level | See XInitThreads(3X11) |
|_____________________________|_____________________________|
X Version 11 Last change: libX11 1.3.5 6