XGetWindowProperty man page

XGetWindowProperty, XListProperties, XChangeProperty, XRotateWindowProperties, XDeleteProperty — obtain and change window properties

Syntax

int XGetWindowProperty(Display *display, Window w, Atom property, 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 property, 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 property);

Arguments

actual_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 a list of 8-bit, 16-bit, or 32-bit quantities. Possible values are 8, 16, and 32. This information allows the X server to correctly perform byte-swap operations as necessary. If the format is 16-bit 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 (in 32-bit quantities)  where the data is to be retrieved.

mode

Specifies the mode of the operation. You can pass PropModeReplace, PropModePrepend, or PropModeAppend.

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 is represented as a char array. If the returned format is 16, the returned data is represented as a array of short int type and should be cast to that type to obtain the elements. If the returned format is 32, the property data will be stored as an array 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.

type

Specifies the type of the property. The X server does not interpret the type but simply passes it back to an application that later calls  XGetWindowProperty.

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 number of 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:

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 in prop_return  (even if the property is zero length)  and sets it to zero so that simple properties consisting of characters do not have to be copied into yet another string before use.

If delete is  True and bytes_after_return is zero,  XGetWindowProperty deletes the property  from the window and generates 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 the specified window and causes the X server to generate a PropertyNotify event on that window. XChangeProperty performs the following:

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 generate PropertyNotify events. If the property names in the properties array are viewed as being numbered  starting from zero and 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 all I 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 npositions). If npositions mod N is nonzero, the X server generates 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.

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.  Any argument defined as a set of alternatives can generate this error.

BadWindow

A value for a Window argument does not name a defined Window.

See Also

XFree(3), XInternAtom(3)
Xlib - C Language X Interface

Referenced By

XInternAtom(3), XPropertyEvent(3).

XChangeProperty(3), XDeleteProperty(3), XListProperties(3) and XRotateWindowProperties(3) are aliases of XGetWindowProperty(3).

libX11 1.6.4 X Version 11 XLIB FUNCTIONS