xchangeproperty(3) [hpux man page]
XChangeProperty() XChangeProperty()
Name
XChangeProperty - change a property associated with a window.
Synopsis
XChangeProperty(display, w, property, type, format, mode, data, nelements)
Display *display;
Window w;
Atom property, type;
int format;
int mode;
unsigned char *data;
int nelements;
Arguments
display Specifies a connection to an X server; returned from XOpenDisplay().
w Specifies the ID of the window whose property you want to change.
property Specifies the property atom.
type Specifies the type of the property. X does not interpret the type, but simply passes it back to an application that later calls
XGetWindowProperty.
format Specifies whether the data should be viewed as a list of 8-bit, 16-bit, or 32-bit quantities. 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 a (char *) in the call to XChangeProperty(). Possible values are 8, 16, and 32.
mode Specifies the mode of the operation. Possible values are PropModeReplace, PropModePrepend, PropModeAppend.
data Specifies the property data.
nelements Specifies the number of elements in the property.
Description
XChangeProperty() changes a property and generates PropertyNotify events if they have been selected.
XChangeProperty() does the following according to the mode argument:
o PropModeReplace
Discards the previous property value and stores the new data.
o PropModePrepend
Inserts the data before the beginning of the existing data. If the property is undefined, it is treated as defined with the correct
type and format with zero-length data. type and format arguments must match the existing property value; otherwise a BadMatch error
occurs.
o PropModeAppend
Appends the data onto the end of the existing data. If the property is undefined, it is treated as defined with the correct type and
format with zero-length data. type and format arguments must match the existing property value; otherwise a BadMatch error occurs.
The property may remain defined even after the client which defined it exits. The property becomes undefined only if the application calls
XDeleteProperty(), destroys the specified window, or closes the last connection to the X server.
The maximum size of a property is server-dependent and can vary dynamically if the server has insufficient memory.
For more information, see Volume One, Chapter 12, Interclient Communication.
Errors
BadAlloc
BadAtom
BadMatch
BadValue
BadWindow
See Also
XDeleteProperty(), XGetAtomName(), XGetFontProperty(), XGetWindowProperty(), XInternAtom(), XListProperties(), XRotateWindowProperties(),
XSetStandardProperties().
Xlib - Properties XChangeProperty()
Check Out this Related Man Page
XGetWindowProperty(3X11) XLIB FUNCTIONS XGetWindowProperty(3X11)
NAME
XGetWindowProperty, XListProperties, XChangeProperty, XRotateWindowProperties, XDeleteProperty - obtain and change window properties
SYNTAX
int XGetWindowProperty(display, w, property, long_offset, long_length, delete, req_type,
actual_type_return, actual_format_return, nitems_return, bytes_after_return,
prop_return)
Display *display;
Window w;
Atom property;
long long_offset, 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, w, num_prop_return)
Display *display;
Window w;
int *num_prop_return;
XChangeProperty(display, w, property, type, format, mode, data, nelements)
Display *display;
Window w;
Atom property, type;
int format;
int mode;
unsigned char *data;
int nelements;
XRotateWindowProperties(display, w, properties, num_prop, npositions)
Display *display;
Window w;
Atom properties[];
int num_prop;
int npositions;
XDeleteProperty(display, w, property)
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.
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. XGetWin-
dowProperty sets the return arguments as follows:
o If the specified property does not exist for the specified window, XGetWindowProperty returns None to actual_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 returns the actual property type
to actual_type_return, the actual property format (never zero) to actual_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 argument. The nitems_return argument is empty.
o If the specified property exists and either you assign AnyPropertyType to the req_type argument or the specified type matches the
actual property type, XGetWindowProperty returns the actual property type to actual_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 property (indexing from zero), and its length in bytes is L. If the value for
long_offset causes L to be negative, a BadValue error results. The value of bytes_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 repre-
sented 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 repre-
sented 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:
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 treated as defined with the correct type and format with zero-length data.
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 argu-
ment, 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(3X11), XInternAtom(3X11)
Xlib - C Language X Interface
X Version 11 Release 6.6 XGetWindowProperty(3X11)