Manual pages › X Window and screen libraries (3X)
XGetWProp(3X)
obtain and change window properties
From the original Amiga UNIX 2.1 manual. Some things it mentions may not be in this release.
NAME · SYNTAX · ARGUMENTS · DESCRIPTION · DIAGNOSTICS · SEE ALSO
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;
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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 XWIN server.
format Specifies whether the data should be viewed as a
list of 8-bit, 16-bit, or 32-bit quantities. Pos-
sible values are 8, 16, and 32. This information
allows the XWIN 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.
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.
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npositions
Specifies the rotation amount.
prop_return
Returns a pointer to 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 XWIN
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 specified property does not exist for the speci-
fied 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.
• 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 argu-
ment. The nitems_return argument is empty.
• If the specified property exists and either you assign
AnyPropertyType to the req_type argument or the speci-
fied type matches the actual property type, XGetWin-
dowProperty returns the actual property type to
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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 pro-
perty (indexing from zero), and its length in bytes is
L. If the value for long_offset causes L to be nega-
tive, a BadValue error results. The value of
bytes_after_return is A, giving the number of trailing
unread bytes in the stored property.
XGetWindowProperty always allocates one extra byte in
prop_return (even if the property is zero length) and sets
it to ASCII null 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 win-
dow 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 XWIN server to generate a
PropertyNotify event on that window. XChangeProperty per-
forms the following:
• If mode is PropModeReplace, XChangeProperty discards
the previous property value and stores the new data.
• If mode is PropModePrepend or PropModeAppend,
XChangeProperty inserts the specified data before the beginning of the existing data or onto the end of the
XWIN 3.0 Last change: 9/1/88 .ie t 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.
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 XWIN server is closed, see section 2.5, Xlib-C Language X Inter- face. 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 XWIN server to gen- erate 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 pro- perty names (right for positive npositions, left for nega- tive npositions). If npositions mod N is nonzero, the XWIN 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 XWIN 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
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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
XInternAtom(3X11)
Xlib - C Language X Interface
XWIN 3.0 Last change: 9/1/88 .ie t
XWIN 3.0 Last change: 9/1/88 .ie t