NAME XGetWindowProperty, XListProperties, XChangeProperty, XRotateWindow‐
Properties, XDeleteProperty - obtain and change window properties SYNTAX int XGetWindowProperty(Display *display, Window w, Atom property, long longoffset, long longlength, Bool delete, Atom reqtype, Atom *actualtypereturn, int *actualformatreturn, unsigned long *nitemsreturn, unsigned long *bytesafterreturn, unsigned char **propreturn); Atom *XListProperties(Display *display, Window w, int *numpropreturn); 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 proper‐ ties[], int numprop, int npositions); int XDeleteProperty(Display *display, Window w, Atom property); ARGUMENTS actualformatreturn Returns the actual format of the property. actualtypereturn Returns the atom identifier that defines the actual type of the property. bytesafterreturn Returns the number of bytes remaining to be read in the prop‐ erty if a partial read was performed. data Specifies the property data. delete Specifies a Boolean value that determines whether the prop‐ erty 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 cor‐
rectly 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 XChange‐ Property. longlength
Specifies the length in 32-bit multiples of the data to be retrieved. longoffset
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 PropMod‐ eReplace, PropModePrepend, or PropModeAppend. nelements Specifies the number of elements of the specified data for‐ mat. nitemsreturn
Returns the actual number of 8-bit, 16-bit, or 32-bit items stored in the propreturn data. numprop Specifies the length of the properties array. numpropreturn Returns the length of the properties array. npositions Specifies the rotation amount. propreturn 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. reqtype 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 applica‐ tion 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 prop‐
erty; 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: · If the specified property does not exist for the specified window, XGetWindowProperty returns None to actualtypereturn and the value zero to actualformatreturn and bytesafterreturn. The nitemsreturn argument is empty. In this case, the delete argu‐ ment is ignored. · If the specified property exists but its type does not match the specified type, XGetWindowProperty returns the actual property type to actualtypereturn, the actual property format (never zero) to actualformatreturn, and the property length in bytes (even if the actualformatreturn is 16 or 32) to bytesafterreturn. It also ignores the delete argument. The nitemsreturn argument is empty. · If the specified property exists and either you assign AnyProper‐ tyType to the reqtype argument or the specified type matches the actual property type, XGetWindowProperty returns the actual prop‐ erty type to actualtypereturn and the actual property format (never zero) to actualformatreturn. It also returns a value to bytesafterreturn and nitemsreturn, by defining the following values: N = actual length of the stored property in bytes (even if the format is 16 or 32) I = 4 * longoffset
T = N - I L = MINIMUM(T, 4 * longlength)
A = N - (I + L) The returned value starts at byte index I in the property (index‐ ing from zero), and its length in bytes is L. If the value for longoffset causes L to be negative, a BadValue error results. The value of bytesafterreturn is A, giving the number of trail‐ ing 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 ele‐ ments. 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 propreturn (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 bytesafterreturn 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 func‐ tion, use XFree. XListProperties can generate a BadWindow error. The XChangeProperty function alters the property for the specified win‐ dow and causes the X server to generate a PropertyNotify event on that window. XChangeProperty performs 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 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. Proper‐ ties 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 depend‐ ing 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 numprop 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 nposi‐ tions, 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 win‐ dow, 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 X Version 11 libX11 1.6.5 XGetWindowProperty(3)