The KeySym into which the KeyCode from the event was mapped is returned in the keysym_return argument if it is non-NULL and the status_return argument indicates that a KeySym was returned. If both a string and a KeySym are returned, the KeySym value does not necessarily correspond to the string returned.
XmbLookupString and Xutf8LookupString return the length of the string in bytes, and XwcLookupString returns the length of the string in characters. Both XmbLookupString and XwcLookupString return text in the encoding of the locale bound to the input method of the specified input context, and Xutf8LookupString returns text in UTF-8 encoding.
Each string returned by XmbLookupString and XwcLookupString begins in the initial state of the encoding of the locale (if the encoding of the locale is state-dependent).
To ensure proper input processing, it is essential that the client pass only KeyPress events to XmbLookupString, XwcLookupString and Xutf8LookupString. Their behavior when a client passes a KeyRelease event is undefined.
Clients should check the status_return argument before using the other returned values. These three functions each return a value to status_return that indicates what has been returned in the other arguments. The possible values returned are:
| XBufferOverflow |
The input string to be returned is too large for the supplied buffer_return.
The required size (for
XmbLookupString,
Xutf8LookupString
in bytes; for
XwcLookupString
in characters) is returned as the value of the function,
and the contents of buffer_return and keysym_return are not modified.
The client should recall the function with the same event
and a buffer of adequate size to obtain the string.
|
| XLookupNone |
No consistent input has been composed so far.
The contents of buffer_return and keysym_return are not modified,
and the function returns zero.
|
| XLookupChars |
Some input characters have been composed.
They are placed in the buffer_return argument, using the encoding
described above,
and the string length is returned as the value of the function.
The content of the keysym_return argument is not modified.
|
| XLookupKeySym |
A KeySym has been returned instead of a string
and is returned in keysym_return.
The content of the buffer_return argument is not modified,
and the function returns zero.
|
| XLookupBoth |
Both a KeySym and a string are returned;
XLookupChars
and
XLookupKeySym
occur simultaneously.
|
It does not make any difference if the input context passed as an argument to XmbLookupString, XwcLookupString and Xutf8LookupString is the one currently in possession of the focus or not. Input may have been composed within an input context before it lost the focus, and that input may be returned on subsequent calls to XmbLookupString, XwcLookupString or Xutf8LookupString even though it does not have any more keyboard focus.
The function Xutf8LookupString is an extension introduced by The XFree86 Project, Inc. in their 4.0.2 release. Its presence is indicated by the macro X_HAVE_UTF8_STRING.