Hooks into the Library
These functions allow you to define procedures that are to be
called when various circumstances occur.
The procedures include the creation of a new GC for a connection,
the copying of a GC, the freeing of a GC, the creating and freeing of fonts,
the conversion of events defined by extensions to and from wire
format, and the handling of errors.
All of these functions return the previous procedure defined for this
extension.
To define a procedure to be called whenever
XCloseDisplay()
is called, use
XESetCloseDisplay().
To define a procedure to be called whenever a new GC is created, use
XESetCreateGC().
To define a procedure to be called whenever a GC is copied, use
XESetCopyGC().
To define a procedure to be called whenever a GC is freed, use
XESetFreeGC().
To define a procedure to be called whenever
XLoadQueryFont()
and
XQueryFont()
are called, use
XESetCreateFont().
To define a procedure to be called whenever a font is freed, use
XESetFreeFont().
The
XESetWireToEvent()
and
XESetEventToWire()
functions allow you to define new events to the library.
An
XEvent
structure always has a type code (type
int)
as the first component.
This uniquely identifies what kind of event it is.
The second component is always the serial number (type
unsigned
long)
of the last request processed by the server.
The third component is always a Boolean (type
Bool)
indicating whether the event came from a
SendEvent
protocol request.
The fourth component is always a pointer to the display
the event was read from.
The fifth component is always a resource ID of one kind or another,
usually a window, carefully selected to be useful to toolkit dispatchers.
The fifth component should always exist, even if
the event does not have a natural destination;
if there is no value
from the protocol to put in this component, initialize it to zero.
Note
There is an implementation limit such that your host event
structure size cannot be bigger than the size of the
XEvent
union of structures.
There also is no way to guarantee that more than 24 elements or 96 characters
in the structure will be fully portable between machines.
To initialize the serial number component of the event, call
_XSetLastRequestRead()
with the event and use the return value.
To define a procedure to be called whenever an extension error needs to be
converted from wire format to host format, use
XESetWireToError().
To install an error procedure, use
XESetError().
To define a procedure to be called to define an error message, use
XESetErrorString().
To define a procedure to be called when an extension error is printed,
to print the error value, use
XESetPrintErrorValues().
To define a procedure to be called whenever a GC cache
needs to be updated in the server, use
XESetFlushGC().
To define a procedure to be called whenever data is about to be sent
to the server, use
XESetBeforeFlush().
Christophe Tronche, [email protected]
