An
OpenAlias class that allows a plug-in to detect selected Alias events.
Synopsis
#include <AlObserver.h>
class AlObserver
enum ObserverMessage
{kMaximizeWindow,
kMinimizeWindow,
kLowerWindow,
kRaiseWindow,
};
static statusCode create();
static statusCode deleteObject();
static statusCode installHandler( ObserverMessage, void (*)(void) );
static statusCode removeHandler( ObserverMessage, void (*)(void) );
Description
AlObserver is a static
OpenAlias class. Currently, it allows a user to detect when the Alias window
is minimized, maximized, lowered or raised. This class cannot trap
events that are handled by the Window Manager.
An example of an event
that cannot be trapped is the raising of a window by clicking on its
window bar. However, this situation can be detected by an X-event
handler installed by the AlXevents class, so to test if a window
is below the Alias window on ConfigureNotify events use the
method AlXevents::belowAliasWindow().
statusCode AlObserver::create()
Description
Initializes
the API observer class. Note that this method should always be called
by a plug-in that wants to observe events. If the observer class
is already initialized, this routine will return successfully.
Return Codes
sSuccess - the method
succeeded
sFailure - the method
failed
statusCode AlObserver::deleteObject()
Description
Terminates
the observation of events if there are no handlers installed. This
allows several plug-ins loaded into Alias to call deleteObject().
The observer is not removed until the last plug-in has removed its
handlers and called this routine.
Return Codes
sSuccess - the method
succeeded
sFailure - the method
failed. There may be handlers still installed.
sInvalidObject - the
observer has not been initialized; call AlObserver::create()
statusCode AlObserver::installHandler(
ObserverMessage observerType, void (*function)(void) )
Description
Installs
a callback handler for a specific observerType.
Arguments
< observerType - one
of kMaximizeWindow, kMinimizeWindow, kLowerWindow, kRaiseWindow
< function - pointer
to a void function
Return Codes
sSuccess - the method
succeeded
sFailure - the method
failed or the observer type was invalid
sInvalidObject - the
observer has not been initialized; call AlObserver::create()
sInvalidArgument - function
parameter was NULL
statusCode AlObserver::removeHandler(
ObserverMessage observerType, void (*function)(void) )
Description
Removes
a callback handler for a specific observer type. Plug-ins must
properly remove observer handlers to avoid Alias calling a
routine that no longer exists in memory.
Arguments
< observerType - one
of kMaximizeWindow, kMinimizeWindow, kLowerWindow, kRaiseWindow
< function - pointer
to a void function
Return Codes
sSuccess - the method
succeeded
sFailure - the method
failed or the observer type was invalid
sInvalidObject - the
observer has not been initialized; call AlObserver::create()
