[platform-swt-dev] Efficient eventHandlers in a subclass

[Mauk van der Laan <mauk@xxxxxxxxxxxx>]

Hi,

I create a lot of Composite or Canvas subclasses. To be able to handle 
their events,
the following code is used:

class X extends Canvas implements Listener {
   X() {
       ...
       addListener(SWT.Paint, this);
       addListener(SWT.MouseMove,this);
       ... lots more
   }
   public void handleEvent(Event e) {
       switch(e.type) {
       case SWT.Paint:   
           onPaint();
           break;
       ... etc


This is too 'heavy' in my opinion: each component has a big EventTable 
and must do a lookup
for every event, only to send it to the same handleEvent() method where 
it is tested again
by the switch.

It would be better to override some public method, the eventTable would 
be empty that way
(unless another component registers). The problem is that 
Widget.sendEvent() isn't public.

To make this possible, i propose one of the following changes:
- make Widget.sendEvent() public,
- let it call a new public method 'handleAllEvents()' before it does the 
EventTable lookup
- create a special 'catch-all' event constant like SWT.AllEvents which 
is checked in 
EventTable.sendEvent() to that it sends all events to a handler that is 
registered with
that constant.

Regards,
Mauk