Re: Event mechanisms for GUI's

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 26 Sep 2006 10:28:04 -0700, Lucretia wrote:

[...]
> So, there would possibly be 3 types: observer (abstract tagged),
> subject (tagged), listener (interface). Then the control (e.g. a
> window) would then have to implement an "Add_<whatever>_Listener" per
> event type, which would add a <whatever>_Listener to a
> <whatever>_Observer. Seems overly complex to me.

The mechanisms themselves are not so important as composability of.
Messages are not, as Windows perfectly illustrates. Events are even less. 

And if publisher/subscriber looks too complex to you, then, well, the thing
you have described as complex is in fact just an oversimplification of what
really needed. Consider bidirectional publisher/subscriber relations, data
consistency, timing constraints issues, etc.

Also don't forget about clean separation of actions and notifications.
Button_Click vs. On_Button_Click. Hierarchy of events (Hover_Event vs.
Mouse_Move) and actions.

The bottom line, it is not simple.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de