On Tue, Aug 07, 2001 at 08:43:37AM -0700, Andreas Raab wrote:
> Josh,
> 
> > However, I can't figure out how to get access to
> > mouseEnter/Leave events without generating my own
> > by watching when and where mouseOver events happen.
> > It seems that the processEvent:using: hook just provides
> > access to the raw hardware input events, and not to
> > events that are subsequently derived from
> > these events.  Is this correct?
> 
> Almost. Enter/leave events are generated based on which morphs the hand is
> currently "over". This is determined by sending mouse over events which are
> handled by morphs in such a way that they tell the hand if the event ends up
> inside. Based on this information, the hand sends enter/leave events
> directly to those morphs. 

Yes, this was my understanding after reading the code.

> Note that we really can't go through the event
> dispatcher here - we need to figure out what has changed since the last
> mouse position which is different from just delivering an event to the right
> receiver.

Perhaps I'm a bit confused about the intended purpose of the hook
provided by processEvent:using:

> > Can anyone with experience with custom event handlers suggest
> > another way?
> 
> For what? I don't quite see how one would reasonably implement a dispatch
> strategy for enter/leave. I'm also a bit confused about the subject of your
> message - what you're describing in the above means you're changing the way
> events are dispatched (e.g., delivered); not how they are handled. Perhaps
> you can explain what you're trying to achieve?!

Your confusion is entirely based on my confusion.

I'm implementing a drawing app where there are multiple 'tools'
available, one of which is active at any given time.  Depending on the
tool selected, mouse actions have different effects.  For example, if
the 'selection' tool is active, clicking on a morph will toggle
whether it is selected.  If the 'delete' tool is active, clicking on a
morph will delete it (and possibly other morphs in its group).

One reason that I care about mouseEnter/Leave is that I want all
morphs in a group to be highlighted whenever the pointer enters any
morph in the group.

An alternate approach that I discarded involved installing my own
event handlers.  In effect, edited morphs would be told: "Whenever the
mouse enters or leaves you, tell the drawing app and let it decide
what to do."  This is problematic because I might want to edit the
graphical properties of morphs that already have their own event
handlers.

I suppose that I could hack EventHandler so that each event type is
associated with a collection of target/selector/argument tuples,
instead of a single one.  #on:send:to would then add the tuple to
the event handler instead of replacing it.

Does this sound reasonable?  Do you have another suggestion?

Thanks,
Joshua


> 
> Cheers,
>   - Andreas
> 
>