Inappropriate Interface Behaviour during mouseDown

Igor de Oliveira Couto info at
Mon Nov 18 17:23:01 EST 2002

Dear Rob,

Thank you for your feedback!

On Tuesday, November 19, 2002, at 02:46  AM, Rob Cozens wrote:

>> Similarly, if a user presses a mouse button OUTSIDE a clickable area, 
>> and then moves the cursor OVER a clickable area, then the clickable 
>> area should change its appearance, indicating that if the user lets 
>> go of the mouse at that location, an action will trigger.
> Frankly, I don't believe I've ever seen this implemented, and I really 
> question whether it is desirable behavior.  The reasoning for using 
> mouseUp instead of mouseDown to trigger an event is so a user can 
> reverse the mouseDown action without triggering the event by moving 
> the mouse outside the control before releasing it.  The idea of 
> triggering an event by holding the mouse down before entering a 
> control and releasing it once it is over the control seems totally 
> foreign and non-intuitive to me (except for pull-down menus).

Imagine the following situation: user presses mouse button down on 
button1, but then changes their mind and moves over (without letting 
go) to button2, where they DO let go... Or: imagine that I want to 
setup a 'piano keyboard'-style array of buttons, where the user may 
press down on one button, triggering an event, but then 'drag' the 
cursor over the other buttons, triggering more events as they go. This 
would have to be achieved currently by perhaps placing another object 
on top of the array, and evaluating mouse positions while the mouse is 
down and moving, and then sending the appropriate messages to the right 

All I wanted to point out, was that the way the current 'mouseLeave' 
and 'mouseEnter' messages work is extremely misleading - and in my 
'newbie' way of thinking, they certainly do not appear to be 
functioning as they should. If I leave a button - regardless of whether 
the mouse is down or up - I should get a 'mouseLeave'. Similarly, if I 
enter a button - with my mouse button down or not - then I should get a 
'mouseEnter'. If the button disappears from or appears under the mouse, 
I should get the appropriate 'mouseEnter/Leave' message as well. None 
of this happens. If the messages were implemented in this way, there 
would be no need for a 'mouseReleased' message, either. And most 
importantly: if the messages were implemented as I described, everybody 
would be able to implement the interface functionality they wanted, 
without too much programming. Right now, I'm being forced to have my 
interface work a certain specific way...

Many thanks for your feedback, though.

Kind Regards,

Igor de Oliveira Couto
info at

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