[vtkusers] Mouse button release event is still broken in VTK 6.0.0 !

David Cole dlrdave at aol.com
Mon Dec 9 00:39:33 EST 2013

> Yes. Subclass of InteractorStyle has no problem getting both left
> button down and up events.

> However, my question was why the render window interactor only "eats"
> left button up, but not the left button down event. Should the render
> window interactor also invokes the button up observers if possible,
> or just remove invoking the button down observers? This will make
> sure up and down are handled together or otherwise strange
> behaviors may occur.

Personally, I think it would be good to make them match. (i.e. -- 
either both up and down are fired, or both up and down are *not* fired)

I'm not sure it's possible in all situations -- I think it largely 
depends on what interactor style you choose to use.

Does anybody listening in here know if there's a reason why there's a 
mismatch between the interactor's up and down events? Could they be 
made to match without breaking something critical?

On the other hand, I don't think mouse down and up are always 
guaranteed to match in a given window. You could put the mouse down 
outside the window, then drag over to the window, and then let up... So 
your program should be robust against possible mismatches in these 
events anyhow. The only thing you can guarantee is that you will get a 
mouse up later on *if* you capture the mouse during your mouse down 
event handler. But if you don't, it's not guaranteed. And you might get 
an extra mouse up in the scenario I just described if some other window 
does *not* capture the mouse during its mouse down handler...


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