fix issue with panning #344

[RebeccaNowak]

now manually setting pan to false on EndDragging (also works for middle mouse button / pan)

[haraldsteinlechner]

cool thanks for finding out this one! What's going on here in a broader sense?

   | StartDragging _,_,_ 
   | Dragging _,_,_ 
   //| MouseOut _,_,_
   | EndDragging _,_,_ -> 
     let m' =
           match m.multiSelectBox with
           | Some x -> { m with multiSelectBox = None }
           | None -> m
     m' //{m' with navigation = {m'.navigation with camera = {m'.navigation.camera with pan = false }}}

All of those, StartDragging, Dragging and EndTragging do the same, namely setting multiselectBox to none. Btw, MouseIn and MouseOut are never emitted in ViewerGui.

Seems to be related to multiselectBox - which is dead? isn't it? shall we remove all of those altogether (createMultiSelectBox and all those handlers listed above?)

[RebeccaNowak]

What's going on in a broader sense: The middle mouse button is used by browsers for various actions, and they sometimes (and depending on the browser of course) interfere when you want to use middle mouse button events. Also, browsers sometimes even override/ignore "preventDefault()" for these actions. I suspect that's why the mouseOut event does not fire while the middle mouse button is pressed (I tried this out). So we can't use mouseOut / mouseIn to solve this. However, onMouseUp does fire and so we can use this.

As for the multiselectBox: I didn't know anything about that, so I left the functionality as it was. If it's not in use any more we can remove that code entirely.

[haraldsteinlechner]

Let's merge this one - but let's keep the issue open, after updating the media packages we can clean up the code and remove the unnecessary handlers.