Fix scroll legend under Mac OS

[McGiverGim]

Fixes #213

I think this will work for Mac too, in my windows systems it works perfectly and now I can scroll with the wheel mouse.

What I'm not too sure is about the keys used, in Windows they are perfect, but I don't know if Mac needs other.

Please test this version to see how it behaves in Mac.

[etracer65]

Well it mostly works on Mac. The scrolling seems somewhat intermittent as it seems like there are certain spots in the legend where it won't work - not sure which elements. The mouse will be in the legend and scrolling won't work, move the mouse a little and it will start working. Can't really consistently replicate but it happens pretty frequently.

Also "ctrl + scroll" can be problematic on Mac as this combination is commonly used for zooming the entire screen. But I don't see that as a deal breaker. Also the equivalent to "alt + scroll" on Mac is "option + scroll" (it works fine to adjust expo).

Note that I was testing with the app running in Chrome - not the standalone version. I'm not currently set up to build the standalone.

[McGiverGim]

Ok, I will recheck to see if I have forgotten some tag.

[McGiverGim]

I have been trying to reproduce the intermittent behaviour (but under Windows) without luck.

There were two problems:

• Mac OS hides by default scrollbar until the wheel is used.
• The Blackbox intercepted the wheel, under ALL operating systems.

With this fix:

• The scrollbar appears under Mac OS (first problem fixed)
• It does not intercept the wheel. Under Windows the wheel works perfectly and in theory it must work exactly in the same manner for other OS.

Maybe I'm not reproducing it in the right manner. Some idea?