Control Click fixes

[chaosphere2112]

This goes with CDAT/cdat#1163. There are a number of issues with modified clicks in Qt– for one, it reads ctrl + left on a mac as a right click. Presumably to work around this, they map the control modifier to the command button, and the meta modifier to the control button. I originally changed it to use the meta button, but that led me to discover the issue with Qt interpreting ctrl+left as a right click.

Another issue that was happening is that VTK doesn't know how to interpret the Qt Keyboard Modifier objects– it would wind up setting the interactor's ControlKey and ShiftKey attributes to ridiculously high numbers that would evaluate to truth-y, but wouldn't be == True, which was the check I tend to use.

A third issue is that since I now use the command key as a modifier, command clicking inside a cell in the spreadsheet would toggle it to unselected. This was annoying, and it doesn't look like it's actually a useful feature at all, so I just made it so we don't pass the control modifier to the cellActivated function, and instead pass False for the toggle value.

@remram44 @doutriaux1 If you can test this on Ubuntu, that'd be great… my mac is converting the control + left click into a right click before it gets through to my VM, so I'm not certain if it's set up correctly there.

[remram44]

What is the expected behavior here? Can test on Debian.

[chaosphere2112]

If you open up the configure menu on a plot, click the left one of the buttons on the top right (if you hover over it, it'll say it will let you add a marker) and click somewhere on the plot, it'll drop a marker; a tooltip will show up in the bottom left of the plot, saying you can press "ctrl + click" to drop another marker. At that point, you should be able to control + leftclick to drop more markers on the plot.

[remram44]

Can't find said button...
cc @vvpalav

[chaosphere2112]

Click the pencil button here:

That should make these show up:

Click the leftmost of these two:

Click anywhere on the plot to place the initial marker

This should show up in the bottom left (but should say "Ctrl" for you):

Ctrl+click on places on the plot, and then more squares should show up. When you click normally on the plot, you'll see dots where the squares were.

[remram44]

Yep, works as expected! 0d687e6 doesn't: ctrl+click selects/deselects the cell instead.

[chaosphere2112]

@remram44 Cool! Are we good to merge?

[chaosphere2112]

@remram44 Checking on the status for this... can we go ahead with the merge?

[remram44]

I do not know what else this could affect. Other cell types could be reacting to clicks. What I did test worked.