So the reason why the screenshots are taken any time another tab is selected is for the tooltips you see when you hover over a tab header. To make sure that an out-of-date screenshot is not shown in those tooltips everytime you change the tab all the
other tabs are cycled through and their screenshots are updated.
Luckily this is open source so you can hack the code up any way you need....so if you don't care about the tooltips being up-to-date you should be able to simply do this:
In FabTabControl comment out every line in OnSelectionChanged() with the exception of base.OnSelectionChanged(e). So, you could turn the tooltips off by setting the ShowToolTipImages to false on the FabTabControl in your XAML. However, I think
that if you do this when you go the Content tab it will also be out of date---so you may need to have some explicit check added into the FabTabControl to see if the currently selected tab is the content tab and THEN call the code in OnSelectionChanged that
you just commented out.
Or you could turn the Content tab off altogether--but I'm not sure which specific FabTab functionality you are wanting, and that's the most common feature that people use I think.
Hope that helps.