The zoom on scrollwheel function has a rather unpleasant bug under Linux
At the moment, the function seems to zoom and also re-centre the cursor position, but this only works for single
If you zoom a single
step of the scrollwheel, it works fine.
If you zoom more than one step, and the cursor is not centred on the screen when you start the zoom then you end up with the cursor centred and the chart zoomed in to an incorrect position (the zoom centre being used must be incorrect for the zoom actions which are queued up after the first one).
So you probably lose the place you were zooming in to...
If zooming using the scrollwheel, I think the cursor position should be maintained, and the zoom should be centred at that position. No cursor centre action should occur!