I don't think there's a built in feature for what you want. My best hint would be to create your own component and make it function the way you want. You could try extending the HScroller and see if the method that control the measurement and the placement of data can be overriddent. If they can be overridden then all you need to do is reverse the way it calculates the values when you move the scroll head.
With best regards,
EDIT: I just took a look and it seems that most of the stuff can be overridden so you should be able to replace the existing calculations with your own. I can't think of a better way to do this.
as a workaround for your task can set negative value and get abs from the value.
So you need to inverse data: set minimum to -50 and max to 0.
Also you need to set function dataTipFormatFunction and others to show user only positive values.
Also you can create your own extendedSlider to reverse all data this way.
I know it has been a long time since this issue has been posted. But since I found a workaround, I thought it could be nice for eventual people encoutering the same problem to come here finding the answer...
Using the spark slider classes, HSlider for instance, the solution is utterly simple : just use layout mirroring with the
layoutDirectionproperty, and set it to
rtlfor "right to left" or
ltrfor "left to right" according to your needs.