When I use logarithm scale for X axis, pan working incorrect. It squeezes/unsqueezes the view when moving mouse.

Steps to reproduce:
1) create chart with axis X using log scale.
2) generate XValues from 0.000001 to 10 (the wider interval produces the more obvious effect)
3) add zoom and pan tool to the chart
4) zoom an area and try to pan.

Looks like you are using linear panning while you should apply log to the difX when moving mouse, just change it to log(difX)