I have a problem with background elements for the chart. I
need to create a chart with horizontal lines on its background.
Each line must have width = 250 points. (Look at the code below).
With this code chart shows correctly. But if width and height
of 'mainBox' equal 40%, than width of GridLines became 500 points
and tick marks on vertical axes are 100, 200, ..., 1000 (not 50,
100, 150, ...., 1000 as we need).
The width of the grid lines is based on the values shown on
the chart's axis (in this case, using the horizontalChangeCount
property). When you shrink or expand the chart, you are changing
the number of grid lines that are visible, and therefore changing
the width and number of visible grid lines.
If you need to have the grid lines display in points, then
you should draw the elements on the chart rather than use the grid