interface slider - scale 1px off

While updating Kitty's Zoom Levels to 1.2.2 (using patches for better future compatibility) I noticed a minor bug in the interface that causes the "type" : "slider" to start centred one pixel to the left of the gridImage and then jump 1 pixel to the right in the middle, causing uneven spacing.

This is slightly annoying since the thumb-slider and zoomSlider thing is exactly the right size for ten steps (/nine intervals) of 4 pixels with no margin for error.

The table below shows the slider-offset from the left edge of the grid-

• as observed
• as calculated using method that yields consistent results (for this case)
• as calculated using a method that yields the desired results (for this case)

-	Observed	width/steps*(step-1)-1	(width-1)/steps*(step-1)
step 1 2 3 4 5 6 7 8 9 10	offset interval -1 3 4 7 4 11 4 15 4 20 5 24 4 28 4 32 4 36 4	offset interval -1.0 3.1 4.111 7.2 4.111 11.3 4.111 15.4 4.111 19.6 4.111 23.7 4.111 27.8 4.111 31.9 4.111 36.0 4.111	offset interval 0 4 4 8 4 12 4 16 4 20 4 24 4 28 4 32 4 36 4
total	37	37	36

Attached are- kitty_zoomlevel_bug.7z, the mod/test-case demonstrating the effect this has on the slider with all ten steps (nine intervals) marked evenly.
And kitty_zoomlevel.7z, the same mod with only steps {1,4,7 and 10} marked as they are currently rendered. Not as noticeably off. as a userfriendly pak file (not allowed to upload?)


edit: Windowed mode, Windows 7 (64 bit)