core.UiManager.Colorbar cannot map from minimal value to maximal value

[PietvdD]

I am using geoplot to visualize air pressure at 10 m level. Air pressure values are always between 870 and 1084 hPa
I am happy to feed the data as actual_data - minimum_value. I am not happy with the color bar which consequently reaches
from 0 to 214 hPa and will have labels accordingly. I tried to overlay the colorbar class of UiManager, but did not have succes yet. Please see my proposed changes
Proposedcolorbar.pdf