Just an update and or interesting information for users of Goo::Canvas. I have been messing with an application were the user can click on a map to insert a waypoint. The problem I was having was that when you zoom in and add a waypoint, the point would be off a distance. This increased greatly as you zoom in. Well using excel and some testing I think I found a correction factor for this zoom error:

z = zoom in percent (ex 100)
x0 = x pixel of real pixel
y0 = y pixel of real pixel
x = x pixel of fake pixel
y = y pixel of fake pixel

x0 = (100*(x+0.6105))/z
y0 = (100*(y+0.2526))/z
[download]

I don't know if this is dependent on the starting canvas size or not. I do encourage users to test this correction and see if it works for other situations. If this needs to be moved somewhere else let me know, I just put it in the most familiar place.