Comment 57 for bug 170049

I tried to simply add a multiplier and an offset for each ruler which seems to work as expected. (I did not yet manage to link scalar input values of the gui to the actual values but this should not be hard.)

This idea could solve the problem of some users I guess, however there would be a few open questions or issues:
- should new grids by default have their origin set at the current ruler origin?
- coordinates in the svg are not influenced, it's just the ruler numbers that change
- what's the best way to integrate in the gui? 4 number input fields for multipliers and offsets could be used
- for my default A4 page, setting an inverted y axis requires the user to enter a non integer ruler offset, that's not user friendly at all
- with this solution, an inverted y axis might introduce precision issues due to a double transformation
- an advantage is compatibility, nothing changes (except additional metadata how to display the rulers)

Would this be an acceptable solution? How should the gui look like?