mathog wrote
"we are currently using mm, user wants inches, MULTIPLY document transform by mm to inches conversion"
then the single unit transform itself might not be numerically stable.
Personally I expect this behavior. I see changing the document unit (not the GUI input and visualization unit) as a deep operation that means that all internal numbers should be recalculated with respect to this new selected unit, if this is really what the user wants. I see the "document unit" as the user selection about how the numbers should be internally represented. Of course if you change the document unit having existing objects already created in a different unit, rounding errors could happen in the conversion. I assume that one usually first selects the document unit and then starts drawing. The document unit is not supposed to change at all during a document lifetime, unless a real need arises and then you should know what you are doing. If this is the case, Tav's description perfectly fits; unless I misinterpreted it and what he meant was that only the root viewbox was going to change and so 1 mm would become 1 inch (this sound so crazy that I feel it can only be a wrong interpretation).
Luca
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