You're missing the point. I make an app that prints charts. It includes a function that subtracts user-specified margins from the paper width, to calculate avai

You're missing the point. I make an app that prints charts. It includes a function that subtracts user-specified margins from the paper width, to calculate available space. Some of my customers are in the U.S (inches), others are not (cm). If I call printPage(0.75, 0.75); you really think it's going to be all the same whether "0.75" represents inches or centimetres?