Joel de Guzman wrote:
Vladimir Prus wrote:
Stefan Seefeld wrote:
Device coordinates are not ok to determine object size, because that means that objects have differing sizes on different output devices (multiple screens, printers, etc.) and so users wrongly tweak resolution to get back their wanted object sizes.
You should never specify object size at all. The size of main window should be set the GUI library, or set as proportion of screen size. The child windows should be laid out by GUI or resizes as proportion of main windows size. So, you don't care what unit is used, since you never specify absolute sizes.
I think you are mising each other by miles. Volodya, as much as I want to and tried to, I can't understand what you are trying to say.
I'm trying to say that the choice of coordinate unit -- pixel, millimeter, inch, whatever, is only important if you need to write: window.setWidth(10cm); and in a proper GUI library you should never set width to absolute value like that. Instead, you should do: window.setWidth(screen_width()*some_constant); In that case "screen_width()" can return SomeVeryOpaqueType that you can multiply by float, but can't convert to pixel, or to to inch, or to anything else.
So, I believe that the ideal coordinate system unit is nothing more that "int".
For vector graphics, that would be float/double (or fixed-point).
Well, for SVG it's already float, and we can't change that part. Still I'm not sure why float is a good idea for drawing operations in a GUI library. - Volodya