Joel de Guzman wrote:
Vladimir Prus wrote:
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.
Hmmmm....
I'm not sure about this. Say for example that I am writing a WYSIWYG CAD application and I'd like to draw vertical and horizontal rulers. At 100% page view, I'd like the ruler to be a 1:1 with the actual screen at the designated resolution (say 72 DPI). How would I draw my ruler if the coordinates are abstracted in terms of percentage?
You mean the the rule has millimeters as the unit an at 1:1 zoom you want 1 millimeter of the ruler to be 1 millimeter on the screen? Then yes, you'll need some way to convert millimetres to units used on screen. Though I don't understand why you want such strict equality. You won't measure distances on the screen with a physical ruler anyway, right? - Volodya