Re: [boost] GUI coordinate units (Was: GUI foundations)

From: Stefan Seefeld (seefeld_at_[hidden])
Date: 2005-10-05 09:38:07

Vladimir Prus wrote:
> Joel de Guzman wrote:

>>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?

Yes ! I think that's exactly the point. If the user doesn't *explicitely*
set a different scale, an object's physical size expresses how it wants
to be rendered on the output device. Why should users ever have to think
about 'device coordinates' ?

Regards,
                Stefan