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

From: Stefan Seefeld (seefeld_at_[hidden])
Date: 2005-10-04 08:34:36

Vladimir Prus wrote:

>>I agree. In particular, I'd strongly suggest to draw a clear distinction
>>between physical dimension and resolution. Most current GUIs did get that
>>wrong, I believe in that they conditioned us all to think of size when
>>talking about number of pixels.
>>
>>The consequence is similar to the Y2K bug: applications won't easily adapt
>>to displays with different resolutions (well, may be within a narrow
>>range), and so a lot of efford is needed on a high (application) level to
>>compensate for that lack of abstraction.
> 
> 
> Can you elaborate on this? For explicit 2D graphics "pixel" is already just
> a convention, since you can scale that as you like. And for window layout,
> well, you should not do manual window layout at all. GUI library should
> select font size and other things, and everything will be laid out. What
> problems do you have in mind?

Sizes are usually given in resolution-dependent coordinates (i.e. pixels).
If you change resolution, you typically don't do that to expose more detail,
but to make your desktop 'bigger' (by making text, widgets, etc. smaller).

If 'pixel' is only a convention that isn't related to device coordinates,
great. Still, 'pixels' have a physical size of their own that varies between
devices. I think it would be best to remove this degree of freedom, or at
least, be explicit about when the user (GUI developer) is operating in
device coordinates and when he is not.

Regards,
                Stefan