Why EDID is not trustworthy for DPI

[Simo Sorce]

On Wed, 2011-10-05 at 12:49 -0700, Adam Williamson wrote:
> On Wed, 2011-10-05 at 15:44 -0400, Simo Sorce wrote:
> > On Wed, 2011-10-05 at 12:31 -0700, Adam Williamson wrote:
> > > On Wed, 2011-10-05 at 18:49 +0100, Matthew Garrett wrote:
> > > 
> > > > So, ok, now you have some belief about the DPI. But which DPI? If you're 
> > > > dual head, you've got two. Unless they match you're screwed - there's no 
> > > > magic way to get applications to reflow text just because you've moved 
> > > > the window between screens, and what would you do with a window that's 
> > > > halfway between? You can argue that this is a corner case and obviously 
> > > > yes it's a corner case but if you can't even pretend to fix the corner 
> > > > case then your solution isn't a solution any more than 96dpi is.
> > > 
> > > There's no _magic_ way to fix anything, no. Things get fixed by code
> > > writers writing code. That would seem to be the obvious thing to do...
> > > 
> > > Like I replied to ajax, I suspect when the problem of assuming
> > > everything's 96dpi becomes simply too acute, instead of fixing
> > > everything really properly so that all displays correct report their
> > > size and all desktops actually do resolution independence perfectly so
> > > it doesn't _matter_ if one of your displays is 98dpi and the other is
> > > 215dpi, everything still looks perfect, the industry will just wind up
> > > with a slightly more sophisticated bodge where we have a few 'standard'
> > > resolutions and just figure out which one your displays are closest to.
> > > But that's still going to require some kind of sensible handling of the
> > > case where one monitor is roughly 100dpi and the other is roughly
> > > 200dpi, unless we simply say 'you can't do that, all your displays have
> > > to be in the same DPI Category'.
> > 
> > Are you saying fonts should change on the fly when I move an app between
> > 2 monitors that have different DPIs ?
> 
> If they're sufficiently different in DPI, sure. Or would you really want
> everything to suddenly become twice as small if you were moving a window
> from a 100dpi monitor to a 200dpi one?

Are you also proposing to automatically resize all windows when you move
them from one display to another ? There lies the road to disaster an
pain imo.

At least untill all rendering is done with something like svg and not
with absolute pixel values this is just going to be a very bad
experience.

Simo.

-- 
Simo Sorce * Red Hat, Inc * New York