David Dawes wrote: > On Thu, Aug 21, 2003 at 12:33:49PM -0700, Nathan Gray wrote: >> >>This is my point exactly. When I raised this issue it was not to elicit a >>"correct" solution, but rather to point out that the whole notion of DPI >>is >>nonsense WRT Xinerama/MergedFB. I would suggest this as a "correct-ish" >>solution: If Xinerama/MergedFB detects that both screens have nearly the >>same resolution (to within some configurable tolerance) then use the >>average of the two. Otherwise the user has to specify the DPI to use with >>the -dpi command line switch or some other mechanism. (Is there a DPI >>option in the XF86Config file?) It might be nice to be able to specify >>"use DPI from screen foo" in the ServerLayout section to simplify the >>process a bit. > > There is no DPI option in the XF86Config file, but one could be added. > (Separate question: does it make sense to have most/all command line > options available as XF86Config file options?)
I would argue definitely so. It's pretty easy for the average user to edit the /etc/X11/XF86Config file but almost infeasible for him to unravel the mess of scripts that invoke X. (The same goes for env. variables, by the way.) It *vastly* simplifies things to have all configuration options for XFree86 in one place. >>> IMO either you want the same DPI on both screens (fake whatever >>> value you want with DisplaySize or X -dpi NN) or you want two >>> non-xinerama heads - display:0.0 and display:0.1, which allows >>> apps on each head to get the right answer for that screen*, and >>> stops the DPI changes which would occur if the window was allowed to >>> move between screens. >> >>I agree, but I think that Xinerama/MergedFB could at least be smart enough >>to either: A. do the right thing if you have two displays with the same >>DPI or B. throw in the towel when you have two displays with very >>different DPI. > > I guess the Xinerama extension could be enhanced to allow applications > to query the DPI of individual screens. While it might be useful for > non-overlapping screens, especially when the application windows don't > span screens, I don't know how useful it would be when one or more of > the Xinerama screens overlap. In such cases a single pixel can > simultaneously be displayed at multiple DPI. In those cases your "use > DPI from screen foo" idea would probably be the answer. As an application programmer I can't see how I would use such a capability. App writers don't want to have to do extra work because the screen might actually be multiple screens. > Then there's the video projector example, but I'd suggest that for most > applications "DPI" needs to represent the effective pixel size of the > image in a plane located at the typical viewing distance of a monitor > in front of a computer user (i.e., be representative of the pixel's > angular size). That sounds like a sensible definition, though harder for a user to measure precisely. > The non-Xinerama case of when the physical screen resolution can be > different from the root window size was also mentioned. Applications > can use the XFree86-VidMode extension to query the physical resolution. > Unfortunately though, the XFree86-VidMode extension doesn't yet have > support for allowing clients to get an event when video mode (or viewport) > changes happen. It would be good if such a notification existed. Cheers, -n8 -- >>>-- Nathaniel Gray -- Caltech Computer Science ------> >>>-- Mojave Project -- http://mojave.cs.caltech.edu --> _______________________________________________ Devel mailing list [EMAIL PROTECTED] http://XFree86.Org/mailman/listinfo/devel
