What are the dimensions of a projector, whose pixels-per-inch or dots-per-inch value is a distance of how far away the projector is for the wall, or, in a keystoned case, isn't even constant across the display?
For limited scenarios, you can make it work (with caution, see [0]). But we cannot calculate a sensible DPI value in the general case. [0] https://lists.fedoraproject.org/pipermail/devel/2011-October/157671.html On Wed, May 4, 2016 at 10:45 AM, Mattias Andrée <maand...@member.fsf.org> wrote: > On Wed, 4 May 2016 19:01:09 +0200 > Alberto Salvia Novella <es204904...@gmail.com> wrote: > >> Mattias Andrée: >> > What's wrong with dots per inch? >> >> How can an application reliably know which is the current >> pixel density of the desktop? >> >> > > Well, you cannot know anything reliably. The EDID > does contain all information you need for DPI, however > with limited precision. X.org reports a bogus DPI. But > if pretend that all monitors' dimensions are in whole > centimetres, than the number of pixels per centimetre > can be calculated > > ppc_x = output_width_px(monitor) / output_width_cm(monitor); > ppc_y = output_height_px(monitor) / output_height_cm(monitor); > > Notice that this is easier to calculate than the pixels per inch. > > ppi_x = output_width_px(monitor) / output_width_cm(monitor) * 2.540; > ppi_y = output_height_px(monitor) / output_height_cm(monitor) * 2.540; > > But why is pixels preferred over dots? > > _______________________________________________ > xdg mailing list > xdg@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/xdg > -- Jasper _______________________________________________ xdg mailing list xdg@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/xdg
