GNOME Bugzilla – Bug 724960
Wrong screensize detected
Last modified: 2014-03-05 17:15:45 UTC
XServer gave me to the same display the same resolution (which is wrong) for HDMI and VGA port: HDMI: http://www.pic-upload.de/view-22349633/Bildschirmfoto-von---2014-02-22-18-27-07--.png.html VGA: http://www.pic-upload.de/view-22349639/Bildschirmfoto-von---2014-02-22-18-30-42--.png.html Based on this information it is expected for me that the display shows everything on the same scale on VGA and HDMI, but is doesn't. It also shows over VGA up as an 19" Display and HDMI as an 7" display. Both are wrong, but 7" is far to small. The display is 48cm x 26cm which means 72 dpi x 75 dpi and ~21.5". Maximal resolution is 1360 x 768. Gnome should select the screensize on XServer informations not try to detect that on its on, should't it? It's not impossible for me to fix this, because my distro-information says I should fix the XServer DPI or real screen-size definition, which does not work here because gnome does not use this.
(In reply to comment #0) > XServer gave me to the same display the same resolution (which is wrong) for > HDMI and VGA port: > > HDMI: > http://www.pic-upload.de/view-22349633/Bildschirmfoto-von---2014-02-22-18-27-07--.png.html > VGA: > http://www.pic-upload.de/view-22349639/Bildschirmfoto-von---2014-02-22-18-30-42--.png.html > > Based on this information it is expected for me that the display shows > everything on the same scale on VGA and HDMI, but is doesn't. It also shows > over VGA up as an 19" Display and HDMI as an 7" display. Both are wrong, but 7" > is far to small. > > The display is 48cm x 26cm which means 72 dpi x 75 dpi and ~21.5". Maximal > resolution is 1360 x 768. > > Gnome should select the screensize on XServer informations not try to detect > that on its on, should't it? That's what it does. It gets all the information over XRandr directly from the XServer.
It should be remembered that the size in xdpyinfo is the size for the *screen* which is potentially the combination Looking at the Xorg code, the screen physical size is computed using the following things in order: a) The dpi set on the Xorg command line with the -dpi option b) The *user configured* size of the monitor for the "compat output", which is a somewhat arbitrarily selected monitor. c) A default DPI of 96. Monitor reported EDID information is not used at all. On the other hand, the information reported by 'xrandr' is actually what the monitor reports (modulo various heuristics and "quirk" workarounds.) Treating all monitors as if they are 96dpi is not useful in figuring out whether we should turn hi-dpi support on or not, so this is what we need to use. You can force GNOME to use a particular scaling factor with: gsettings set org.gnome.desktop.interface scaling-factor 1 And as I suggested in the other bug you filed, we probably should reject using a scaling factor of 2 just because your vertical resolution (768) is not big enough to work. The only other real way to move forward would be to try and figure out if there's any way to get the Xorg code to parse the EDID information reported when you are connected via HDMI better - to apply a quirk or improve some heuristic. There's nothing really we can do on the GNOME side. Thanks for taking the time to report this bug. However, you are using a version that is too old and not supported anymore. GNOME developers are no longer working on that version, so unfortunately there will not be any bug fixes for the version that you use. By upgrading to a newer version of GNOME you could receive bug fixes and new functionality. You may need to upgrade your Linux distribution to obtain a newer version of GNOME. Please feel free to reopen this bug if the problem still occurs with a newer version of GNOME.