I have a switch box. The switch box doesn't appear to send DDC signals
through, whether or not the monitor is live when X starts.

If I start X with the monitor connected directly to the computer,  X
sets DPI at 95, 96 . If the monitor is not connected, it sets the DPI at
75. At 75dpi, the fonts are usually intolerably small.

The most common screen resolutions/sizes tend to be (appx) :
Diagonal Width   Height  ResolutionWxH  DPI
14.1" 11.28 8.46 1024X768  90.5 90.5 
15"  12 9   1024x768              85 85
17"  13.25  10.65  1280x1024  97 96
19"   14.8  11.85 1280x1024   86  86

The most common resolution today is probably 17" 1280x1024. for
desktops, and something close to 14.1" 1024x768 for laptops. The
weighted average is probably around 92dpi.

We must assume that it is not always possible to determine the monitor's
characteristics - any of them. Screen size, H/V sync, max resolution,
DPI.

Where no information is available, we need to set sensible defaults so
that the user can at least get something on screen to make initial
changes..

If the user has not set preferences (ie all fields are on autodetect in
the attached example) and we have no DDC information whatsoever, AND no
settings have been put in xorg.conf, then 800x600,60Hz75dpi is a
sensible default.

However, if a resolution has been set and a DPI has not been set, I suggest we 
have an automatic DPI mapping based on the highest resolution axis as follows: 
<700 56dpi    (eg 640x480)
<950 75dpi    (eg 800x600)
<1200 85dpi    (eg 1024x768)
<1400 95dpi    (eg 1280x1024)
>1400 100dpi.    (eg 1440x1024)

Whenever display settings changes are made within Gnome, I suggest we
also store the mtime for file /etc/X11/xorg.conf. If xorg.conf exists,
and the time stamp differs, then all settings in Gnome should be re-set
to Autodetect / default. Otherwise, Gnome settings should take
precedence.

This way, if the user does dpkg-reconfigure xserver-xorg, the settings
will take precedence. If the user then logs into Gnome then changes
settings, they then take precedence.

So we have an order of precedence for each parameter Res, Freq, DPI:

Resoution
1) The most recently changed of Gnome or xorg.conf
2) DDC
3) 800x600

Frequency (refresh rate)
1) The most recently changed of Gnome or xorg.conf
2) DDC
3) 60Hz

DPI:
1) The setting in Gnome
2) DDC
3) 
<700 56dpi    (eg 640x480)
<950 75dpi    (eg 800x600)
<1200 85dpi    (eg 1024x768)
<1400 95dpi    (eg 1280x1024)
>1400 100dpi.    (eg 1440x1024)


** Attachment added: "Image of example resolution/DPI/Frequency box"
   http://launchpadlibrarian.net/8281386/resolutionexample.png

-- 
Font sizes in Gutsy are vulnerable to bad X.org DPI detection
https://bugs.launchpad.net/bugs/118745
You received this bug notification because you are a member of Ubuntu
Desktop Bugs, which is a bug assignee.

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