DPI changes on radeon dual screen with MetaModes

Richard Stellingwerff remenic at gmail.com
Thu Jun 1 03:30:15 PDT 2006


I have a dualscreen setup and I'm using MergedFB to span my desktop
across the two screens. My MetaModes looks like this:

Option      "MetaModes" "1400x1050-1024x768 1400x1050+1024x768
1024x768 800x600 640x480"

This works pretty well, except for a little issue with the DPI
settings. The DPI keeps changing when I switch resolution, causing
some applications to behave very oddly with the fonts.

Is there a way to set the DPI to a fixed value? I already tried
"startx -- -dpi <value>" but this doesn't seem to help.

Here's what happens when I switch between modes:

$ xrandr
 SZ:    Pixels          Physical       Refresh
*0   2424 x 1050   ( 641mm x 278mm )  *25179
 1   1400 x 1050   ( 641mm x 278mm )   -8331
 2   1024 x 768    ( 641mm x 278mm )   -8331
 3    800 x 600    ( 641mm x 278mm )   -8337
 4    640 x 480    ( 641mm x 278mm )   -8343

$ xrandr -s 0
$ xdpyinfo | grep resolution
 resolution:    96x96 dots per inch

$ xrandr -s 1
$ xdpyinfo | grep resolution
 resolution:    55x96 dots per inch

My hardware is:
ATI Technologies Inc M9+ 5C61 [Radeon Mobility 9200 (AGP)] (rev 01)
using the radeon driver.

It appears that the "physical size" always counts both screens, even
in MetaModes where I specify one screen only. If I could just tell the
driver not to calculate the DPI but use a predefined value, the
problem would be "solved" for as far as I'm concerned. Can this be

Kind regards,
Richard Stellingwerff.

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