Tag Archives: drivers

Putting DPI into perspective

Prior to the purchase of brand new workstations at work, Justin and Andy were working from Macbook Pro laptops. We had these Matrox DualHead2Go boxes which took a video signal and split it in two, for the purposes of connecting two monitors to a non-dualhead video card. I cannot tell you how much of a pain it was getting not only DVI output working under Linux through the proprietary ATI driver (although now that I know how, it’s pretty easy), but also getting it to talk to these Matrox boxes.. modelines.. resolutions.. triple displays.. gahh..

Never-the-less, I did get it to work. The final setup consisted of the laptop screen being enabled as the primary desktop, then the secondary desktop through the DVI output connecting to the Matrox box at a resolution of 2560×1024, which the box then split across two LCD screens. One of the problems was that the DPI resolution for the dualscreen setup was very wrong and as a result the fonts on the monitors were TINY.

So, the next trick was to tell the secondary monitor (the dualview box) what DPI it should run at (in this case, 96×96).

Even on my main box at work using the NVIDIA driver on a dualscreen setup, the DPI is wrong.
chris@gentoo ~ $ xdpyinfo |grep -A1 dimensions
dimensions: 3360x1050 pixels (948x303 millimeters)
resolution: 90x88 dots per inch

Should you need to specify your DPI too, here’s how you can!
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