Attaching a monitor via vga

Polytropon freebsd at
Wed Jun 20 13:14:54 UTC 2012

Allow me to mention an additional approach (but I think using
xrandr is fine - it sometimes works where "bare X" fails).

Depending on the options of the GPU in your laptop, you can
use /etc/rc.conf to make specific settings depending on
what "connector" (internal dotmatrix display, external
VGA, be it CRT or LCD) you use.

For X to find out resolution and screen size properly, in
Section "Monitor" you can use

	Option "Preferredmode" "NNNNxNNNN"


	DisplaySize MMM MMM

(where MMM is to be given in millimeters) to "hardcode" the
parameters of the screen. Modern screens should provide them
by theirselves (especially all LCDs should do that), but it
can be helpful to define them in a "mixed mode setting" as
what an external monitor on a laptop can be considered.

If DPI calculation doesn't work as intended (results in too
small or too big text for example), you can add

	Option "DPI" "DD x DD"

to Section "Device" where you define your driver. Use values
of between 70 and 120. For dotmatrix displays, you can easily
calculate the correct value (horizontal size in pixels divided
by width in inch; vertical similarly) in case it isn't obtained
automatically. The correct value should also be found in the
documentation of the screen. Note that flatpanels only have one
fixed amount of pixels and therefore also one fixed DPI resolution,
whereas CRTs are more versatile.

A last option would be to check out TwinView if it's supported
by your GPU. Settings like

	Option "ConnectedMonitor" "CRT, CRT"

can be used to tell X what monitors to connect on startup and
how to initialize them.

Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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