Problem using Cygwin, Dual Monitor, with External DVI

Andy Glew
Sun Sep 25 13:47:00 GMT 2005

I have a problem whereby X text does not render correctly, in a
configuration involving dual monitors, an external DVI monitor in
addition to the LCD monitor on my laptop. It renders in other
configurations using these monitors and this laptop.

I am using Cygwin/X [*] on an IBM ThinkPad T42p. The T42p is docked in
an IBM 2878 docking station. The docking station is connected to an
IBM ThinkVision monitor via a DVI cable.

When I am in dual monitor mode (i.e. driving both monitors
independently, with the external DVI monitor Windows' primary
desktop), Cygwin/X applications such as xterm and GNU EMACS do not
render on the external DVI monitor.  Their X windows (I am running
Cygwin/X in multiwindow mode, so their X windows are also Windows
windows) are blank - nothing displays.

When I drag these windows over to the secondary monitor, the laptop's
LCD display, they render.  Moreover, it is obvious that everything I
typed while the window was on the external DVI monitor is now visible.
Therefore, stuff is being added to X Windows' concept of what should
be displayed on the window - it is just not getting sent to the

Similarly, when I drag the X windows back from the secondary, laptop,
LCD, onto the external DVI monitor, the windows drag correctly. The
old contents of the window display on the external DVI monitor, but
nothing new gets drawn.


However, when I am driving only the external DVI monitor, but not also
driving the LCD at the same time, everything is drawn. That is how I
am writing this message.


Normally, at home I use Cygwin/X with an external analog video monitor
in dual display mode with my laptop's LCD tablet.  This is one of the
first times I habve used an external DVI monitor.


Configuration info:

Now, how can I tell what versions of Cygwind and Cygwin/X I am running?

The external DVI monitor is reported by Window's device manager as a
Plug and Play monitor, on an ATI Monility Fire GL T2.

The laptop LCD panel is an IBM Thinkpad 1400 x 1050 LCD panel, also on
ATI Monility Fire GL T2.

Andy Glew
   Although I am trying to quit Outlook,
   I fetchmail all of my Outlook/Exchange email
   to UNIX to read


Potential bias: employed now by Intel
	past by AMD, Intel, Motorola, Gould ...
This post is personal, and is not the opinion of 
	any of my employers, past or present.

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