Setting up a multi monitor touch system in Linux can be a little trickier than for other systems due to the flexibility offered by the operating system in terms of configuration and usage. This article describes the basic steps to configure a UPDD installation for some very basic scenarios. For more complex scenarios, such as multi seat, multi server or irregular segment maps please reference the more comprehensive Linux documents here.
Touch interfaces
UPDD supports two touch interfaces, uinput and xtouch as described here. This document describes the setup for uinput (the default). xtouch multi-monitor setup is described here.
Step 1. Determine monitor layout
Use the option "upddutils monitors"
Example 1: Each physical monitor is listed in the system
In this example the system has two monitors connected and these are reported as separate monitors.
If both these monitors are associated with DISPLAY :0 then it is likely that no special user mode setup is required for this case and you can go to step 3.
Example 2: Number of monitors listed do not match the number physically connected
In this example two monitors are connected each with resolution 640 x 480, but only one monitor is reported
We describe this as a system having 1 logical; but 2 physical monitors.
From the example above it can be seen that the system sees this as a single co-ordinate system with the second monitor having the co-ordinate range
640,0 to 1279,478
Step 2. Set the updd configuration
Where the number of reported monitors does not match the the number of physical monitors the driver needs to be informed of this arrangement using the monitor_segment_map setting. In the case of the above example using the following command:
More complex arrangements are of course possible with different stacking, e.g. vertical, multiple rows etc and differing screen resolutions.
The use of monitor_segment_map is explained in more detail here.
Step 3. Run configure
Once the correct settings have been made to reflect the multi-monitor layout you can then run the configuration process as described here.
A screen will be shown as follows.
Follow the prompts. If you have set the monitor segment map correctly this should be shown on each screen in turn; including non-touch screens.
At the end of this process a further 4 point calibration screen may be shown (if the previous phase determined that touches were inaccurate).
If not, but calibration is inaccurate you may execute configure a second time to explicitly calibrate.