Xorg servers starting from version 1.7 have a feature called "multi-pointer". Basically it allows to have multiple mouse cursors (each with its own keyboard focus) on the screen and control them with separate physical input devices. It can be used as a crude multiseat solution.
Master and slave devices
With the introduction of XInput2, input devices are organised in a two-level hierarchy:
- Master devices, which correspond to cursors on the screen
- Slave devices, which correspond to physical input devices
Master devices come in pairs, one for pointer and one for keyboard. Each master device can have a number of slave devices attached, so that cursor of a master device can be controlled by all slave devices attached to it.
When an application grabs input (e.g. a fullscreen game), it grabs a master device that is set as its client pointer. By default, the client pointer is set to "Virtual core pointer", but it can be set to a different one with a "xinput" utility.
More pointers can be added with
xinput CLI utility. Here is how to do it:
Create a new pair of master devices named "name pointer" and "name keyboard":
xinput create-master [name]
Find out names and ids of existing slave devices:
Reattach slave devices to newly created master devices:
xinput reattach [slave device name or id] [master device name or id]
It is possible to use multi-pointer with software that doesn't explicitly support it, but with limited functionality. Applications which do not support it won't distinguish between multiple pointers and will interpret all actions as if done by single master device pair.
In window managers multi-pointer support could mean:
- recognizing multiple focuses
- setting the client pointer of a focused window to the pointer that "focused" it
- letting move and resize windows simultaneously
As of 26 September 2010, none of major window managers support multi-pointer.