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X Multi-Touch: Pointer Emulation, Getting Events

X.Org

Published on 22 December 2011 10:17 AM EST
Written by Michael Larabel in X.Org
2 Comments

Peter Hutterer has supplied some detailed information about the new X.Org multi-touch support as supplied by X Input 2.2 and to be found in X.Org Server 1.12. This information concerns pointer emulation and getting the new input events.

Peter Hutterer, the Red Hat input expert responsible for much of the multi-touch support and MPX support in X.Org, blogged this morning at first about Multitouch in X - Getting events. In that first post he outlines how to identify touch devices and register for touch events using the X Input 2.2 extension. Unless you're into low-level input handling, this read won't be of interest to you.

Peter immediately followed up with another X multi-touch blog post, but the next one is about pointer emulation. Pointer emulation in X.Org is for generating pointer events based upon a sequence of touch events. "The conditions for emulation are that the the touch sequence is eligible for pointer emulation and that no other client has a touch selection on that window/grab."

Peter additionally explains, "One of the base requirements of adding multitouch support to the X server was that traditional, non-multitouch applications can still be used. Multitouch should be a transparent addition, available where needed, not required where not supported. So we do pointer emulation for multitouch events, and it's actually specified in the protocol how we do it. Mainly so it's reliable and predictable for clients."

This second blog post covers pointer emulation on direct-touch devices, depenedent-touch devices, and button events and button state. Again, if you're really into input handling or working on multi-touch support for a tool-kit or an advanced application it's a worthwhile read, but otherwise it's not exactly a fun read.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
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