Good afternoon, I am new to the list so please excuse me for jumping in, however I develop software for use with touch screens. I have experienced the exact same problem but with Windows 7 (I know, wrong platform). However the root cause was with the device itself either missing event signals or them being out of order.
>From your email you imply you've only looked at the output of X, rather than what is coming from the device via USB. Regards Phil On 12 October 2012 14:38, Thierry Reding <[email protected]>wrote: > Hi, > > I've been seeing a very strange issue. Originally this was observed when > using a browser with an onscreen keyboard. It would sometimes happen > that the keys on the keyboard would get stuck and be repeatedly sent. > > While trying to debug this, I came across a reliable way to reproduce it > using xwininfo. Basically I would run xwininfo and select the onscreen > keyboard. This would immediately result in the key being pressed and not > receiving a release event. Using other keys on the onscreen keyboard > would make them pressed as well, but never released either, resulting in > repeated keypresses received by the browser. It seems like X for some > reason believes that the press event is actually a release and vice- > versa. > > In order to find out what exactly was going on, I fired up xev with the > window XID as reported by xwininfo. This would indeed show the repeated > key events sent to the onscreen keyboard's window. Strangely enough, if > xev is started without an existing window XID, generating touch events > in that window seems to "fix" the issue. The keyboard can be used > reliably again. > > Furthermore, when running xwininfo and selecting the onscreen keyboard, > a second call to xwininfo would fail, saying it cannot grab the mouse. > This issue can be reliably reproduced independent of the onscreen > keyboard and works with any X window. So opening an xterm for instance, > then running xwininfo and selecting xterm will cause any subsequent > calls to xwininfo to fail. Running xev and generating touch events in > its window again fixes things. > > It seems like the X server doesn't properly release the grab and gets > the touch down and up events mixed up. Note that all of this only > happens when using a touchscreen device. Performing the same tests using > a regular USB mouse to select the X window for xwininfo doesn't show the > same behaviour. > > I'm using version 1.13 of the X server and xf86-input-evdev 2.7.3. Can > anybody else reproduce this? > > If you need any more information I'd be happy to provide it. > > Thierry > > _______________________________________________ > [email protected]: X.Org development > Archives: http://lists.x.org/archives/xorg-devel > Info: http://lists.x.org/mailman/listinfo/xorg-devel >
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