Debugging touch input problem

Daniel d'Andrada daniel.dandrada at
Thu Sep 26 13:32:25 UTC 2013

On 26/09/13 02:52, Neal Peacock wrote:
> I'm running down a touch screen input problem and I'm trying to figure 
> out the right place to look.  I am porting ubuntu touch and the using 
> mir.  My last issue is the touch screen input.  I was getting some 
> very erratic results and I'm trying to figure out where it breaks.  
> The screen will react a little to touches but not accurately and most 
> of the gestures do not work, the few that will are sporadic.  I have 
> dumped out the touch results from the kernel and all the x,y and id 
> values looks correct as far as I can tell. This driver works under 
> LXDE and Android.  lsof  seems to show unity is the only process 
> watching these events and it looks like the mir library might be what 
> actually handles input.
> Is the mir server what handles touch input?

Yes, it has android-input inside it.

> I've been checking through the source and I see a references to the 
> Android touch input code.  I tried to enable the input report log but 
> I don't seem to see any output with the upstart logs or in logcat.  
> Where does that report go?
> Does the Android container need to have some touch input service 
> running for it to work?  I can't see a service an obvious name.
> Any help or thoughts appreciated, thank you.

So, if I understood you correctly you're trying it out on a new device? 
If that's the case it might be that you didn't provide a .idc file for 
your touchscreen (I guess idc stands for "input device configuration"). 
Take a look at InputDevice.cpp and its log messages.

Running mir_demo_standalone_inputfilter as root is the best way to 
diagnose input issues. If you're using the latest mir (from bzr repo), 
to get log messages from android-input you will also have to set a 
ANDROID_LOG_TAGS environment variable appropriately. Set it to "*:v" to 
get the most verbose log.

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