{"id":407,"date":"2009-12-02T15:30:45","date_gmt":"2009-12-02T14:30:45","guid":{"rendered":"http:\/\/www.enricoros.com\/blog\/?p=407"},"modified":"2013-04-21T15:51:15","modified_gmt":"2013-04-21T22:51:15","slug":"im-going-multi-touch","status":"publish","type":"post","link":"https:\/\/www.enricoros.com\/oldblog\/2009\/12\/im-going-multi-touch\/","title":{"rendered":"I’m going Multi-Touch"},"content":{"rendered":"

This is one of the hottest topics<\/em> of the moment: Multi-Touch<\/a> (see the trends\u00a0here<\/a>). Every review of the\u00a0just released<\/a> Qt 4.6<\/a> mentions the Touch-and-Gestures framework and KDE is getting ready to use the technology<\/a> — still it doesn’t work on X11<\/span> (yet<\/em>).<\/p>\n

MultiTouch can be Fun <\/em>!<\/h3>\n

\"Wacom_Bamboo-Fun-small\"I couldn’t resist, so for 99\u20ac (120$) I bought a Bamboo Fun Pen & Touclh<\/em> tablet. I find this really affordable, since you get: A. the precision of a graphics tablet (with 1024 pressure levels, back eraser, etc..) and B. a real 2-Pointers input device!<\/p>\n

I tried the tablet on vista, with the latest drivers and the bundled applications bot I got disappointed because:
\n1.<\/em> the scroll gesture\u00a0is remapped to the mouse wheel<\/em>.. so you lose all the ‘analog’ fun and it feels unconfortable.
\n2. the zoom gesture is remapped to CTRL+wheel<\/em>, awkward fixed-steps again.
\n3. the rotate gesture is not supported by any app<\/em> even the bundled ones i tried.<\/p>\n

In the end I thought this was not “multi-touch”, but some silly gesture-detection broken hardware. I was wrong<\/em>.<\/p>\n

Linux to the rescue<\/h3>\n

\"gesture-vortex-2S\"<\/a>
\nStep 1<\/span>. After loading the wacom.ko module (updated with this<\/a> patch) the Linux kernel prints out stuff like this:<\/p>\n

\r\n[default   ] data: 02 00  00 00 00 00 00  00 00 00 00  00 00 00 00 00  00 00 00 00\r\n[finger 1  ] data: 02 00  7d 80 fe 00 8a  80 fc 00 87  00 00 00 00 00  81 11 00 00\r\n[finger 1+2] data: 02 00  ae 80 b6 00 72  81 08 00 70  87 81 5b 00 72  81 21 00 00\r\n[finger   2] data: 02 00  00 00 00 00 00  81 59 00 b4  6d 81 59 00 ba  80 11 00 00\r\n<\/pre>\n
Can you see it ? This is<\/strong> a 2-finger device! \ud83d\ude42<\/p>\n
Step 2<\/span>. The Kernel understands the data and splits it into 2 input devices that Udev maps to\u00a0\/dev\/input\/wacom<\/em> and \/dev\/input\/wacom-touch<\/em>. From here you can read higher level information for each finger<\/strong> such as the decoded position<\/strong>, pressure<\/strong>, click type (tap<\/strong>, doubletab<\/strong>), and more.<\/p>\n
I WANT QTouchEvents AND QGestures !!<\/h3>\n
I do too \ud83d\ude00 And I wanted to hack something about that. But I stopped here:<\/p>\n
\"schema-problem\"<\/p>\n
We get the input from evdev<\/em> and the Application needs QTouchEvent<\/a>s and QGesture<\/a>s, so the easy way would be to hack up a touchpoint feeder to the Qt framework that directly reads from evdev (evdev -> qt<\/strong>). This would work fine for 1 application, but what about two? And what about moving the X cursor too? I think evdev->Xdriver->XInput2->qt<\/strong> is the solution, but we must be sure that no valuable information is lost in the chain<\/em>, that the event filtering is done in the right place<\/em> and obviously, that the X driver does a good job. Unfortunately xf86-input-wacom<\/a> (X input driver for wacom’s kernel driver) doesn’t support my Bamboo Fun Touch & Pen yet and moreover I don’t see MPX support in the sources, so I’m wondering how far away is the Qt multi-touch backend from seeing the light.<\/p>\n
Conclusion<\/h3>\n
I don’t know which way the multi-touch will happen on linux, but I know for sure that\u00a0we want to play with gestures and we want it soon \ud83d\ude00<\/p>\n
For more information:<\/p>\n