You often think “this KDE idea of mine would kick ass” but then you don’t have time to implement it and finally you forget about it? Welcome to the club!

Collecting Ideas

I want to blog about some cool things to do for the KDE project on week-1 2010. I’ve got just a couple of good ideas, so I’m asking you to add your ideas so we can make a good collection of nice things to do. You can either reply to this post (don’t be shy, just post it!) or send it to me at <enrico.ros@gmail.com>.

Sharing your idea with the community raises the chance of seeing it implemented! 😉

The KDE login Manager

The login manager is the “insert password” dialog that gets in the way when you want to use your computer. Of course you may not be the only user of the machine, so it’s somewhat needed when you share the seat. Some facts:

Kdm Top to Bottom

Qml to the rescue!

What if we throw away (or keep for “retro-compatibility”) the classic and themer frontends and just add a frontend using QML? This is the name of the language of the Qt Declarative module, that has just seen the light and will be merged into Qt for the 4.7 release.

Imagine this:

• theme creators will have 100X or more expressive power: make snow! login via a tetris puzzle! bounce my webcam picture!
• there will be animated themes (for login, user change, logout, etc..) or simple ones for more ‘classic’ kind of people
• kdm only needs to add a couple of bindings to the qml runtime, like functions for logging in and shutting down / suspend the system
• there is no need for compiled binaries, packages will be interpreted by the qml runtime – finally a painless get-hot-new-stuff (compared to plasma widgets, at least).

Conclusion

This is one of the hottest topics of the moment: Multi-Touch (see the trends here). Every review of the just released Qt 4.6 mentions the Touch-and-Gestures framework and KDE is getting ready to use the technology — still it doesn’t work on X11 (yet).

MultiTouch can be Fun !

I couldn’t resist, so for 99€ (120$) I bought a Bamboo Fun Pen & Touclh 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!

I tried the tablet on vista, with the latest drivers and the bundled applications bot I got disappointed because:
1. the scroll gesture is remapped to the mouse wheel.. so you lose all the ‘analog’ fun and it feels unconfortable.
2. the zoom gesture is remapped to CTRL+wheel, awkward fixed-steps again.
3. the rotate gesture is not supported by any app even the bundled ones i tried.

In the end I thought this was not “multi-touch”, but some silly gesture-detection broken hardware. I was wrong.

Linux to the rescue

Step 1. After loading the wacom.ko module (updated with this patch) the Linux kernel prints out stuff like this:

[default   ] data: 02 00  00 00 00 00 00  00 00 00 00  00 00 00 00 00  00 00 00 00
[finger 1  ] data: 02 00  7d 80 fe 00 8a  80 fc 00 87  00 00 00 00 00  81 11 00 00
[finger 1+2] data: 02 00  ae 80 b6 00 72  81 08 00 70  87 81 5b 00 72  81 21 00 00
[finger   2] data: 02 00  00 00 00 00 00  81 59 00 b4  6d 81 59 00 ba  80 11 00 00

Can you see it ? This is a 2-finger device! 🙂

Step 2. The Kernel understands the data and splits it into 2 input devices that Udev maps to /dev/input/wacom and /dev/input/wacom-touch. From here you can read higher level information for each finger such as the decoded position, pressure, click type (tap, doubletab), and more.

I WANT QTouchEvents AND QGestures !!

I do too 😀 And I wanted to hack something about that. But I stopped here:

We get the input from evdev and the Application needs QTouchEvents and QGestures, so the easy way would be to hack up a touchpoint feeder to the Qt framework that directly reads from evdev (evdev -> qt). 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 is the solution, but we must be sure that no valuable information is lost in the chain, that the event filtering is done in the right place and obviously, that the X driver does a good job. Unfortunately xf86-input-wacom (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.

Conclusion

I don’t know which way the multi-touch will happen on linux, but I know for sure that we want to play with gestures and we want it soon 😀

For more information:

• Peter Hutterer’s blog. Peter is the MPX (Multi Pointer X) author and plays a big role in the X.org community.
• X Input Extension 2.0 features.
• The Linux Wacom project. A community-driven effort to develop kernel and X drivers.