Test kernel: Zoom bar acting as multitouch pinch to zoom

Someone asked what the point of the new .39 kernel is, well here's a new feature I've coded up that was made possible due to the more modern kernel.

I have modified the touchscreen driver in the kernel so that the zoom bar is now working, and it sends signals to Android that make it think you're sending a multitouch pinch-to-zoom.

I've got it set so that it sends an input from the center of the screen. As you slide right, the driver tells Android two fingers are moving apart from the center. As you slide left, the driver tells Android two fingers are sliding from the sides towards the center. The net result is that the zoom bar works in any app that supports pinch to zoom.

I've uploaded a video showing it in action:
http://www.youtube.com/watch?v=GRWUzPveU14

I'm going to submit this patch soon, and I'd like it if some people would try it out and give any feedback before I do so. I suppose things to pay attention to would be any increased wonkiness in the touch response, as well as boundaries for the zoom bar. Also, if you have a better idea on how this should work, it's now or never.

Unfortunately, this is a modification of the new .39 kernel, which means that a lot of things are not working on it, and this test kernel will most likely not be suitable for daily use if you like wifi and the other things that don't work on .39 yet.

In order to install you must do the following:
1. Replace your zImage with the one attached.
2. Use the .39 haret (included in the zip for your convenience) with the .39 startup.txt line (set initrd_offset 0x00a00000)
3. Place the included android.hardware.touchscreen.multitouch.xml under /system/etc/permissions. I tried bind-mounting it from conf, but for some reason that did not work for me. If you don't do add this permission file, the multitouch points will still be sent to Android (and will show up in the app Multitouch Test), but Google's own apps like Browser will ignore them.

arrrghhh said:

Alright, settle down children.

I think you're looking a little too far ahead fortunz, but that's just my opinion.

To manekineko - holy crap dude, that was fast! Nice work, definitely want to check it out.

But if you're on CDMA... then I'd imagine the experience is painful with data connected... still, great work. I'm sure the .39 kernel folk will gladly accept your patches, that's seriously cool!

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Yeah, after I got the .39 kernel, it took me like 30 minutes to get it working for the first time, and then a bit more time to clean up the code to look nicer.

Whereas I'd spent hours banging my head on the wall with .27, never quite sure where the problem was, since I thought I was sending all the right events in the driver. Now I know I was sending the right events (because it works in .39) which means that the problem must have been something in the kernel not passing along the multitouch sync events (I know it's that event missing from debugging the userland). That narrows things down quite a lot, but I don't think I really want to go back and spend the time fixing things up in the obsolete .27 kernel though.

fortunz said:

I assume pinch-to-zoom is pretty well supported in Android. Does this mean the zoom bar is now more supported (for zooming, button hacks aside) in XDAndroid than it ever was in officially baked HTC WinMo?

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Yes it does

fortunz said:

As for functionality, the p2z is cool, but not something I've been pining for. I don't know exactly what your plans are, but I'd love it if that function could be switched off easily (a line in startup.txt?), so future hacks creating, say, soft buttons on the bar instead could be more easily implemented.

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Thanks for the suggestion. I'm not going to be implementing it at this time, but the way things are structured in the code, it wouldn't be hard for it to be done by someone interested in the future.

When I was fighting with getting .27 working, I considered at one point simply turning the zoom bar into soft buttons. However, I was never able to come up with a practical use for soft buttons on the zoom bar. The thing that makes it hard is that the list of keyevents Android understand are extremely limited.

You can see for yourself here:
http://developer.android.com/reference/android/view/KeyEvent.html
Set the filter level to API level 8 to see what's available on Froyo. Unfortunately, really useful keyevents like button zoom in/out only became available in Honeycomb (API level 11).

I'm not sure that soft buttons for things like home or power or search would be very convenient when they're not visible on the physical device, are right next to the screen, and could instantly rip you out of what you're doing.

Just in case anyone happens across this that is interested in doing so, here is how you'd probably want to do it:
Android's KeyInputQueue.java, which handles inputs from the touchscreen (and everything else). Do a search for readVirtualKeys and see that it reads from /sys/board_properties/virtualkeys.tssc_manager. Edit the driver so that it generates the virtualkeys file in the format specified in KeyInputQueue, and disable all of the topaz/rhodium zoom bar code.

If anybody could find an app that supports touch pressure on a regular kernel on XDAndroid, that would be really helpful. I need to check how much we support pressure to start with and make sure that still is the case with this patch.

I tried Crayon Doodle Lite from the Market, which claims to support pressure, but I'm not seeing any pressure on a regular no-zoom-bar build, so that's not working as a test. Or it may simply be the case that pressure touch has always been broken.