Scrolling doesn't work properly when first focusable item is outside first page

Original issue 137 created by codenameone on 2012-04-10T17:26:45.000Z:

What steps will reproduce the problem?

1. build attached source in CN1
2. start it in WTK emulator, press up arrow
3. see that it scrolls to the first focusable item, though it should stay unchanged

What is the expected output? What do you see instead?

What version of the product are you using? On what operating system?
last from trunk. The same was in LWUIT

Please provide any additional information below.

reproducible in CN1 simulator as well

Comment #1 originally posted by codenameone on 2012-04-10T18:02:49.000Z:

Can you have a look?

Comment #2 originally posted by codenameone on 2012-04-10T20:19:23.000Z:

I have a partial fix for this, pressing up won't move the scroll, but if you already down pressing down again will reset to the 0 position.
Let me know if this is good enough, it is a very sensitive piece of code and I don't want to create big changes here.

Comment #3 originally posted by codenameone on 2012-04-12T12:15:36.000Z:

Yes, it fixed the problem. It even worked for me for LWUIT 1.5 - I merged the fix and some related code. Thanks a lot.

Comment #4 originally posted by codenameone on 2012-04-12T12:17:21.000Z:

Could you please put revisions numbers next time into issue tracker, when closing an issue? I would help finding the changes in SVN

Comment #5 originally posted by codenameone on 2012-04-12T12:52:47.000Z:

We usually don't do that since committing is a separate process from closing the bug. The revision number won't help that much since we commit major blocks of code at once.

Comment #6 originally posted by codenameone on 2012-04-12T15:46:09.000Z:

Please consider attached example - it has an 'invisible' component at the bottom, because if you remove it, the last TextArea won't be seen (scroll can't go there). The example has a problem anyway - probably something like you mentioned, but when pressing UP key when scroll is at bottom. Also I observed some cases when pressing DOWN key at bottom changed scroll to top.

It's probably better than it was before, but not ideal anyway. I can live with this fix, but please consider it for general improvements. I mean that you do not need to issue a path right away, I think it's better to rework scrolling code later.

Frankly speaking, I was never able to get smart scrolling for BoxLayout(Y_AXIS) in LWUIT, and some issues always remained. I think that there's some flaw in scrolling approach which should be addressed in general way.