Backwards compatibility and auto updates

[Daniel Zwolenski]

Hey guys,

I've touched on this before but I am a bit (ok, very) worried about
backwards compatibility and auto-updates, particularly in the area of
visual appearance, and most obviously with CSS.

Let's take a seemingly innocent fix like this one:
http://javafx-jira.kenai.com/browse/RT-16589

So now suddenly when JavaFX auto-updates itself (which I have very little
control over), some of my font sizes may suddenly halve if they were
impacted by this fix?

What if the fix was to do with visibility and suddenly an all important
button is no longer visible, or to do with colours and now my white text is
suddenly on a white background and can't be read. Aside from CSS, what if
the fix was to an animation class, and suddenly my animation is 'fixed' so
maybe a bug in the fade was making my node invisible, but now the fix makes
it visible when I'm not expecting it to be, etc. This has the potential to
completely break my GUI.

All of these *visual* aspects can't be tested with regression testing and
API compatibility tests. A UI toolkit is not like a normal Java API where
we can just say, yep it compiles and the unit tests all still work, so it
will be fine. Even if we could do this, would we want to? We need to be
able to fix visual things, and given the incredibly loose, highly-coupled
way CSS does it's selectors (one tiny change to your CSS file can change
everything) it will be pretty much impossible to do this without 'breaking'
existing GUIs.

The problem in my mind is that we cannot 'fix' our apps to a particular
version of JFX. This auto-update (and co-bundling) stuff is going to make
life very hard in this field.

What are your thoughts? Does anyone else share these concerns?

Cheers,
Dan