Comment 3 for bug 1540240

Adding a reference to the G+ post where the discussion has started.
https://plus.google.com/u/0/104470462565851394948/posts/58xHJVYUYmj

It has been required to provide some case for which the default behaviour is not suitable.

I'm working on a note-taking app which would like to make use of a "Flexible space header"[1][2]:
https://www.youtube.com/watch?v=elFUk7bY7Ho

Currently the documentation for the PageHeader claims the ability to set any custom Item as extension as long as they have an height, so I decided to implement the "flexible space" as header extension.[3]
While this works properly when using a PageStack, I got a completely different result with an AdaptivePageLayout:
https://www.youtube.com/watch?v=jigZVlCPCkk

[1] Android UI guidelines - http://www.google.com/design/spec/patterns/scrolling-techniques.html#scrolling-techniques-scrolling
[2] The video is pretty old, sorry for the double header, but it was a fully custom implementation at the time.
[3] http://bazaar.launchpad.net/~ubuntu-sdk-team/ubuntu-ui-toolkit/staging/view/head:/src/Ubuntu/Components/1.3/PageHeader.qml#L214