Anchoring warnings in Buttons page in UITK Gallery

[Andrea Bernabei]

ubuntu-ui-toolkit/staging, r2090

1) Build uitk
2) run gallery with ./gallery.sh
3) Open Buttons page

Expected outcome:
no warnings

Actual outcome:
A few "QML Scrollbar: Cannot anchor to an item that isn't a parent or sibling."

Explanation:
That happens because Scrollbar anchors to the flickable item, but the ComboButton code has a hack that changes the parent of the Flickable to actually be Flickable's child. As a consequence Flickable is not a sibling of the scrollbar anymore, thus producing the anchor-related warning.

See http://bazaar.launchpad.net/~ubuntu-sdk-team/ubuntu-ui-toolkit/staging/annotate/2090/src/Ubuntu/Components/1.3/ComboButton.qml#L354

[Zsombor Egri (zsombi)]

I can confirm that revision 2045 brought these warnings in.

http://bazaar.launchpad.net/~ubuntu-sdk-team/ubuntu-ui-toolkit/staging/revision/2045

[Zsombor Egri (zsombi)]

This worked without any warnings before.

[Andrea Bernabei (faenil)]

rev2045 changes the order in which Scrollbar anchors to the flickable. since r2045 it waits for the flickable to be initialized before anchoring to it.

before:
Scrollbar anchors to flickable. Flickable parent changes, engine says nothing.

now:
Flickable is initialized, its parent changes. Scrollbar waits for flickable to be initialized, then anchors to it. QML engine notices that Flickable is not a sibling/parent, and warns about failed anchoring

My opinion:
I think we should double and triplecheck if we really need the flickable parent hack, otherwise we should remove it. An alternative could be to try and change the scrollbar parent at the same as the flickable parent changes, but I'm not sure that's going to prevent the warning from showing, as there should still be a moment when Flickable and Scrollbar are anchored but not in a relationship that allows anchoring one to the other.

[Zsombor Egri (zsombi)]

The Flickable and the Scrollbar could be replaced with a ScrollView. The Flickable stays inactive if the ComboButton content is set to be an other Flickable. Having a ScrollView we could reparent it to the visual's dropdown holder.

And we need to do this reparenting. The style's dropdown holder specifies the area and the place of the dropdown, and the way it expands (i.e. size expansion or overlay).

[Cris Dywan (kalikiana)]

=== modified file 'src/imports/Components/1.3/ComboButton.qml'
--- src/imports/Components/1.3/ComboButton.qml 2016-09-13 15:01:14 +0000
+++ src/imports/Components/1.3/ComboButton.qml 2016-09-13 15:57:46 +0000
@@ -395,6 +395,7 @@
         }
     }
     Scrollbar {
+ parent: comboHolder.parent
         flickableItem: comboHolder
     }

This appears to work. However no test seems to catch this problem - we need to find a way to test that this is actually fixed.