Merge lp:~aacid/unity8/workaround_qt47709 into lp:unity8

[Albert Astals Cid]

Workaround for bug 1473471

After three days of debugging I've been able to figure out why it is crashing, why it's random and i can provide a quick workaround in unity8 code.

## Why is it crashing? ##

The problem exists because we use the QML cache and because Qt has this bug https://bugreports.qt.io/browse/QTBUG-47709

The bug in Qt means that if for types with extended properties (Image and "source" in our case coming from the SDK) an Item is created before the type is extended, all subsquent items of the same type won't see the extended property either.

Since we're using the QML cache this means that the code loaded from the cache expects the extended property to be there, so when it access such property, it will crash.

## Why is it random? ##

It's random because the QML file loading is not always done in the *exact* same order, and thus in some cases the first Image is created in a file that imports Ubuntu.Components and in some cases the first image is created in a file that does not.

## How to workaround it? ##

A quick workaround is making sure Ubuntu.Components is imported in the first file that is imported, in unity8's case UnityInputInfo.qml that is a singleton imported from the root file (OrientedShell.qml)

 * Are there any related MPs required for this MP to build/function as expected?
No

 * Did you perform an exploratory manual test run of your code change and any related functionality?
Yes

 * Did you make sure that your branch does not contain spurious tags?
Yes

 * If you changed the packaging (debian), did you subscribe the ubuntu-unity team to this MP?
N/A

 * If you changed the UI, has there been a design review?
N/A

[Gerry Boland (gerboland)]

Explanation makes sense, happy to approve

review: Approve

[Gerry Boland (gerboland)]

 * Did you perform an exploratory manual test run of the code change and any related functionality?
Y
 * Did CI run pass? If not, please explain why.
give it time
 * Did you make sure that the branch does not contain spurious tags?
Y

=== modified file 'qml/Components/UnityInputInfo/UnityInputInfo.qml'
--- qml/Components/UnityInputInfo/UnityInputInfo.qml	2015-06-30 11:43:14 +0000
+++ qml/Components/UnityInputInfo/UnityInputInfo.qml	2015-08-11 11:37:24 +0000
@@ -18,6 +18,8 @@
 
 import QtQuick 2.3
 import Unity.InputInfo 0.1
+// Workaround https://bugs.launchpad.net/ubuntu/+source/unity8/+bug/1473471
+import Ubuntu.Components 1.2
 
 Item {
     id: root

=== modified file 'qml/OrientedShell.qml'
--- qml/OrientedShell.qml	2015-07-06 12:52:08 +0000
+++ qml/OrientedShell.qml	2015-08-11 11:37:24 +0000
@@ -21,6 +21,9 @@
 import "Components"
 import "Components/UnityInputInfo"
 import "Rotation"
+// Backup Workaround https://bugs.launchpad.net/ubuntu/+source/unity8/+bug/1473471
+// in case we remove the UnityInputInfo import
+import Ubuntu.Components 1.2
 
 Rectangle {
     id: root