Let specifying the fallback style for custom styles

For example, you can call QQuickStyle::setStyle(":/mycontrols") and
QQuickStyle::setFallbackStyle("Material") to select a custom style so
that the missing files will fallback to the Material style.

Notice that the Material and Universal styles do not contain all files.
For example, the non-visual Control.qml, Container.qml are not duplicated.
For these, we must fallback to the Default style that is guaranteed to
contain them all.

[ChangeLog][Controls] Added support for specifying the fallback style for
custom styles via :/qtquickcontrols2.conf, QT_QUICK_CONTROLS_FALLBACK_STYLE
or QQuickStyle::setFallbackStyle().

Change-Id: I00be1c8c6aaca875ef851c90d018e9b5e2f501b7
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 2 insertions, 0 deletions

diff --git a/tests/auto/qquickstyleselector/data/Control.qml b/tests/auto/qquickstyleselector/data/Control.qml
new file mode 100644
index 00000000..697662f6
--- /dev/null
+++ b/tests/auto/qquickstyleselector/data/Control.qml
@@ -0,0 +1,2 @@
+import QtQuick.Templates 2.1 as T
+T.Control { }