Allow DelegateModel-based views to support multiple delegate types

This patch adds a specific abstract QQmlComponent subclass,
QQmlAbstractDelegateComponent, and a default implementation,
DelegateChooser, that, together with the type DelegateChoice
allows determining the delegate type by role and/or index.

The patch also adds QQmlAbstractDelegateComponent support
to QQmlTableInstanceModel, that is a simplified version of
the delegate model, currently only used in the new table view.

DelegateChoosers are intended to behave just like Components
in the context of the view. This means that they can be declared
outside of the view, and also in separate files, and the same
delegate component can be used at the same time in multiple views.

[ChangeLog][QtQuick][Item Views] Added a DelegateChooser Component
to host DelegateChoice instances to choose different delegates in
an Item View (e.g. TableView) depending on model roles.

Done-with: Michael Brasser <michael.brasser@live.com>
Task-number: QTBUG-26681
Change-Id: Ibe24a31daf9142c8a9ff45ef6c65da0aec8a14dc
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 5 insertions, 1 deletions

diff --git a/src/qml/types/qqmltableinstancemodel_p.h b/src/qml/types/qqmltableinstancemodel_p.h
index 93ef4a697f..03761af326 100644
--- a/src/qml/types/qqmltableinstancemodel_p.h
+++ b/src/qml/types/qqmltableinstancemodel_p.h
@@ -57,6 +57,7 @@
 QT_BEGIN_NAMESPACE
 
 class QQmlTableInstanceModel;
+class QQmlAbstractDelegateComponent;
 
 class QQmlTableInstanceModelIncubationTask : public QQDMIncubationTask
 {
@@ -128,8 +129,11 @@ Q_SIGNALS:
     void itemReused(int index, QObject *object);
 
 private:
-    QQmlComponent *m_delegate = nullptr;
+    QQmlComponent *resolveDelegate(int index);
+
     QQmlAdaptorModel m_adaptorModel;
+    QQmlAbstractDelegateComponent *m_delegateChooser = nullptr;
+    QQmlComponent *m_delegate = nullptr;
     QPointer<QQmlContext> m_qmlContext;
     QQmlDelegateModelItemMetaType *m_metaType;