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>

4 files changed, 209 insertions, 0 deletions

diff --git a/examples/quick/delegatechooser/delegatechooser.pro b/examples/quick/delegatechooser/delegatechooser.pro
new file mode 100644
index 0000000000..f06864ba89
--- /dev/null
+++ b/examples/quick/delegatechooser/delegatechooser.pro
@@ -0,0 +1,8 @@
+TEMPLATE = app
+QT += quick qml
+
+SOURCES += main.cpp
+RESOURCES += qml.qrc ../shared/shared.qrc
+
+target.path = $$[QT_INSTALL_EXAMPLES]/quick/delegatechooser
+INSTALLS += target
diff --git a/examples/quick/delegatechooser/delegatechooser.qml b/examples/quick/delegatechooser/delegatechooser.qml
new file mode 100644
index 0000000000..afb8518abf
--- /dev/null
+++ b/examples/quick/delegatechooser/delegatechooser.qml
@@ -0,0 +1,145 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.12
+import QtQml.Models 2.12
+import QtQuick.Layouts 1.12
+import Qt.labs.qmlmodels 1.0
+
+Rectangle {
+    visible: true
+    width: 640
+    height: 640
+
+    ListModel {
+        id: listModel
+        ListElement { dataType: "rect"; color: "green" }
+        ListElement { dataType: "image"; source: "../shared/images/qt-logo.png" }
+        ListElement { dataType: "rect"; color: "green" }
+        ListElement { dataType: "image"; source: "../shared/images/qt-logo.png" }
+        ListElement { dataType: "rect"; color: "blue" }
+        ListElement { dataType: "rect"; color: "blue" }
+        ListElement { dataType: "rect"; color: "blue" }
+        ListElement { dataType: "rect"; color: "blue" }
+        ListElement { dataType: "rect"; color: "blue" }
+        ListElement { dataType: "rect"; color: "blue" }
+    }
+
+    ListModel {
+        id: listModel2
+        ListElement { dataType: "rect"; color: "blue" }
+        ListElement { dataType: "rect"; color: "blue" }
+        ListElement { dataType: "rect"; color: "green" }
+        ListElement { dataType: "image"; source: "../shared/images/qt-logo.png" }
+        ListElement { dataType: "rect"; color: "green" }
+        ListElement { dataType: "image"; source: "../shared/images/qt-logo.png" }
+        ListElement { dataType: "rect"; color: "blue" }
+        ListElement { dataType: "rect"; color: "lightsteelblue" }
+        ListElement { dataType: "rect"; color: "fuchsia" }
+        ListElement { dataType: "rect"; color: "lime" }
+    }
+
+    DelegateChooser {
+        id: fancyDelegate
+        role: "dataType"
+        DelegateChoice {
+            roleValue: "rect"
+            delegate: DelegateChooser {
+                DelegateChoice {
+                    row: 0
+                    Rectangle {
+                        width: parent.width
+                        height: 50
+                        color: "red"
+                        border.color: "black"
+                        border.width: 1
+                    }
+                }
+                DelegateChoice {
+                    Rectangle {
+                        width: parent.width
+                        height: 50
+                        color: model.color
+                        border.color: "black"
+                        border.width: 1
+                    }
+                }
+            }
+        }
+        DelegateChoice {
+            roleValue: "image"
+            delegate: Image {
+                width: parent.width
+                height: 100
+                source: model.source
+                fillMode: Image.PreserveAspectFit
+            }
+        }
+    }
+
+    Item {
+        anchors.fill: parent
+        id: ite
+        RowLayout {
+            ListView {
+                Layout.preferredHeight: ite.height
+                Layout.preferredWidth: ite.width * 0.5
+                model: listModel
+                delegate: fancyDelegate
+            }
+            ListView {
+                Layout.preferredHeight: ite.height
+                Layout.preferredWidth: ite.width * 0.5
+                model: listModel2
+                delegate: fancyDelegate
+            }
+        }
+    }
+}
diff --git a/examples/quick/delegatechooser/main.cpp b/examples/quick/delegatechooser/main.cpp
new file mode 100644
index 0000000000..5df9207e24
--- /dev/null
+++ b/examples/quick/delegatechooser/main.cpp
@@ -0,0 +1,51 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+#include "../shared/shared.h"
+DECLARATIVE_EXAMPLE_MAIN(delegatechooser)
diff --git a/examples/quick/delegatechooser/qml.qrc b/examples/quick/delegatechooser/qml.qrc
new file mode 100644
index 0000000000..0788f84c64
--- /dev/null
+++ b/examples/quick/delegatechooser/qml.qrc
@@ -0,0 +1,5 @@
+<RCC>
+    <qresource prefix="/">
+        <file>delegatechooser.qml</file>
+    </qresource>
+</RCC>