Add the extended' example of the QML reference examples

Task-number: PYSIDE-841
Task-number: PYSIDE-1709
Change-Id: If6e52c9f1d8d6d980727143e20de031e750607a4
Reviewed-by: Shyamnath Premnadh <Shyamnath.Premnadh@qt.io>
Reviewed-by: Christian Tismer <tismer@stackless.com>

4 files changed, 231 insertions, 0 deletions

diff --git a/examples/declarative/referenceexamples/extended/doc/extended.rst b/examples/declarative/referenceexamples/extended/doc/extended.rst
new file mode 100644
index 000000000..1f78ac1b8
--- /dev/null
+++ b/examples/declarative/referenceexamples/extended/doc/extended.rst
@@ -0,0 +1,41 @@
+.. _qml-extension-objects-example
+
+Extending QML - Extension Objects Example
+=========================================
+
+This example builds on the the :ref:`qml-adding-types-example`.
+
+Shows how to use QmlExtended decorator to provide an extension object to a
+QLineEdit without modifying or subclassing it.
+
+Firstly, the LineEditExtension class is registered with the QML system as an
+extension of QLineEdit. We declare a foreign type to do this as we cannot
+modify Qt's internal QLineEdit class.
+
+.. code-block:: python
+
+    @QmlNamedElement("QLineEdit")
+    @QmlExtended(LineEditExtension)
+    @QmlForeign(QLineEdit)
+    class LineEditForeign(QObject):
+
+
+Note the usage of ``QmlNamedElement()`` instead of ``QmlElement()``.
+``QmlElement()`` uses the name of the containing type by default,
+``LineEditExtension`` in this case. As the class being an extension class is
+an implementation detail, we choose the more natural name ``QLineEdit``
+instead.
+
+The QML engine then instantiates a QLineEdit.
+
+In QML, a property is set on the line edit that only exists in the
+``LineEditExtension`` class:
+
+.. code-block:: javascript
+
+    QLineEdit {
+        left_margin: 20
+    }
+
+The extension type performs calls on the ``QLineEdit`` that otherwise will not
+be accessible to the QML engine.
diff --git a/examples/declarative/referenceexamples/extended/example.qml b/examples/declarative/referenceexamples/extended/example.qml
new file mode 100644
index 000000000..e905f7c3e
--- /dev/null
+++ b/examples/declarative/referenceexamples/extended/example.qml
@@ -0,0 +1,55 @@
+/****************************************************************************
+**
+** Copyright (C) 2022 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 examples.extend 1.0
+
+QLineEdit {
+    left_margin: 20
+}
diff --git a/examples/declarative/referenceexamples/extended/extended.pyproject b/examples/declarative/referenceexamples/extended/extended.pyproject
new file mode 100644
index 000000000..127a3a76a
--- /dev/null
+++ b/examples/declarative/referenceexamples/extended/extended.pyproject
@@ -0,0 +1,3 @@
+{
+    "files": ["main.py", "example.qml"]
+}
diff --git a/examples/declarative/referenceexamples/extended/main.py b/examples/declarative/referenceexamples/extended/main.py
new file mode 100644
index 000000000..c553a1fa8
--- /dev/null
+++ b/examples/declarative/referenceexamples/extended/main.py
@@ -0,0 +1,132 @@
+#############################################################################
+##
+## Copyright (C) 2022 The Qt Company Ltd.
+## Contact: http://www.qt.io/licensing/
+##
+## This file is part of the Qt for Python examples of the Qt Toolkit.
+##
+## $QT_BEGIN_LICENSE:BSD$
+## 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."
+##
+## $QT_END_LICENSE$
+##
+#############################################################################
+
+"""PySide6 port of the qml/examples/qml/referenceexamples/extended example from Qt v6.x"""
+
+from pathlib import Path
+import sys
+
+from PySide6.QtCore import QObject, QUrl, Property
+from PySide6.QtWidgets import QApplication, QLineEdit
+from PySide6.QtQml import (QQmlComponent, QQmlEngine, QmlForeign, QmlExtended,
+                           QmlNamedElement)
+
+
+# To be used on the @QmlElement decorator
+# (QML_IMPORT_MINOR_VERSION is optional)
+QML_IMPORT_NAME = "examples.extend"
+QML_IMPORT_MAJOR_VERSION = 1
+
+
+class LineEditExtension(QObject):
+
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        self._line_edit = parent
+
+    @Property(int)
+    def left_margin(self):
+        return self._line_edit.textMargins().left()
+
+    @left_margin.setter
+    def left_margin(self, m):
+        margins = self._line_edit.textMargins()
+        margins.setLeft(m)
+        self._line_edit.setTextMargins(margins)
+
+    @Property(int)
+    def right_margin(self):
+        return self._line_edit.textMargins().right()
+
+    @right_margin.setter
+    def right_margin(self, m):
+        margins = self._line_edit.textMargins()
+        margins.setRight(m)
+        self._line_edit.setTextMargins(margins)
+
+    @Property(int)
+    def top_margin(self):
+        return self._line_edit.textMargins().top()
+
+    @top_margin.setter
+    def top_margin(self, m):
+        margins = self._line_edit.textMargins()
+        margins.setTop(m)
+        self._line_edit.setTextMargins(margins)
+
+    @Property(int)
+    def bottom_margin(self):
+        return self._line_edit.textMargins().bottom()
+
+    @bottom_margin.setter
+    def bottom_margin(self, m):
+        margins = self._line_edit.textMargins()
+        margins.setBottom(m)
+        self._line_edit.setTextMargins(margins)
+
+
+@QmlNamedElement("QLineEdit")
+@QmlExtended(LineEditExtension)
+@QmlForeign(QLineEdit)
+class LineEditForeign(QObject):
+
+    def __init__(self, parent=None):
+        super().__init__(parent)
+
+
+if __name__ == '__main__':
+    app = QApplication(sys.argv)
+
+    qml_file = Path(__file__).parent / "example.qml"
+    url = QUrl.fromLocalFile(qml_file)
+    engine = QQmlEngine()
+    component = QQmlComponent(engine, url)
+    widget = component.create()
+    if not widget:
+        print(component.errors())
+        del engine
+        sys.exit(-1)
+
+    widget.show()
+    r = app.exec()
+    # Deleting the engine before it goes out of scope is required to make sure
+    # all child QML instances are destroyed in the correct order.
+    del engine
+    sys.exit(r)