shiboken6: Add opaque containers for C++ sequence containers

Add a class that directly wraps a C++ sequence container,
allow for modifying them.

For all instantiated containers, generate a special (sequence) type
that wraps the C++ container directly. For example, it will be
accessible as a QList_int.

This is achieved via providing a template for a type private
that relies on a conversion traits template for conversion.
Only the  conversion traits specialization code needs to be generated.

Use cases:
- Allowing for modifying Fields of such container types
  (non-owning)
- Pass it into functions taking such containers instead of converting
  back and forth from a PyList (constructed in Python, owning)

[ChangeLog][shiboken6] Support for opaque C++ sequence scontainers
has been added, allowing to pass a wrapped C++ container
directly instead of converting it back and forth from
Python sequences.

Task-number: PYSIDE-1605
Change-Id: I49d378eb1a0151730d817d5bdd4b71a7c3b5cdda
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>

2 files changed, 108 insertions, 0 deletions

diff --git a/examples/widgets/painting/plot/plot.py b/examples/widgets/painting/plot/plot.py
new file mode 100644
index 000000000..156a6408d
--- /dev/null
+++ b/examples/widgets/painting/plot/plot.py
@@ -0,0 +1,105 @@
+#############################################################################
+##
+## Copyright (C) 2021 The Qt Company Ltd.
+## Contact: https://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."
+##
+## $QT_END_LICENSE$
+##
+#############################################################################
+
+import math
+import sys
+
+from PySide6.QtWidgets import QWidget, QApplication
+from PySide6.QtCore import QPoint, QRect, QTimer, Qt, Slot
+from PySide6.QtGui import (QColor, QPainter, QPaintEvent, QPen, QPointList,
+                           QTransform)
+
+
+WIDTH = 680
+HEIGHT = 480
+
+
+class PlotWidget(QWidget):
+    """Illustrates the use of opaque containers. QPointList
+       wraps a C++ QList<QPoint> directly, removing the need to convert
+       a Python list in each call to QPainter.drawPolyline()."""
+
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        self._timer = QTimer(self)
+        self._timer.setInterval(20)
+        self._timer.timeout.connect(self.shift)
+
+        self._points = QPointList()
+        self._x = 0
+        self._delta_x = 0.05
+        self._half_height = HEIGHT / 2
+        self._factor = 0.8 * self._half_height
+
+        for i in range(WIDTH):
+            self._points.append(QPoint(i, self.next_point()))
+
+        self.setFixedSize(WIDTH, HEIGHT)
+
+        self._timer.start()
+
+    def next_point(self):
+        result = self._half_height - self._factor * math.sin(self._x)
+        self._x += self._delta_x
+        return result
+
+    def shift(self):
+        last_x = self._points[WIDTH - 1].x()
+        self._points.pop_front()
+        self._points.append(QPoint(last_x + 1, self.next_point()))
+        self.update()
+
+    def paintEvent(self, event):
+        painter = QPainter()
+        painter.begin(self)
+        rect = QRect(QPoint(0, 0), self.size())
+        painter.fillRect(rect, Qt.white)
+        painter.translate(-self._points[0].x(), 0)
+        painter.drawPolyline(self._points)
+        painter.end()
+
+
+if __name__ == "__main__":
+
+    app = QApplication(sys.argv)
+
+    w = PlotWidget()
+    w.show()
+    sys.exit(app.exec())
diff --git a/examples/widgets/painting/plot/plot.pyproject b/examples/widgets/painting/plot/plot.pyproject
new file mode 100644
index 000000000..0ac776c83
--- /dev/null
+++ b/examples/widgets/painting/plot/plot.pyproject
@@ -0,0 +1,3 @@
+{
+    "files": ["plot.py"]
+}