Add the Quick custom geometry example

Task-number: PYSIDE-1345
Change-Id: I7000878e3b2e83570653ca10ba084e133fec3cce
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>

4 files changed, 196 insertions, 0 deletions

diff --git a/examples/quick/scenegraph/scenegraph_customgeometry/doc/scenegraph_customgeometry.rst b/examples/quick/scenegraph/scenegraph_customgeometry/doc/scenegraph_customgeometry.rst
new file mode 100644
index 000000000..190ab80c2
--- /dev/null
+++ b/examples/quick/scenegraph/scenegraph_customgeometry/doc/scenegraph_customgeometry.rst
@@ -0,0 +1,7 @@
+Scene Graph - Custom Geometry
+=============================
+
+The custom geometry example shows how to create a QQuickItem which uses the
+scene graph API to build a custom geometry for the scene graph. It does this
+by creating a BezierCurve item which is made part of the CustomGeometry module
+and makes use of this in a QML file.
diff --git a/examples/quick/scenegraph/scenegraph_customgeometry/main.py b/examples/quick/scenegraph/scenegraph_customgeometry/main.py
new file mode 100644
index 000000000..60a904065
--- /dev/null
+++ b/examples/quick/scenegraph/scenegraph_customgeometry/main.py
@@ -0,0 +1,152 @@
+# Copyright (C) 2022 The Qt Company Ltd.
+# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+"""PySide6 port of the Qt Quick customgeometry example from Qt v6.x"""
+
+import sys
+from pathlib import Path
+
+from PySide6.QtQuick import (QQuickView, QQuickItem, QSGNode, QSGGeometryNode,
+                             QSGGeometry, QSGFlatColorMaterial)
+from PySide6.QtQml import QmlElement
+from PySide6.QtGui import QGuiApplication, QColor
+from PySide6.QtCore import (QPointF, QUrl, Property, Signal, Slot)
+
+# To be used on the @QmlElement decorator
+# (QML_IMPORT_MINOR_VERSION is optional)
+QML_IMPORT_NAME = "CustomGeometry"
+QML_IMPORT_MAJOR_VERSION = 1
+
+
+@QmlElement
+class BezierCurve(QQuickItem):
+    p1Changed = Signal()
+    p2Changed = Signal()
+    p3Changed = Signal()
+    p4Changed = Signal()
+    segmentCountChanged = Signal()
+
+    def __init__(self, parent=None):
+        super().__init__(parent)
+
+        self._p1 = QPointF(0, 0)
+        self._p2 = QPointF(1, 0)
+        self._p3 = QPointF(0, 1)
+        self._p4 = QPointF(1, 1)
+        self._segmentCount = 32
+
+        self._node = None
+        self._geometry = None
+        self.setFlag(QQuickItem.Flags.ItemHasContents, True)
+
+    def p1(self):
+        return self._p1
+
+    def p2(self):
+        return self._p2
+
+    def p3(self):
+        return self._p3
+
+    def p4(self):
+        return self._p4
+
+    def segmentCount(self):
+        return self._segmentCount
+
+    @Slot(QPointF)
+    def setP1(self, p):
+        if p != self._p1:
+            self._p1 = p
+            self.p1Changed.emit()
+            self.update()
+
+    @Slot(QPointF)
+    def setP2(self, p):
+        if p != self._p2:
+            self._p2 = p
+            self.p2Changed.emit()
+            self.update()
+
+    @Slot(QPointF)
+    def setP3(self, p):
+        if p != self._p3:
+            self._p3 = p
+            self.p3Changed.emit()
+            self.update()
+
+    @Slot(QPointF)
+    def setP4(self, p):
+        if p != self._p4:
+            self._p4 = p
+            self.p4Changed.emit()
+            self.update()
+
+    @Slot(int)
+    def setSegmentCount(self, p):
+        if p != self._segmentCount:
+            self._segmentCount = p
+            self.segmentCountChanged.emit()
+            self.update()
+
+    def updatePaintNode(self, oldNode, updatePaintNodeData):
+        self._node = oldNode
+        if not self._node:
+            self._default_attributes = QSGGeometry.defaultAttributes_Point2D()
+            self._geometry = QSGGeometry(self._default_attributes, self._segmentCount)
+            self._geometry.setLineWidth(2)
+            self._geometry.setDrawingMode(QSGGeometry.DrawingMode.DrawLineStrip)
+
+            self._node = QSGGeometryNode()
+            self._node.setGeometry(self._geometry)
+            self._node.setFlag(QSGNode.Flags.OwnsGeometry)
+            self._material = QSGFlatColorMaterial()
+            self._material.setColor(QColor(255, 0, 0))
+            self._node.setMaterial(self._material)
+            self._node.setFlag(QSGNode.Flags.OwnsMaterial)
+        else:
+            self._geometry = self._node.geometry()
+            self._geometry.allocate(self._segmentCount)
+
+        item_size = self.size()
+        item_width = float(item_size.width())
+        item_height = float(item_size.height())
+        vertices = self._geometry.vertexDataAsPoint2D()
+        for i in range(self._segmentCount):
+            t = float(i) / float(self._segmentCount - 1)
+            inv_t = 1 - t
+            pos = ((inv_t * inv_t * inv_t * self._p1)
+                   + (3 * inv_t * inv_t * t * self._p2)
+                   + (3 * inv_t * t * t * self._p3)
+                   + (t * t * t * self._p4))
+            vertices[i].set(pos.x() * item_width, pos.y() * item_height)
+
+        self._geometry.setVertexDataAsPoint2D(vertices)
+
+        self._node.markDirty(QSGNode.DirtyGeometry)
+        return self._node
+
+    p1 = Property(QPointF, p1, setP1, notify=p1Changed)
+    p2 = Property(QPointF, p2, setP2, notify=p2Changed)
+    p3 = Property(QPointF, p3, setP3, notify=p3Changed)
+    p4 = Property(QPointF, p4, setP4, notify=p4Changed)
+
+    segmentCount = Property(int, segmentCount, setSegmentCount,
+                            notify=segmentCountChanged)
+
+
+if __name__ == "__main__":
+    app = QGuiApplication([])
+    view = QQuickView()
+    format = view.format()
+    format.setSamples(16)
+    view.setFormat(format)
+
+    qml_file = Path(__file__).parent / "main.qml"
+    view.setSource(QUrl.fromLocalFile(qml_file))
+    if not view.rootObject():
+        sys.exit(-1)
+    view.show()
+    ex = app.exec()
+    del view
+    sys.exit(ex)
diff --git a/examples/quick/scenegraph/scenegraph_customgeometry/main.qml b/examples/quick/scenegraph/scenegraph_customgeometry/main.qml
new file mode 100644
index 000000000..88431a176
--- /dev/null
+++ b/examples/quick/scenegraph/scenegraph_customgeometry/main.qml
@@ -0,0 +1,34 @@
+// Copyright (C) 2022 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+import QtQuick
+import CustomGeometry
+
+Item {
+    width: 300
+    height: 200
+
+    BezierCurve {
+        id: line
+        anchors.fill: parent
+        anchors.margins: 20
+        property real t
+        SequentialAnimation on t {
+            NumberAnimation { to: 1; duration: 2000; easing.type: Easing.InOutQuad }
+            NumberAnimation { to: 0; duration: 2000; easing.type: Easing.InOutQuad }
+            loops: Animation.Infinite
+        }
+
+        p2: Qt.point(t, 1 - t)
+        p3: Qt.point(1 - t, t)
+    }
+
+    Text {
+        anchors.bottom: line.bottom
+        x: 20
+        width: parent.width - 40
+        wrapMode: Text.WordWrap
+
+        text: "This curve is a custom scene graph item, implemented using GL_LINE_STRIP"
+    }
+}
diff --git a/examples/quick/scenegraph/scenegraph_customgeometry/scenegraph_customgeometry.pyproject b/examples/quick/scenegraph/scenegraph_customgeometry/scenegraph_customgeometry.pyproject
new file mode 100644
index 000000000..a5247ef6c
--- /dev/null
+++ b/examples/quick/scenegraph/scenegraph_customgeometry/scenegraph_customgeometry.pyproject
@@ -0,0 +1,3 @@
+{
+    "files": ["main.py","main.qml"]
+}