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-rw-r--r--examples/widgets/painting/plot/doc/plot.pngbin0 -> 13030 bytes
-rw-r--r--examples/widgets/painting/plot/doc/plot.rst36
-rw-r--r--examples/widgets/painting/plot/plot.py66
-rw-r--r--examples/widgets/painting/plot/plot.pyproject3
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diff --git a/examples/widgets/painting/plot/doc/plot.png b/examples/widgets/painting/plot/doc/plot.png
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diff --git a/examples/widgets/painting/plot/doc/plot.rst b/examples/widgets/painting/plot/doc/plot.rst
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+Plot Example
+============
+
+The Plot example shows how to display a graph from data using an
+`opaque container <https://doc.qt.io/qtforpython-6/shiboken6/typesystem_containers.html>`_.
+
+It draws an sine graph using ``QPainter.drawPolyline()`` from a list of points.
+The list of points is continuously updated, as is the case for a example for a
+graph of an oscilloscope or medical patient monitor.
+In this case, it makes sense from a performance point of view to avoid the
+conversion of a Python list of data to a C++ list (``QList<QPoint>``)
+for each call to the plot function ``QPainter.drawPolyline()``.
+This is where opaque containers come into play.
+
+Instead of Python list of points, a ``QPointList`` is instantiated to store
+the data. ``QPointList`` is an opaque container wrapping a ``QList<QPoint>``.
+It can be passed to ``QPainter.drawPolyline()`` instead of a Python list of
+points.
+
+The type is declared in the entry for the ``QList`` container type in the
+type system file of the ``QtCore`` library:
+
+.. code-block:: xml
+
+ <container-type name="QList" type="list"
+ opaque-containers="int:QIntList;QPoint:QPointList;QPointF:QPointFList">
+ ...
+ </container-type>
+
+In the ``shift()`` member function, new data are appended to the list while
+old data moving out of the visible window are removed from the front of the
+list.
+
+.. image:: plot.png
+ :width: 400
+ :alt: Plot Screenshot
diff --git a/examples/widgets/painting/plot/plot.py b/examples/widgets/painting/plot/plot.py
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+# Copyright (C) 2022 The Qt Company Ltd.
+# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+import math
+import sys
+
+from PySide6.QtWidgets import QWidget, QApplication
+from PySide6.QtCore import QPoint, QRect, QTimer, Qt
+from PySide6.QtGui import QPainter, QPointList
+
+
+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._points.reserve(WIDTH)
+ 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):
+ with QPainter(self) as painter:
+ rect = QRect(QPoint(0, 0), self.size())
+ painter.fillRect(rect, Qt.white)
+ painter.translate(-self._points[0].x(), 0)
+ painter.drawPolyline(self._points)
+
+
+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
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+{
+ "files": ["plot.py"]
+}