Add example for Threads and Signals

The goal of this file is to provide an example for signals being
emitted from one thread to another.

Task-number: PYSIDE-841
Change-Id: If494fbfef6d8c46b37d5b750163c909bc6c55c7a
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>

1 files changed, 98 insertions, 0 deletions

diff --git a/examples/widgets/threads/thread_signals.py b/examples/widgets/threads/thread_signals.py
new file mode 100644
index 000000000..e12fdcecf
--- /dev/null
+++ b/examples/widgets/threads/thread_signals.py
@@ -0,0 +1,98 @@
+#############################################################################
+##
+## Copyright (C) 2020 The Qt Company Ltd.
+## Contact: https://www.qt.io/licensing/
+##
+## This file is part of the Qt for Python project.
+##
+## $QT_BEGIN_LICENSE:LGPL$
+## 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.
+##
+## GNU Lesser General Public License Usage
+## Alternatively, this file may be used under the terms of the GNU Lesser
+## General Public License version 3 as published by the Free Software
+## Foundation and appearing in the file LICENSE.LGPL3 included in the
+## packaging of this file. Please review the following information to
+## ensure the GNU Lesser General Public License version 3 requirements
+## will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+##
+## GNU General Public License Usage
+## Alternatively, this file may be used under the terms of the GNU
+## General Public License version 2.0 or (at your option) the GNU General
+## Public license version 3 or any later version approved by the KDE Free
+## Qt Foundation. The licenses are as published by the Free Software
+## Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+## included in the packaging of this file. Please review the following
+## information to ensure the GNU General Public License requirements will
+## be met: https://www.gnu.org/licenses/gpl-2.0.html and
+## https://www.gnu.org/licenses/gpl-3.0.html.
+##
+## $QT_END_LICENSE$
+##
+#############################################################################
+
+import sys
+from PySide2.QtCore import QObject, QThread, Signal, Slot
+from PySide2.QtWidgets import QApplication, QPushButton, QVBoxLayout, QWidget
+
+
+# Create a basic window with a layout and a button
+class MainForm(QWidget):
+    def __init__(self):
+        QWidget.__init__(self)
+        self.setWindowTitle("My Form")
+        self.layout = QVBoxLayout()
+        self.button = QPushButton("Click me!")
+        self.button.clicked.connect(self.start_thread)
+        self.layout.addWidget(self.button)
+        self.setLayout(self.layout)
+
+    # Instantiate and start a new thread
+    def start_thread(self):
+        instanced_thread = WorkerThread(self)
+        instanced_thread.start()
+
+    # Create the Slots that will receive signals
+    @Slot(str)
+    def update_str_field(self, message):
+        print(message)
+
+    @Slot(int)
+    def update_int_field(self, value):
+        print(value)
+
+
+# Signals must inherit QObject
+class MySignals(QObject):
+    signal_str = Signal(str)
+    signal_int = Signal(int)
+
+
+# Create the Worker Thread
+class WorkerThread(QThread):
+    def __init__(self, parent=None):
+        QThread.__init__(self, parent)
+        # Instantiate signals and connect signals to the slots
+        self.signals = MySignals()
+        self.signals.signal_str.connect(parent.update_str_field)
+        self.signals.signal_int.connect(parent.update_int_field)
+
+    def run(self):
+        # Do something on the worker thread
+        a = 1 + 1
+        # Emit signals whenever you want
+        self.signals.signal_int.emit(a)
+        self.signals.signal_str.emit("This text comes to Main thread from our Worker thread.")
+
+
+if __name__ == "__main__":
+    app = QApplication(sys.argv)
+    window = MainForm()
+    window.show()
+    sys.exit(app.exec_())