wasm: add manual tests for main() and exec()

Add minimal examples which demonstrates how exec() works
on Qt for WebAssembly and how to implement main() without
calling QApplication::exec().

Change-Id: I44f1d16af19c538380cc56faf3f0f4cc9d66cf11
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

10 files changed, 367 insertions, 0 deletions

diff --git a/tests/manual/wasm/CMakeLists.txt b/tests/manual/wasm/CMakeLists.txt
index af319541d5..cd594e7112 100644
--- a/tests/manual/wasm/CMakeLists.txt
+++ b/tests/manual/wasm/CMakeLists.txt
@@ -1,3 +1,4 @@
+add_subdirectory(eventloop)
 if(QT_FEATURE_widgets)
 add_subdirectory(cursors)
 add_subdirectory(localfiles)
diff --git a/tests/manual/wasm/README.md b/tests/manual/wasm/README.md
index 4b205027db..23dffe6045 100644
--- a/tests/manual/wasm/README.md
+++ b/tests/manual/wasm/README.md
@@ -9,4 +9,5 @@ Content
 -------
 
     cursors         Cursor handling
+    eventloop       Event loops, application startup, dialog exec()
     localfiles      Local file download and upload
diff --git a/tests/manual/wasm/eventloop/CMakeLists.txt b/tests/manual/wasm/eventloop/CMakeLists.txt
new file mode 100644
index 0000000000..4dbb3cacf9
--- /dev/null
+++ b/tests/manual/wasm/eventloop/CMakeLists.txt
@@ -0,0 +1,5 @@
+add_subdirectory(main_exec)
+add_subdirectory(main_noexec)
+if(QT_FEATURE_widgets)
+add_subdirectory(dialog_exec)
+endif()
diff --git a/tests/manual/wasm/eventloop/README.md b/tests/manual/wasm/eventloop/README.md
new file mode 100644
index 0000000000..7b15a7d0ca
--- /dev/null
+++ b/tests/manual/wasm/eventloop/README.md
@@ -0,0 +1,13 @@
+Event loop exec() and main() on Qt for WebAssembly
+==================================================
+
+These examples demonstrate how QEventLoop::exec() works on
+Qt for WebAssembly, and also shows how to implement main()
+without calling QApplication::exec().
+
+Contents
+========
+
+    main_exec       Standard Qt main(), where QApplication::exec() does not return
+    main_noexec     Qt main() without QApplication::exec()
+    dialog_exec     Shows how QDialog::exec() also does not return
diff --git a/tests/manual/wasm/eventloop/dialog_exec/CMakeLists.txt b/tests/manual/wasm/eventloop/dialog_exec/CMakeLists.txt
new file mode 100644
index 0000000000..00bbca0b9d
--- /dev/null
+++ b/tests/manual/wasm/eventloop/dialog_exec/CMakeLists.txt
@@ -0,0 +1,9 @@
+qt_internal_add_manual_test(dialog_exec
+    GUI
+    SOURCES
+        main.cpp
+    PUBLIC_LIBRARIES
+        Qt::Core
+        Qt::Gui
+        Qt::Widgets
+)
diff --git a/tests/manual/wasm/eventloop/dialog_exec/main.cpp b/tests/manual/wasm/eventloop/dialog_exec/main.cpp
new file mode 100644
index 0000000000..d10230262d
--- /dev/null
+++ b/tests/manual/wasm/eventloop/dialog_exec/main.cpp
@@ -0,0 +1,95 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 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."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+#include <QtGui>
+#include <QtWidgets>
+
+// This example show how calling QDialog::exec() shows the dialog,
+// but does not return.
+
+class ClickWindow: public QRasterWindow
+{
+public:
+    ClickWindow() {
+        qDebug() << "ClickWindow constructor";
+    }
+
+    ~ClickWindow() {
+        qDebug() << "ClickWindow destructor";
+    }
+
+    void paintEvent(QPaintEvent *ev) override {
+        QPainter p(this);
+        p.fillRect(ev->rect(), QColorConstants::Svg::deepskyblue);
+        p.drawText(50, 100, "Application has started. See the developer tools console for debug output");
+    }
+
+    void mousePressEvent(QMouseEvent *) override {
+        qDebug() << "mousePressEvent(): calling QMessageBox::exec()";
+
+        QMessageBox messageBox;
+        messageBox.setText("Hello! This is a message box.");
+        connect(&messageBox, &QMessageBox::buttonClicked, [](QAbstractButton *button) {
+           qDebug() << "Button Clicked" << button;
+        });
+        messageBox.exec(); // <-- does not return
+
+        qDebug() << "mousePressEvent(): done"; // <---  will not be printed
+    }
+};
+
+int main(int argc, char **argv)
+{
+    QApplication app(argc, argv);
+
+    ClickWindow window;
+    window.show();
+
+    return app.exec();
+}
diff --git a/tests/manual/wasm/eventloop/main_exec/CMakeLists.txt b/tests/manual/wasm/eventloop/main_exec/CMakeLists.txt
new file mode 100644
index 0000000000..b5d987f8cb
--- /dev/null
+++ b/tests/manual/wasm/eventloop/main_exec/CMakeLists.txt
@@ -0,0 +1,8 @@
+qt_internal_add_manual_test(main_exec
+    GUI
+    SOURCES
+        main.cpp
+    PUBLIC_LIBRARIES
+        Qt::Core
+        Qt::Gui
+)
diff --git a/tests/manual/wasm/eventloop/main_exec/main.cpp b/tests/manual/wasm/eventloop/main_exec/main.cpp
new file mode 100644
index 0000000000..d1eeaeaae3
--- /dev/null
+++ b/tests/manual/wasm/eventloop/main_exec/main.cpp
@@ -0,0 +1,114 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 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."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+#include <QtGui>
+
+// This example demonstrates how the standard Qt main()
+// pattern works on Emscripten/WebAssambly, where exec()
+// does not return.
+
+class ClickWindow: public QRasterWindow
+{
+public:
+    ClickWindow() {
+        qDebug() << "ClickWindow constructor";
+    }
+    ~ClickWindow() {
+        qDebug() << "ClickWindow destructor";
+    }
+
+    void paintEvent(QPaintEvent *ev) override {
+        QPainter p(this);
+        p.fillRect(ev->rect(), QColorConstants::Svg::deepskyblue);
+        p.drawText(50, 100, "Application has started. See the developer tools console for debug output");
+    }
+
+    void mousePressEvent(QMouseEvent *) override {
+        qDebug() << "mousePressEvent(): calling QGuiApplication::quit()";
+        QGuiApplication::quit();
+    }
+};
+
+int main(int argc, char **argv)
+{
+    qDebug() << "main(): Creating QGuiApplication object";
+    QGuiApplication app(argc, argv);
+
+    QObject::connect(&app, &QCoreApplication::aboutToQuit, [](){
+        qDebug() << "QCoreApplication::aboutToQuit";
+    });
+
+    ClickWindow window;
+    window.show();
+
+    qDebug() << "main(): calling exec()";
+    app.exec();
+
+    // The exec() call above never returns; instead, a JavaScript exception
+    // is thrown such that control returns to the browser while preserving
+    // the C++ stack.
+
+    // This means that the window object above is not destroyed, and that
+    // shutdown code after exec() does not run.
+
+    qDebug() << "main(): after exit"; // <- will not be printed
+}
+
+// Global variables are created before main() as usual, but not destroyed
+class Global
+{
+public:
+    Global() {
+        qDebug() << "Global constructor";
+    }
+    ~Global() {
+        qDebug() << "Global destructor"; // <- will not be printed
+    }
+};
+Global global;
diff --git a/tests/manual/wasm/eventloop/main_noexec/CMakeLists.txt b/tests/manual/wasm/eventloop/main_noexec/CMakeLists.txt
new file mode 100644
index 0000000000..23d48b626f
--- /dev/null
+++ b/tests/manual/wasm/eventloop/main_noexec/CMakeLists.txt
@@ -0,0 +1,8 @@
+qt_internal_add_manual_test(main_noexec
+    GUI
+    SOURCES
+        main.cpp
+    PUBLIC_LIBRARIES
+        Qt::Core
+        Qt::Gui
+)
diff --git a/tests/manual/wasm/eventloop/main_noexec/main.cpp b/tests/manual/wasm/eventloop/main_noexec/main.cpp
new file mode 100644
index 0000000000..16f5a2b026
--- /dev/null
+++ b/tests/manual/wasm/eventloop/main_noexec/main.cpp
@@ -0,0 +1,113 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 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."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+#include <QtGui>
+
+// This example demonstrates how to create QGuiApplication
+// without calling exec(), and then exiting main() without
+// shutting down the Qt event loop.
+
+class ClickWindow: public QRasterWindow
+{
+public:
+
+    ClickWindow() {
+        qDebug() << "ClickWindow constructor";
+    }
+    ~ClickWindow() {
+        qDebug() << "ClickWindow destructor";
+    }
+
+    void paintEvent(QPaintEvent *ev) override {
+        QPainter p(this);
+        p.fillRect(ev->rect(), QColorConstants::Svg::deepskyblue);
+        p.drawText(50, 100, "Application has started. See the developer tools console for debug output");
+    }
+
+    void mousePressEvent(QMouseEvent *) override {
+        qDebug() << "mousePressEvent(): calling QGuiApplication::quit()";
+        QGuiApplication::quit();
+    }
+};
+
+int main(int argc, char **argv)
+{
+    qDebug() << "main(): Creating QGuiApplication object";
+    QGuiApplication *app = new QGuiApplication(argc, argv);
+
+    QObject::connect(app, &QCoreApplication::aboutToQuit, [](){
+        qDebug() << "QCoreApplication::aboutToQuit";
+    });
+
+    qDebug() << "main(): Creating ClickWindow object";
+    ClickWindow *window = new ClickWindow();
+    window->show();
+
+    // We can exit main; the Qt event loop and the emscripten runtime
+    // will keep running, as long as Emscriptens EXIT_RUNTIME option
+    // has not been enabled.
+
+    qDebug() << "main(): exit";
+}
+
+// Global variables are created before main() as usual, but not destroyed
+class Global
+{
+public:
+    Global() {
+        qDebug() << "Global constructor";
+    }
+    ~Global() {
+        qDebug() << "Global destructor"; // <- will not be printed
+    }
+};
+Global global;
+
+
+