doc: Add a section about singleton types in qt_add_qml_module

QT_QML_SINGLETON_TYPE was only documented on the qt_target_qml_sources
page. Add a short section about singletons to the qt_add_qml_module
page and reference the other page.

Adjust the example in qt_target_qml_sources to show case how to set
the singleton source property.

Pick-to: 6.2
Fixes: QTBUG-97541
Change-Id: I11aa3cb7c0feb748eba1d7ac9ef81a8ac6cb16b1
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>

2 files changed, 60 insertions, 0 deletions

diff --git a/src/qml/doc/snippets/cmake/qt_target_qml_sources/CMakeLists.txt b/src/qml/doc/snippets/cmake/qt_target_qml_sources/CMakeLists.txt
index 0bba788b20..d33f009e38 100644
--- a/src/qml/doc/snippets/cmake/qt_target_qml_sources/CMakeLists.txt
+++ b/src/qml/doc/snippets/cmake/qt_target_qml_sources/CMakeLists.txt
@@ -14,6 +14,9 @@ set_source_files_properties(TemplateFile.qml PROPERTIES
     QT_QML_SKIP_QMLLINT TRUE
     QT_QML_SKIP_CACHEGEN TRUE
 )
+set_source_files_properties(FunnySingleton.qml PROPERTIES
+    QT_QML_SINGLETON_TYPE TRUE
+)
 qt_add_qml_module(qt_target_qml_sources_example
     URI Example
     VERSION 2.3
@@ -21,6 +24,7 @@ qt_add_qml_module(qt_target_qml_sources_example
     QML_FILES
         nested/way/down/File.qml
         TemplateFile.qml
+        FunnySingleton.qml
 )
 
 set_source_files_properties(some_old_thing.qml PROPERTIES
diff --git a/src/qml/doc/snippets/cmake/qt_target_qml_sources/FunnySingleton.qml b/src/qml/doc/snippets/cmake/qt_target_qml_sources/FunnySingleton.qml
new file mode 100644
index 0000000000..4aec01c32d
--- /dev/null
+++ b/src/qml/doc/snippets/cmake/qt_target_qml_sources/FunnySingleton.qml
@@ -0,0 +1,56 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the documentation 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."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+//! [0]
+pragma Singleton
+import QtQml
+
+QtObject {}
+//! [0]