Doc: Fix documentation warnings for Qt GUI

* Drop deprecation warnings for now-dropped items
* Use the 'qt6' define and a new \nothing doc macro to conditionally
  document items on Qt 6
* Add a custom module header for docs that pulls in also Vulkan headers
* Add \internal command for internal classes/functions
* Move QtGUI-related code snippets from widgets to gui docs

Change-Id: Ieb386b96631a49568d09059906d307c45c01d93a
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

3 files changed, 243 insertions, 0 deletions

diff --git a/src/gui/doc/snippets/code/src_gui_kernel_qaction.cpp b/src/gui/doc/snippets/code/src_gui_kernel_qaction.cpp
new file mode 100644
index 0000000000..763238076c
--- /dev/null
+++ b/src/gui/doc/snippets/code/src_gui_kernel_qaction.cpp
@@ -0,0 +1,59 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 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]
+QApplication app(argc, argv);
+app.setAttribute(Qt::AA_DontShowIconsInMenus);  // Icons are *no longer shown* in menus
+// ...
+QAction *myAction = new QAction();
+// ...
+myAction->setIcon(SomeIcon);
+myAction->setIconVisibleInMenu(true);   // Icon *will* be shown in menus for *this* action.
+//! [0]
diff --git a/src/gui/doc/snippets/code/src_gui_kernel_qshortcut.cpp b/src/gui/doc/snippets/code/src_gui_kernel_qshortcut.cpp
new file mode 100644
index 0000000000..bac264fcfc
--- /dev/null
+++ b/src/gui/doc/snippets/code/src_gui_kernel_qshortcut.cpp
@@ -0,0 +1,65 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 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]
+shortcut = new QShortcut(QKeySequence(tr("Ctrl+O", "File|Open")),
+                         parent);
+//! [0]
+
+
+//! [1]
+setKey(0);                  // no signal emitted
+setKey(QKeySequence());     // no signal emitted
+setKey(0x3b1);              // Greek letter alpha
+setKey(Qt::Key_D);              // 'd', e.g. to delete
+setKey('q');                // 'q', e.g. to quit
+setKey(Qt::CTRL + Qt::Key_P);       // Ctrl+P, e.g. to print document
+setKey("Ctrl+P");           // Ctrl+P, e.g. to print document
+//! [1]
diff --git a/src/gui/doc/snippets/code/src_gui_util_qundostack.cpp b/src/gui/doc/snippets/code/src_gui_util_qundostack.cpp
new file mode 100644
index 0000000000..8f59fe9cb3
--- /dev/null
+++ b/src/gui/doc/snippets/code/src_gui_util_qundostack.cpp
@@ -0,0 +1,119 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 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]
+class AppendText : public QUndoCommand
+{
+public:
+    AppendText(QString *doc, const QString &text)
+        : m_document(doc), m_text(text) { setText("append text"); }
+    void undo() override
+        { m_document->chop(m_text.length()); }
+    void redo() override
+        { m_document->append(m_text); }
+private:
+    QString *m_document;
+    QString m_text;
+};
+//! [0]
+
+
+//! [1]
+MyCommand *command1 = new MyCommand();
+stack->push(command1);
+MyCommand *command2 = new MyCommand();
+stack->push(command2);
+
+stack->undo();
+
+MyCommand *command3 = new MyCommand();
+stack->push(command3); // command2 gets deleted
+//! [1]
+
+
+//! [2]
+QUndoCommand *insertRed = new QUndoCommand(); // an empty command
+insertRed->setText("insert red text");
+
+new InsertText(document, idx, text, insertRed); // becomes child of insertRed
+new SetColor(document, idx, text.length(), Qt::red, insertRed);
+
+stack.push(insertRed);
+//! [2]
+
+
+//! [3]
+bool AppendText::mergeWith(const QUndoCommand *other)
+{
+    if (other->id() != id()) // make sure other is also an AppendText command
+        return false;
+    m_text += static_cast<const AppendText*>(other)->m_text;
+    return true;
+}
+//! [3]
+
+
+//! [4]
+stack.beginMacro("insert red text");
+stack.push(new InsertText(document, idx, text));
+stack.push(new SetColor(document, idx, text.length(), Qt::red));
+stack.endMacro(); // indexChanged() is emitted
+//! [4]
+
+
+//! [5]
+QUndoCommand *insertRed = new QUndoCommand(); // an empty command
+insertRed->setText("insert red text");
+
+new InsertText(document, idx, text, insertRed); // becomes child of insertRed
+new SetColor(document, idx, text.length(), Qt::red, insertRed);
+
+stack.push(insertRed);
+//! [5]