Add general UI introduction

Adds a Help > UI Introduction, which highlights basic aspects of the Qt
Creator UI.

The pages to show are defined in a format that can later move into a
text based configuration file like JSON. It specifies an optional object
name of a widget to highlight, a title, a brief description and a longer
description (potentially with tables, lists and other simple HTML).

Fixes: QTCREATORBUG-21585
Change-Id: Idb64c87e1d752bc24437588278093a96be0eeddb
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

src/plugins/welcome/introductionwidget.h

@@ -0,0 +1,82 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** 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 General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** 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-3.0.html.
+**
+****************************************************************************/
+
+#pragma once
+
+#include <QImage>
+#include <QPointer>
+#include <QWidget>
+
+#include <memory>
+
+QT_BEGIN_NAMESPACE
+class QLabel;
+class QSettings;
+QT_END_NAMESPACE
+
+namespace Welcome {
+namespace Internal {
+
+struct Item
+{
+    QString pointerAnchorObjectName;
+    QString title;
+    QString brief;
+    QString description;
+};
+
+class IntroductionWidget : public QWidget
+{
+    Q_OBJECT
+public:
+    explicit IntroductionWidget(QWidget *parent = nullptr);
+
+    static void askUserAboutIntroduction(QWidget *parent, QSettings *settings);
+
+protected:
+    bool event(QEvent *e) override;
+    bool eventFilter(QObject *obj, QEvent *ev) override;
+    void paintEvent(QPaintEvent *ev) override;
+    void keyPressEvent(QKeyEvent *ke) override;
+    void mouseReleaseEvent(QMouseEvent *me) override;
+
+private:
+    void finish();
+    void step();
+    void setStep(uint index);
+    void resizeToParent();
+
+    QWidget *m_textWidget;
+    QLabel *m_stepText;
+    QLabel *m_continueLabel;
+    std::unique_ptr<QImage> m_borderImage;
+    QString m_bodyCss;
+    std::vector<Item> m_items;
+    QPointer<QWidget> m_stepPointerAnchor;
+    uint m_step = 0;
+};
+
+} // namespace Internal
+} // namespace Welcome