Ref T404, added horizontal combobox for hotkeys

src/blackgui/horizontalcombobox.h

@@ -0,0 +1,41 @@
+/* Copyright (C) 2018
+ * swift project Community / Contributors
+ *
+ * This file is part of swift Project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+//! \file
+
+#ifndef BLACKGUI_HORIZONTALCOMBOBOX_H
+#define BLACKGUI_HORIZONTALCOMBOBOX_H
+
+#include <QComboBox>
+#include <QListView>
+
+namespace BlackGui
+{
+    //! A combobox where the dropdown is horizontally and not vertically
+    class CHorizontalComboBox : public QComboBox
+    {
+        Q_OBJECT
+
+    public:
+        //! ComboBox displaying the values horizontally
+        explicit CHorizontalComboBox(QWidget *parent = nullptr);
+
+        //! \copydoc QComboBox::showPopup
+        virtual void showPopup() override;
+
+        //! Width of the popup
+        void setPopupWidth(int w);
+
+    private:
+        QListView *m_view = nullptr;
+        int m_popupWidth = -1;
+    };
+} // ns
+
+#endif // guard