add sidepanel button to make UI more intuitive and accessible without keyboard (tablets, etc.) (#631)

* add sidepanel toggle button and close button #613

* add side panel toggle button option

* make sidepanel button draggable

src/widgets/orientablepushbutton.h

@@ -0,0 +1,51 @@
+// Copyright(c) 2017-2019 Alejandro Sirgo Rica & Contributors
+//
+// This file is part of Flameshot.
+//
+//     Flameshot is free software: you can redistribute it and/or modify
+//     it under the terms of the GNU General Public License as published by
+//     the Free Software Foundation, either version 3 of the License, or
+//     (at your option) any later version.
+//
+//     Flameshot is distributed in the hope that it will be useful,
+//     but WITHOUT ANY WARRANTY; without even the implied warranty of
+//     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//     GNU General Public License for more details.
+//
+//     You should have received a copy of the GNU General Public License
+//     along with Flameshot.  If not, see <http://www.gnu.org/licenses/>.
+
+// Based on https://stackoverflow.com/a/53135675/964478
+
+#pragma once
+
+#include <QPushButton>
+
+class OrientablePushButton : public QPushButton
+{
+  Q_OBJECT
+public:
+  enum Orientation
+  {
+    Horizontal,
+    VerticalTopToBottom,
+    VerticalBottomToTop
+  };
+
+  OrientablePushButton(QWidget* parent = nullptr);
+  OrientablePushButton(const QString& text, QWidget* parent = nullptr);
+  OrientablePushButton(const QIcon& icon,
+                       const QString& text,
+                       QWidget* parent = nullptr);
+
+  QSize sizeHint() const;
+
+  OrientablePushButton::Orientation orientation() const;
+  void setOrientation(const OrientablePushButton::Orientation& orientation);
+
+protected:
+  void paintEvent(QPaintEvent* event);
+
+private:
+  Orientation m_orientation = Horizontal;
+};