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.cpp

@@ -0,0 +1,87 @@
+// 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
+
+#include "orientablepushbutton.h"
+#include <QDebug>
+#include <QPainter>
+#include <QStyleOptionButton>
+#include <QStylePainter>
+
+OrientablePushButton::OrientablePushButton(QWidget* parent)
+  : QPushButton(parent)
+{}
+
+OrientablePushButton::OrientablePushButton(const QString& text, QWidget* parent)
+  : QPushButton(text, parent)
+{}
+
+OrientablePushButton::OrientablePushButton(const QIcon& icon,
+                                           const QString& text,
+                                           QWidget* parent)
+  : QPushButton(icon, text, parent)
+{}
+
+QSize
+OrientablePushButton::sizeHint() const
+{
+  QSize sh = QPushButton::sizeHint();
+
+  if (m_orientation != OrientablePushButton::Horizontal) {
+    sh.transpose();
+  }
+
+  return sh;
+}
+
+void
+OrientablePushButton::paintEvent(QPaintEvent* event)
+{
+  Q_UNUSED(event)
+
+  QStylePainter painter(this);
+  QStyleOptionButton option;
+  initStyleOption(&option);
+
+  if (m_orientation == OrientablePushButton::VerticalTopToBottom) {
+    painter.rotate(90);
+    painter.translate(0, -1 * width());
+    option.rect = option.rect.transposed();
+  }
+
+  else if (m_orientation == OrientablePushButton::VerticalBottomToTop) {
+    painter.rotate(-90);
+    painter.translate(-1 * height(), 0);
+    option.rect = option.rect.transposed();
+  }
+
+  painter.drawControl(QStyle::CE_PushButton, option);
+}
+
+OrientablePushButton::Orientation
+OrientablePushButton::orientation() const
+{
+  return m_orientation;
+}
+
+void
+OrientablePushButton::setOrientation(
+  const OrientablePushButton::Orientation& orientation)
+{
+  m_orientation = orientation;
+}