RoundedMessageBox.h

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/*
  RoundedMessageBox
  https://github.com/mpaperno/maxLibQt

  COPYRIGHT: (c)2019 Maxim Paperno; All Rights Reserved.
  Contact: http://www.WorldDesign.com/contact

  LICENSE:

  Commercial License Usage
  Licensees holding valid commercial licenses may use this file in
  accordance with the terms contained in a written agreement between
  you and the copyright holder.

  GNU General Public License Usage
  Alternatively, this file may be used 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.

  This program 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.

  A copy of the GNU General Public License is available at <http://www.gnu.org/licenses/>.
*/

#ifndef ROUNDEDMESSAGEBOX_H
#define ROUNDEDMESSAGEBOX_H

#include <QMessageBox>
#include <QPainter>
#include <QPalette>
#include <QStyle>
#include <QStyleOption>

class RoundedMessageBox : public QMessageBox
{
    Q_OBJECT
  public:
    explicit RoundedMessageBox(QWidget *parent = nullptr) :
      QMessageBox(parent)
    {
      // The FramelessWindowHint flag and WA_TranslucentBackground attribute are vital.
      setWindowFlags(windowFlags() | Qt::FramelessWindowHint | Qt::WindowSystemMenuHint);
      setAttribute(Qt::WA_TranslucentBackground);
    }

    qreal radius = 0.0;        
    qreal borderWidth = -1.0;  

  protected:
    void paintEvent(QPaintEvent *) override
    {
      if (!(windowFlags() & Qt::FramelessWindowHint) && !testAttribute(Qt::WA_TranslucentBackground))
        return;  // nothing to do

      QPainter p(this);
      p.setRenderHint(QPainter::Antialiasing);

      // Have style sheet?
      if (testAttribute(Qt::WA_StyleSheetTarget)) {
        // Let QStylesheetStyle have its way with us.
        QStyleOption opt;
        opt.initFrom(this);
        style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
        p.end();
        return;
      }

      // Paint thyself.
      QRectF rect(QPointF(0, 0), size());
      // Check for a border size.
      qreal penWidth = borderWidth;
      if (penWidth < 0.0) {
        QStyleOption opt;
        opt.initFrom(this);
        penWidth = style()->pixelMetric(QStyle::PM_DefaultFrameWidth, &opt, this);
      }
      // Got pen?
      if (penWidth > 0.0) {
        p.setPen(QPen(palette().brush(foregroundRole()), penWidth));
        // Ensure border fits inside the available space.
        const qreal dlta = penWidth * 0.5;
        rect.adjust(dlta, dlta, -dlta, -dlta);
      }
      else {
        // QPainter comes with a default 1px pen when initialized on a QWidget.
        p.setPen(Qt::NoPen);
      }
      // Set the brush from palette role.
      p.setBrush(palette().brush(backgroundRole()));
      // Got radius?  Otherwise draw a quicker rect.
      if (radius > 0.0)
        p.drawRoundedRect(rect, radius, radius, Qt::AbsoluteSize);
      else
        p.drawRect(rect);

      // C'est finí
      p.end();
    }
};

#endif // ROUNDEDMESSAGEBOX_H