paintarea.cpp Example File | Qt Widgets 5.12.6

Qt 5.12 | Qt Widgets | Plug & Paint Example | paintarea.cpp Example File

Qt 5.12.6 Reference Documentation

# paintarea.cpp Example File

tools/plugandpaint/app/paintarea.cpp

      /****************************************************************************
      **
      ** Copyright (C) 2016 The Qt Company Ltd.
      ** Contact: https://www.qt.io/licensing/
      **
      ** This file is part of the examples of the Qt Toolkit.
      **
      ** $QT_BEGIN_LICENSE:BSD$
      ** 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.
      **
      ** BSD License Usage
      ** Alternatively, you may use this file under the terms of the BSD license
      ** as follows:
      **
      ** "Redistribution and use in source and binary forms, with or without
      ** modification, are permitted provided that the following conditions are
      ** met:
      **   * Redistributions of source code must retain the above copyright
      **     notice, this list of conditions and the following disclaimer.
      **   * Redistributions in binary form must reproduce the above copyright
      **     notice, this list of conditions and the following disclaimer in
      **     the documentation and/or other materials provided with the
      **     distribution.
      **   * Neither the name of The Qt Company Ltd nor the names of its
      **     contributors may be used to endorse or promote products derived
      **     from this software without specific prior written permission.
      **
      **
      ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
      ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
      ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
      ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
      ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
      ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
      ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
      ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
      ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
      ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
      ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
      **
      ** $QT_END_LICENSE$
      **
      ****************************************************************************/

      #include "interfaces.h"
      #include "paintarea.h"

      #include <QMouseEvent>
      #include <QPainter>

      PaintArea::PaintArea(QWidget *parent) :
          QWidget(parent)
      {
          setAttribute(Qt::WA_StaticContents);
          setAttribute(Qt::WA_NoBackground);

          theImage.fill(qRgb(255, 255, 255));
      }

      bool PaintArea::openImage(const QString &fileName)
      {
          QImage image;
          if (!image.load(fileName))
              return false;

          setImage(image);
          return true;
      }

      bool PaintArea::saveImage(const QString &fileName, const char *fileFormat)
      {
          return theImage.save(fileName, fileFormat);
      }

      void PaintArea::setImage(const QImage &image)
      {
          theImage = image.convertToFormat(QImage::Format_RGB32);
          update();
          updateGeometry();
      }

      void PaintArea::insertShape(const QPainterPath &path)
      {
          pendingPath = path;
      #ifndef QT_NO_CURSOR
          setCursor(Qt::CrossCursor);
      #endif
      }

      void PaintArea::setBrushColor(const QColor &color)
      {
          this->color = color;
      }

      void PaintArea::setBrushWidth(int width)
      {
          thickness = width;
      }

      void PaintArea::setBrush(BrushInterface *brushInterface, const QString &brush)
      {
          this->brushInterface = brushInterface;
          this->brush = brush;
      }

      QSize PaintArea::sizeHint() const
      {
          return theImage.size();
      }

      void PaintArea::paintEvent(QPaintEvent * /* event */)
      {
          QPainter painter(this);
          painter.drawImage(QPoint(0, 0), theImage);
      }

      void PaintArea::mousePressEvent(QMouseEvent *event)
      {
          if (event->button() == Qt::LeftButton) {
              if (!pendingPath.isEmpty()) {
                  QPainter painter(&theImage);
                  setupPainter(painter);

                  const QRectF boundingRect = pendingPath.boundingRect();
                  QLinearGradient gradient(boundingRect.topRight(),
                                           boundingRect.bottomLeft());
                  gradient.setColorAt(0.0, QColor(color.red(), color.green(),
                                                  color.blue(), 63));
                  gradient.setColorAt(1.0, QColor(color.red(), color.green(),
                                                  color.blue(), 191));
                  painter.setBrush(gradient);
                  painter.translate(event->pos() - boundingRect.center());
                  painter.drawPath(pendingPath);

                  pendingPath = QPainterPath();
      #ifndef QT_NO_CURSOR
                  unsetCursor();
      #endif
                  update();
              } else {
                  if (brushInterface) {
                      QPainter painter(&theImage);
                      setupPainter(painter);
                      const QRect rect = brushInterface->mousePress(brush, painter,
                                                                    event->pos());
                      update(rect);
                  }

                  lastPos = event->pos();
              }
          }
      }

      void PaintArea::mouseMoveEvent(QMouseEvent *event)
      {
          if ((event->buttons() & Qt::LeftButton) && lastPos != QPoint(-1, -1)) {
              if (brushInterface) {
                  QPainter painter(&theImage);
                  setupPainter(painter);
                  const QRect rect = brushInterface->mouseMove(brush, painter, lastPos,
                                                               event->pos());
                  update(rect);
              }

              lastPos = event->pos();
          }
      }

      void PaintArea::mouseReleaseEvent(QMouseEvent *event)
      {
          if (event->button() == Qt::LeftButton && lastPos != QPoint(-1, -1)) {
              if (brushInterface) {
                  QPainter painter(&theImage);
                  setupPainter(painter);
                  QRect rect = brushInterface->mouseRelease(brush, painter,
                                                            event->pos());
                  update(rect);
              }

              lastPos = QPoint(-1, -1);
          }
      }

      void PaintArea::setupPainter(QPainter &painter)
      {
          painter.setRenderHint(QPainter::Antialiasing, true);
          painter.setPen(QPen(color, thickness, Qt::SolidLine, Qt::RoundCap,
                         Qt::RoundJoin));
      }