Qt 5.11 | Qt Widgets | Gradients | gradients.cpp Example File

Qt 5.11.3 Reference Documentation

# gradients.cpp Example File

painting/gradients/gradients.cpp

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      #include "gradients.h"
      #include "hoverpoints.h"

      #include <algorithm>

      ShadeWidget::ShadeWidget(ShadeType type, QWidget *parent)
          : QWidget(parent), m_shade_type(type), m_alpha_gradient(QLinearGradient(0, 0, 0, 0))
      {

          // Checkers background
          if (m_shade_type == ARGBShade) {
              QPixmap pm(20, 20);
              QPainter pmp(&pm);
              pmp.fillRect(0, 0, 10, 10, Qt::lightGray);
              pmp.fillRect(10, 10, 10, 10, Qt::lightGray);
              pmp.fillRect(0, 10, 10, 10, Qt::darkGray);
              pmp.fillRect(10, 0, 10, 10, Qt::darkGray);
              pmp.end();
              QPalette pal = palette();
              pal.setBrush(backgroundRole(), QBrush(pm));
              setAutoFillBackground(true);
              setPalette(pal);

          } else {
              setAttribute(Qt::WA_NoBackground);
          }

          QPolygonF points;
          points << QPointF(0, sizeHint().height())
                 << QPointF(sizeHint().width(), 0);

          m_hoverPoints = new HoverPoints(this, HoverPoints::CircleShape);
      //     m_hoverPoints->setConnectionType(HoverPoints::LineConnection);
          m_hoverPoints->setPoints(points);
          m_hoverPoints->setPointLock(0, HoverPoints::LockToLeft);
          m_hoverPoints->setPointLock(1, HoverPoints::LockToRight);
          m_hoverPoints->setSortType(HoverPoints::XSort);

          setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);

          connect(m_hoverPoints, &HoverPoints::pointsChanged,
                  this, &ShadeWidget::colorsChanged);
      }

      QPolygonF ShadeWidget::points() const
      {
          return m_hoverPoints->points();
      }

      uint ShadeWidget::colorAt(int x)
      {
          generateShade();

          QPolygonF pts = m_hoverPoints->points();
          for (int i=1; i < pts.size(); ++i) {
              if (pts.at(i-1).x() <= x && pts.at(i).x() >= x) {
                  QLineF l(pts.at(i-1), pts.at(i));
                  l.setLength(l.length() * ((x - l.x1()) / l.dx()));
                  return m_shade.pixel(qRound(qMin(l.x2(), (qreal(m_shade.width() - 1)))),
                                       qRound(qMin(l.y2(), qreal(m_shade.height() - 1))));
              }
          }
          return 0;
      }

      void ShadeWidget::setGradientStops(const QGradientStops &stops)
      {
          if (m_shade_type == ARGBShade) {
              m_alpha_gradient = QLinearGradient(0, 0, width(), 0);

              for (int i=0; i<stops.size(); ++i) {
                  QColor c = stops.at(i).second;
                  m_alpha_gradient.setColorAt(stops.at(i).first, QColor(c.red(), c.green(), c.blue()));
              }

              m_shade = QImage();
              generateShade();
              update();
          }
      }

      void ShadeWidget::paintEvent(QPaintEvent *)
      {
          generateShade();

          QPainter p(this);
          p.drawImage(0, 0, m_shade);

          p.setPen(QColor(146, 146, 146));
          p.drawRect(0, 0, width() - 1, height() - 1);
      }

      void ShadeWidget::generateShade()
      {
          if (m_shade.isNull() || m_shade.size() != size()) {

              if (m_shade_type == ARGBShade) {
                  m_shade = QImage(size(), QImage::Format_ARGB32_Premultiplied);
                  m_shade.fill(0);

                  QPainter p(&m_shade);
                  p.fillRect(rect(), m_alpha_gradient);

                  p.setCompositionMode(QPainter::CompositionMode_DestinationIn);
                  QLinearGradient fade(0, 0, 0, height());
                  fade.setColorAt(0, QColor(0, 0, 0, 255));
                  fade.setColorAt(1, QColor(0, 0, 0, 0));
                  p.fillRect(rect(), fade);

              } else {
                  m_shade = QImage(size(), QImage::Format_RGB32);
                  QLinearGradient shade(0, 0, 0, height());
                  shade.setColorAt(1, Qt::black);

                  if (m_shade_type == RedShade)
                      shade.setColorAt(0, Qt::red);
                  else if (m_shade_type == GreenShade)
                      shade.setColorAt(0, Qt::green);
                  else
                      shade.setColorAt(0, Qt::blue);

                  QPainter p(&m_shade);
                  p.fillRect(rect(), shade);
              }
          }
      }

      GradientEditor::GradientEditor(QWidget *parent)
          : QWidget(parent)
      {
          QVBoxLayout *vbox = new QVBoxLayout(this);
          vbox->setSpacing(1);
          vbox->setMargin(1);

          m_red_shade = new ShadeWidget(ShadeWidget::RedShade, this);
          m_green_shade = new ShadeWidget(ShadeWidget::GreenShade, this);
          m_blue_shade = new ShadeWidget(ShadeWidget::BlueShade, this);
          m_alpha_shade = new ShadeWidget(ShadeWidget::ARGBShade, this);

          vbox->addWidget(m_red_shade);
          vbox->addWidget(m_green_shade);
          vbox->addWidget(m_blue_shade);
          vbox->addWidget(m_alpha_shade);

          connect(m_red_shade, &ShadeWidget::colorsChanged,
                  this, &GradientEditor::pointsUpdated);
          connect(m_green_shade, &ShadeWidget::colorsChanged,
                 this, &GradientEditor::pointsUpdated);
          connect(m_blue_shade, &ShadeWidget::colorsChanged,
                  this, &GradientEditor::pointsUpdated);
          connect(m_alpha_shade, &ShadeWidget::colorsChanged,
                  this, &GradientEditor::pointsUpdated);
      }

      inline static bool x_less_than(const QPointF &p1, const QPointF &p2)
      {
          return p1.x() < p2.x();
      }

      void GradientEditor::pointsUpdated()
      {
          qreal w = m_alpha_shade->width();

          QGradientStops stops;

          QPolygonF points;

          points += m_red_shade->points();
          points += m_green_shade->points();
          points += m_blue_shade->points();
          points += m_alpha_shade->points();

          std::sort(points.begin(), points.end(), x_less_than);

          for (int i = 0; i < points.size(); ++i) {
              qreal x = int(points.at(i).x());
              if (i + 1 < points.size() && x == points.at(i + 1).x())
                  continue;
              QColor color((0x00ff0000 & m_red_shade->colorAt(int(x))) >> 16,
                           (0x0000ff00 & m_green_shade->colorAt(int(x))) >> 8,
                           (0x000000ff & m_blue_shade->colorAt(int(x))),
                           (0xff000000 & m_alpha_shade->colorAt(int(x))) >> 24);

              if (x / w > 1)
                  return;

              stops << QGradientStop(x / w, color);
          }

          m_alpha_shade->setGradientStops(stops);

          emit gradientStopsChanged(stops);
      }

      static void set_shade_points(const QPolygonF &points, ShadeWidget *shade)
      {
          shade->hoverPoints()->setPoints(points);
          shade->hoverPoints()->setPointLock(0, HoverPoints::LockToLeft);
          shade->hoverPoints()->setPointLock(points.size() - 1, HoverPoints::LockToRight);
          shade->update();
      }

      void GradientEditor::setGradientStops(const QGradientStops &stops)
      {
          QPolygonF pts_red, pts_green, pts_blue, pts_alpha;

          qreal h_red = m_red_shade->height();
          qreal h_green = m_green_shade->height();
          qreal h_blue = m_blue_shade->height();
          qreal h_alpha = m_alpha_shade->height();

          for (int i = 0; i < stops.size(); ++i) {
              qreal pos = stops.at(i).first;
              QRgb color = stops.at(i).second.rgba();
              pts_red << QPointF(pos * m_red_shade->width(), h_red - qRed(color) * h_red / 255);
              pts_green << QPointF(pos * m_green_shade->width(), h_green - qGreen(color) * h_green / 255);
              pts_blue << QPointF(pos * m_blue_shade->width(), h_blue - qBlue(color) * h_blue / 255);
              pts_alpha << QPointF(pos * m_alpha_shade->width(), h_alpha - qAlpha(color) * h_alpha / 255);
          }

          set_shade_points(pts_red, m_red_shade);
          set_shade_points(pts_green, m_green_shade);
          set_shade_points(pts_blue, m_blue_shade);
          set_shade_points(pts_alpha, m_alpha_shade);

      }

      GradientWidget::GradientWidget(QWidget *parent)
          : QWidget(parent)
      {
          setWindowTitle(tr("Gradients"));

          m_renderer = new GradientRenderer(this);

          QGroupBox *mainGroup = new QGroupBox(this);
          mainGroup->setTitle(tr("Gradients"));

          QGroupBox *editorGroup = new QGroupBox(mainGroup);
          editorGroup->setTitle(tr("Color Editor"));
          m_editor = new GradientEditor(editorGroup);

          QGroupBox *typeGroup = new QGroupBox(mainGroup);
          typeGroup->setTitle(tr("Gradient Type"));
          m_linearButton = new QRadioButton(tr("Linear Gradient"), typeGroup);
          m_radialButton = new QRadioButton(tr("Radial Gradient"), typeGroup);
          m_conicalButton = new QRadioButton(tr("Conical Gradient"), typeGroup);

          QGroupBox *spreadGroup = new QGroupBox(mainGroup);
          spreadGroup->setTitle(tr("Spread Method"));
          m_padSpreadButton = new QRadioButton(tr("Pad Spread"), spreadGroup);
          m_reflectSpreadButton = new QRadioButton(tr("Reflect Spread"), spreadGroup);
          m_repeatSpreadButton = new QRadioButton(tr("Repeat Spread"), spreadGroup);

          QGroupBox *defaultsGroup = new QGroupBox(mainGroup);
          defaultsGroup->setTitle(tr("Defaults"));
          QPushButton *default1Button = new QPushButton(tr("1"), defaultsGroup);
          QPushButton *default2Button = new QPushButton(tr("2"), defaultsGroup);
          QPushButton *default3Button = new QPushButton(tr("3"), defaultsGroup);
          QPushButton *default4Button = new QPushButton(tr("Reset"), editorGroup);

          QPushButton *showSourceButton = new QPushButton(mainGroup);
          showSourceButton->setText(tr("Show Source"));
      #ifdef QT_OPENGL_SUPPORT
          QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
          enableOpenGLButton->setText(tr("Use OpenGL"));
          enableOpenGLButton->setCheckable(true);
          enableOpenGLButton->setChecked(m_renderer->usesOpenGL());
          if (!QGLFormat::hasOpenGL())
              enableOpenGLButton->hide();
      #endif
          QPushButton *whatsThisButton = new QPushButton(mainGroup);
          whatsThisButton->setText(tr("What's This?"));
          whatsThisButton->setCheckable(true);

          // Layouts
          QHBoxLayout *mainLayout = new QHBoxLayout(this);
          mainLayout->addWidget(m_renderer);
          mainLayout->addWidget(mainGroup);

          mainGroup->setFixedWidth(180);
          QVBoxLayout *mainGroupLayout = new QVBoxLayout(mainGroup);
          mainGroupLayout->addWidget(editorGroup);
          mainGroupLayout->addWidget(typeGroup);
          mainGroupLayout->addWidget(spreadGroup);
          mainGroupLayout->addWidget(defaultsGroup);
          mainGroupLayout->addStretch(1);
          mainGroupLayout->addWidget(showSourceButton);
      #ifdef QT_OPENGL_SUPPORT
          mainGroupLayout->addWidget(enableOpenGLButton);
      #endif
          mainGroupLayout->addWidget(whatsThisButton);

          QVBoxLayout *editorGroupLayout = new QVBoxLayout(editorGroup);
          editorGroupLayout->addWidget(m_editor);

          QVBoxLayout *typeGroupLayout = new QVBoxLayout(typeGroup);
          typeGroupLayout->addWidget(m_linearButton);
          typeGroupLayout->addWidget(m_radialButton);
          typeGroupLayout->addWidget(m_conicalButton);

          QVBoxLayout *spreadGroupLayout = new QVBoxLayout(spreadGroup);
          spreadGroupLayout->addWidget(m_padSpreadButton);
          spreadGroupLayout->addWidget(m_repeatSpreadButton);
          spreadGroupLayout->addWidget(m_reflectSpreadButton);

          QHBoxLayout *defaultsGroupLayout = new QHBoxLayout(defaultsGroup);
          defaultsGroupLayout->addWidget(default1Button);
          defaultsGroupLayout->addWidget(default2Button);
          defaultsGroupLayout->addWidget(default3Button);
          editorGroupLayout->addWidget(default4Button);

          connect(m_editor, &GradientEditor::gradientStopsChanged,
                  m_renderer, &GradientRenderer::setGradientStops);
          connect(m_linearButton, &QRadioButton::clicked,
                  m_renderer, &GradientRenderer::setLinearGradient);
          connect(m_radialButton, &QRadioButton::clicked,
                  m_renderer, &GradientRenderer::setRadialGradient);
          connect(m_conicalButton,&QRadioButton::clicked,
                  m_renderer, &GradientRenderer::setConicalGradient);

          connect(m_padSpreadButton, &QRadioButton::clicked,
                  m_renderer, &GradientRenderer::setPadSpread);
          connect(m_reflectSpreadButton, &QRadioButton::clicked,
                  m_renderer, &GradientRenderer::setReflectSpread);
          connect(m_repeatSpreadButton, &QRadioButton::clicked,
                  m_renderer, &GradientRenderer::setRepeatSpread);

          connect(default1Button, &QPushButton::clicked,
                  this, &GradientWidget::setDefault1);
          connect(default2Button, &QPushButton::clicked,
                  this, &GradientWidget::setDefault2);
          connect(default3Button, &QPushButton::clicked,
                  this, &GradientWidget::setDefault3);
          connect(default4Button, &QPushButton::clicked,
                  this, &GradientWidget::setDefault4);

          connect(showSourceButton, &QPushButton::clicked,
                  m_renderer, &GradientRenderer::showSource);
      #ifdef QT_OPENGL_SUPPORT
          connect(enableOpenGLButton, QOverload<bool>::of(&QPushButton::clicked),
                  m_renderer, &ArthurFrame::enableOpenGL);
      #endif

          connect(whatsThisButton, QOverload<bool>::of(&QPushButton::clicked),
                  m_renderer, &ArthurFrame::setDescriptionEnabled);
          connect(whatsThisButton, QOverload<bool>::of(&QPushButton::clicked),
                  m_renderer->hoverPoints(), &HoverPoints::setDisabled);
          connect(m_renderer, QOverload<bool>::of(&ArthurFrame::descriptionEnabledChanged),
                  whatsThisButton, &QPushButton::setChecked);
          connect(m_renderer, QOverload<bool>::of(&ArthurFrame::descriptionEnabledChanged),
                  m_renderer->hoverPoints(), &HoverPoints::setDisabled);

          m_renderer->loadSourceFile(":res/gradients/gradients.cpp");
          m_renderer->loadDescription(":res/gradients/gradients.html");

          QTimer::singleShot(50, this, SLOT(setDefault1()));
      }

      void GradientWidget::setDefault(int config)
      {
          QGradientStops stops;
          QPolygonF points;
          switch (config) {
          case 1:
              stops << QGradientStop(0.00, QColor::fromRgba(0));
              stops << QGradientStop(0.04, QColor::fromRgba(0xff131360));
              stops << QGradientStop(0.08, QColor::fromRgba(0xff202ccc));
              stops << QGradientStop(0.42, QColor::fromRgba(0xff93d3f9));
              stops << QGradientStop(0.51, QColor::fromRgba(0xffb3e6ff));
              stops << QGradientStop(0.73, QColor::fromRgba(0xffffffec));
              stops << QGradientStop(0.92, QColor::fromRgba(0xff5353d9));
              stops << QGradientStop(0.96, QColor::fromRgba(0xff262666));
              stops << QGradientStop(1.00, QColor::fromRgba(0));
              m_linearButton->animateClick();
              m_repeatSpreadButton->animateClick();
              break;

          case 2:
              stops << QGradientStop(0.00, QColor::fromRgba(0xffffffff));
              stops << QGradientStop(0.11, QColor::fromRgba(0xfff9ffa0));
              stops << QGradientStop(0.13, QColor::fromRgba(0xfff9ff99));
              stops << QGradientStop(0.14, QColor::fromRgba(0xfff3ff86));
              stops << QGradientStop(0.49, QColor::fromRgba(0xff93b353));
              stops << QGradientStop(0.87, QColor::fromRgba(0xff264619));
              stops << QGradientStop(0.96, QColor::fromRgba(0xff0c1306));
              stops << QGradientStop(1.00, QColor::fromRgba(0));
              m_radialButton->animateClick();
              m_padSpreadButton->animateClick();
              break;

          case 3:
              stops << QGradientStop(0.00, QColor::fromRgba(0));
              stops << QGradientStop(0.10, QColor::fromRgba(0xffe0cc73));
              stops << QGradientStop(0.17, QColor::fromRgba(0xffc6a006));
              stops << QGradientStop(0.46, QColor::fromRgba(0xff600659));
              stops << QGradientStop(0.72, QColor::fromRgba(0xff0680ac));
              stops << QGradientStop(0.92, QColor::fromRgba(0xffb9d9e6));
              stops << QGradientStop(1.00, QColor::fromRgba(0));
              m_conicalButton->animateClick();
              m_padSpreadButton->animateClick();
              break;

          case 4:
              stops << QGradientStop(0.00, QColor::fromRgba(0xff000000));
              stops << QGradientStop(1.00, QColor::fromRgba(0xffffffff));
              break;

          default:
              qWarning("bad default: %d\n", config);
              break;
          }

          QPolygonF pts;
          int h_off = m_renderer->width() / 10;
          int v_off = m_renderer->height() / 8;
          pts << QPointF(m_renderer->width() / 2, m_renderer->height() / 2)
              << QPointF(m_renderer->width() / 2 - h_off, m_renderer->height() / 2 - v_off);

          m_editor->setGradientStops(stops);
          m_renderer->hoverPoints()->setPoints(pts);
          m_renderer->setGradientStops(stops);
      }

      GradientRenderer::GradientRenderer(QWidget *parent)
          : ArthurFrame(parent)
      {
          m_hoverPoints = new HoverPoints(this, HoverPoints::CircleShape);
          m_hoverPoints->setPointSize(QSize(20, 20));
          m_hoverPoints->setConnectionType(HoverPoints::NoConnection);
          m_hoverPoints->setEditable(false);

          QVector<QPointF> points;
          points << QPointF(100, 100) << QPointF(200, 200);
          m_hoverPoints->setPoints(points);

          m_spread = QGradient::PadSpread;
          m_gradientType = Qt::LinearGradientPattern;
      }

      void GradientRenderer::setGradientStops(const QGradientStops &stops)
      {
          m_stops = stops;
          update();
      }

      void GradientRenderer::mousePressEvent(QMouseEvent *)
      {
          setDescriptionEnabled(false);
      }

      void GradientRenderer::paint(QPainter *p)
      {
          QPolygonF pts = m_hoverPoints->points();

          QGradient g;

          if (m_gradientType == Qt::LinearGradientPattern) {
              g = QLinearGradient(pts.at(0), pts.at(1));

          } else if (m_gradientType == Qt::RadialGradientPattern) {
              g = QRadialGradient(pts.at(0), qMin(width(), height()) / 3.0, pts.at(1));

          } else {
              QLineF l(pts.at(0), pts.at(1));
              qreal angle = l.angle(QLineF(0, 0, 1, 0));
              if (l.dy() > 0)
                  angle = 360 - angle;
              g = QConicalGradient(pts.at(0), angle);
          }

          for (int i = 0; i < m_stops.size(); ++i)
              g.setColorAt(m_stops.at(i).first, m_stops.at(i).second);

          g.setSpread(m_spread);

          p->setBrush(g);
          p->setPen(Qt::NoPen);

          p->drawRect(rect());

      }