proportional widget resize

[momesana]

Hi,
I have a simple question regardin widget resizes. I want my widget that has a certain aspect ratio to shrink/grow without affecting that ratio. How do I do that? I thought about heightForWidth but I am not sure and it doesn't really work.

Thanks in advance
momesana

[axeljaeger]

heightForWidth is what you are looking for. What happens if you try it?

[momesana]

well,
nothing happens!
I probably have to activate set the hasWidthForHeight flag somewhere. All I know is that it doesn't work right now :-(.

[axeljaeger]

Yes you have to set hasHeightForWidth in the sizePolicy of your widget.

[momesana]

I did but it still doesn't work. Here is the code

#include <QApplication>
 #include <QStylePainter>
 #include <QStyleOption>
 #include <QMouseEvent>
 #include <QDebug>
 #include <cmath>
 #include <QWidget>
 #include <QList>
 #include <QRect>
 
 class RgbBitMaskWidget : public QWidget
 {
   Q_OBJECT
   public:
     RgbBitMaskWidget(QWidget* parent = 0);
     ~RgbBitMaskWidget();
     uchar red() const;
     uchar green() const;
     uchar blue() const;
     virtual int heightForWidth(int) const;
     virtual QSize sizeHint() const;
   protected:
     virtual void resizeEvent(QResizeEvent*);
     virtual void paintEvent(QPaintEvent*);
     virtual void mousePressEvent(QMouseEvent* );
   signals:
     void rgbBitMaskChanged(int, int, int) const;
   private:
     uchar mBits[3];
     QList<QList<QRect> > mGeometryRects;
 
     void recalculateRectGeometries();
 };
 
 RgbBitMaskWidget::RgbBitMaskWidget(QWidget* parent)
     : QWidget(parent)
 {
   // initialize array
   for (int i = 0; i < 3; ++i)
       mBits[i] = 255;
 
   // initialize list of arrays
   for (int i = 0; i < 3; ++i) {
     QList<QRect> l;
     for (int j = 0; j < 8; ++j)
       l << QRect();
     mGeometryRects << l;
   }
 
   // set sizePolicy (important for heightForWidth)
   QSizePolicy sizePolicy(QSizePolicy::Minimum, QSizePolicy::Minimum);
   sizePolicy.setHeightForWidth(true);
   setSizePolicy(sizePolicy);
 
   const int minWidth = 150;
   setMinimumSize(minWidth, minWidth / (8 / 3.0));
 }
 
 RgbBitMaskWidget::~RgbBitMaskWidget()
 {
 }
 
 void RgbBitMaskWidget::recalculateRectGeometries()
 {
   const int MARGIN = 2;
   QRect r = contentsRect().adjusted(MARGIN, MARGIN, -MARGIN, -MARGIN);
 
   int x = 0;
   int y = 0;
   int w = r.width() / 8;
   int h = r.height() / 3;
 
   for (int i = 0; i < mGeometryRects.size(); ++i) {
     QList<QRect> rectList = mGeometryRects[i];
     x = 0;
     for (int j = 0; j < rectList.size(); ++j) {
       mGeometryRects[i][j] = QRect(x, y, w, h);
       x += w;
     }
     y += h;
   }
 }
 
 void RgbBitMaskWidget::resizeEvent(QResizeEvent* event)
 {
   Q_UNUSED(event);
   recalculateRectGeometries();
 }
 
 void RgbBitMaskWidget::mousePressEvent(QMouseEvent* event)
 {
   QPoint pos = event->pos();
   for (int i = 0; i < 3; ++i) {
     for (int j = 0; j < 8; ++j) {
       if (mGeometryRects[i][j].contains(pos)) {
         uchar flag = std::pow(2, 7 - j);
         if (flag == (mBits[i] & flag))
           mBits[i] = mBits[i] & (~flag);
         else
           mBits[i] = mBits[i] | flag ;
       }
     }
   }
   QWidget::mousePressEvent(event);
   update();
 }
 
 void RgbBitMaskWidget::paintEvent(QPaintEvent* event)
 {
   Q_UNUSED(event);
 
   QStyleOption opt;
   opt.init(this);
   QStylePainter painter(this);
   style()->drawPrimitive(QStyle::PE_Widget, &opt, &painter, this);
 
   QList<QColor> colors;
   colors << QColor(Qt::red) << QColor(Qt::green) << QColor(Qt::blue);
   // paint rects
   QPen pen(Qt::white);
   pen.setWidth(3);
   painter.setPen(pen);
   for(int i = 0; i < 3; ++i) {
     QList<QRect> l = mGeometryRects[i];
     QColor c = colors[i];
       for (int j = 0; j < 8; ++j) {
         uchar flags = std::pow(2, 7 - j);
         if ((mBits[i] & flags) == flags)
           painter.setBrush(c);
         else
           painter.setBrush(c.lighter(185));
 
         painter.drawRect(mGeometryRects[i][j]);
       }
     }
   }
 
 int RgbBitMaskWidget::heightForWidth(int) const
 {
   double ratio = 8 / 3;
   return static_cast<int>(height() / ratio);
 }
 
 QSize RgbBitMaskWidget::sizeHint() const
 {
   int w = width();
   return QSize(w, heightForWidth(w));
 }
 
 int main(int argc, char *argv[])
 {
     QApplication a(argc, argv);
     RgbBitMaskWidget rgb;
     rgb.show();
     return a.exec();
 }
 
 #include "main.moc"

#include <QApplication>
 #include <QStylePainter>
 #include <QStyleOption>
 #include <QMouseEvent>
 #include <QDebug>
 #include <cmath>
 #include <QWidget>
 #include <QList>
 #include <QRect>
 
 class RgbBitMaskWidget : public QWidget
 {
   Q_OBJECT
   public:
     RgbBitMaskWidget(QWidget* parent = 0);
     ~RgbBitMaskWidget();
     uchar red() const;
     uchar green() const;
     uchar blue() const;
     virtual int heightForWidth(int) const;
     virtual QSize sizeHint() const;
   protected:
     virtual void resizeEvent(QResizeEvent*);
     virtual void paintEvent(QPaintEvent*);
     virtual void mousePressEvent(QMouseEvent* );
   signals:
     void rgbBitMaskChanged(int, int, int) const;
   private:
     uchar mBits[3];
     QList<QList<QRect> > mGeometryRects;
 
     void recalculateRectGeometries();
 };
 
 RgbBitMaskWidget::RgbBitMaskWidget(QWidget* parent)
     : QWidget(parent)
 {
   // initialize array
   for (int i = 0; i < 3; ++i)
       mBits[i] = 255;
 
   // initialize list of arrays
   for (int i = 0; i < 3; ++i) {
     QList<QRect> l;
     for (int j = 0; j < 8; ++j)
       l << QRect();
     mGeometryRects << l;
   }
 
   // set sizePolicy (important for heightForWidth)
   QSizePolicy sizePolicy(QSizePolicy::Minimum, QSizePolicy::Minimum);
   sizePolicy.setHeightForWidth(true);
   setSizePolicy(sizePolicy);
 
   const int minWidth = 150;
   setMinimumSize(minWidth, minWidth / (8 / 3.0));
 }
 
 RgbBitMaskWidget::~RgbBitMaskWidget()
 {
 }
 
 void RgbBitMaskWidget::recalculateRectGeometries()
 {
   const int MARGIN = 2;
   QRect r = contentsRect().adjusted(MARGIN, MARGIN, -MARGIN, -MARGIN);
 
   int x = 0;
   int y = 0;
   int w = r.width() / 8;
   int h = r.height() / 3;
 
   for (int i = 0; i < mGeometryRects.size(); ++i) {
     QList<QRect> rectList = mGeometryRects[i];
     x = 0;
     for (int j = 0; j < rectList.size(); ++j) {
       mGeometryRects[i][j] = QRect(x, y, w, h);
       x += w;
     }
     y += h;
   }
 }
 
 void RgbBitMaskWidget::resizeEvent(QResizeEvent* event)
 {
   Q_UNUSED(event);
   recalculateRectGeometries();
 }
 
 void RgbBitMaskWidget::mousePressEvent(QMouseEvent* event)
 {
   QPoint pos = event->pos();
   for (int i = 0; i < 3; ++i) {
     for (int j = 0; j < 8; ++j) {
       if (mGeometryRects[i][j].contains(pos)) {
         uchar flag = std::pow(2, 7 - j);
         if (flag == (mBits[i] & flag))
           mBits[i] = mBits[i] & (~flag);
         else
           mBits[i] = mBits[i] | flag ;
       }
     }
   }
   QWidget::mousePressEvent(event);
   update();
 }
 
 void RgbBitMaskWidget::paintEvent(QPaintEvent* event)
 {
   Q_UNUSED(event);
 
   QStyleOption opt;
   opt.init(this);
   QStylePainter painter(this);
   style()->drawPrimitive(QStyle::PE_Widget, &opt, &painter, this);
 
   QList<QColor> colors;
   colors << QColor(Qt::red) << QColor(Qt::green) << QColor(Qt::blue);
   // paint rects
   QPen pen(Qt::white);
   pen.setWidth(3);
   painter.setPen(pen);
   for(int i = 0; i < 3; ++i) {
     QList<QRect> l = mGeometryRects[i];
     QColor c = colors[i];
       for (int j = 0; j < 8; ++j) {
         uchar flags = std::pow(2, 7 - j);
         if ((mBits[i] & flags) == flags)
           painter.setBrush(c);
         else
           painter.setBrush(c.lighter(185));
 
         painter.drawRect(mGeometryRects[i][j]);
       }
     }
   }
 
 int RgbBitMaskWidget::heightForWidth(int) const
 {
   double ratio = 8 / 3;
   return static_cast<int>(height() / ratio);
 }
 
 QSize RgbBitMaskWidget::sizeHint() const
 {
   int w = width();
   return QSize(w, heightForWidth(w));
 }
 
 int main(int argc, char *argv[])
 {
     QApplication a(argc, argv);
     RgbBitMaskWidget rgb;
     rgb.show();
     return a.exec();
 }
 
 #include "main.moc"

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Thanks in advance

[axeljaeger]

I think you should not reimplement sizeHint then. But anyway maybe heightForWidth is not supported for toplevel-widgets. Reason: How should the widget be resized when the user clicks "maximize" and the display has an aspect ratio != your heightForWidth?

[momesana]

I just added it to a QWidget that itself is the centralWidget of a QMainWindow. But it still loses the aspect ratio when it is resized. Btw, the widget itself is supposed to be placed into a QDockWidget later. So how can I make it work so that it keeps its aspect ratio and only grows proportionally? Any Ideas?

Thanks in advance
momesana

#include <QtGui>
#include <cmath>
 
 class RgbBitMaskWidget : public QWidget
 {
   Q_OBJECT
   public:
     RgbBitMaskWidget(QWidget* parent = 0);
     ~RgbBitMaskWidget();
     uchar red() const;
     uchar green() const;
     uchar blue() const;
     virtual int heightForWidth(int) const;
     virtual QSize sizeHint() const;
   protected:
     virtual void resizeEvent(QResizeEvent*);
     virtual void paintEvent(QPaintEvent*);
     virtual void mousePressEvent(QMouseEvent* );
   signals:
     void rgbBitMaskChanged(int, int, int) const;
   private:
     uchar mBits[3];
     QList<QList<QRect> > mGeometryRects;
 
     void recalculateRectGeometries();
 };
 
 RgbBitMaskWidget::RgbBitMaskWidget(QWidget* parent)
     : QWidget(parent)
 {
   // initialize array
   for (int i = 0; i < 3; ++i)
       mBits[i] = 255;
 
   // initialize list of arrays
   for (int i = 0; i < 3; ++i) {
     QList<QRect> l;
     for (int j = 0; j < 8; ++j)
       l << QRect();
     mGeometryRects << l;
   }
 
   // set sizePolicy (important for heightForWidth)
   QSizePolicy sizePolicy(QSizePolicy::Minimum, QSizePolicy::Minimum);
   sizePolicy.setHeightForWidth(true);
   setSizePolicy(sizePolicy);
 
   const int minWidth = 150;
   setMinimumSize(minWidth, minWidth / (8 / 3.0));
 }
 
 RgbBitMaskWidget::~RgbBitMaskWidget()
 {
 }
 
 void RgbBitMaskWidget::recalculateRectGeometries()
 {
   const int MARGIN = 2;
   QRect r = contentsRect().adjusted(MARGIN, MARGIN, -MARGIN, -MARGIN);
 
   int x = 0;
   int y = 0;
   int w = static_cast<int>(r.width() / 8.0);
   int h = static_cast<int>(r.height() / 3.0);
 
   for (int i = 0; i < mGeometryRects.size(); ++i) {
     QList<QRect> rectList = mGeometryRects[i];
     x = 0;
     for (int j = 0; j < rectList.size(); ++j) {
       mGeometryRects[i][j] = QRect(x, y, w, h);
       x += w;
     }
     y += h;
   }
 }
 
 void RgbBitMaskWidget::resizeEvent(QResizeEvent* event)
 {
   Q_UNUSED(event);
   recalculateRectGeometries();
 }
 
 void RgbBitMaskWidget::mousePressEvent(QMouseEvent* event)
 {
   QPoint pos = event->pos();
   for (int i = 0; i < 3; ++i) {
     for (int j = 0; j < 8; ++j) {
       if (mGeometryRects[i][j].contains(pos)) {
         uchar flag = std::pow(2, 7 - j);
         if (flag == (mBits[i] & flag))
           mBits[i] = mBits[i] & (~flag);
         else
           mBits[i] = mBits[i] | flag ;
       }
     }
   }
   QWidget::mousePressEvent(event);
   update();
 }
 
 void RgbBitMaskWidget::paintEvent(QPaintEvent* event)
 {
   Q_UNUSED(event);
 
   QStyleOption opt;
   opt.init(this);
   QStylePainter painter(this);
   style()->drawPrimitive(QStyle::PE_Widget, &opt, &painter, this);
 
   QList<QColor> colors;
   colors << QColor(Qt::red) << QColor(Qt::green) << QColor(Qt::blue);
   // paint rects
   QPen pen(Qt::white);
   pen.setWidth(3);
   painter.setPen(pen);
   for(int i = 0; i < 3; ++i) {
     QList<QRect> l = mGeometryRects[i];
     QColor c = colors[i];
       for (int j = 0; j < 8; ++j) {
         uchar flags = std::pow(2, 7 - j);
         if ((mBits[i] & flags) == flags)
           painter.setBrush(c);
         else
           painter.setBrush(c.lighter(185));
 
         painter.drawRect(mGeometryRects[i][j]);
       }
     }
   }
 
 int RgbBitMaskWidget::heightForWidth(int width) const
 {
   return static_cast<int>(width / (8 / 3.0));
 }
 
 QSize RgbBitMaskWidget::sizeHint() const
 {
   int w = width();
   return QSize(w, heightForWidth(w));
 }
 
 int main(int argc, char *argv[])
 {
     QApplication a(argc, argv);
     // central widget
     QWidget* cw = new QWidget;
     QVBoxLayout* lo = new QVBoxLayout;
     cw->setLayout(lo);
 
     RgbBitMaskWidget* rgb = new RgbBitMaskWidget();
     cw->layout()->addWidget(rgb);
 
     QMainWindow* mw = new QMainWindow;
     mw->setCentralWidget(cw);
     mw->show();
     return a.exec();
 }
 
 #include "main.moc"

#include <QtGui>
#include <cmath>
 
 class RgbBitMaskWidget : public QWidget
 {
   Q_OBJECT
   public:
     RgbBitMaskWidget(QWidget* parent = 0);
     ~RgbBitMaskWidget();
     uchar red() const;
     uchar green() const;
     uchar blue() const;
     virtual int heightForWidth(int) const;
     virtual QSize sizeHint() const;
   protected:
     virtual void resizeEvent(QResizeEvent*);
     virtual void paintEvent(QPaintEvent*);
     virtual void mousePressEvent(QMouseEvent* );
   signals:
     void rgbBitMaskChanged(int, int, int) const;
   private:
     uchar mBits[3];
     QList<QList<QRect> > mGeometryRects;
 
     void recalculateRectGeometries();
 };
 
 RgbBitMaskWidget::RgbBitMaskWidget(QWidget* parent)
     : QWidget(parent)
 {
   // initialize array
   for (int i = 0; i < 3; ++i)
       mBits[i] = 255;
 
   // initialize list of arrays
   for (int i = 0; i < 3; ++i) {
     QList<QRect> l;
     for (int j = 0; j < 8; ++j)
       l << QRect();
     mGeometryRects << l;
   }
 
   // set sizePolicy (important for heightForWidth)
   QSizePolicy sizePolicy(QSizePolicy::Minimum, QSizePolicy::Minimum);
   sizePolicy.setHeightForWidth(true);
   setSizePolicy(sizePolicy);
 
   const int minWidth = 150;
   setMinimumSize(minWidth, minWidth / (8 / 3.0));
 }
 
 RgbBitMaskWidget::~RgbBitMaskWidget()
 {
 }
 
 void RgbBitMaskWidget::recalculateRectGeometries()
 {
   const int MARGIN = 2;
   QRect r = contentsRect().adjusted(MARGIN, MARGIN, -MARGIN, -MARGIN);
 
   int x = 0;
   int y = 0;
   int w = static_cast<int>(r.width() / 8.0);
   int h = static_cast<int>(r.height() / 3.0);
 
   for (int i = 0; i < mGeometryRects.size(); ++i) {
     QList<QRect> rectList = mGeometryRects[i];
     x = 0;
     for (int j = 0; j < rectList.size(); ++j) {
       mGeometryRects[i][j] = QRect(x, y, w, h);
       x += w;
     }
     y += h;
   }
 }
 
 void RgbBitMaskWidget::resizeEvent(QResizeEvent* event)
 {
   Q_UNUSED(event);
   recalculateRectGeometries();
 }
 
 void RgbBitMaskWidget::mousePressEvent(QMouseEvent* event)
 {
   QPoint pos = event->pos();
   for (int i = 0; i < 3; ++i) {
     for (int j = 0; j < 8; ++j) {
       if (mGeometryRects[i][j].contains(pos)) {
         uchar flag = std::pow(2, 7 - j);
         if (flag == (mBits[i] & flag))
           mBits[i] = mBits[i] & (~flag);
         else
           mBits[i] = mBits[i] | flag ;
       }
     }
   }
   QWidget::mousePressEvent(event);
   update();
 }
 
 void RgbBitMaskWidget::paintEvent(QPaintEvent* event)
 {
   Q_UNUSED(event);
 
   QStyleOption opt;
   opt.init(this);
   QStylePainter painter(this);
   style()->drawPrimitive(QStyle::PE_Widget, &opt, &painter, this);
 
   QList<QColor> colors;
   colors << QColor(Qt::red) << QColor(Qt::green) << QColor(Qt::blue);
   // paint rects
   QPen pen(Qt::white);
   pen.setWidth(3);
   painter.setPen(pen);
   for(int i = 0; i < 3; ++i) {
     QList<QRect> l = mGeometryRects[i];
     QColor c = colors[i];
       for (int j = 0; j < 8; ++j) {
         uchar flags = std::pow(2, 7 - j);
         if ((mBits[i] & flags) == flags)
           painter.setBrush(c);
         else
           painter.setBrush(c.lighter(185));
 
         painter.drawRect(mGeometryRects[i][j]);
       }
     }
   }
 
 int RgbBitMaskWidget::heightForWidth(int width) const
 {
   return static_cast<int>(width / (8 / 3.0));
 }
 
 QSize RgbBitMaskWidget::sizeHint() const
 {
   int w = width();
   return QSize(w, heightForWidth(w));
 }
 
 int main(int argc, char *argv[])
 {
     QApplication a(argc, argv);
     // central widget
     QWidget* cw = new QWidget;
     QVBoxLayout* lo = new QVBoxLayout;
     cw->setLayout(lo);
 
     RgbBitMaskWidget* rgb = new RgbBitMaskWidget();
     cw->layout()->addWidget(rgb);
 
     QMainWindow* mw = new QMainWindow;
     mw->setCentralWidget(cw);
     mw->show();
     return a.exec();
 }
 
 #include "main.moc"

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[Onanymous]

Sorry to pick up the old thread, but have you found a solution?
I failed to solve it within spacers, layouts and heightForWidth, setHeightForWidth etc. functions.
Basically the question is how to force a widget to keep proportions under resizing its parent?