Resize rectangle with mouse events

[coder2020]

Hi

I'm trying to resize a rectangle and move it with the mouse.

at the moment i managed to move it with the mouse but i have a little problem resizing it.

When I resize it from the top of the rectangle, I have no problem but when I resize it from the bottom, I manage to do it as long as I don't release the mouse button but once release it, I can't resize it anymore until I move the rectangle.

In addition, there are traces in the window when I decrease the height of the bottom rectangle.

can you help me find where the bug is coming from?```

main.cpp

#include <QApplication>


int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Fenetre w;
    w.show();

    return a.exec();
}

fenetre.h

#ifndef FENETRE_H
#define FENETRE_H

#include <QGraphicsScene>
#include <QMainWindow>

#include "myrectangle.h"
#include <QGraphicsView>

#include <QMouseEvent>
#include <QObject>

namespace Ui {
class Fenetre;
}

class Fenetre : public QMainWindow
{
    Q_OBJECT

public:
    explicit Fenetre(QWidget *parent = nullptr);
    ~Fenetre();

    bool eventFilter(QObject *obj, QEvent *event);

protected:


private:
    Ui::Fenetre *ui;

    QGraphicsScene *scene;
    QGraphicsView *view;

    MyRectangle *rectangle;

signals:
    void clickedMouse(int x, int y);
};

#endif // FENETRE_H

fenetre.cpp

#include "fenetre.h"
#include "ui_fenetre.h"


Fenetre::Fenetre(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::Fenetre)
{
    ui->setupUi(this);
    
    QBrush greenBrush(Qt::green);
    QBrush blueBrush(Qt::blue);
    QPen pen(Qt::black);
    pen.setWidth(2);
    
    rectangle = new MyRectangle ();  
    
    QColor c (242,251,235);
    QBrush brush (c, Qt::SolidPattern);
    
    scene = new QGraphicsScene(this);
    scene->setBackgroundBrush(brush);
    scene->addItem(rectangle);  
    
    view = new QGraphicsView(scene);    
    scene->setSceneRect(0, 0, 400, 400);
    
    ui->graphicsView->setScene(scene);
    
    view->viewport()->installEventFilter(this); // Meilleur Fonctionne
    //    view->installEventFilter(this); // Fonctionne
    //    ui->graphicsView->viewport()->installEventFilter(this);
    
    setCentralWidget(view);
    view->show();
    
    connect(this, SIGNAL(clickedMouse(int, int)), rectangle, SLOT(recevedClickedMouse(int, int)));
}

Fenetre::~Fenetre()
{
    delete ui;
}

bool Fenetre::eventFilter(QObject *obj, QEvent *event)
{    
    if (event->type() == QEvent::MouseMove)
    {
        //        qDebug() << "AAAAAA eventFilter  MouseMove" << endl;
        QMouseEvent *mouseEvent = static_cast<QMouseEvent*>(event);
        statusBar()->showMessage(QString("Mouse move (%1,%2)").arg(mouseEvent->pos().x()).arg(mouseEvent->pos().y()));
        
        //      emit clickedMouse(mouseEvent->pos().x(), mouseEvent->pos().y());        
    }
    else if (event->type() == QEvent::MouseButtonPress)
    {
        qDebug() << "BBBBBB eventFilter MouseButtonPress " << endl;
        QMouseEvent *mouseEvent = static_cast<QMouseEvent*>(event);
        statusBar()->showMessage(QString("Mouse move (%1,%2)").arg(mouseEvent->pos().x()).arg(mouseEvent->pos().y()));
                
        ///////////////////////////
        
        //      qDebug() << "rectangle->pos().x() " << rectangle->pos().x() << "rectangle->pos().y()" << rectangle->pos().y() << endl;
        //      qDebug() << "rectangle->scenePos().x() " << rectangle->scenePos().x() << "rectangle->scenePos().y()" << rectangle->scenePos().y() << endl;
                
        //      QPoint point_mouse_move = ui->graphicsView->mapFrom(ui->graphicsView, QPoint(rectangle->pos().x(), rectangle->pos().y()));
        //      qDebug() << "OK 1111 BBB ui->graphicsView->mapFrom(point_mouse_move.x() = " << point_mouse_move.x() << "point_mouse_move.y() " << point_mouse_move.y();//okkk INUTILE
        
        QPoint pointRec2 =  view->mapFromScene(rectangle->pos().x(), rectangle->pos().y());
        qDebug() << "OKKKKKK 2222 BBBBBB   view->mapFromScene(myRect.x() = " << pointRec2.x() << "myRect.y() " << pointRec2.y(); //okkk IMPORTANT
        
        ///////////////////////////        
        emit clickedMouse(mouseEvent->pos().x(), mouseEvent->pos().y());
    }
    
    return false;
}

myrectangle.h

#ifndef MYRECTANGLE_H
#define MYRECTANGLE_H

#include <QPainter>
#include <QGraphicsItem>
#include <QDebug>

#include <QApplication>
#include <QColor>
#include <QPen>

#include <QGraphicsSceneHoverEvent>
#include <QObject>

class MyRectangle : public QObject, public QGraphicsItem
{
    Q_OBJECT

public:
    MyRectangle();
    QRectF boundingRect() const;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);

    QColor color;   // the hover event handlers will toggle this between red and black
    QPen pen;       // the pen is used to paint the red/black border

private:
    qreal   width;
    qreal   height;

    int mouseDownX;
    int mouseDownY;

    bool pressedToSize;
    int avant = 0;

protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event);
    void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
    void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);

    void hoverEnterEvent(QGraphicsSceneHoverEvent *event);
    void hoverMoveEvent(QGraphicsSceneHoverEvent *event);
    void hoverLeaveEvent(QGraphicsSceneHoverEvent *event);

protected slots:
    void recevedClickedMouse(int x, int y);
};
#endif // MYRECTANGLE_H

myrectangle.cpp

#include "myrectangle.h"

MyRectangle::MyRectangle()
{
    width = 100;
    height = 50;

    pressedToSize = false;
    setFlag(ItemIsMovable);

    setAcceptHoverEvents(true);
    color = Qt::yellow;
    pen.setColor(color);
}

QRectF MyRectangle::boundingRect() const
{
    return QRectF(0, 0, width, height);
}

void MyRectangle::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    QRectF rec = boundingRect();
    QBrush brush(Qt::blue);

    if(pressedToSize)
    {
        brush.setColor(color);
    }
    else
    {
        brush.setColor(color);
    }

    painter->fillRect(rec, brush);
    painter->drawRect(rec);
}


void MyRectangle::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
    //        qDebug() << "mousePressEvent" << endl;
    qDebug() << "PPPPPPPP mousePressEvent event->pos().x() = " << event->pos().x() << "event->pos().y() = "<< event->pos().y() <<  endl;
    if(event->pos().y() < 10 || event->pos().y() > height - 10)
    {
        pressedToSize = true;
        QApplication::setOverrideCursor(Qt::SizeVerCursor);
        mouseDownX = event->pos().x();
        mouseDownY = event->pos().y();
    }
    else
    {
        QApplication::setOverrideCursor(Qt::OpenHandCursor);
    }
    update();

    QGraphicsItem::mousePressEvent(event); // OK Décomenter
}

void MyRectangle::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
//    qDebug() << ">>>>>>> mouseMoveEvent() width() = " << width << "height = "<< height;
    qDebug() << ">>>>>>> mouseMoveEvent() par rapport à lui meme  event->pos().x() = " << event->pos().x() << "event->pos().y() = "<< event->pos().y();
    qDebug() << ">>>>>>> position du rectangle par rapport à la scene this->pos().x() = " << this->pos().x() << "this->pos().y() = " << this->pos().y();
//    qDebug() << ">>>>>>> mouseMoveEvent mouseDownX = " << mouseDownX << "mouseDownY = "<< mouseDownY <<  endl <<  endl;

    if(pressedToSize)
    {
        if((mouseDownY <= 10)) // En haut du rectangle
        {
            qDebug() << "haut   ";
            height -=  event->pos().y();
//            setPos(pos().x() ,  pos().y() + event->pos().y() );
            moveBy(0, event->pos().y());
        }

        else if( (avant >= height -10)) // En bas du rectangle
        {
            qDebug() << "bas   ";
            height =  event->pos().y();
//            setPos(pos().x() ,  pos().y());
//            moveBy(0, 0);
        }
    }

    avant = event->pos().y();


    update();
    if(!pressedToSize)
    {
        qDebug() << "!!!!!pressedToSize  ";
        QGraphicsItem::mouseMoveEvent(event); //Decommenter si setFlag(ItemIsMovable)
    }
}

void MyRectangle::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{
    pressedToSize = false;
    if((event->pos().y() >= 0 && (event->pos().y() <= 10)) || ((event->pos().y() <= height) && (event->pos().y() >= (height - 10)) ))
    {
//        qDebug() << "mouseReleaseEvent width, height" << width << height << endl;
        QApplication::setOverrideCursor(Qt::SizeVerCursor);
    }
    else
    {
        QApplication::setOverrideCursor(Qt::OpenHandCursor);
    }
    update();

    QGraphicsItem::mouseReleaseEvent(event); // OK 
}

void MyRectangle::hoverEnterEvent(QGraphicsSceneHoverEvent *event)
{
//    qDebug() << ">>>>>>>>>>>>>>> hoverEnterEvent x() = " << event->pos().x() << "y() = " << event->pos().y() << endl;
    color = Qt::red;
    if((event->pos().y() > 0 && (event->pos().y() < 10)) || ((event->pos().y() < height) && (event->pos().y() > (height - 10)) ))
    {
        QApplication::setOverrideCursor(Qt::SizeVerCursor);
    }
    else
    {
        QApplication::setOverrideCursor(Qt::OpenHandCursor);
    }
    update();

}

void MyRectangle::hoverMoveEvent(QGraphicsSceneHoverEvent *event)
{
//    qDebug() << ">>>>>>>>>>>>>>> hoverMoveEvent x() = " << event->pos().x() << "y() = " << event->pos().y() ;
    //    qDebug() << ">>>>>>>>>>>>>>> hoverMoveEvent mouseDownX  = " << mouseDownX << "mouseDownY = " << mouseDownY << endl;
//    qDebug() << ">>>>>>>>>>>>>>> hoverMoveEvent x() = width << height "  << width << height << endl;

    color = Qt::red;
    if((event->pos().y() > 0 && (event->pos().y() < 10)) || ((event->pos().y() < height) && (event->pos().y() > (height - 10)) ))
    {
        QApplication::setOverrideCursor(Qt::SizeVerCursor);
    }
    else
    {
        QApplication::setOverrideCursor(Qt::OpenHandCursor);
    }
    update();
}

void MyRectangle::hoverLeaveEvent(QGraphicsSceneHoverEvent *event)
{
//    qDebug() << ">>>>>>>>>>>>>>> hoverLeaveEvent x() = " << event->pos().x() << "y() = " << event->pos().y() << endl;
    color = Qt::green;
    if((event->pos().y() >= 0 && (event->pos().y() <= 10)) || ((event->pos().y() <= height) && (event->pos().y() >= height - 10) ))
    {
        QApplication::setOverrideCursor(Qt::SizeVerCursor);
    }
    else
    {
        QApplication::setOverrideCursor(Qt::ArrowCursor);
    }
    update();
}

void MyRectangle::recevedClickedMouse(int x, int y)
{
    qDebug() << "7777 COUCOU x = " << x << "y = " << y << endl;
}

[Pl45m4]

@coder2020 said in Resize rectangle with mouse events:

In addition, there are traces in the window when I decrease the height of the bottom rectangle.
can you help me find where the bug is coming from?

Without looking into your code, I can say, that it's not a bug.

Try to call prepareGeometryChange() before changing your item size.
https://doc.qt.io/qt-5/qgraphicsitem.html#prepareGeometryChange

[coder2020]

@Pl45m4
thank you so much.

it works fine now.