Error : No match for the operand

Question

I trying to implement snapping but getting an error

error: no match for 'operator%' (operand types are 'const int' and 'const QSize')
     const int firstLeftGridLine = realLeft - (realLeft % gridSize);

My code to it as follows: cadgraphicsscene.cpp

    void CadGraphicsScene::drawBackground(QPainter *painter, const QRectF &rect)
    {
        const int realLeft = static_cast<int>(std::floor(rect.left()));
        const int realRight = static_cast<int>(std::ceil(rect.right()));
        const int realTop = static_cast<int>(std::floor(rect.top()));
        const int realBottom = static_cast<int>(std::ceil(rect.bottom()));

        // Draw grid.
        const int firstLeftGridLine = realLeft - (realLeft % gridSize);
        const int firstTopGridLine = realTop -(realTop % gridSize);
        QVarLengthArray<QLine, 100> lines;

        for (qreal x = firstLeftGridLine; x <= realRight; x += gridSize)
            lines.append(QLine(x, realTop, x, realBottom));
        for (qreal y = firstTopGridLine; y <= realBottom; y += gridSize)
            lines.append(QLine(realLeft, y, realRight, y));

        painter->setPen(QPen(QColor(220, 220, 220), 0.0));
        painter->drawLines(lines.data(), lines.size());

        // Draw axes.
        painter->setPen(QPen(Qt::lightGray, 0.0));
        painter->drawLine(0, realTop, 0, realBottom);
        painter->drawLine(realLeft, 0, realRight, 0);
    }

void CadGraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    mDragged = qgraphicsitem_cast<QGraphicsItem*>(itemAt(mouseEvent->scenePos(),
QTransform()));
    if (mDragged) {
        mDragOffset = mouseEvent->scenePos() - mDragged->pos();
    } else
        QGraphicsScene::mousePressEvent(mouseEvent);
}

void CadGraphicsScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
   if (mDragged) {
        int x = floor(mouseEvent->scenePos().x() / gridSize.width()) * gridSize.width();
        int y = floor(mouseEvent->scenePos().y() / gridSize.height()) * gridSize.height();
        mDragged->setPos(x, y);
        mDragged = 0;
    } else
        QGraphicsScene::mouseReleaseEvent(mouseEvent);
}

void CadGraphicsScene::mouseMoveEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    if (mDragged) {
        // Ensure that the item's offset from the mouse cursor stays the same.
        mDragged->setPos(mouseEvent->scenePos() - mDragOffset);
    } else
        QGraphicsScene::mouseMoveEvent(mouseEvent);
}

cadgraphicsscene.h

private:
    const QSize gridSize;
    QGraphicsItem *mDragged;
    QPointF mDragOffset;

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

I am getting error in cadgraphicsscene.cpp file.Can you please help me to solve the error?

How can you divide int to QSize()? Even compiler cannot. You need to bring both arguments to the type `int`. For example: `realLeft % gridSize.width()` — vahancho, Nov 25 '14 at 14:14

score 2 · Answer 1 · answered Nov 25 '14 at 14:22

2

QSize is a class that describes a two-dimensional size (width and height). I suspect you meant to use

realLeft % gridSize.width()

and

realTop  % gridSize.height()

respectively.

answered Nov 25 '14 at 14:22

seldon

510
2
4

When i use as stated above my system crashes. Unexpected thing but happens :(. Even I changed QSize datatype to int even then the it crashes. Please help me out to solve this – user3859872 Nov 25 '14 at 14:25
Make sure that neither gridSize.width() nor gridSize.height() are zero; that's about the only way this could cause a crash. – seldon Nov 25 '14 at 16:08
Even after assigning the value it crashes. I have added gridSize.width ==10; gridSize.width == 10; – user3859872 Nov 25 '14 at 16:21
Then you have a different error somewhere else, possibly in completely different code. Use your debugger. Reliably reproducible crashes are usually easy to find with it. – seldon Nov 25 '14 at 17:03

Error : No match for the operand

1 Answers1