QGraphicsView 90 degree Rotation

[kshegunov]

Use two QTransform objects - one for rotation and one for scaling, then multiply them in the proper order (the order of multiplication matters as scaling and rotation don't commute). After that apply your transform to whatever you need.

[keksi venksi]

@kshegunov
Thanks for your reply .
Can you give some example code .

[kshegunov]

QTransform rotation;
rotation.rotate(90);

QTransform scaling;
scaling.scale(0.5, 1);

setTransform(rotation * scaling);
// Or
QVector2D vector;
vector = rotation * scaling * vector;

Modify according to your needs.

[keksi venksi]

@kshegunov

Thanks for your reply .

In my case I dont want to use scale to zoom

I wish to use fitInView() to achieve zoom.

In short note after applying transform (rotate 90 degree) fitInView() does not works fine . I want fitInView() to do zoom

[keksi venksi]

@keksi-venksi

Can any one help me on it .
Helps are really appreciable

[A Former User]

customgraphicsview.h

#ifndef CUSTOMGRAPHICSVIEW_H
#define CUSTOMGRAPHICSVIEW_H

#include <QGraphicsView>

class CustomGraphicsView : public QGraphicsView
{
    Q_OBJECT
public:
    enum class Mode
    {
        x,
        y
    };

    explicit CustomGraphicsView(QWidget *parent = nullptr);
    void reset();
    void fit();
    void setMode(Mode mode);

protected:
    void wheelEvent(QWheelEvent* event) override;

private:
    void updateTransform();
    Mode m_mode = Mode::x;
    double m_scale = 1.0;
};

#endif // CUSTOMGRAPHICSVIEW_H

customgraphicsview.cpp

#include "customgraphicsview.h"
#include <QBrush>
#include <QColor>
#include <QWheelEvent>
#include <QDebug>

CustomGraphicsView::CustomGraphicsView(QWidget *parent)
    : QGraphicsView(parent)
{
    setBackgroundBrush(QBrush(QColor("grey")));
}

void CustomGraphicsView::reset()
{
    m_mode = Mode::x;
    m_scale = 1.0;
    updateTransform();
}

void CustomGraphicsView::fit()
{
    auto const r = scene()->itemsBoundingRect();
    switch (m_mode) {
    case Mode::x: {
        double f1 = width() / (r.width() + 2);
        double f2 = height() / (r.height() + 2);
        m_scale = qMin(f1,f2);
        updateTransform();
        break;
    }
    case Mode::y: {
        double f1 = height() / (r.width() + 2);
        double f2 = width() / (r.height() + 2);
        m_scale = qMin(f1,f2);
        updateTransform();
        break;
    }
    }
}

void CustomGraphicsView::setMode(CustomGraphicsView::Mode mode)
{
    if (m_mode == mode)
        return;
    m_mode = mode;
    updateTransform();
}

void CustomGraphicsView::wheelEvent(QWheelEvent *event)
{
    auto const delta = (event->delta() <0.0) ? -1.0 : 1.0;
    m_scale += 0.1 * delta;
    updateTransform();
}

void CustomGraphicsView::updateTransform()
{
    QTransform t;
    if (m_mode == Mode::y)
        t.rotate(90);
    t.scale(m_scale, m_scale);
    setTransform(t);
}

[keksi venksi]

@keksi-venksi

I would like to continue with this thread

in the normal mode im using view->fitInView(rect.x(),0,rect.width(),30)

in the 90 degree rotated mode im using view->fitInView(0,rect.y(),30,rect.height())

I have tried with different combinations of fitInView for 90 degree rotataion Nothing works

Can any one suggest me the coordinates for the fitInView() for the rotated view

Help me on it

[A Former User]

@keksi-venksi Please try the code above that I just posted. If I understood you right, then it should meet your requirements :)

[keksi venksi]

@Wieland
@Wieland

Thanks for your reply

I am using fitInView in many places in my project to work stable . So I would like to get some suggestions for fitInView() coordinates

[A Former User]

@keksi-venksi said in QGraphicsView 90 degree Rotation:

I am using fitInView in many places in my project to work stable . So I would like to get some suggestions for fitInView() coordinates

This is probably my last posting here because I think I can't help you. Have you seen my code above? The fit() function? It does just what you want, look:

[keksi venksi]

Hi

Thanks for your reply

In this example in fit method you are trying it to fit the view in the frame when we click a button but my case i have used fitInView() while zooming .So it should adjust the view with the zooming delta

So when ever we zoom fitInView() should be adjusted accordingly to the scene and update the scene as well

[keksi venksi]

@keksi-venksi

To All The issue has been fixed

what i did was simple

X mode fitinview(0,0,calcValue,viewRectHeight)

Y Mode fitinview(0,0,viewRectWidth,calcValue) ; rotate(90)

After calling fitinview again im calling rotate of 90 degree

[Eddy]

@keksi-venksi
Could you please mark this topic as solved then. Others will find it easier if they have similar questions.