move QGraphicsView around QGraphicsScene

Question

I'm making a side view drag racing game in QT c++. I want to move my view around my scene from left to right. I have the scene set to 3600x800, but i want the view the be at the far left of my scene not at the center at the start. When i press W on my keyboard I want the view to move to the left for 1px. How do I do that? I can't find anything online

scene=new QGraphicsScene(this);
view = new QGraphicsView;
scene->setSceneRect(0,0,3600,800);
view->setScene(scene);

eyllanesc eyllanesc · Accepted Answer · 2018-02-27T18:25:43

You will never find something so particular on the internet, you should look for each part separately:

If you want it to appear on the left side then you must use horizontalScrollBar() of the GraphicsView when it is displayed, we can do that with the showEvent method.
if you want to do an action when you press any key you could overwrite the keyPressEvent method.
To move the sceneRect() you must make a copy, move it and set it again.

#include <QApplication>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QKeyEvent>
#include <QScrollBar>

class GraphicsView: public QGraphicsView{
public:
    using QGraphicsView::QGraphicsView;
protected:
    void keyPressEvent(QKeyEvent *event){
        if(event->key() == Qt::Key_W){
            if(scene()){
                QRectF rect = scene()->sceneRect();
                rect.translate(1, 0);
                scene()->setSceneRect(rect);
            }
        }
    }
    void showEvent(QShowEvent *event){
        QGraphicsView::showEvent(event);
        if(isVisible()){
            horizontalScrollBar()->setValue(0);
        }
    }
};
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QGraphicsScene scene;
    GraphicsView view;
    scene.setSceneRect(0,0,3600,800);
    view.setScene(&scene);
    scene.addRect(0, 200, 400, 400, Qt::NoPen, Qt::red);
    view.show();
    return a.exec();
}

move QGraphicsView around QGraphicsScene

1 Answers