I am currently able to load my image into a grahpics scene, and then again into a QGraphicsViewer.
I am able to implement a zoom feature by dtecting a QEvent::Wheel and then calling the graphicsViews's scale() function.
However, I can't seem to figure out how to get the pan functionality working. I basically want to detect when a mouse has clicked down on the image, and then move the image left, right, up or down along with the mouse.
As of right now, I basically have a MouseFilter class that is detecting events, and doing different things depending on the event type. I attached that listener to the QGraphicsView object
In case someone is wondering how to do it on their own, it's actually quite simple. Here's the code from my app:
class ImageView : public QGraphicsView
{
public:
ImageView(QWidget *parent);
~ImageView();
private:
virtual void mouseMoveEvent(QMouseEvent *event);
virtual void mousePressEvent(QMouseEvent *event);
virtual void mouseReleaseEvent(QMouseEvent *event);
bool _pan;
int _panStartX, _panStartY;
};
You need to store the start position of the drag, for example like this (I used the right button):
void ImageView::mousePressEvent(QMouseEvent *event)
{
if (event->button() == Qt::RightButton)
{
_pan = true;
_panStartX = event->x();
_panStartY = event->y();
setCursor(Qt::ClosedHandCursor);
event->accept();
return;
}
event->ignore();
}
Also, you need to clear the flag and restore the cursor once the button is released:
void ImageView::mouseReleaseEvent(QMouseEvent *event)
{
if (event->button() == Qt::RightButton)
{
_pan = false;
setCursor(Qt::ArrowCursor);
event->accept();
return;
}
event->ignore();
}
To actually manage the drag, you need to override the mouse move event. QGraphicsView inherits a QAbstractScrollArea, and its scrollbars are easily accessible. You also need to update the pan position:
void ImageView::mouseMoveEvent(QMouseEvent *event)
{
if (_pan)
{
horizontalScrollBar()->setValue(horizontalScrollBar()->value() - (event->x() - _panStartX));
verticalScrollBar()->setValue(verticalScrollBar()->value() - (event->y() - _panStartY));
_panStartX = event->x();
_panStartY = event->y();
event->accept();
return;
}
event->ignore();
}