How to restore a QGraphicsView zoom to 100%, i.e., the zoom when the program started?

Question

So, far I have this code:

from PyQt4 import QtGui, QtCore

class MyFrame(QtGui.QGraphicsView):
    """
        Python PyQt: How can I move my widgets on the window with mouse?
        https://stackoverflow.com/questions/12213391/python-pyqt-how-can-i-move-my-widgets-on-the-window-with-mouse
    """
    def __init__( self, parent = None ):
        super( MyFrame, self ).__init__( parent )

        scene = QtGui.QGraphicsScene()
        self.setScene( scene )
        self.resize( 400, 340 )

        # http://pyqt.sourceforge.net/Docs/PyQt4/qpen.html
        pencil = QtGui.QPen( QtCore.Qt.black, 1)
        pencil.setStyle( QtCore.Qt.SolidLine )

        scene.addLine( QtCore.QLineF( 0, -50, 0, 50 ), pencil )
        scene.addLine( QtCore.QLineF( -50, 0, 50, 0 ), pencil )

        fitInViewButton = QtGui.QPushButton( 'Fit In View', self )
        fitInViewButton.clicked.connect( self.handleFitInView )

        scene.addWidget( fitInViewButton )

    def handleFitInView( self ):
        # Auto scale a QGraphicsView
        # http://www.qtcentre.org/threads/42917-Auto-scale-a-QGraphicsView
        self.ensureVisible ( self.scene().itemsBoundingRect() )
        self.fitInView( self.scene().itemsBoundingRect(), QtCore.Qt.KeepAspectRatio )

    def wheelEvent( self, event ):
        """
            PyQT4 WheelEvent? how to detect if the wheel have been use?
            https://stackoverflow.com/questions/9475772/pyqt4-wheelevent-how-to-detect-if-the-wheel-have-been-use

            QGraphicsView Zooming in and out under mouse position using mouse wheel
            https://stackoverflow.com/questions/19113532/qgraphicsview-zooming-in-and-out-under-mouse-position-using-mouse-wheel
        """

        # Zoom Factor
        zoomInFactor = 1.1
        zoomOutFactor = 1 / zoomInFactor

        # Set Anchors
        self.setTransformationAnchor( QtGui.QGraphicsView.NoAnchor )
        self.setResizeAnchor( QtGui.QGraphicsView.NoAnchor )

        # Save the scene pos
        oldPos = self.mapToScene( event.pos() )

        # Zoom
        if event.delta() > 0:
            zoomFactor = zoomInFactor
        else:
            zoomFactor = zoomOutFactor
        self.scale( zoomFactor, zoomFactor )

        # Get the new position
        newPos = self.mapToScene( event.pos() )

        # Move scene to old position
        delta = newPos - oldPos
        self.translate( delta.x(), delta.y() )

if ( __name__ == '__main__' ):
    app = QtGui.QApplication( [] )
    f = MyFrame()
    f.show()
    app.exec_()

It generates this window which initially opens as:

However latter I can zoom in like:

Then I would like to have a reset zoom button which sets the zoom as the default zoom when the program opened:

But the button I have for now is only fitting the visible parts in the full screen, instead of restore the original zoom, after the zoom scroll by mouse:

Answer 1

To reset the index you must reset the transformation:

{your_graphicsview}.setTransform(QtGui.QTransform())