Reimplement QGraphicsItem setRotation and setScale methods with QTransform

ktechhydle

Hello all. I am trying to reimplement the setRotation and setScale methods of my qgraphicsitem with a QTransform.

So far, I have this:

    def setRotation(self, angle):
        self._rotation = angle
        self.updateTransform()

    def setScale(self, scale):
        self._scale = scale
        self.updateTransform()

    def rotation(self):
        return self._rotation

    def scale(self):
        return self._scale

    def updateTransform(self):
        # Compute the custom transformation
        transform = self.transform()
        transform.translate(self.boundingRect().center().x(), self.boundingRect().center().y())
        transform.rotate(self._rotation)
        transform.scale(self._scale, self._scale)
        transform.translate(-self.boundingRect().center().x(), -self.boundingRect().center().y())
        self.setTransform(transform)

The major issue is how the transforms stack on top of each other, causing the problem where trying to reset the rotation/scale to 0 doesn't change anything. This means if I rotate the item to 45 and try to then rotate it back to 0, nothing happens because the item transform is already at 0 for rotation.

Any help is greatly appreciated.

SGaist

Hi,

As silly as it may sound: why not start from a fresh transform ?

ktechhydle

@SGaist
The problem with doing that is that it will reset the current transform, defeating the purpose of scaling/rotating the item.