PySide: Resizable scene in QGraphicsView

Question

I'm trying to find a way to mark the border of a QGraphicsScene, and make it resizable inside a QGraphicsView, to create something similar to Microsoft Paint.

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In other words, my current QGraphicsView looks like this:

But my image is only this big, as indicated by the red box:

I want my QGraphicsView to be like this (the little black boxes are cornergrabbers for resizing the canvas):

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Functionally, I want it to be similar to MS Paint:

The canvas (scene) is resizable, and the scrollbars on the window (view) appear when needed. The blue background color (solid gray background) appears behind the canvas.

How would I go about accomplishing this?

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To try to get the grey background, I've been experimenting with QGraphicsView.setBackgroundBrush() and QGraphicsScene.setBackgroundBrush(). I've learned that QGraphicsView's background brush completely overrides QGraphicsScene's background brush if one is set. Even if I only set the background brush for QGraphicsScene, that background brush extends over the image's original boundaries.

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Here is a link to my test code. Help is appreciated!

Answer 1

I have to struggle with your constructors...dunno if it works on Windows, but have to make it to work with Linux. Try :

def setPixmap(self, pixmap):
    if self.pixmap_item:
        self.removeItem(self.pixmap_item)

    self.pixmap_item = self.addPixmap(pixmap)

    self.setPixBackGround()

def setPixBackGround(self):
    # put Background rect for image
    pixR = self.pixmap_item.pixmap().rect()
    bgRectangle = self.addRect(pixR.x()-10, pixR.y()-10, 
                    pixR.width()+20, pixR.height()+20)
    # set color and Z value to put it behind image
    bgColor = QColor(58, 176, 176)
    bgRectangle.setBrush(bgColor)
    bgRectangle.setZValue(-.1)
    # take coordinates for brabbers
    bgR = bgRectangle.rect()
    grab1R = QRect(-5,-5,10,10)
    # put grabbers as wish...
    grab1 = self.addRect(grab1R)
    grab1.setPos(bgR.topLeft())

    grab2 = self.addRect(grab1R)
    grab2.setPos(bgR.topRight())
    # ....etc....