Yes, of course, my bad. If you call setPixmap() before show() is called, recalculate() will calculate the new pixmap based on incorrect width and height of the widget (although it's a bit strange as the showEvent should trigger a resizeEvent). You can reimplement showEvent() and call recalculate() and update() there and everything should be fine. The widget will repaint itself twice, but that's a minor problem as one of the runs will return immediately. If you want to fix it, you should for example assign m_px to m_scaled in setPixmap and set the margins to 0 instead of calling recalculate(). If the size hint of the widget is kept, the image will be fine.