The rotate action (Space) turned a picture through QGraphicsItem's
plain rotation, which DiagramImageItem::toXml() does not save -- it
saves the rotation of the picture's own transform. The picture came
back unrotated once the project was reopened. Turn it through
"rotationAngle" instead, around its own pivot, and when a selection
is turned as a group, move the picture so that its pivot, not its
top-left corner, orbits the group's centre.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Beat Hangartner
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