Cancel a picture's handle drag with Escape

Pressing Escape while a handle of a picture was dragged went to
DiagramView, which clears the selection. That removed the handles under
the mouse, so the drag stopped where it was: the picture kept the new
size, angle or pivot, and since the release never arrived, no undo step
was recorded and the change could not be undone.

Diagram gets a keyboardItem: an item in a state Escape must end. While
a resize, rotate, skew or pivot handle is dragged, the picture is that
item; DiagramView sends each key to it first, and only keys it does not
take reach the view's own shortcuts. Escape puts the picture back as it
was when the handle was pressed (position, transform, and whether the
pivot was placed by hand) and ignores the rest of the gesture, so no
undo step is recorded. The drag also ends when the handles go away.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

sources/diagramview.cpp

@@ -1155,6 +1155,17 @@ void DiagramView::keyPressEvent(QKeyEvent *e)
 	if (m_event_interface && m_event_interface->keyPressEvent(e))
 		return;
 
+		//An item in a state Escape must end -- a picture while one of its
+		//handles is dragged -- sees each key before the shortcuts below,
+		//which would otherwise clear the selection under it.
+	QGraphicsObject *keyboard_item = m_diagram ? m_diagram->keyboardItem() : nullptr;
+	if (keyboard_item && keyboard_item->scene() == m_diagram) {
+		e->ignore();
+		m_diagram->sendEvent(keyboard_item, e);
+		if (e->isAccepted())
+			return;
+	}
+
 	ProjectView *current_project = this->diagramEditor()->currentProjectView();
 	DiagramContent dc(m_diagram);
 	switch(e -> key())