moveAnnotationDrag method
Moves an annotation during a drag operation.
Call this from AnnotationWidget's GestureDetector.onPanUpdate. The delta is already in graph coordinates since GestureDetector is inside InteractiveViewer's transformed space - no conversion needed.
Parameters:
graphDelta: The movement delta in graph coordinates
Implementation
void moveAnnotationDrag(Offset graphDelta) {
annotations.internalMoveAnnotationDrag(graphDelta, _nodes);
}