Freeciv

In the GTK4 client, if you open the tech tree diagram / research report, then scroll it to the right, then switch back to another view, then switch back to the research report, your scroll position has moved, and the right-click doesn't open the tech under the mouse cursor. Also you cannot see the left edge of the tech tree even when you scroll all the way left.

It looks like the gtk_viewport handles all the scrolling and positioning of the diagram, but there is leftover code that modifies the underlying diagram based on the scrollbar position, so when the redraw happens the offset is effectively doubled.

The attached works for me.