Function ViewportRotateSingleInternal

src/openrct2/interface/Viewport.cpp:751–791

    }

    static void ViewportRotateSingleInternal(WindowBase& w, int32_t direction)
    {
        auto* viewport = w.viewport;
        if (viewport == nullptr)
            return;

        auto windowPos = ScreenCoordsXY{ (viewport->width >> 1), (viewport->height >> 1) } + viewport->pos;

        // has something to do with checking if middle of the viewport is obstructed
        Viewport* other;
        auto mapXYCoords = ScreenGetMapXY(windowPos, &other);
        CoordsXYZ coords{};

        // other != viewport probably triggers on viewports in ride or guest window?
        // mapXYCoords is nullopt if middle of viewport is obstructed by another window?
        if (!mapXYCoords.has_value() || other != viewport)
        {
            auto viewPos = ScreenCoordsXY{ (viewport->ViewWidth() >> 1), (viewport->ViewHeight() >> 1) } + viewport->viewPos;

            coords = ViewportAdjustForMapHeight(viewPos, viewport->rotation);
        }
        else
        {
            coords.x = mapXYCoords->x;
            coords.y = mapXYCoords->y;
            coords.z = TileElementHeight(coords);
        }

        viewport->rotation = (viewport->rotation + direction) & 3;

        auto centreLoc = centre2dCoordinates(coords, viewport);

        if (centreLoc.has_value())
        {
            w.savedViewPos = centreLoc.value();
            viewport->viewPos = *centreLoc;
        }

        w.invalidate();
        w.onViewportRotate();
    }

    void ViewportRotateSingle(WindowBase* window, int32_t direction)
    {