Function ViewportMove

src/openrct2/interface/Viewport.cpp:446–477

    }

    static void ViewportMove(const ScreenCoordsXY& coords, WindowBase* w, Viewport* viewport)
    {
        // Note: do not do the subtraction and then divide!
        // Note: Due to arithmetic shift != /zoom a shift will have to be used
        // hopefully when 0x006E7FF3 is finished this can be converted to /zoom.
        auto x_diff = viewport->zoom.ApplyInversedTo(viewport->viewPos.x) - viewport->zoom.ApplyInversedTo(coords.x);
        auto y_diff = viewport->zoom.ApplyInversedTo(viewport->viewPos.y) - viewport->zoom.ApplyInversedTo(coords.y);

        viewport->viewPos = coords;

        // If no change in viewing area
        if ((!x_diff) && (!y_diff))
            return;

        const int32_t left = std::max(viewport->pos.x, 0);
        const int32_t top = std::max(viewport->pos.y, 0);
        const int32_t right = std::min(left + viewport->width + std::min(viewport->pos.x, 0), ContextGetWidth());
        const int32_t bottom = std::min(top + viewport->height + std::min(viewport->pos.y, 0), ContextGetHeight());

        if (left >= right || top >= bottom)
            return;

        if (DrawingEngineHasDirtyOptimisations())
        {
            RenderTarget& rt = DrawingEngineGetRT();
            ViewportShiftPixels(rt, w, { left, top, right, bottom }, { x_diff, y_diff });
        }
        else
        {
            GfxInvalidateScreen();
        }
    }

    // rct2: 0x006E7A15
    static void ViewportSetUndergroundFlag(int32_t underground, WindowBase* window, Viewport* viewport)