free(w->viewport);

	w->viewport = NULL;

}

/**

 * Initialize viewport of the window for use.

 * @param w Window to use/display the viewport in

 * @param x Offset of left edge of viewport with respect to left edge window \a w

 * @param y Offset of top edge of viewport with respect to top edge window \a w

 * @param width Width of the viewport

 * @param height Height of the viewport

 * @param follow_flags Flags controlling the viewport.

 *        - If bit 31 is clear, it is a #TileIndex.

 * @param zoom Zoomlevel to display

 */

void InitializeWindowViewport(Window *w, int x, int y,

	int width, int height, uint32 follow_flags, ZoomLevel zoom)

{

	assert(w->viewport == NULL);

	ViewportData *vp = CallocT<ViewportData>(1);

	vp->left = x + w->left;

	vp->top = y + w->top;

	vp->height = height;

	vp->zoom = zoom;

	vp->virtual_width = ScaleByZoom(width, zoom);

	vp->virtual_height = ScaleByZoom(height, zoom);

	Point pt;

	if (follow_flags & 0x80000000) {

		const Vehicle *veh;

		veh = Vehicle::Get(vp->follow_vehicle);

		pt = MapXYZToViewport(vp, veh->x_pos, veh->y_pos, veh->z_pos);

	} else {

		uint x = TileX(follow_flags) * TILE_SIZE;

		uint y = TileY(follow_flags) * TILE_SIZE;

		vp->follow_vehicle = INVALID_VEHICLE;

		pt = MapXYZToViewport(vp, x, y, GetSlopeZ(x, y));

	}

	vp->scrollpos_x = pt.x;

	vp->scrollpos_y = pt.y;