/// <summary>
/// Compute the new location for a node, given another node that is controlling its movement.
/// </summary>
/// <param name="moving">the <see cref="Northwoods.GoXam.Node"/> being dragged</param>
/// <param name="pt">the <c>Point</c> in model coordinates to which the node is being dragged</param>
/// <param name="snapper">the <see cref="Northwoods.GoXam.Node"/>, typically a grid, which is controlling the drag snapping</param>
/// <param name="draggedparts">a <c>Dictionary</c> of <see cref="Part"/>s being dragged</param>
/// <returns>a new node location, in model coordinates</returns>
/// <remarks>
/// <para>
/// This is called by <see cref="ComputeMove"/>.
/// </para>
/// <para>
/// When there is a <paramref name="snapper"/>,
/// if the <paramref name="snapper"/>'s <see cref="Part.DragOverSnapEnabled"/> property is false,
/// this method just returns the unmodified <paramref name="pt"/> value.
/// Otherwise this uses the <see cref="Part.DragOverSnapCellSize"/> and
/// <see cref="Part.DragOverSnapCellSpot"/>
/// to compute the nearest grid point that should be the location of the
/// <paramref name="moving"/> node.
/// </para>
/// <para>
/// If there is no <paramref name="snapper"/>, this uses the <see cref="Northwoods.GoXam.Diagram"/>'s
/// <see cref="Northwoods.GoXam.Diagram.GridSnapCellSize"/>,
/// <see cref="Northwoods.GoXam.Diagram.GridSnapCellSpot"/>, and
/// <see cref="Northwoods.GoXam.Diagram.GridSnapOrigin"/>
/// properties to calculate and return the nearest grid point.
/// </para>
/// </remarks>
protected virtual Point SnapTo(Node moving, Point pt, Node snapper, Dictionary<Part, Info> draggedparts) {
if (moving == null) return pt;
if (snapper == null) {
Diagram diagram = this.Diagram;
if (diagram == null || !diagram.GridSnapEnabled) return pt;
Size cell = diagram.GridSnapCellSize;
Point origin = diagram.GridSnapOrigin;
Point s = diagram.GridSnapCellSpot.PointInRect(new Rect(0, 0, cell.Width, cell.Height));
Point q = FindNearestInfiniteGridPoint(pt, s, origin, cell);
return q;
} else {
if (!snapper.DragOverSnapEnabled) return pt;
Rect r = snapper.GetElementBounds(snapper.LocationElement);
if (Double.IsNaN(r.X) || Double.IsNaN(r.Y)) return pt;
Rect mb = moving.Bounds;
Point oldloc = moving.Location;
//if (ds.KeepsOutside) { //???
// Point p = oldloc;
// if (oldloc.X <= r.Left) {
// p.X = r.Left - mb.Width + (oldloc.X-mb.X);
// } else if (oldloc.X >= r.Right) {
// p.X = r.Right + (oldloc.X-mb.X);
// }
// if (oldloc.Y <= r.Top) {
// p.Y = r.Top - mb.Height + (oldloc.Y-mb.Y);
// } else if (oldloc.Y >= r.Bottom) {
// p.Y = r.Bottom + (oldloc.Y-mb.Y);
// }
// return p;
//}
double left = Math.Max(0, oldloc.X - mb.Left);
double right = Math.Max(0, mb.Right - oldloc.X);
double top = Math.Max(0, oldloc.Y - mb.Top);
double bottom = Math.Max(0, mb.Bottom - oldloc.Y);
Size cell = snapper.DragOverSnapCellSize;
Point origin = snapper.DragOverSnapOrigin;
r.X += origin.X;
r.Y += origin.Y;
Point s = snapper.DragOverSnapCellSpot.PointInRect(new Rect(0, 0, cell.Width, cell.Height));
Point q = FindNearestInfiniteGridPoint(pt, s, new Point(r.X, r.Y), cell);
if (q.X - left < r.Left) {
q.X += cell.Width * (int)Math.Ceiling((r.Left-(q.X-left))/cell.Width);
}
if (q.X + right > r.Right) {
q.X -= cell.Width * (int)Math.Ceiling(((q.X+right)-r.Right)/cell.Width);
}
if (right > 0 && q.X - left < r.Left) {
q.X += cell.Width * (int)Math.Ceiling((r.Left-(q.X-left))/cell.Width);
}
if (q.Y - top < r.Top) {
q.Y += cell.Height * (int)Math.Ceiling((r.Top-(q.Y-top))/cell.Height);
}
if (q.Y + bottom > r.Bottom) {
q.Y -= cell.Height * (int)Math.Ceiling(((q.Y+bottom)-r.Bottom)/cell.Height);
}
if (bottom > 0 && q.Y - top < r.Top) {
q.Y += cell.Height * (int)Math.Ceiling((r.Top-(q.Y-top))/cell.Height);
}
return q;
}
}
