public static double AngleBetween(Vector v1, Vector v2)
{
double val = Dot (v1, v2) / (v1.Length * v2.Length);
val = Math.Acos (val);
if (!Right (v1, v2))
return -val;
return val;
}
bool DragUpdate()
{
if (!dragging)
return false;
if (!rotate) {
return MoveWindow ();
} else {
Gdk.Point initial = start_root;
Gdk.Point hot = start_hot;
Gdk.Point win = Gdk.Point.Zero;
hot.X += win.X;
hot.Y += win.Y;
initial.X -= hot.X;
initial.Y -= hot.Y;
Gdk.Point now = root_pos;
now.X -= hot.X;
now.Y -= hot.Y;
var v1 = new Vector (initial);
var v2 = new Vector (now);
double angleBetween = Vector.AngleBetween (v1, v2);
Angle = start_angle + angleBetween;
return false;
}
}
public double AngleBetween(Vector v)
{
return AngleBetween (this, v);
}
public static double Dot(Vector v1, Vector v2)
{
return v1.X * v2.X + v1.Y * v2.Y;
}
static bool Right(Vector v1, Vector v2)
{
return (v1.X * v2.Y - v1.Y * v2.X) > 0;
}