Application of the subtract and add methods in the point struct when dragging controls

The Methods subtract () and add () in the struct point can be used to calculate the relative positions between two points in the same coordinate system:

Public static point subtract (
Point PT,
Size SZ
)

Public static point add (
Point PT,
Size SZ
)

The size can be converted by point, as shown in the following constructor:
Public size (
Point PT
)

Label1 and label2 are two components in the same container (form1). When label1 is dragged, label2 is also moved.

1. Define global fields:

Private point label1startpos, offsetpoint;
Private bool canmove = false;

2. Related event methods:

Private void labeldomainmousedown (Object sender, mouseeventargs E)
{
Canmove = true;
Label1startpos = E. location;
Offsetpoint = point. Subtract (label2.location, new size (label1.location ));
}

Private void labeldomainmouseup (Object sender, mouseeventargs E)
{
Canmove = false;
}

Private void label1_mousemove (Object sender, mouseeventargs E)
{
If (canmove)
{
Label1.location = This. pointtoclient (point. Subtract (label1.pointtoscreen (E. Location), new size (label1startpos )));
Label2.location = point. Add (label1.location, new size (offsetpoint ));
}
}

You can.