From Xojo Documentation
The mouse button was pressed inside the control's region at the location passed in to x, y.
The coordinates x and y are local to the control, i.e. they represent the position of the mouse click relative to the upper-left corner or the Slider.
- The Action event, if any, will not execute and the state of the object will not change.
- You will receive the MouseDrag and MouseUp events.
The MouseDown event uses the DragItem constructor when the user drags the contents of the control. It is:
d = New DragItem(Self, Me.Left, Me.Top, Me.Width, Me.Height)
d.Picture = Me.Image
d.Drag // Allow the drag