Handles.CapFunction

Declaration

public delegate void CapFunction(int controlID, Vector3 position, Quaternion rotation, float size, EventType eventType);

controlID	The control ID for the handle.
position	The position of the handle in the space of Handles.matrix.
rotation	The rotation of the handle in the space of Handles.matrix.
size	The size of the handle in world-space units.
eventType	Event type for the handle to act upon. By design it handles EventType.Layout and EventType.Repaint events.

The function to use for drawing the handle e.g. Handles.RectangleCap.

Custom CapFunction has two responsibilities:

For EventType.Layout event, call HandleUtility.AddControl to inform Unity about the distance of the handle from mouse position.
For EventType.Repaint event, render the actual handle.