ContextDummyEditor.cs

using UnityEngine;
using System.Collections;
using UnityEditor;

[CustomEditor(typeof(ContextDummy))]
public class ContextDummyEditor : Editor
{
    Event prevMouseEvent;
    bool contextIsOpen;

    void OnSceneGUI()
    {
        Event currentEvent = Event.current;

        /*
        if (currentEvent.isMouse)
            Debug.Log("Current event: " + Event.current);

        Debug.Log("id: " + GUIUtility.hotControl);
        */

        // After exiting the generic menu:
        if (currentEvent.type == EventType.mouseDown
            && contextIsOpen)
        {
            Debug.Log("Exited context");

            // RENABLE SCENE CONTROLS ????

            //currentEvent.type = EventType.DragExited;
            //Event.current.type = EventType.Layout;
            EditorGUIUtility.hotControl = 0;

            HandleUtility.Repaint();
            SceneView.RepaintAll();
            contextIsOpen = false;

            currentEvent.Use();
        }

        // Show context menu:
        if (currentEvent.isMouse
            && currentEvent.type == EventType.mouseUp
            && currentEvent.button == 1
            && prevMouseEvent.type != EventType.mouseDrag)
        {

            Debug.Log("Current event is: " + Event.current + " and last swas: " + prevMouseEvent);
            Debug.Log("Opened context");

            DisplayContext(currentEvent.mousePosition);

            currentEvent.Use();

            // GUIUtility.hotControl = 0;
        }

        if (currentEvent != null && currentEvent.isMouse)
            prevMouseEvent = new Event(currentEvent);
    }

    void DisplayContext(Vector2 at)
    {
        contextIsOpen = true;

        GenericMenu menu = new GenericMenu();
        menu.AddItem(new GUIContent("IN Connect to closest"), false, Callback, "item 1");
        menu.AddItem(new GUIContent("OUT Connect to closest"), false, Callback, "item 2");
        menu.AddSeparator("");
        menu.AddItem(new GUIContent("SubMenu/MenuItem3"), false, Callback, "item 3");
        menu.ShowAsContext();
    }

    void Callback(object obj)
    {
        Debug.Log("Selected: " + obj);
    }
}