EditorWindow not getting MouseDrag event at startup

Hi,

It seems that when I create my own EditorWindow class and monitor the mouse and drag events the 'MouseDrag' event doesn't act correctly when I first startup Unity. The first time I launch unity and attempt a drag and drop in my editor window I do not get a MouseDrag event until I let go of the mouse button (Instead of getting it when I first click and move the mouse). If, after that, I go in the 'Hierarchy' window and drag and drop anything, go back to my editor window all the events seem to work normally again until I restart Unity.

To test this I wrote the following script that, after creating an empty project, I put in Assets/Editor/MyEditorWindow.cs :

Code (CSharp):

1. using UnityEngine;
2. using UnityEditor;
3.  
4. class MyEditorWindow : EditorWindow
5. {
6.     bool m_dragging = false;
7.  
8.     [MenuItem("Window/MyEditorWindow")]
9.     public static void ShowWindow()
10.     {
11.         EditorWindow.GetWindow(typeof(MyEditorWindow));
12.     }
13.  
14.     void OnGUI()
15.     {
16.         Event e = Event.current;
17.  
18.         if (m_dragging)
19.         {
20.             DragAndDrop.visualMode = DragAndDropVisualMode.Link;
21.         }
22.  
23.         if ((e.type == EventType.DragUpdated) ||
24.             (e.type == EventType.MouseDown) ||
25.             (e.type == EventType.MouseUp))
26.         {
27.             Debug.Log(e.type);
28.         }
29.         else if((e.type == EventType.DragExited) ||
30.                 (e.type == EventType.DragPerform))
31.         {
32.             m_dragging = false;
33.             Debug.Log(e.type);
34.         }
35.         else if (e.type == EventType.mouseDrag)
36.         {
37.             DragAndDrop.PrepareStartDrag();
38.             DragAndDrop.StartDrag("MyEditorWindow_drag");
39.             Debug.Log(e.type);
40.             m_dragging = true;
41.         }
42.     }
43. }
44.  

When I do a drag and drop in my window after starting Unity I get the following log :
- mouseDown
- mouseDrag (happens when I let go of the mouse button)
- DragExited

If I do a drag and drop in the 'hierarchy' window and try a drag and drop in my editor after that I get the expected :
- mouseDown
- mouseDrag
- DragUpdated (Many times)
- DragPerform
- DragExited

Anybody got any clues on how to solve this ?

Thanks

 

Sorry for zombie post, but I just ran into this with Unity 5.6.2. Anyone halp?

 

OK, I found an answer elsewhere, so I'll repost here. The DragAndDrop system needs to be initialized and isn't done so until you drag something within a built-in editor window (I consider this a bug in Unity).

To work around...

Code (csharp):

1. [InitializeOnLoad]
2. public class EditorStartup
3. {
4.     static EditorStartup()
5.     {
6.         DragAndDrop.objectReferences = new Object[0];
7.     }
8. }