(Solution) - Can't use GUILayout stuff in PropertyDrawer.OnGUI?

So, I was writing a property drawer for a type I had, everything went well, nothing out of the ordinary - everything is ‘usual’ - and by usual I mean I was writing everything using GUILayouts! - I thought oh well, that’s nice! they finally added support to GUILayout stuff to property drawers! yay!

So I went ahead and asked a few friends just to confirm it, unfortunately, they didn’t experience the same, they had ArgumentExceptions, GUILayoutMismatch and all sorts of nastiness.

I thought it was because they were using an older version of Unity, so I asked them to update, but still, the same results, GUILayout is not working for them, but for me!

This is what I have:

public class SerializedMBActionDrawer : PropertyDrawer
	public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)

public class MyType : MonoBehaviour { }

Any idea why is this working for me, but not for them?

EDIT: For a better solution altogether, I released my VFW for free. The framework contains a much better drawing API (which lets you write drawers for any object type) with a much better (allocation friendly) and faster GUI layout system.

Well, we made a little debugging session me and @Jamora - it’s very obvious that I have something in my project, that is making it work.

So we started out from an empty project - I tried doing the same thing ^ - it didn’t work! I got all the nasty stuff he got - and that proves it, there’s something in my other project that made it work.

Next step was to import stuff step by step, I kept importing till I reached a point where I imported my Editor folder, and suddenly I got no errors!

So now it’s definitely something in the editor folder from my old project, but what is it?

We kept deleting and deleting, util finally we figured it out!

It came down to this:

If you have a custom editor, for the MonoBehaviour that contains an instance of the type you have the drawer for, it will work!


public class Test : MonoBehaviour
   public MyType type;

public class TestEditor : Editor
   // you don't even need to override OnInspectorGUI!

public class MyType { }

public class MyTypeDrawer : PropertyDrawer
   public override void OnGUI(...)
       GUILayout("WHO'S THE TOUGH GUY NOW, HUH?!");

And that’s it! :slight_smile:

I don’t know if that’s a bug in Unity or not, I don’t know if other people know about this, but hey, it works :smiley:

I’m not sure I have an explanation, other than: The property is being drawing inside the custom inspector of Test?

Just thought I’d share.

Let me know if this worked for you or not.

But even if it didn’t, we could still make our own GUILayouts - if you look into any of the GUILayout methods, like Button for example you’ll notice that the first thing they do, is just get the position of the button, and then call the corresponding GUI method, in this case GUI.Button and pass it the position - if we could get the position ourselves, then it’s a piece of cake! - Unfortunately .NET Reflector is acting funny with me at the moment, if I manage to get it running and get my idea to life, I’ll post it here as well.

I do not recommend however to ‘heavily’ depend on this ‘hack’? I should say? - Because high chances are this wasn’t intended - or maybe it was? who knows… It’s subject to change, which if it does, breaks any code that depended on it. That’s why it’s better for one to make his own GUI wrappers.

@vexe: I stumbled upon this problem, too. But I didn’t know that we usually can’t use GUILayout. I created a custom Editor and property drawers for my serialized classes. When I added arrays of these classes I wondered, why the hell my array has so much empty space. (See picture)
So after debugging I’ve found out, that if you don’t use a custom Editor you’ll get many errors when using GUILayout and I think the bug here is, that my custom Editor somehow let the errors disappear. In short: the combination of custom Editor and GUILayout seems to work but I think it is not intended to work.
In my case the Editor for my array calculated its size for the amount of elements and because I used GUILayout in the property drawer my elements are getting rendered after the “reserved” space from my array.