Adding Reorderable Lists in Unity

Often I find myself in need of reorderable list functionality in my various custom editor interfaces, and so I decided to create a generalised implementation which works with generic lists List<T> and with SerializedProperty.

Screenshot of Reorderable List Field

This list control provides drag and drop reordering and supports mixed item heights when using custom property drawers. It is generally better to present lists for serialized properties since Unity provides automatic undo/redo support for these. You can also implement your very own list adaptor to present entirely custom lists.

This control is provided as open source under the BSD license and can be downloaded from the following repository:

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Automatic Initialisation at Runtime with Easy Maintenance!

Often when working with Unity I have the need to automatically initialise “controller” objects which live across scenes. In the past I have typically created an initialisation scene and used DontDestroyOnLoad. Whilst this works it makes debugging scenes a lot tricky since you cannot just hit the “Play” button.

It would be really great if Unity provided a runtime equivalent of InitializeOnLoad or better still a way to define scriptable objects which automatically spring into life when a certain runtime criteria is met (please vote here!).

I have been thinking of ways to circumvent this limitation and feel that I have come up with a pretty good solution. I would like to tip my hat to @Superpig for suggesting use of a ScriptableObject for game configuration.

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Adding the little padlock button to your EditorWindow!

One of the less well known features of Unity is the little padlock button that lives in the upper-right corner of the Inspector window. This button is fantastic because it causes the inspector to ignore future selections and thus allowing you to select other objects without affecting the contents of the inspector.

Those who are needing (or just want the fancy little padlock!) to achieve a similar type of locking functionality in their own custom editor windows can simply by adding the magic method “ShowButton” to their editor window class. In fact, you don’t have to add a padlock, you could add some other icon!

Screenshot of custom editor window with lock icon.
Screenshot of custom editor window with lock icon.

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Syntax Highlighting with DITA

Syntax highlighting is something that I like in user documentation because I feel that it helps make source listings easier for people to understand.

When I first examined the possibilities several months back there did not appear to be a ready solution that worked with Ditac by XMLmind. Additionally the DITA specification does not seem to specify a standard technique for identifying the syntax used in code blocks. I had planned to integrate XSLTHL into my XHTML and XSL:FO stylesheets but I couldn’t really spare the time.

Fortunately it seems that XMLmind have themselves implemented syntax highlighting using XSLTHL. As a bonus they have implemented this for each of the supported deliverables and customizing the output styles and colours is super easy.

A good selection of syntaxes are supported which can be activated using the outputclass attribute.

<codeblock outputclass="language-csharp"><![CDATA[
public class SomeCoolClass {

    public void DoSomething() {
        Debug.WriteLine("Hello World!");


Here is an example from the Rotorz Tile System user guide:

Working with DITA Topic Identifiers

When writing my new user documentation using DITA I have found myself attempting to maintain a consistent naming convention for my unique topic IDs. The problem with this approach (to me at least) is that it would be fairly easy to inadvertently reuse the same “unique” identifier for two separate topics.

So I pondered on a better solution and did some searching through online user documentation that uses DITA (or something very similar). One of the things that I noticed about these various websites is that they use a GUID instead of a carefully named identifier. A much easier solution! All I needed was an easy way to generate GUIDs in my XML documentation.

Unfortunately the XML software that I use (OxygenXML) doesn’t appear to have a GUID generator built-in as standard. Instead of wasting too much time trying to figure out how to write a Java plugin for Oxygen I decided to write a simple application using C# which registers a system-wide hotkey Ctrl+Shift+V which generates a new GUID (with a custom prefix “guid-“) and pastes that into the application that I am working with (Oxygen and NotePad++). Another nice touch is that because this uses the clipboard Ctrl+V can be used to re-paste the same GUID over and over until a new GUID is generated (or until something else is copied to the clipboard!)

I added a few extra options which others might benefit from and uploaded the source (BSD) and a compiled executable to GitHub for those who might find this of use!

Choosing an Extensible Documentation Solution

For a while I have been using Microsoft Word to author user guides and to be fair this has been a good solution up until now. Since beginning work on Rotorz Tile System there have been a number of product updates which have required multiple updates of the user documentation. Despite using style presets the process of maintaining consistent formatting and updating illustrations is extremely time consuming. I also feel that there is a need for a web based version of the documentation to make it easier for some people to find their way around.

So… ultimately I required a solution that takes a number of document fragments that can be composed in a variety of ways to provide at least two deliverables (PDF plus web based documentation). After some careful thought I also decided that I would like to avoid directly formatting the documentation that I write to save valuable time; this should be handled automatically by the documentation solution.

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Possibility of reusing custom editors in custom window?

This functionality has since been added in Unity 4!

Several weeks ago I had some ideas that would add lots of flexibility to my custom editor window. In a nutshell the idea was to add, modify and remove certain components. To be honest I thought that this would be relatively easy because this functionality is already available within Unity inspector windows. I remembered seeing `EditorGUILayout.PropertyField` and I foolishly assumed that would do the trick, but I was wrong…

My next attempt was to enumerate component properties using `SerializedObject` and `SerializedProperty`. Whilst this approach did in fact provide something that resembled a custom inspector, it was extremely lacking. When I realised, this couldn’t possibly utilise custom editors!

For example, the `Transform` component has a custom inspector which is tailored specifically for it. In Rotorz Tile System we use a custom inspector on `RotorzTileSystem` components which allows properties to be modified and actions to be performed. These custom inspectors are easily defined using the `CustomEditor` attribute. So the idea here is to reuse these custom editors (which are not necessarily created by myself) within my editor window!

With thanks to MonoDevelop’s fantastic assembly browser I came across the undocumented class `UnityEditor.ActiveEditorTracker`. The publicly exposed methods are well named and fairly self-explanatory. So I had a go at creating a rough mockup of a custom inspector. I was pleasantly surprised at how easy this had now become. Creating a rudimentary custom inspector is as simple as shown below:

using UnityEngine;
using UnityEditor;

public class CustomWindow : EditorWindow {

    public static void Test() {

    GameObject activeGO;
    Editor editor;

    void Update() {
        if (activeGO == Selection.activeGameObject)

        activeGO = Selection.activeGameObject;
        editor = null;

        if (activeGO != null)
            editor = UnityEditor.ActiveEditorTracker.MakeCustomEditor(activeGO.transform);


    void OnGUI() {
        GameObject go = Selection.activeGameObject;
        if (go == null)

        // Use the registered editor for `Transform`


Unfortunately this functionality is not currently documented and as such cannot be used in a commercial Unity extension because there is no guarantee that it will continue to work in future versions of Unity. This is a great shame because I could put this to good use! I also suspect that the developers of PlayMaker could utilise this functionality if it were documented for customisable action GUIs.

Please consider voting for Unity Technologies to add a basic level of documentation for this functionality 🙂