Merge pull request #26 from marc-antoine-girard/#24-Add-None-Option-CustomDrawers

Author: Thundernerd

Editor/Drawers/CustomObjectDrawer.cs

@@ -94,6 +94,7 @@ private void HandleMouseDown(Rect position, Rect positionWithoutThumb)
             else if (Event.button == 1 && positionWithoutThumb.Contains(Event.mousePosition))
             {
                 GenericMenu menu = new GenericMenu();
+                menu.AddItem(new GUIContent("Clear"), false, () => { DeletePressed?.Invoke(); });
                 menu.AddItem(new GUIContent("Properties..."), false, () => { PropertiesClicked?.Invoke(); });
                 menu.DropDown(position);
                 Event.Use();

Editor/Items/NoneDropdownItem.cs

@@ -0,0 +1,16 @@
+using UnityEditor.IMGUI.Controls;
+
+namespace TNRD.Items
+{
+    public class NoneDropdownItem  : AdvancedDropdownItem, IDropdownItem
+    {
+        public NoneDropdownItem() : base("None") { }
+
+        ReferenceMode IDropdownItem.Mode => ReferenceMode.Raw;
+
+        public object GetValue()
+        {
+            return null;
+        }
+    }
+}

Editor/Items/NoneDropdownItem.cs.meta

@@ -48,6 +48,11 @@ protected override AdvancedDropdownItem BuildRoot()
                 .AddChild(new ClassesItemBuilder(interfaceType).Build())
                 .AddChild(new SceneItemBuilder(interfaceType, relevantScene).Build());
 
+            foreach (AdvancedDropdownItem dropdownItem in item.children)
+            {
+                dropdownItem.AddChild(new NoneDropdownItem());
+            }
+            
             if (canSort)
             {
                 sortChildrenMethod.Invoke(item,
@@ -62,6 +67,12 @@ protected override AdvancedDropdownItem BuildRoot()
 
         private int Sort(AdvancedDropdownItem a, AdvancedDropdownItem b)
         {
+            // For aesthetic reasons. Always puts the None first
+            if (a is NoneDropdownItem)
+                return -1;
+            if (b is NoneDropdownItem)
+                return 1;
+            
             int childrenA = a.children.Count();
             int childrenB = b.children.Count();