Adding 'ReadOnly' attributions for Unity Editor UI

Author: kimryan0416

.gitignore

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+**/*.meta

ReadOnly/Editor/ReadOnlyDrawer.cs

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+using UnityEditor;
+using UnityEngine;
+
+[CustomPropertyDrawer( typeof( ReadOnlyAttribute ) )]
+public class ReadOnlyDrawer : PropertyDrawer {
+
+    public override float GetPropertyHeight( SerializedProperty property, GUIContent label ) {
+        return EditorGUI.GetPropertyHeight( property, label, true );
+    }
+
+    public override void OnGUI( Rect position, SerializedProperty property, GUIContent label ) {
+        using (var scope = new EditorGUI.DisabledGroupScope(true)) {
+            EditorGUI.PropertyField( position, property, label, true );
+        }
+    }
+
+}
+
+[CustomPropertyDrawer( typeof( BeginReadOnlyGroupAttribute ) )]
+public class BeginReadOnlyGroupDrawer : DecoratorDrawer {
+
+    public override float GetHeight() { return 0; }
+
+    public override void OnGUI( Rect position ) {
+        EditorGUI.BeginDisabledGroup( true );
+    }
+
+}
+
+[CustomPropertyDrawer( typeof( EndReadOnlyGroupAttribute ) )]
+public class EndReadOnlyGroupDrawer : DecoratorDrawer {
+
+    public override float GetHeight() { return 0; }
+
+    public override void OnGUI( Rect position ) {
+        EditorGUI.EndDisabledGroup();
+    }
+
+}

ReadOnly/ReadOnlyAttribute.cs

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+using UnityEngine;
+
+/// <summary>
+/// Display a field as read-only in the inspector.
+/// CustomPropertyDrawers will not work when this attribute is used.
+/// </summary>
+/// <seealso cref="BeginReadOnlyGroupAttribute"/>
+/// <seealso cref="EndReadOnlyGroupAttribute"/>
+public class ReadOnlyAttribute : PropertyAttribute { }
+
+/// <summary>
+/// Display one or more fields as read-only in the inspector.
+/// Use <see cref="EndReadOnlyGroupAttribute"/> to close the group.
+/// Works with CustomPropertyDrawers.
+/// </summary>
+/// <seealso cref="EndReadOnlyGroupAttribute"/>
+/// <seealso cref="ReadOnlyAttribute"/>
+public class BeginReadOnlyGroupAttribute : PropertyAttribute { }
+
+/// <summary>
+/// Use with <see cref="BeginReadOnlyGroupAttribute"/>.
+/// Close the read-only group and resume editable fields.
+/// </summary>
+/// <seealso cref="BeginReadOnlyGroupAttribute"/>
+/// <seealso cref="ReadOnlyAttribute"/>
+public class EndReadOnlyGroupAttribute : PropertyAttribute { }