UIFlippable.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using System;

namespace UnityEngine.UI
{
    [RequireComponent( typeof( RectTransform ) ), RequireComponent( typeof( Graphic ) ), DisallowMultipleComponent, AddComponentMenu( "UI/Flippable" )]
    public class UIFlippable : MonoBehaviour, IMeshModifier
    {

        [SerializeField]
        private bool m_Horizontal = false;
        [SerializeField]
        private bool m_Veritical = false;

        /// <summary>
        /// Gets or sets a value indicating whether this <see cref="UnityEngine.UI.UIFlippable"/> should be flipped horizontally.
        /// </summary>
        /// <value><c>true</c> if horizontal; otherwise, <c>false</c>.</value>
        public bool horizontal
        {
            get { return this.m_Horizontal; }
            set { this.m_Horizontal = value; this.GetComponent<Graphic>().SetVerticesDirty(); }
        }

        /// <summary>
        /// Gets or sets a value indicating whether this <see cref="UnityEngine.UI.UIFlippable"/> should be flipped vertically.
        /// </summary>
        /// <value><c>true</c> if vertical; otherwise, <c>false</c>.</value>
        public bool vertical
        {
            get { return this.m_Veritical; }
            set { this.m_Veritical = value; this.GetComponent<Graphic>().SetVerticesDirty(); }
        }

        protected void OnValidate()
        {
            this.GetComponent<Graphic>().SetVerticesDirty();
        }

        public void ModifyVertices( List<UIVertex> verts )
        {
            RectTransform rt = this.transform as RectTransform;

            for ( int i = 0; i < verts.Count; ++i )
            {
                UIVertex v = verts[ i ];

                // Modify positions
                v.position = new Vector3(
                    ( this.m_Horizontal ? ( v.position.x + ( rt.rect.center.x - v.position.x ) * 2 ) : v.position.x ),
                    ( this.m_Veritical ? ( v.position.y + ( rt.rect.center.y - v.position.y ) * 2 ) : v.position.y ),
                    v.position.z
                );

                // Apply
                verts[ i ] = v;
            }
        }

        public void ModifyMesh( Mesh mesh )
        {
        }

        public void ModifyMesh( VertexHelper verts )
        {
            List<UIVertex> buffer = new List<UIVertex>();
            verts.GetUIVertexStream( buffer );
            ModifyVertices( buffer );
            verts.AddUIVertexTriangleStream( buffer );
        }
    }
}