Simple UGUI Underline

Underline.cs

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

/// <summary>
/// 
/// Unity 引擎的 mesh 顶点顺序如下：
/// 
/// (0)-------(1)(4)-------(5)
///  |         |  |         |
///  |         |  |         |
/// (3)-------(2)(7)-------(6)
/// 
/// 上面这个四边形的三角形 index 如下：
/// 
/// 0 1 2, 2 3 0, 4 5 6, 6 7 4
/// 
/// 其中，1 和 4 共用一个顶点，2 和 7 共用一个顶点，一共 4 个三角形，6 个顶点
/// 
/// </summary>
[RequireComponent(typeof(Text))]
public class Underline : BaseMeshEffect
{
	private static readonly List<UIVertex> verts = new List<UIVertex>();
	private static readonly UIVertex[] data = new UIVertex[4];

	public Text text;

	public Color UnderlineColor = Color.black;
	public float LineOffset = 1;
	public float LineThickness = 2;

	protected Underline() { }

	protected override void Awake()
	{
		base.Awake();
		text = GetComponent<Text>();
		if (text.font == null)
		{
			Destroy(this);
			Debug.LogWarning("Text.font is null");
			return;
		}
		text.RegisterDirtyMaterialCallback(OnFontMaterialChanged);
		text.font.RequestCharactersInTexture("*", text.fontSize, text.fontStyle);
	}

	protected override void OnDestroy()
	{
		text.UnregisterDirtyMaterialCallback(OnFontMaterialChanged);
		base.OnDestroy();
	}

	private void OnFontMaterialChanged()
	{
		text.font.RequestCharactersInTexture("*", text.fontSize, text.fontStyle);
	}

	private Vector2 GetUnderlineCharUV()
	{
		var ch = '*';
		CharacterInfo info;
		if (text.font.GetCharacterInfo(ch, out info, text.fontSize, text.fontStyle))
		{
			return (info.uvBottomLeft + info.uvBottomRight + info.uvTopLeft + info.uvTopRight) * 0.25f;
		}
		Debug.LogWarning("GetCharacterInfo failed");
		return Vector2.zero;
	}

	public override void ModifyMesh(VertexHelper vh)
	{
		if (!IsActive())
			return;
		if (vh.currentVertCount < 3)
			return;

		verts.Clear();
		vh.GetUIVertexStream(verts);

		var neededCpacity = verts.Count + 6;
		if (verts.Capacity < neededCpacity)
			verts.Capacity = neededCpacity;

		UIVertex vert = UIVertex.simpleVert;

		vh.PopulateUIVertex(ref vert, 3);
		var pos_a = vert.position;
		vh.PopulateUIVertex(ref vert, verts.Count * 2 / 3 - 2);
		var pos_b = vert.position;
		var y = (pos_a.y + pos_b.y) * 0.5f;

		var pos0 = new Vector3(pos_a.x, y - LineOffset);
		var pos1 = new Vector3(pos_b.x, y - LineOffset);
		var pos2 = new Vector3(pos_b.x, y - LineOffset - LineThickness);
		var pos3 = new Vector3(pos_a.x, y - LineOffset - LineThickness);

		vert.color = UnderlineColor;
		vert.uv0 = GetUnderlineCharUV();

		vert.position = pos0;
		data[0] = vert;
		vert.position = pos1;
		data[1] = vert;
		vert.position = pos2;
		data[2] = vert;
		vert.position = pos3;
		data[3] = vert;

		vh.AddUIVertexQuad(data);
	}
}

这个文本换行就有问题，可以增加换行的处理吗