NGUI深入理解-----------------UIRoot

总览：NGUI深入理解

UIRoot，顾名思义，它是UI的根，非常重要。它保证gameobject的localScale保持在2/height。

使用UIRoot时要注意，他不能与UIOrthoCamera一起使用。

UIRoot中最重要的是activeHeight属性。

	public int activeHeight
	{
		get
		{
			int height = Mathf.Max(2, Screen.height);
			if (scalingStyle == Scaling.FixedSize) return manualHeight;

#if UNITY_IPHONE || UNITY_ANDROID
			if (scalingStyle == Scaling.FixedSizeOnMobiles)
				return manualHeight;
#endif
			if (height < minimumHeight) return minimumHeight;
			if (height > maximumHeight) return maximumHeight;
			return height;
		}
	}

以为这个属性决定了localScale，决定了pixelSizeAdjustment

	void Update ()
	{
		if (mTrans != null)
		{
			float calcActiveHeight = activeHeight;

			if (calcActiveHeight > 0f )
			{
				float size = 2f / calcActiveHeight;
				
				Vector3 ls = mTrans.localScale;
	
				if (!(Mathf.Abs(ls.x - size) <= float.Epsilon) ||
					!(Mathf.Abs(ls.y - size) <= float.Epsilon) ||
					!(Mathf.Abs(ls.z - size) <= float.Epsilon))
				{
					mTrans.localScale = new Vector3(size, size, size);
				}
			}
		}
	}

UIRoot脚本很简单，核心Update就实现了一个功能，根据activeHeight来实时更新localScale。