ReferenceResolution.cs

using UnityEngine.EventSystems;

namespace UnityEngine.UI
{

[RequireComponent (typeof (Canvas))]
[ExecuteInEditMode]
[AddComponentMenu("Layout/Reference Resolution", 101)]
public class ReferenceResolution : UIBehaviour
{
	[SerializeField] protected Vector2 m_Resolution = new Vector2 (800, 600);
	public Vector2 resolution { get { return m_Resolution; } set { m_Resolution = value; } }
	
	[Range (0, 1)]
	[SerializeField] protected float m_MatchWidthOrHeight = 0;
	public float matchWidthOrHeight { get { return m_MatchWidthOrHeight; } set { m_MatchWidthOrHeight = value; } }
	
	private Canvas m_Canvas;
	private Vector2 m_PrevScreenSize = Vector2.zero;
	
	// The log base doesn't have any influence on the results whatsoever, as long as the same base is used everywhere.
	private const float kLogBase = 2;

	protected ReferenceResolution()
	{}

	protected override void OnEnable()
	{
		m_Canvas = GetComponent<Canvas> ();
		SetScaleFactor();
	}

	protected virtual void Update()
	{
		SetScaleFactor();
	}
	
	protected virtual void SetScaleFactor()
	{
		Vector2 screenSize = new Vector2 (Screen.width, Screen.height);
		if (m_Canvas == null || screenSize == m_PrevScreenSize)
			return;
		
		m_PrevScreenSize = screenSize;
		
		// We take the log of the relative width and height before taking the average.
		// Then we transform it back in the original space.
		// the reason to transform in and out of logarithmic space is to have better behavior.
		// If one axis has twice resolution and the other has half, it should even out if widthOrHeight value is at 0.5.
		// In normal space the average would be (0.5 + 2) / 2 = 1.25
		// In logarithmic space the average is (-1 + 1) / 2 = 0
		float logWidth = Mathf.Log (screenSize.x / m_Resolution.x, kLogBase);
		float logHeight = Mathf.Log (screenSize.y / m_Resolution.y, kLogBase);
		float logWeightedAverage = Mathf.Lerp (logWidth, logHeight, m_MatchWidthOrHeight);
		m_Canvas.scaleFactor = Mathf.Pow (kLogBase, logWeightedAverage);
	}
}
}