PhysicalResolution.cs

using UnityEngine.EventSystems;

namespace UnityEngine.UI
{

[RequireComponent (typeof (Canvas))]
[ExecuteInEditMode]
[AddComponentMenu("Layout/Physical Resolution", 102)]
public class PhysicalResolution : UIBehaviour
{
	public enum Unit { Centimeters, Millimeters, Inches, Points, Picas }
	
	[SerializeField] protected Unit m_Unit = Unit.Points;
	public Unit unit { get { return m_Unit; } set { m_Unit = value; } }
	
	[SerializeField] protected float m_DefaultDPI = 96;
	public float defaultDPI { get { return m_DefaultDPI; } set { m_DefaultDPI = value; } }
	
	private Canvas m_Canvas;
	private float m_PrevDpi = -1;
	
	protected PhysicalResolution() 
	{}
	
	protected override void OnEnable()
	{
		m_Canvas = GetComponent<Canvas>();
		SetScaleFactor();
	}
	
	protected virtual void Update()
	{
		SetScaleFactor();
	}
	
	protected virtual void SetScaleFactor()
	{
		float currentDpi = Screen.dpi;
		if (m_Canvas == null || currentDpi == m_PrevDpi)
			return;
		
		m_PrevDpi = currentDpi;
		float dpi = (currentDpi == 0 ? m_DefaultDPI : currentDpi);
		float targetDPI = 1;
		switch (m_Unit)
		{
			case Unit.Centimeters: targetDPI = 2.54f; break;
			case Unit.Millimeters: targetDPI = 25.4f; break;
			case Unit.Inches:      targetDPI =     1; break;
			case Unit.Points:      targetDPI =    72; break;
			case Unit.Picas:       targetDPI =     6; break;
		}
		
		m_Canvas.scaleFactor = dpi / targetDPI;
	}
}

}