update

Runtime/editor/editor_window.cs

             }
         }
 
+        protected bool displayMetricsChanged() {
+            if (this._devicePixelRatio != this.queryDevicePixelRatio()) {
+                return true;
+            }
+            var size = this.queryWindowSize();
+            if (this._lastWindowWidth != size.x
+                || this._lastWindowHeight != size.y) {
+                return true;
+            }
+
+            return false;
+        }
+
-                bool dirty = false;
-
-                if (this._devicePixelRatio != this.queryDevicePixelRatio()) {
-                    dirty = true;
-                }
-
-                var size = this.queryWindowSize();
-                if (this._lastWindowWidth != size.x
-                    || this._lastWindowHeight != size.y) {
-                    dirty = true;
-                }
-
-                if (dirty) {
+                if (this.displayMetricsChanged()) {
+                    var size = this.queryWindowSize();
                     this._lastWindowWidth = size.x;
                     this._lastWindowHeight = size.y;
                     this._physicalSize = new Size(

Runtime/engine/DisplayMetrics.cs

+using System;
 using System.Runtime.InteropServices;
 using UnityEngine;
 
 
         static float _devicePixelRatio = 0;
+
+        static Func<float> _devicePixelRatioGetter;
+
+        public static void SetDevicePixelRatioGetter(Func<float> f) {
+            _devicePixelRatioGetter = f;
+        }
+
+                if (_devicePixelRatioGetter != null) {
+                    return _devicePixelRatioGetter();
+                }
+
                 if (_devicePixelRatio > 0) {
                     return _devicePixelRatio;
                 }
                 return _devicePixelRatio;
             }
             
-        }
+        }      
 
         static float DevicePixelRatioAndroid() {
             using (

Runtime/engine/WidgetCanvas.cs

 
 
         public override void OnGUI(Event evt) {
+            if (this.displayMetricsChanged()) {
+                this._needsPaint = true;
+            }
             if (evt.type == EventType.Repaint) {
                 if (!this._needsPaint) {
                     return;

Editor/editor/EditorUtils.cs

+using Unity.UIWidgets.engine;
+using UnityEditor;
+
+namespace Unity.UIWidgets.Editor {
+    
+    [InitializeOnLoad]
+    public class Startup {
+        static Startup() {
+            DisplayMetrics.SetDevicePixelRatioGetter(() => { return EditorGUIUtility.pixelsPerPoint; });
+        }
+    }
+}

Editor/editor/EditorUtils.cs.meta

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