Fi the issue that the icon of errorProvider is not scaled well on HDPI screen

Author: LeafShi1

src/System.Windows.Forms.Primitives/src/System/Windows/Forms/Internals/DpiHelper.cs

@@ -353,6 +353,17 @@ public static void ScaleBitmapLogicalToDevice(ref Bitmap logicalBitmap, int devi
         }
     }
 
+    /// <summary>
+    ///  Get X, Y metrics at DPI, IF icon is not already that size, create and return a new one.
+    /// </summary>
+    internal static Icon ScaleSmallIconToDpi(Icon icon, int dpi)
+    {
+        int width = PInvoke.GetCurrentSystemMetrics(SYSTEM_METRICS_INDEX.SM_CXSMICON, (uint)dpi);
+        int height = PInvoke.GetCurrentSystemMetrics(SYSTEM_METRICS_INDEX.SM_CYSMICON, (uint)dpi);
+
+        return (icon.Width == width && icon.Height == height) ? icon : new(icon, width, height);
+    }
+
     /// <summary>
     ///  Indicates whether the first (Parking)Window has been created. From that moment on,
     ///  we will not be able nor allowed to change the Process' DpiMode.

src/System.Windows.Forms/src/System/Windows/Forms/ErrorProvider.ErrorWindow.cs

@@ -484,7 +484,8 @@ protected override void WmDpiChangedBeforeParent(ref Message m)
             }
 
             double factor = ((double)currentDpi) / _parent._deviceDpi;
-            using Icon icon = _provider.Icon;
+            Icon icon = _provider.Icon;
+            _provider.CurrentDpi = currentDpi;
             _provider.Icon = new Icon(icon, (int)(icon.Width * factor), (int)(icon.Height * factor));
         }
     }

src/System.Windows.Forms/src/System/Windows/Forms/ErrorProvider.IconRegion.cs

@@ -15,9 +15,9 @@ internal class IconRegion : IHandle<HICON>
         private Region? _region;
         private readonly Icon _icon;
 
-        public IconRegion(Icon icon)
+        public IconRegion(Icon icon, int currentDpi)
         {
-            _icon = new Icon(icon, DefaultIcon.Size);
+            _icon = DpiHelper.ScaleSmallIconToDpi(icon, currentDpi);
         }
 
         /// <summary>

src/System.Windows.Forms/src/System/Windows/Forms/ErrorProvider.cs

@@ -25,10 +25,11 @@ public partial class ErrorProvider : Component, IExtenderProvider, ISupportIniti
 {
     private readonly Dictionary<Control, ControlItem> _items = new();
     private readonly Dictionary<Control, ErrorWindow> _windows = new();
-    private Icon _icon = DefaultIcon;
+    private Icon _icon;
     private IconRegion? _region;
     private int _itemIdCounter;
     private int _blinkRate;
+    private int _currentDpi;
     private ErrorBlinkStyle _blinkStyle;
     private bool _showIcon = true; // used for blinking
     private bool _inSetErrorManager;
@@ -314,7 +315,7 @@ public object? DataSource
         {
             if (_parentControl is not null && _parentControl.BindingContext is not null && value is not null && !string.IsNullOrEmpty(_dataMember))
             {
-                // Let's check if the datamember exists in the new data source
+                // Let's check if the data member exists in the new data source
                 try
                 {
                     _errorManager = _parentControl.BindingContext[value, _dataMember];
@@ -552,13 +553,8 @@ private static Icon DefaultIcon
                 if (t_defaultIcon is null)
                 {
                     // Error provider uses small Icon.
-                    Size LogicalSmallSystemIconSize = OsVersion.IsWindows10_1607OrGreater()
-                        ? new(
-                            PInvoke.GetSystemMetricsForDpi(SYSTEM_METRICS_INDEX.SM_CXSMICON, 96),
-                            PInvoke.GetSystemMetricsForDpi(SYSTEM_METRICS_INDEX.SM_CXSMICON, 96))
-                        : new(16, 16);
-                    using Icon defaultIcon = new(typeof(ErrorProvider), "Error");
-                    t_defaultIcon = new Icon(defaultIcon, LogicalSmallSystemIconSize);
+                    Icon defaultIcon = new(typeof(ErrorProvider), "Error");
+                    t_defaultIcon = DpiHelper.ScaleSmallIconToDpi(defaultIcon, DpiHelper.DeviceDpi);
                 }
             }
 
@@ -576,10 +572,7 @@ private static Icon DefaultIcon
     [SRDescription(nameof(SR.ErrorProviderIconDescr))]
     public Icon Icon
     {
-        get
-        {
-            return _icon;
-        }
+        get => _icon ??= DefaultIcon;
         set
         {
             _icon = value.OrThrowIfNull();
@@ -592,10 +585,21 @@ public Icon Icon
         }
     }
 
+    /// <summary>
+    ///  Gets or sets the DPI at which the current error is displayed.
+    ///  If currentDpi is not set, it defaults to _parentControl.DeviceDpi
+    ///  or the system DPI.
+    /// </summary>
+    private int CurrentDpi
+    {
+        get => _currentDpi != 0 ? _currentDpi : _parentControl?.DeviceDpi ?? DpiHelper.DeviceDpi;
+        set => _currentDpi = value;
+    }
+
     /// <summary>
     ///  Create the icon region on demand.
     /// </summary>
-    internal IconRegion Region => _region ??= new IconRegion(Icon);
+    internal IconRegion Region => _region ??= new IconRegion(Icon, CurrentDpi);
 
     /// <summary>
     ///  Begin bulk member initialization - deferring binding to data source until EndInit is reached
@@ -769,7 +773,7 @@ internal ErrorWindow EnsureErrorWindow(Control parent)
     [SRDescription(nameof(SR.ErrorProviderIconPaddingDescr))]
     public int GetIconPadding(Control control) => EnsureControlItem(control).IconPadding;
 
-    private void ResetIcon() => Icon = DefaultIcon;
+    private void ResetIcon() => _icon = null;
 
     [EditorBrowsable(EditorBrowsableState.Advanced)]
     protected virtual void OnRightToLeftChanged(EventArgs e)
@@ -814,5 +818,5 @@ public void SetIconPadding(Control control, int padding)
         EnsureControlItem(control).IconPadding = padding;
     }
 
-    private bool ShouldSerializeIcon() => Icon != DefaultIcon;
+    private bool ShouldSerializeIcon() => _icon is not null && _icon != DefaultIcon;
 }