Add ColorContrastPreference to the PlatformColorValues

native/Avalonia.Native/src/OSX/PlatformSettings.mm

@@ -17,15 +17,17 @@ public:
             if (@available(macOS 10.14, *))
             {
                 if (NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAqua
-                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameVibrantLight
-                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastAqua
-                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastVibrantLight) {
+                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameVibrantLight) {
                     return AvnPlatformThemeVariant::Light;
                 } else if (NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameDarkAqua
-                           || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameVibrantDark
-                           || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastDarkAqua
-                           || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastVibrantDark) {
+                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameVibrantDark) {
                     return AvnPlatformThemeVariant::Dark;
+                } else if (NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastAqua
+                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastVibrantLight) {
+                    return AvnPlatformThemeVariant::HighContrastLight;
+                } else if (|| NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastDarkAqua
+                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastVibrantDark) {
+                    return AvnPlatformThemeVariant::HighContrastDark;
                 }
             }
             return AvnPlatformThemeVariant::Light;

src/Android/Avalonia.Android/Platform/AndroidPlatformSettings.cs

@@ -3,6 +3,8 @@ using Android;
 using Android.Content;
 using Android.Content.Res;
 using Android.Graphics;
+using Android.Provider;
+using Android.Views.Accessibility;
 using AndroidX.Core.Content.Resources;
 using Avalonia.Media;
 using Avalonia.Platform;
@@ -46,11 +48,14 @@ internal class AndroidPlatformSettings : DefaultPlatformSettings
             var accent2 = context.Resources.GetColor(17170507, context.Theme); // Resource.Color.SystemAccent2500
             var accent3 = context.Resources.GetColor(17170520, context.Theme); // Resource.Color.SystemAccent3500
 
-            _latestValues = new PlatformColorValues(
-                systemTheme,
-                new Color(accent1.A, accent1.R, accent1.G, accent1.B),
-                new Color(accent2.A, accent2.R, accent2.G, accent2.B),
-                new Color(accent3.A, accent3.R, accent3.G, accent3.B));
+            _latestValues = new PlatformColorValues
+            {
+                ThemeVariant = systemTheme,
+                ContrastPreference = IsHighContrast(context),
+                AccentColor1 = new Color(accent1.A, accent1.R, accent1.G, accent1.B),
+                AccentColor2 = new Color(accent2.A, accent2.R, accent2.G, accent2.B),
+                AccentColor3 = new Color(accent3.A, accent3.R, accent3.G, accent3.B),
+            };
         }
         else if (OperatingSystem.IsAndroidVersionAtLeast(23))
         {
@@ -58,9 +63,12 @@ internal class AndroidPlatformSettings : DefaultPlatformSettings
             var array = context.Theme.ObtainStyledAttributes(new[] { 16843829 }); // Resource.Attribute.ColorAccent
             var accent = array.GetColor(0, 0);
 
-            _latestValues = new PlatformColorValues(
-                systemTheme,
-                new Color(accent.A, accent.R, accent.G, accent.B));
+            _latestValues = new PlatformColorValues
+            {
+                ThemeVariant = systemTheme,
+                ContrastPreference = IsHighContrast(context),
+                AccentColor1 = new Color(accent.A, accent.R, accent.G, accent.B)
+            };
             array.Recycle();
         }
         else
@@ -70,4 +78,17 @@ internal class AndroidPlatformSettings : DefaultPlatformSettings
 
         OnColorValuesChanged(_latestValues);
     }
+
+    private static ColorContrastPreference IsHighContrast(Context context)
+    {
+        try
+        {
+            return Settings.Secure.GetInt(context.ContentResolver, "high_text_contrast_enabled", 0) == 1
+                ? ColorContrastPreference.High : ColorContrastPreference.NoPreference;
+        }
+        catch
+        {
+            return ColorContrastPreference.NoPreference;
+        }
+    }
 }

src/Avalonia.Base/Platform/DefaultPlatformSettings.cs

@@ -31,7 +31,10 @@ namespace Avalonia.Platform
         
         public virtual PlatformColorValues GetColorValues()
         {
-            return new PlatformColorValues(PlatformThemeVariant.Light);
+            return new PlatformColorValues
+            {
+                ThemeVariant = PlatformThemeVariant.Light
+            };
         }
 
         public event EventHandler<PlatformColorValues>? ColorValuesChanged;

src/Avalonia.Base/Platform/PlatformColorValues.cs

@@ -11,32 +11,58 @@ public enum PlatformThemeVariant
     Dark
 }
 
+/// <summary>
+/// System high contrast preference.
+/// </summary>
+public enum ColorContrastPreference
+{
+    NoPreference,
+    High
+}
+
 /// <summary>
 /// Information about current system color values, including information about dark mode and accent colors.
 /// </summary>
-/// <param name="ThemeVariant">System theme variant or mode.</param>
-/// <param name="AccentColor1">Primary system accent color.</param>
-/// <param name="AccentColor2">Secondary system accent color. On some platforms can return the same value as AccentColor1.</param>
-/// <param name="AccentColor3">Tertiary system accent color. On some platforms can return the same value as AccentColor1.</param>
-public record struct PlatformColorValues(
-    PlatformThemeVariant ThemeVariant,
-    Color AccentColor1,
-    Color AccentColor2,
-    Color AccentColor3)
+public record PlatformColorValues
 {
-    public PlatformColorValues(
-        PlatformThemeVariant ThemeVariant,
-        Color AccentColor1)
-        : this(ThemeVariant, AccentColor1, AccentColor1, AccentColor1)
+    private static Color DefaultAccent => new(255, 0, 120, 215);
+    private Color _accentColor2, _accentColor3;
+
+    /// <summary>
+    /// System theme variant or mode.
+    /// </summary>
+    public PlatformThemeVariant ThemeVariant { get; init; }
+
+    /// <summary>
+    /// System high contrast preference.
+    /// </summary>
+    public ColorContrastPreference ContrastPreference { get; init; }
+    
+    /// <summary>
+    /// Primary system accent color.
+    /// </summary>
+    public Color AccentColor1 { get; init; }
+
+    /// <summary>
+    /// Secondary system accent color. On some platforms can return the same value as <see cref="AccentColor1"/>.
+    /// </summary>
+    public Color AccentColor2
     {
-            
+        get => _accentColor2 != default ? _accentColor2 : AccentColor1;
+        init => _accentColor2 = value;
     }
-        
-    public PlatformColorValues(PlatformThemeVariant ThemeVariant)
-        : this(ThemeVariant, DefaultAccent)
+
+    /// <summary>
+    /// Tertiary system accent color. On some platforms can return the same value as <see cref="AccentColor1"/>.
+    /// </summary>
+    public Color AccentColor3
     {
+        get => _accentColor3 != default ? _accentColor3 : AccentColor1;
+        init => _accentColor3 = value;
+    }
 
+    public PlatformColorValues()
+    {
+        AccentColor1 = DefaultAccent;
     }
-        
-    private static Color DefaultAccent => new(255, 0, 120, 215);
 }

src/Avalonia.FreeDesktop/DBusPlatformSettings.cs

@@ -41,7 +41,7 @@ internal class DBusPlatformSettings : DefaultPlatformSettings
             {
                 var value = await colorSchemeTask;
                 _lastColorValues = GetColorValuesFromSetting(value);
-                OnColorValuesChanged(_lastColorValues.Value);
+                OnColorValuesChanged(_lastColorValues);
             }
             catch (Exception ex)
             {
@@ -62,13 +62,16 @@ internal class DBusPlatformSettings : DefaultPlatformSettings
             <member>2: Prefer light appearance</member>
             */
             _lastColorValues = GetColorValuesFromSetting(tuple.value);
-            OnColorValuesChanged(_lastColorValues.Value);
+            OnColorValuesChanged(_lastColorValues);
         }
     }
     
     private static PlatformColorValues GetColorValuesFromSetting(object value)
     {
         var isDark = value?.ToString() == "1";
-        return new PlatformColorValues(isDark ? PlatformThemeVariant.Dark : PlatformThemeVariant.Light);
+        return new PlatformColorValues
+        {
+            ThemeVariant = isDark ? PlatformThemeVariant.Dark : PlatformThemeVariant.Light
+        };
     }
 }

src/Avalonia.Native/NativePlatformSettings.cs

@@ -18,16 +18,32 @@ internal class NativePlatformSettings : DefaultPlatformSettings
 
     public override PlatformColorValues GetColorValues()
     {
-        var theme = (PlatformThemeVariant)_platformSettings.PlatformTheme;
+        var (theme, contrast) = _platformSettings.PlatformTheme switch
+        {
+            AvnPlatformThemeVariant.Dark => (PlatformThemeVariant.Dark, ColorContrastPreference.NoPreference),
+            AvnPlatformThemeVariant.Light => (PlatformThemeVariant.Light, ColorContrastPreference.NoPreference),
+            AvnPlatformThemeVariant.HighContrastDark => (PlatformThemeVariant.Dark, ColorContrastPreference.High),
+            AvnPlatformThemeVariant.HighContrastLight => (PlatformThemeVariant.Dark, ColorContrastPreference.High),
+            _ => throw new ArgumentOutOfRangeException()
+        };
         var color = _platformSettings.AccentColor;
 
         if (color > 0)
         {
-            _lastColorValues = new PlatformColorValues(theme, Color.FromUInt32(color));
+            _lastColorValues = new PlatformColorValues
+            {
+                ThemeVariant = theme,
+                ContrastPreference = contrast,
+                AccentColor1 = Color.FromUInt32(color)
+            };
         }
         else
         {
-            _lastColorValues = new PlatformColorValues(theme);
+            _lastColorValues = new PlatformColorValues
+            {
+                ThemeVariant = theme,
+                ContrastPreference = contrast
+            };
         }
 
         return _lastColorValues;

src/Avalonia.Native/avn.idl

@@ -476,7 +476,9 @@ enum AvnWindowTransparencyMode
 enum AvnPlatformThemeVariant
 {
     Light,
-    Dark
+    Dark,
+    HighContrastLight,
+    HighContrastDark,
 }
 
 [uuid(809c652e-7396-11d2-9771-00a0c9b4d50c)]

src/Browser/Avalonia.Browser/BrowserPlatformSettings.cs

@@ -6,21 +6,26 @@ namespace Avalonia.Browser;
 internal class BrowserPlatformSettings : DefaultPlatformSettings
 {
     private bool _isDarkMode;
+    private bool _isHighContrast;
     
     public BrowserPlatformSettings()
     {
-        _isDarkMode = DomHelper.ObserveDarkMode(m =>
+        var obj = DomHelper.ObserveDarkMode((isDarkMode, isHighContrast) =>
         {
-            _isDarkMode = m;
+            _isDarkMode = isDarkMode;
+            _isHighContrast = isHighContrast;
             OnColorValuesChanged(GetColorValues());
         });
+        _isDarkMode = obj.GetPropertyAsBoolean("isDarkMode");
+        _isHighContrast = obj.GetPropertyAsBoolean("isHighContrast");
     }
-    
+
     public override PlatformColorValues GetColorValues()
     {
         return base.GetColorValues() with
         {
-            ThemeVariant = _isDarkMode ? PlatformThemeVariant.Dark : PlatformThemeVariant.Light
+            ThemeVariant = _isDarkMode ? PlatformThemeVariant.Dark : PlatformThemeVariant.Light,
+            ContrastPreference = _isHighContrast ? ColorContrastPreference.High : ColorContrastPreference.NoPreference
         };
     }
 }

src/Browser/Avalonia.Browser/Interop/DomHelper.cs

@@ -27,7 +27,7 @@ internal static partial class DomHelper
         Action<double, double> onDpiChanged);
     
     [JSImport("AvaloniaDOM.observeDarkMode", AvaloniaModule.MainModuleName)]
-    public static partial bool ObserveDarkMode(
-        [JSMarshalAs<JSType.Function<JSType.Boolean>>]
-        Action<bool> onDpiChanged);
+    public static partial JSObject ObserveDarkMode(
+        [JSMarshalAs<JSType.Function<JSType.Boolean, JSType.Boolean>>]
+        Action<bool, bool> onDpiChanged);
 }

src/Browser/Avalonia.Browser/webapp/modules/avalonia/dom.ts

@@ -3,17 +3,25 @@ export class AvaloniaDOM {
         element.classList.add(className);
     }
 
-    static observeDarkMode(observer: (isDarkMode: boolean) => boolean): boolean {
+    static observeDarkMode(observer: (isDarkMode: boolean, isHighContrast: boolean) => boolean) {
         if (globalThis.matchMedia === undefined) {
             return false;
         }
 
-        const media = globalThis.matchMedia("(prefers-color-scheme: dark)");
-        media.addEventListener("change", (args: MediaQueryListEvent) => {
-            observer(args.matches);
+        const colorShemeMedia = globalThis.matchMedia("(prefers-color-scheme: dark)");
+        const prefersContrastMedia = globalThis.matchMedia("(prefers-contrast: more)");
+
+        colorShemeMedia.addEventListener("change", (args: MediaQueryListEvent) => {
+            observer(args.matches, prefersContrastMedia.matches);
+        });
+        prefersContrastMedia.addEventListener("change", (args: MediaQueryListEvent) => {
+            observer(colorShemeMedia.matches, args.matches);
         });
 
-        return media.matches;
+        return {
+            isDarkMode: colorShemeMedia.matches,
+            isHighContrast: prefersContrastMedia.matches
+        };
     }
 
     static createAvaloniaHost(host: HTMLElement) {

src/Windows/Avalonia.Win32/Win32Platform.cs

@@ -287,6 +287,17 @@ namespace Avalonia.Win32
                     }
                 }
             }
+
+            if (msg == (uint)WindowsMessage.WM_SETTINGCHANGE 
+                && PlatformSettings is Win32PlatformSettings win32PlatformSettings)
+            {
+                var changedSetting = Marshal.PtrToStringAuto(lParam);
+                if (changedSetting == "ImmersiveColorSet" // dark/light mode
+                    || changedSetting == "WindowsThemeElement") // high contrast mode
+                {
+                    win32PlatformSettings.OnColorValuesChanged();   
+                }
+            }
             
             TrayIconImpl.ProcWnd(hWnd, msg, wParam, lParam);
 

src/Windows/Avalonia.Win32/Win32PlatformSettings.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Runtime.InteropServices;
 using Avalonia.Input;
 using Avalonia.Platform;
 using Avalonia.Win32.Interop;
@@ -38,18 +39,44 @@ internal class Win32PlatformSettings : DefaultPlatformSettings
             return base.GetColorValues();
         }
 
-        var settings = NativeWinRTMethods.CreateInstance<IUISettings3>("Windows.UI.ViewManagement.UISettings");
-        var accent = settings.GetColorValue(UIColorType.Accent).ToAvalonia();
-        var background = settings.GetColorValue(UIColorType.Background).ToAvalonia();
+        var uiSettings = NativeWinRTMethods.CreateInstance<IUISettings3>("Windows.UI.ViewManagement.UISettings");
+        var accent = uiSettings.GetColorValue(UIColorType.Accent).ToAvalonia();
 
-        return _lastColorValues = new PlatformColorValues(
-            background.R + background.G + background.B < (255 * 3 - background.R - background.G - background.B)
-                ? PlatformThemeVariant.Dark
-                : PlatformThemeVariant.Light,
-            accent, accent, accent);
+        var accessibilitySettings = NativeWinRTMethods.CreateInstance<IAccessibilitySettings>("Windows.UI.ViewManagement.AccessibilitySettings");
+        if (accessibilitySettings.HighContrast == 1)
+        {
+            // Windows 11 has 4 different high contrast schemes:
+            // - Aquatic - High Contrast Black
+            // - Desert - High Contrast White
+            // - Dusk - High Contrast #1
+            // - Night sky - High Contrast #2
+            // Only "Desert" one can be considered a "light" preference. 
+            using var highContrastScheme = new HStringInterop(accessibilitySettings.HighContrastScheme);
+            return _lastColorValues = new PlatformColorValues
+            {
+                ThemeVariant = highContrastScheme.Value?.Contains("White", StringComparison.OrdinalIgnoreCase) == true ?
+                    PlatformThemeVariant.Light :
+                    PlatformThemeVariant.Dark,
+                ContrastPreference = ColorContrastPreference.High,
+                // Windows provides more than one accent color for the HighContrast themes, but with no API for that (at least not in the WinRT)
+                AccentColor1 = accent
+            };
+        }
+        else
+        {
+            var background = uiSettings.GetColorValue(UIColorType.Background).ToAvalonia();
+            return _lastColorValues = new PlatformColorValues
+            {
+                ThemeVariant = background.R + background.G + background.B < (255 * 3 - background.R - background.G - background.B) ?
+                    PlatformThemeVariant.Dark :
+                    PlatformThemeVariant.Light,
+                ContrastPreference = ColorContrastPreference.NoPreference,
+                AccentColor1 = accent
+            };   
+        }
     }
     
-    internal void OnColorValuesChanged(IntPtr handle)
+    internal void OnColorValuesChanged()
     {
         var oldColorValues = _lastColorValues;
         var colorValues = GetColorValues();

src/Windows/Avalonia.Win32/WinRT/NativeWinRTMethods.cs

@@ -22,6 +22,9 @@ namespace Avalonia.Win32.WinRT
         internal static IntPtr WindowsCreateString(string sourceString) 
             => WindowsCreateString(sourceString, sourceString.Length);
 
+        [DllImport("api-ms-win-core-winrt-string-l1-1-0.dll", CallingConvention = CallingConvention.StdCall)]
+        internal static extern unsafe char* WindowsGetStringRawBuffer(IntPtr hstring, uint* length);
+
         [DllImport("api-ms-win-core-winrt-string-l1-1-0.dll", 
             CallingConvention = CallingConvention.StdCall, PreserveSig = false)]
         internal static extern unsafe void WindowsDeleteString(IntPtr hString);
@@ -120,17 +123,38 @@ namespace Avalonia.Win32.WinRT
     class HStringInterop : IDisposable
     {
         private IntPtr _s;
+        private bool _owns;
 
         public HStringInterop(string s)
         {
             _s = s == null ? IntPtr.Zero : NativeWinRTMethods.WindowsCreateString(s);
+            _owns = true;
+        }
+        
+        public HStringInterop(IntPtr str, bool owns = false)
+        {
+            _s = str;
+            _owns = owns;
         }
 
         public IntPtr Handle => _s;
 
+        public unsafe string Value
+        {
+            get
+            {
+                if (_s == IntPtr.Zero)
+                    return null;
+
+                uint length;
+                var buffer = NativeWinRTMethods.WindowsGetStringRawBuffer(_s, &length);
+                return new string(buffer, 0, (int) length);
+            }
+        }
+        
         public void Dispose()
         {
-            if (_s != IntPtr.Zero)
+            if (_s != IntPtr.Zero && _owns)
             {
                 NativeWinRTMethods.WindowsDeleteString(_s);
                 _s = IntPtr.Zero;

src/Windows/Avalonia.Win32/WinRT/winrt.idl

@@ -864,3 +864,10 @@ interface IUISettings3 : IInspectable
 {
     HRESULT GetColorValue([in] UIColorType desiredColor, [out][retval] Color* value);
 }
+
+[uuid(FE0E8147-C4C0-4562-B962-1327B52AD5B9)]
+interface IAccessibilitySettings : IInspectable
+{
+    [propget] HRESULT HighContrast([out] [retval] boolean* value);
+    [propget] HRESULT HighContrastScheme([out] [retval] HSTRING* value);
+}

src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs

@@ -732,14 +732,6 @@ namespace Avalonia.Win32
                         var node = AutomationNode.GetOrCreate(peer);
                         return UiaCoreProviderApi.UiaReturnRawElementProvider(_hwnd, wParam, lParam, node);
                     }
-                    break;
-                case WindowsMessage.WM_SETTINGCHANGE:
-                    if (Marshal.PtrToStringAuto(lParam) == "ImmersiveColorSet"
-                        && Win32Platform.PlatformSettings is Win32PlatformSettings win32PlatformSettings)
-                    {
-                        win32PlatformSettings.OnColorValuesChanged(_hwnd);
-                    }
-
                     break;
             }
 

src/iOS/Avalonia.iOS/PlatformSettings.cs

@@ -17,8 +17,17 @@ internal class PlatformSettings : DefaultPlatformSettings
         var themeVariant = UITraitCollection.CurrentTraitCollection.UserInterfaceStyle == UIUserInterfaceStyle.Dark ?
             PlatformThemeVariant.Dark :
             PlatformThemeVariant.Light;
+
+
+        var contrastPreference = UITraitCollection.CurrentTraitCollection.AccessibilityContrast == UIAccessibilityContrast.High ?
+            ColorContrastPreference.High :
+            ColorContrastPreference.NoPreference;
         
-        return _lastColorValues = new PlatformColorValues(themeVariant);
+        return _lastColorValues = new PlatformColorValues
+        {
+            ThemeVariant = themeVariant,
+            ContrastPreference = contrastPreference
+        };
     }
 
     public void TraitCollectionDidChange()