From bf2a577f83b276fa446d4dbfd6d8e0471cef79fa Mon Sep 17 00:00:00 2001
From: Tom Edwards <tom.edwards@chaos.com>
Date: Tue, 16 Dec 2025 11:50:17 +0100
Subject: [PATCH 1/5] Added support for platform text scaling, disabled by
 default Only TextBlock, Inline, and TextPresenter scale text by themselves No
 change to low-level text rendering or FontSize values Implemented for iOS and
 Windows Windows scaling is currently uniform regardless of base font size,
 which is incorrect

---
 samples/ControlCatalog/MainView.xaml          |  3 +-
 .../Platform/DefaultPlatformSettings.cs       | 10 ++--
 .../Platform/IPlatformSettings.cs             | 12 ++++-
 .../Documents/IInlineHost.cs                  |  2 +-
 src/Avalonia.Controls/Documents/Inline.cs     |  2 +-
 .../Documents/TextElement.cs                  | 23 +++++++++
 .../IPlatformTextScaleable.cs                 | 17 +++++++
 .../Presenters/TextPresenter.cs               | 36 ++++++++++++--
 .../Primitives/TextSelectionCanvas.cs         |  2 +-
 src/Avalonia.Controls/SelectableTextBlock.cs  |  6 +--
 src/Avalonia.Controls/TextBlock.cs            | 35 ++++++++++++--
 src/Avalonia.Controls/TopLevel.cs             | 12 +++++
 .../Avalonia.Win32/Win32PlatformSettings.cs   | 47 +++++++++++++++----
 src/Windows/Avalonia.Win32/WinRT/winrt.idl    |  9 ++++
 src/iOS/Avalonia.iOS/PlatformSettings.cs      | 20 ++++++++
 15 files changed, 210 insertions(+), 26 deletions(-)
 create mode 100644 src/Avalonia.Controls/IPlatformTextScaleable.cs

diff --git a/samples/ControlCatalog/MainView.xaml b/samples/ControlCatalog/MainView.xaml
index 984daf1200..401d96fad2 100644
--- a/samples/ControlCatalog/MainView.xaml
+++ b/samples/ControlCatalog/MainView.xaml
@@ -6,7 +6,8 @@
              xmlns:models="using:ControlCatalog.Models"
              xmlns:pages="using:ControlCatalog.Pages"
              xmlns:viewModels="using:ControlCatalog.ViewModels"
-             x:DataType="viewModels:MainWindowViewModel">
+             x:DataType="viewModels:MainWindowViewModel"
+             TextElement.IsPlatformTextScalingEnabled="True">
   <Grid>
     <Grid.Styles>
       <Style Selector="TextBlock.h2">
diff --git a/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs b/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs
index 5f17627ace..6c07484aa0 100644
--- a/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs
+++ b/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs
@@ -1,10 +1,8 @@
 using System;
 using Avalonia.Input;
 using Avalonia.Input.Platform;
-using Avalonia.Media;
 using Avalonia.Metadata;
 using Avalonia.Threading;
-using Avalonia.VisualTree;
 
 namespace Avalonia.Platform
 {
@@ -49,10 +47,16 @@ namespace Avalonia.Platform
 
         public virtual event EventHandler<PlatformColorValues>? ColorValuesChanged;
 
-        protected void OnColorValuesChanged(PlatformColorValues colorValues)
+        protected virtual void OnColorValuesChanged(PlatformColorValues colorValues)
         {
             Dispatcher.UIThread.Send(
                 _ => ColorValuesChanged?.Invoke(this, colorValues));
         }
+
+        public event EventHandler<EventArgs>? TextScalingChanged;
+
+        protected virtual void OnTextScaleChanged() => Dispatcher.UIThread.Send(_ => TextScalingChanged?.Invoke(this, EventArgs.Empty));
+
+        public virtual double GetScaledFontSize(double baseFontSize) => baseFontSize;
     }
 }
diff --git a/src/Avalonia.Base/Platform/IPlatformSettings.cs b/src/Avalonia.Base/Platform/IPlatformSettings.cs
index 46980c6d51..e94c765593 100644
--- a/src/Avalonia.Base/Platform/IPlatformSettings.cs
+++ b/src/Avalonia.Base/Platform/IPlatformSettings.cs
@@ -42,7 +42,7 @@ namespace Avalonia.Platform
         /// Get a configuration for platform-specific hotkeys in an Avalonia application.
         /// </summary>
         PlatformHotkeyConfiguration HotkeyConfiguration { get; }
-        
+
         /// <summary>
         /// Gets current system color values including dark mode and accent colors.
         /// </summary>
@@ -52,5 +52,15 @@ namespace Avalonia.Platform
         /// Raises when current system color values are changed. Including changing of a dark mode and accent colors.
         /// </summary>
         event EventHandler<PlatformColorValues>? ColorValuesChanged;
+
+        /// <summary>
+        /// Raised when the system text scaling changes.
+        /// </summary>
+        event EventHandler<EventArgs>? TextScalingChanged;
+
+        /// <summary>
+        /// Scales a font size according to the current system text scaling rules.
+        /// </summary>
+        double GetScaledFontSize(double baseFontSize);
     }
 }
diff --git a/src/Avalonia.Controls/Documents/IInlineHost.cs b/src/Avalonia.Controls/Documents/IInlineHost.cs
index e16da219b4..3fa6140bbe 100644
--- a/src/Avalonia.Controls/Documents/IInlineHost.cs
+++ b/src/Avalonia.Controls/Documents/IInlineHost.cs
@@ -3,7 +3,7 @@ using Avalonia.LogicalTree;
 
 namespace Avalonia.Controls.Documents
 {
-    internal interface IInlineHost : ILogical
+    internal interface IInlineHost : ILogical, IPlatformTextScaleable
     {
         void Invalidate();
 
diff --git a/src/Avalonia.Controls/Documents/Inline.cs b/src/Avalonia.Controls/Documents/Inline.cs
index 1ededcf81c..d89cdc9cf9 100644
--- a/src/Avalonia.Controls/Documents/Inline.cs
+++ b/src/Avalonia.Controls/Documents/Inline.cs
@@ -83,7 +83,7 @@ namespace Avalonia.Controls.Documents
             return new GenericTextRunProperties(
                 typeface,
                 FontFeatures, 
-                FontSize,
+                InlineHost?.GetScaledFontSize(FontSize) ?? FontSize,
                 TextDecorations, 
                 Foreground,
                 parentOrSelfBackground,
diff --git a/src/Avalonia.Controls/Documents/TextElement.cs b/src/Avalonia.Controls/Documents/TextElement.cs
index cac8d6f97f..ed77aa9ca6 100644
--- a/src/Avalonia.Controls/Documents/TextElement.cs
+++ b/src/Avalonia.Controls/Documents/TextElement.cs
@@ -14,6 +14,15 @@ namespace Avalonia.Controls.Documents
         public static readonly StyledProperty<IBrush?> BackgroundProperty =
             Border.BackgroundProperty.AddOwner<TextElement>();
 
+        /// <summary>
+        /// Defines the <see cref="IsPlatformTextScalingEnabled"/> property.
+        /// </summary>
+        public static readonly AttachedProperty<bool> IsPlatformTextScalingEnabledProperty =
+            AvaloniaProperty.RegisterAttached<TextElement, Control, bool>(
+                nameof(IsPlatformTextScalingEnabled),
+                defaultValue: false,
+                inherits: true);
+
         /// <summary>
         /// Defines the <see cref="FontFamily"/> property.
         /// </summary>
@@ -102,6 +111,16 @@ namespace Avalonia.Controls.Documents
             set => SetValue(BackgroundProperty, value);
         }
 
+        /// <summary>
+        /// Gets or sets whether the <see cref="FontSize"/> should be scaled according to platform text scaling
+        /// rules when measuring and rendering this control.
+        /// </summary>
+        public bool IsPlatformTextScalingEnabled
+        {
+            get => GetValue(IsPlatformTextScalingEnabledProperty);
+            set => SetValue(IsPlatformTextScalingEnabledProperty, value);
+        }
+
         /// <summary>
         /// Gets or sets the font family.
         /// </summary>
@@ -174,6 +193,9 @@ namespace Avalonia.Controls.Documents
             set => SetValue(LetterSpacingProperty, value);
         }
 
+        public static bool GetIsPlatformTextScalingEnabled(Control control) => control.GetValue(IsPlatformTextScalingEnabledProperty);
+        public static void SetIsPlatformTextScalingEnabled(Control control, bool value) => control.SetValue(IsPlatformTextScalingEnabledProperty, value);
+
         /// <summary>
         /// Gets the value of the attached <see cref="FontFamilyProperty"/> on a control.
         /// </summary>
@@ -359,6 +381,7 @@ namespace Avalonia.Controls.Documents
                 case nameof(Background):
                 case nameof(FontFamily):
                 case nameof(FontSize):
+                case nameof(IsPlatformTextScalingEnabled):
                 case nameof(FontStyle):
                 case nameof(FontWeight):
                 case nameof(FontStretch):
diff --git a/src/Avalonia.Controls/IPlatformTextScaleable.cs b/src/Avalonia.Controls/IPlatformTextScaleable.cs
new file mode 100644
index 0000000000..6cf6c1b742
--- /dev/null
+++ b/src/Avalonia.Controls/IPlatformTextScaleable.cs
@@ -0,0 +1,17 @@
+namespace Avalonia.Controls;
+
+/// <summary>
+/// Represents an object which particpates in platform text scaling. This is an accessibility feature
+/// which allows the user to request that text be drawn larger (or on some platforms smaller) than normal,
+/// without altering other UI elements.
+/// </summary>
+public interface IPlatformTextScaleable
+{
+    bool IsPlatformTextScalingEnabled { get; }
+    void OnPlatformTextScalingChanged();
+
+    /// <summary>
+    /// Scales a font size according to the current system text scaling rules and the value of <see cref="IsPlatformTextScalingEnabled"/>.
+    /// </summary>
+    double GetScaledFontSize(double baseFontSize);
+}
diff --git a/src/Avalonia.Controls/Presenters/TextPresenter.cs b/src/Avalonia.Controls/Presenters/TextPresenter.cs
index 7078650da4..2cf6a2f94b 100644
--- a/src/Avalonia.Controls/Presenters/TextPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/TextPresenter.cs
@@ -15,7 +15,7 @@ using Avalonia.VisualTree;
 
 namespace Avalonia.Controls.Presenters
 {
-    public class TextPresenter : Control
+    public class TextPresenter : Control, IPlatformTextScaleable
     {
         public static readonly StyledProperty<bool> ShowSelectionHighlightProperty =
             AvaloniaProperty.Register<TextPresenter, bool>(nameof(ShowSelectionHighlight), defaultValue: true);
@@ -47,6 +47,12 @@ namespace Avalonia.Controls.Presenters
         public static readonly StyledProperty<int> SelectionEndProperty =
             TextBox.SelectionEndProperty.AddOwner<TextPresenter>(new(coerce: TextBox.CoerceCaretIndex));
 
+        /// <summary>
+        /// Defines the <see cref="IsPlatformTextScalingEnabled"/> property.
+        /// </summary>
+        public static readonly StyledProperty<bool> IsPlatformTextScalingEnabledProperty =
+            TextElement.IsPlatformTextScalingEnabledProperty.AddOwner<TextPresenter>();
+
         /// <summary>
         /// Defines the <see cref="Text"/> property.
         /// </summary>
@@ -124,6 +130,13 @@ namespace Avalonia.Controls.Presenters
             set => SetValue(BackgroundProperty, value);
         }
 
+        /// <inheritdoc cref="TextElement.IsPlatformTextScalingEnabled"/>
+        public bool IsPlatformTextScalingEnabled
+        {
+            get => GetValue(IsPlatformTextScalingEnabledProperty);
+            set => SetValue(IsPlatformTextScalingEnabledProperty, value);
+        }
+
         /// <summary>
         /// Gets or sets a value that determines whether the TextPresenter shows a selection highlight.
         /// </summary>
@@ -181,6 +194,13 @@ namespace Avalonia.Controls.Presenters
             get => TextElement.GetFontSize(this);
             set => TextElement.SetFontSize(this, value);
         }
+        
+        double IPlatformTextScaleable.GetScaledFontSize(double baseFontSize) => IsPlatformTextScalingEnabled && TopLevel.GetTopLevel(this) is { PlatformSettings: { } platformSettings } ? platformSettings.GetScaledFontSize(baseFontSize) : baseFontSize;
+        
+        /// <summary>
+        /// Gets <see cref="FontSize"/> scaled according to the platform's current text scaling rules.
+        /// </summary>
+        protected double EffectiveFontSize => ((IPlatformTextScaleable)this).GetScaledFontSize(FontSize);
 
         /// <summary>
         /// Gets or sets the font style.
@@ -335,6 +355,14 @@ namespace Avalonia.Controls.Presenters
 
         internal TextSelectionHandleCanvas? TextSelectionHandleCanvas { get; set; }
 
+        void IPlatformTextScaleable.OnPlatformTextScalingChanged()
+        {
+            if (IsPlatformTextScalingEnabled)
+            {
+                InvalidateMeasure();
+            }
+        }
+
         /// <summary>
         /// Creates the <see cref="TextLayout"/> used to render the text.
         /// </summary>
@@ -350,7 +378,7 @@ namespace Avalonia.Controls.Presenters
             var maxWidth = MathUtilities.IsZero(constraint.Width) ? double.PositiveInfinity : constraint.Width;
             var maxHeight = MathUtilities.IsZero(constraint.Height) ? double.PositiveInfinity : constraint.Height;
 
-            var textLayout = new TextLayout(text, typeface, FontFeatures, FontSize, foreground, TextAlignment,
+            var textLayout = new TextLayout(text, typeface, FontFeatures, EffectiveFontSize, foreground, TextAlignment,
                 TextWrapping, maxWidth: maxWidth, maxHeight: maxHeight, textStyleOverrides: textStyleOverrides,
                 flowDirection: FlowDirection, lineHeight: LineHeight, letterSpacing: LetterSpacing);
 
@@ -553,7 +581,7 @@ namespace Avalonia.Controls.Presenters
             if (!string.IsNullOrEmpty(preeditText))
             {
                 var preeditHighlight = new ValueSpan<TextRunProperties>(caretIndex, preeditText.Length,
-                        new GenericTextRunProperties(typeface, FontFeatures, FontSize,
+                        new GenericTextRunProperties(typeface, FontFeatures, EffectiveFontSize,
                         foregroundBrush: foreground,
                         textDecorations: TextDecorations.Underline));
 
@@ -569,7 +597,7 @@ namespace Avalonia.Controls.Presenters
                     textStyleOverrides = new[]
                     {
                         new ValueSpan<TextRunProperties>(start, length,
-                        new GenericTextRunProperties(typeface, FontFeatures, FontSize,
+                        new GenericTextRunProperties(typeface, FontFeatures, EffectiveFontSize,
                             foregroundBrush: SelectionForegroundBrush))
                     };
                 }
diff --git a/src/Avalonia.Controls/Primitives/TextSelectionCanvas.cs b/src/Avalonia.Controls/Primitives/TextSelectionCanvas.cs
index 049188008a..1573b4ccd7 100644
--- a/src/Avalonia.Controls/Primitives/TextSelectionCanvas.cs
+++ b/src/Avalonia.Controls/Primitives/TextSelectionCanvas.cs
@@ -154,7 +154,7 @@ namespace Avalonia.Controls.Primitives
                 }
 
                 var point = ToPresenter(handle.IndicatorPosition);
-                point = point.WithY(point.Y - _presenter.FontSize / 2);
+                point = point.WithY(point.Y - ((IPlatformTextScaleable)_presenter).GetScaledFontSize(_presenter.FontSize) / 2);
                 var hit = _presenter.TextLayout.HitTestPoint(point);
                 var position = hit.CharacterHit.FirstCharacterIndex + hit.CharacterHit.TrailingLength;
 
diff --git a/src/Avalonia.Controls/SelectableTextBlock.cs b/src/Avalonia.Controls/SelectableTextBlock.cs
index 55321655cc..5a476ced22 100644
--- a/src/Avalonia.Controls/SelectableTextBlock.cs
+++ b/src/Avalonia.Controls/SelectableTextBlock.cs
@@ -187,7 +187,7 @@ namespace Avalonia.Controls
             var defaultProperties = new GenericTextRunProperties(
                 typeface,
                 FontFeatures,
-                FontSize,
+                EffectiveFontSize,
                 TextDecorations,
                 Foreground);
 
@@ -236,7 +236,7 @@ namespace Avalonia.Controls
                                 new GenericTextRunProperties(
                                     textRun.Properties?.Typeface ?? typeface,
                                     textRun.Properties?.FontFeatures ?? FontFeatures,
-                                    FontSize,
+                                    EffectiveFontSize,
                                     foregroundBrush: SelectionForegroundBrush)));
 
                         accumulatedLength += runLength;
@@ -247,7 +247,7 @@ namespace Avalonia.Controls
                     textStyleOverrides =
                     [
                         new ValueSpan<TextRunProperties>(start, length,
-                            new GenericTextRunProperties(typeface, FontFeatures, FontSize,
+                            new GenericTextRunProperties(typeface, FontFeatures, EffectiveFontSize,
                                 foregroundBrush: SelectionForegroundBrush))
                     ];
                 }
diff --git a/src/Avalonia.Controls/TextBlock.cs b/src/Avalonia.Controls/TextBlock.cs
index c21b8c7cdc..23d31c6e87 100644
--- a/src/Avalonia.Controls/TextBlock.cs
+++ b/src/Avalonia.Controls/TextBlock.cs
@@ -15,7 +15,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// A control that displays a block of text.
     /// </summary>
-    public class TextBlock : Control, IInlineHost
+    public class TextBlock : Control, IInlineHost, IPlatformTextScaleable
     {
         /// <summary>
         /// Defines the <see cref="Background"/> property.
@@ -23,6 +23,12 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<IBrush?> BackgroundProperty =
             Border.BackgroundProperty.AddOwner<TextBlock>();
 
+        /// <summary>
+        /// Defines the <see cref="IsPlatformTextScalingEnabled"/> property.
+        /// </summary>
+        public static readonly StyledProperty<bool> IsPlatformTextScalingEnabledProperty =
+            TextElement.IsPlatformTextScalingEnabledProperty.AddOwner<TextBlock>();
+
         /// <summary>
         /// Defines the <see cref="Padding"/> property.
         /// </summary>
@@ -98,7 +104,7 @@ namespace Avalonia.Controls
         /// Defines the <see cref="LetterSpacing"/> property.
         /// </summary>
         /// <remarks>
-        /// This property uses <see cref="AvaloniaProperty.AddOwner{TOwner}(AvaloniaProperty)"/> to share the same
+        /// This property uses <see cref="StyledProperty{TValue}.AddOwner{TOwner}(StyledPropertyMetadata{TValue}?)"/> to share the same
         /// definition as <see cref="TextElement.LetterSpacingProperty"/>, ensuring consistent behavior across text
         /// elements and templated controls.
         /// </remarks>
@@ -192,6 +198,13 @@ namespace Avalonia.Controls
         /// </summary>
         public TextLayout TextLayout => _textLayout ??= CreateTextLayout(Text);
 
+        /// <inheritdoc cref="TextElement.IsPlatformTextScalingEnabled"/>
+        public bool IsPlatformTextScalingEnabled
+        {
+            get => GetValue(IsPlatformTextScalingEnabledProperty);
+            set => SetValue(IsPlatformTextScalingEnabledProperty, value);
+        }
+
         /// <summary>
         /// Gets or sets the padding to place around the <see cref="Text"/>.
         /// </summary>
@@ -237,6 +250,13 @@ namespace Avalonia.Controls
             set => SetValue(FontSizeProperty, value);
         }
 
+        double IPlatformTextScaleable.GetScaledFontSize(double baseFontSize) => IsPlatformTextScalingEnabled && TopLevel.GetTopLevel(this) is { PlatformSettings: { } platformSettings } ? platformSettings.GetScaledFontSize(baseFontSize) : baseFontSize;
+
+        /// <summary>
+        /// Gets <see cref="FontSize"/> scaled according to the platform's current text scaling rules.
+        /// </summary>
+        protected double EffectiveFontSize => ((IPlatformTextScaleable)this).GetScaledFontSize(FontSize);
+
         /// <summary>
         /// Gets or sets the font style used to draw the control's text.
         /// </summary>
@@ -652,6 +672,14 @@ namespace Avalonia.Controls
             }
         }
 
+        void IPlatformTextScaleable.OnPlatformTextScalingChanged()
+        {
+            if (IsPlatformTextScalingEnabled)
+            {
+                InvalidateMeasure();
+            }
+        }
+
         /// <summary>
         /// Creates the <see cref="TextLayout"/> used to render the text.
         /// </summary>
@@ -663,7 +691,7 @@ namespace Avalonia.Controls
             var defaultProperties = new GenericTextRunProperties(
                 typeface,
                 FontFeatures,
-                FontSize,
+                EffectiveFontSize,
                 TextDecorations,
                 Foreground);
 
@@ -838,6 +866,7 @@ namespace Avalonia.Controls
             switch (change.Property.Name)
             {
                 case nameof(FontSize):
+                case nameof(IsPlatformTextScalingEnabled):
                 case nameof(FontWeight):
                 case nameof(FontStyle):
                 case nameof(FontFamily):
diff --git a/src/Avalonia.Controls/TopLevel.cs b/src/Avalonia.Controls/TopLevel.cs
index 78c2868b88..5156830d4f 100644
--- a/src/Avalonia.Controls/TopLevel.cs
+++ b/src/Avalonia.Controls/TopLevel.cs
@@ -26,6 +26,7 @@ using System.Threading.Tasks;
 using Avalonia.Diagnostics;
 using Avalonia.Rendering.Composition;
 using Avalonia.Threading;
+using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
 {
@@ -252,6 +253,8 @@ namespace Avalonia.Controls
                 PlatformImpl?.SetFrameThemeVariant((PlatformThemeVariant?)variant ?? PlatformThemeVariant.Light);
             });
 
+            PlatformSettings?.TextScalingChanged += OnPlatformTextScalingChanged;
+
             _keyboardNavigationHandler?.SetOwner(this);
             _accessKeyHandler?.SetOwner(this);
 
@@ -341,6 +344,15 @@ namespace Avalonia.Controls
                 }
             });
         }
+
+        private void OnPlatformTextScalingChanged(object? sender, EventArgs e)
+        {
+            foreach (var scaleable in this.GetVisualDescendants().OfType<IPlatformTextScaleable>())
+            {
+                scaleable.OnPlatformTextScalingChanged();
+            }
+        }
+
         /// <summary>
         /// Fired when the window is opened.
         /// </summary>
diff --git a/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs b/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
index c4b016c1b9..cac4191ed7 100644
--- a/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
+++ b/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
@@ -8,11 +8,22 @@ namespace Avalonia.Win32;
 
 internal class Win32PlatformSettings : DefaultPlatformSettings
 {
-    private static readonly Lazy<bool> s_uiSettingsSupported = new(() =>
-        WinRTApiInformation.IsTypePresent("Windows.UI.ViewManagement.UISettings")
-        && WinRTApiInformation.IsTypePresent("Windows.UI.ViewManagement.AccessibilitySettings")); 
-
     private PlatformColorValues? _lastColorValues;
+    private double _textScaleFactor = s_uiSettings2?.TextScaleFactor ?? 1;
+
+    private static readonly IUISettings2? s_uiSettings2;
+    private static readonly bool s_uiSettingsSupported;
+
+    static Win32PlatformSettings()
+    {
+        s_uiSettingsSupported = WinRTApiInformation.IsTypePresent("Windows.UI.ViewManagement.UISettings")
+        && WinRTApiInformation.IsTypePresent("Windows.UI.ViewManagement.AccessibilitySettings");
+
+        if (s_uiSettingsSupported)
+        {
+            s_uiSettings2 = NativeWinRTMethods.CreateInstance<IUISettings2>("Windows.UI.ViewManagement.UISettings");
+        }
+    }
 
     public override Size GetTapSize(PointerType type)
     {
@@ -33,10 +44,10 @@ internal class Win32PlatformSettings : DefaultPlatformSettings
     }
 
     public override TimeSpan GetDoubleTapTime(PointerType type) => TimeSpan.FromMilliseconds(GetDoubleClickTime());
-    
+
     public override PlatformColorValues GetColorValues()
     {
-        if (!s_uiSettingsSupported.Value)
+        if (!s_uiSettingsSupported)
         {
             return base.GetColorValues();
         }
@@ -74,10 +85,10 @@ internal class Win32PlatformSettings : DefaultPlatformSettings
                     PlatformThemeVariant.Light,
                 ContrastPreference = ColorContrastPreference.NoPreference,
                 AccentColor1 = accent
-            };   
+            };
         }
     }
-    
+
     internal void OnColorValuesChanged()
     {
         var oldColorValues = _lastColorValues;
@@ -87,5 +98,25 @@ internal class Win32PlatformSettings : DefaultPlatformSettings
         {
             OnColorValuesChanged(colorValues);
         }
+
+        var newTextScaleFactor = s_uiSettings2?.TextScaleFactor ?? 1;
+        if (newTextScaleFactor != _textScaleFactor)
+        {
+            _textScaleFactor = newTextScaleFactor;
+            OnTextScaleChanged();
+        }
+    }
+
+    /// <summary>
+    /// The algorithm used is undocumented, but <see href="https://github.com/microsoft/microsoft-ui-xaml/blob/5788dee271452753d5b2c70179f976c3e96a45c7/src/dxaml/xcp/core/text/common/TextFormatting.cpp#L181-L204">defined in Microsoft's source code</see>.
+    /// </summary>
+    public override double GetScaledFontSize(double baseFontSize)
+    {
+        if (baseFontSize <= 0)
+        {
+            return baseFontSize;
+        }
+
+        return Math.Max(1, baseFontSize) + Math.Max(-Math.Exp(1) * Math.Log(baseFontSize) + 18, 0.0) * (_textScaleFactor - 1);
     }
 }
diff --git a/src/Windows/Avalonia.Win32/WinRT/winrt.idl b/src/Windows/Avalonia.Win32/WinRT/winrt.idl
index b80a0de11b..b416ccafc9 100644
--- a/src/Windows/Avalonia.Win32/WinRT/winrt.idl
+++ b/src/Windows/Avalonia.Win32/WinRT/winrt.idl
@@ -859,6 +859,15 @@ enum UIColorType
     Complement = 9
 }
 
+[uuid(BAD82401-2721-44F9-BB91-2BB228BE442F)]
+interface IUISettings2 : IInspectable
+{
+    [propget] HRESULT GetTextScaleFactor([out][retval] DOUBLE* value);
+    
+    [eventadd] HRESULT AddTextScaleFactorChanged([in] void* handler, [out][retval] int* token);
+    [eventremove] HRESULT RemoveTextScaleFactorChanged([in] int token);
+}
+
 [uuid(03021BE4-5254-4781-8194-5168F7D06D7B)]
 interface IUISettings3 : IInspectable
 {
diff --git a/src/iOS/Avalonia.iOS/PlatformSettings.cs b/src/iOS/Avalonia.iOS/PlatformSettings.cs
index 43cd731701..46d922c3b1 100644
--- a/src/iOS/Avalonia.iOS/PlatformSettings.cs
+++ b/src/iOS/Avalonia.iOS/PlatformSettings.cs
@@ -1,6 +1,7 @@
 using System;
 using Avalonia.Media;
 using Avalonia.Platform;
+using Foundation;
 using UIKit;
 
 namespace Avalonia.iOS;
@@ -8,8 +9,25 @@ namespace Avalonia.iOS;
 // TODO: ideally should be created per view/activity.
 internal class PlatformSettings : DefaultPlatformSettings
 {
+    private readonly NSObject _contentSizeChangedToken;
+
     private PlatformColorValues? _lastColorValues;
 
+    public PlatformSettings()
+    {
+        _contentSizeChangedToken = UIApplication.Notifications.ObserveContentSizeCategoryChanged(OnContentSizeCategoryChanged);
+    }
+
+    ~PlatformSettings()
+    {
+        _contentSizeChangedToken.Dispose();
+    }
+
+    private void OnContentSizeCategoryChanged(object? sender, UIContentSizeCategoryChangedEventArgs e)
+    {
+        OnTextScaleChanged();
+    }
+
     public override PlatformColorValues GetColorValues()
     {
         var themeVariant = UITraitCollection.CurrentTraitCollection.UserInterfaceStyle == UIUserInterfaceStyle.Dark ?
@@ -61,4 +79,6 @@ internal class PlatformSettings : DefaultPlatformSettings
             OnColorValuesChanged(colorValues);
         }
     }
+
+    public override double GetScaledFontSize(double baseFontSize) => UIFontMetrics.DefaultMetrics.GetScaledValue((nfloat)baseFontSize);
 }

From 762dff0168b340e0de4fc922e10aac6f0b2b6d6e Mon Sep 17 00:00:00 2001
From: Tom Edwards <tom.edwards@chaos.com>
Date: Wed, 17 Dec 2025 10:45:24 +0100
Subject: [PATCH 2/5] Also scale LineHeight, LineSpacing, and LetterSpacing
 Fixed TextBox.MaxLines and TextBox.MinLines calculations when text scaling is
 active Fixed TextBox not updating when LineSpacing changes Removed
 EffectiveFontSize, since it's no longer the only property which scales

---
 .../Documents/TextElement.cs                  |  5 ++-
 .../Presenters/TextPresenter.cs               | 20 ++++-----
 .../Primitives/TextSelectionCanvas.cs         |  2 +-
 src/Avalonia.Controls/SelectableTextBlock.cs  | 13 +++---
 src/Avalonia.Controls/TextBlock.cs            | 18 ++++----
 src/Avalonia.Controls/TextBox.cs              | 45 +++++++------------
 6 files changed, 46 insertions(+), 57 deletions(-)

diff --git a/src/Avalonia.Controls/Documents/TextElement.cs b/src/Avalonia.Controls/Documents/TextElement.cs
index ed77aa9ca6..245d4fd7bf 100644
--- a/src/Avalonia.Controls/Documents/TextElement.cs
+++ b/src/Avalonia.Controls/Documents/TextElement.cs
@@ -112,9 +112,10 @@ namespace Avalonia.Controls.Documents
         }
 
         /// <summary>
-        /// Gets or sets whether the <see cref="FontSize"/> should be scaled according to platform text scaling
-        /// rules when measuring and rendering this control.
+        /// Gets or sets whether <see cref="FontSize"/>, <see cref="LetterSpacing"/>, <see cref="TextBlock.LineHeight"/>, and 
+        /// <see cref="TextBlock.LineSpacing"/> should be scaled according to platform text scaling rules when measuring and rendering this control.
         /// </summary>
+        /// <remarks>Text scaling is typically not uniform. Smaller text scales up faster than larger text.</remarks>
         public bool IsPlatformTextScalingEnabled
         {
             get => GetValue(IsPlatformTextScalingEnabledProperty);
diff --git a/src/Avalonia.Controls/Presenters/TextPresenter.cs b/src/Avalonia.Controls/Presenters/TextPresenter.cs
index 2cf6a2f94b..847da4f390 100644
--- a/src/Avalonia.Controls/Presenters/TextPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/TextPresenter.cs
@@ -195,12 +195,11 @@ namespace Avalonia.Controls.Presenters
             set => TextElement.SetFontSize(this, value);
         }
         
-        double IPlatformTextScaleable.GetScaledFontSize(double baseFontSize) => IsPlatformTextScalingEnabled && TopLevel.GetTopLevel(this) is { PlatformSettings: { } platformSettings } ? platformSettings.GetScaledFontSize(baseFontSize) : baseFontSize;
-        
-        /// <summary>
-        /// Gets <see cref="FontSize"/> scaled according to the platform's current text scaling rules.
-        /// </summary>
-        protected double EffectiveFontSize => ((IPlatformTextScaleable)this).GetScaledFontSize(FontSize);
+        /// <inheritdoc cref="IPlatformTextScaleable.GetScaledFontSize(double)"/>
+        protected double GetScaledFontSize(double baseFontSize) => !double.IsNaN(baseFontSize) && IsPlatformTextScalingEnabled && 
+            TopLevel.GetTopLevel(this) is { PlatformSettings: { } platformSettings } ? platformSettings.GetScaledFontSize(baseFontSize) : baseFontSize;
+
+        double IPlatformTextScaleable.GetScaledFontSize(double baseFontSize) => GetScaledFontSize(baseFontSize);
 
         /// <summary>
         /// Gets or sets the font style.
@@ -378,9 +377,9 @@ namespace Avalonia.Controls.Presenters
             var maxWidth = MathUtilities.IsZero(constraint.Width) ? double.PositiveInfinity : constraint.Width;
             var maxHeight = MathUtilities.IsZero(constraint.Height) ? double.PositiveInfinity : constraint.Height;
 
-            var textLayout = new TextLayout(text, typeface, FontFeatures, EffectiveFontSize, foreground, TextAlignment,
+            var textLayout = new TextLayout(text, typeface, FontFeatures, GetScaledFontSize(FontSize), foreground, TextAlignment,
                 TextWrapping, maxWidth: maxWidth, maxHeight: maxHeight, textStyleOverrides: textStyleOverrides,
-                flowDirection: FlowDirection, lineHeight: LineHeight, letterSpacing: LetterSpacing);
+                flowDirection: FlowDirection, lineHeight: GetScaledFontSize(LineHeight), letterSpacing: GetScaledFontSize(LetterSpacing));
 
             return textLayout;
         }
@@ -569,6 +568,7 @@ namespace Avalonia.Controls.Presenters
             var preeditText = PreeditText;
             var text = GetCombinedText(Text, caretIndex, preeditText);
             var typeface = new Typeface(FontFamily, FontStyle, FontWeight, FontStretch);
+            var effectiveFontSize = GetScaledFontSize(FontSize);
             var selectionStart = SelectionStart;
             var selectionEnd = SelectionEnd;
             var start = Math.Min(selectionStart, selectionEnd);
@@ -581,7 +581,7 @@ namespace Avalonia.Controls.Presenters
             if (!string.IsNullOrEmpty(preeditText))
             {
                 var preeditHighlight = new ValueSpan<TextRunProperties>(caretIndex, preeditText.Length,
-                        new GenericTextRunProperties(typeface, FontFeatures, EffectiveFontSize,
+                        new GenericTextRunProperties(typeface, FontFeatures, effectiveFontSize,
                         foregroundBrush: foreground,
                         textDecorations: TextDecorations.Underline));
 
@@ -597,7 +597,7 @@ namespace Avalonia.Controls.Presenters
                     textStyleOverrides = new[]
                     {
                         new ValueSpan<TextRunProperties>(start, length,
-                        new GenericTextRunProperties(typeface, FontFeatures, EffectiveFontSize,
+                        new GenericTextRunProperties(typeface, FontFeatures, effectiveFontSize,
                             foregroundBrush: SelectionForegroundBrush))
                     };
                 }
diff --git a/src/Avalonia.Controls/Primitives/TextSelectionCanvas.cs b/src/Avalonia.Controls/Primitives/TextSelectionCanvas.cs
index 1573b4ccd7..1911c34926 100644
--- a/src/Avalonia.Controls/Primitives/TextSelectionCanvas.cs
+++ b/src/Avalonia.Controls/Primitives/TextSelectionCanvas.cs
@@ -327,7 +327,7 @@ namespace Avalonia.Controls.Primitives
             {
                 if (_textBox.ContextFlyout is PopupFlyoutBase flyout)
                 {
-                    var verticalOffset = (double.IsNaN(_textBox.LineHeight) ? _textBox.FontSize : _textBox.LineHeight) +
+                    var verticalOffset = ((IPlatformTextScaleable)_textBox).GetScaledFontSize(double.IsNaN(_textBox.LineHeight) ? _textBox.FontSize : _textBox.LineHeight) +
                                          ContextMenuPadding;
 
                     TextSelectionHandle? handle = null;
diff --git a/src/Avalonia.Controls/SelectableTextBlock.cs b/src/Avalonia.Controls/SelectableTextBlock.cs
index 5a476ced22..78c533f0e5 100644
--- a/src/Avalonia.Controls/SelectableTextBlock.cs
+++ b/src/Avalonia.Controls/SelectableTextBlock.cs
@@ -183,18 +183,19 @@ namespace Avalonia.Controls
         protected override TextLayout CreateTextLayout(string? text)
         {
             var typeface = new Typeface(FontFamily, FontStyle, FontWeight, FontStretch);
-
+            var effectiveFontSize = GetScaledFontSize(FontSize);
+            
             var defaultProperties = new GenericTextRunProperties(
                 typeface,
                 FontFeatures,
-                EffectiveFontSize,
+                effectiveFontSize,
                 TextDecorations,
                 Foreground);
 
             var paragraphProperties = new GenericTextParagraphProperties(FlowDirection, TextAlignment, true, false,
-                defaultProperties, TextWrapping, LineHeight, 0, LetterSpacing)
+                defaultProperties, TextWrapping, GetScaledFontSize(LineHeight), 0, GetScaledFontSize(LetterSpacing))
             {
-                LineSpacing = LineSpacing
+                LineSpacing = GetScaledFontSize(LineSpacing),
             };
 
             List<ValueSpan<TextRunProperties>>? textStyleOverrides = null;
@@ -236,7 +237,7 @@ namespace Avalonia.Controls
                                 new GenericTextRunProperties(
                                     textRun.Properties?.Typeface ?? typeface,
                                     textRun.Properties?.FontFeatures ?? FontFeatures,
-                                    EffectiveFontSize,
+                                    effectiveFontSize,
                                     foregroundBrush: SelectionForegroundBrush)));
 
                         accumulatedLength += runLength;
@@ -247,7 +248,7 @@ namespace Avalonia.Controls
                     textStyleOverrides =
                     [
                         new ValueSpan<TextRunProperties>(start, length,
-                            new GenericTextRunProperties(typeface, FontFeatures, EffectiveFontSize,
+                            new GenericTextRunProperties(typeface, FontFeatures, effectiveFontSize,
                                 foregroundBrush: SelectionForegroundBrush))
                     ];
                 }
diff --git a/src/Avalonia.Controls/TextBlock.cs b/src/Avalonia.Controls/TextBlock.cs
index 23d31c6e87..1be9b43e00 100644
--- a/src/Avalonia.Controls/TextBlock.cs
+++ b/src/Avalonia.Controls/TextBlock.cs
@@ -250,12 +250,11 @@ namespace Avalonia.Controls
             set => SetValue(FontSizeProperty, value);
         }
 
-        double IPlatformTextScaleable.GetScaledFontSize(double baseFontSize) => IsPlatformTextScalingEnabled && TopLevel.GetTopLevel(this) is { PlatformSettings: { } platformSettings } ? platformSettings.GetScaledFontSize(baseFontSize) : baseFontSize;
-
-        /// <summary>
-        /// Gets <see cref="FontSize"/> scaled according to the platform's current text scaling rules.
-        /// </summary>
-        protected double EffectiveFontSize => ((IPlatformTextScaleable)this).GetScaledFontSize(FontSize);
+        /// <inheritdoc cref="IPlatformTextScaleable.GetScaledFontSize(double)"/>
+        protected double GetScaledFontSize(double baseFontSize) => !double.IsNaN(baseFontSize) && IsPlatformTextScalingEnabled && 
+            TopLevel.GetTopLevel(this) is { PlatformSettings: { } platformSettings } ? platformSettings.GetScaledFontSize(baseFontSize) : baseFontSize;
+        
+        double IPlatformTextScaleable.GetScaledFontSize(double baseFontSize) => GetScaledFontSize(baseFontSize);
 
         /// <summary>
         /// Gets or sets the font style used to draw the control's text.
@@ -691,14 +690,14 @@ namespace Avalonia.Controls
             var defaultProperties = new GenericTextRunProperties(
                 typeface,
                 FontFeatures,
-                EffectiveFontSize,
+                GetScaledFontSize(FontSize),
                 TextDecorations,
                 Foreground);
 
             var paragraphProperties = new GenericTextParagraphProperties(FlowDirection, IsMeasureValid ? TextAlignment : TextAlignment.Left, true, false,
-                defaultProperties, TextWrapping, LineHeight, 0, LetterSpacing)
+                defaultProperties, TextWrapping, GetScaledFontSize(LineHeight), 0, GetScaledFontSize(LetterSpacing))
             {
-                LineSpacing = LineSpacing
+                LineSpacing = GetScaledFontSize(LineSpacing),
             };
 
             ITextSource textSource;
@@ -880,6 +879,7 @@ namespace Avalonia.Controls
 
                 case nameof(Padding):
                 case nameof(LineHeight):
+                case nameof(LineSpacing):
                 case nameof(LetterSpacing):
                 case nameof(MaxLines):
 
diff --git a/src/Avalonia.Controls/TextBox.cs b/src/Avalonia.Controls/TextBox.cs
index b501722676..52f2900662 100644
--- a/src/Avalonia.Controls/TextBox.cs
+++ b/src/Avalonia.Controls/TextBox.cs
@@ -2382,39 +2382,26 @@ namespace Avalonia.Controls
         {
             if (_scrollViewer != null)
             {
-                var maxHeight = double.PositiveInfinity;
-
-                if (MaxLines > 0 && double.IsNaN(Height))
-                {
-                    var fontSize = FontSize;
-                    var typeface = new Typeface(FontFamily, FontStyle, FontWeight, FontStretch);
-                    var paragraphProperties = TextLayout.CreateTextParagraphProperties(typeface, fontSize, null, default, default, null, default, LineHeight, default, FontFeatures);
-                    var textLayout = new TextLayout(new LineTextSource(MaxLines), paragraphProperties);
-                    var verticalSpace = GetVerticalSpaceBetweenScrollViewerAndPresenter();
-
-                    maxHeight = Math.Ceiling(textLayout.Height + verticalSpace);
-                }
-
-                _scrollViewer.SetCurrentValue(MaxHeightProperty, maxHeight);
-
-
-                var minHeight = 0.0;
+                _scrollViewer.SetCurrentValue(MaxHeightProperty, MaxLines > 0 && double.IsNaN(Height) ? CalculateLineDIPHeight(MaxLines) : double.PositiveInfinity);
+                _scrollViewer.SetCurrentValue(MinHeightProperty, MinLines > 0 && double.IsNaN(Height) ? CalculateLineDIPHeight(MinLines) : 0);
+            }
 
-                if (MinLines > 0 && double.IsNaN(Height))
-                {
-                    var fontSize = FontSize;
-                    var typeface = new Typeface(FontFamily, FontStyle, FontWeight, FontStretch);
-                    var paragraphProperties = TextLayout.CreateTextParagraphProperties(typeface, fontSize, null, default, default, null, default, LineHeight, default, FontFeatures);
-                    var textLayout = new TextLayout(new LineTextSource(MinLines), paragraphProperties);
-                    var verticalSpace = GetVerticalSpaceBetweenScrollViewerAndPresenter();
+            return base.MeasureOverride(availableSize);
+        }
 
-                    minHeight = Math.Ceiling(textLayout.Height + verticalSpace);
-                }
+        /// <returns>Height of <paramref name="numLines"/> lines of text in device-independent pixels.</returns>
+        private double CalculateLineDIPHeight(int numLines)
+        {
+            var textScaler = _presenter as IPlatformTextScaleable;
+            var effectiveFontSize = textScaler?.GetScaledFontSize(FontSize) ?? FontSize;
+            var effectiveLineHeight = textScaler?.GetScaledFontSize(LineHeight) ?? LineHeight;
 
-                _scrollViewer.SetCurrentValue(MinHeightProperty, minHeight);
-            }
+            var typeface = new Typeface(FontFamily, FontStyle, FontWeight, FontStretch);
+            var paragraphProperties = TextLayout.CreateTextParagraphProperties(typeface, effectiveFontSize, null, default, default, null, default, effectiveLineHeight, default, FontFeatures);
+            var textLayout = new TextLayout(new LineTextSource(numLines), paragraphProperties);
+            var verticalSpace = GetVerticalSpaceBetweenScrollViewerAndPresenter();
 
-            return base.MeasureOverride(availableSize);
+            return Math.Ceiling(textLayout.Height + verticalSpace);
         }
 
         private class LineTextSource : ITextSource

From 1a77afdac569aa88f6ed5497130b656a43738374 Mon Sep 17 00:00:00 2001
From: Tom Edwards <tom.edwards@chaos.com>
Date: Wed, 17 Dec 2025 11:02:32 +0100
Subject: [PATCH 3/5] Corrected iOS font size scaling units

---
 src/iOS/Avalonia.iOS/PlatformSettings.cs | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/iOS/Avalonia.iOS/PlatformSettings.cs b/src/iOS/Avalonia.iOS/PlatformSettings.cs
index 46d922c3b1..a6114da363 100644
--- a/src/iOS/Avalonia.iOS/PlatformSettings.cs
+++ b/src/iOS/Avalonia.iOS/PlatformSettings.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using Avalonia.Media;
 using Avalonia.Platform;
 using Foundation;
@@ -10,6 +11,7 @@ namespace Avalonia.iOS;
 internal class PlatformSettings : DefaultPlatformSettings
 {
     private readonly NSObject _contentSizeChangedToken;
+    private readonly Dictionary<double, double> _fontScaleCache = [];
 
     private PlatformColorValues? _lastColorValues;
 
@@ -25,6 +27,7 @@ internal class PlatformSettings : DefaultPlatformSettings
 
     private void OnContentSizeCategoryChanged(object? sender, UIContentSizeCategoryChangedEventArgs e)
     {
+        _fontScaleCache.Clear();
         OnTextScaleChanged();
     }
 
@@ -80,5 +83,19 @@ internal class PlatformSettings : DefaultPlatformSettings
         }
     }
 
-    public override double GetScaledFontSize(double baseFontSize) => UIFontMetrics.DefaultMetrics.GetScaledValue((nfloat)baseFontSize);
+    public override double GetScaledFontSize(double baseFontSize)
+    {
+        if (baseFontSize <= 0)
+        {
+            return baseFontSize;
+        }
+
+        if (!_fontScaleCache.TryGetValue(baseFontSize, out var scaledSize))
+        {
+            var font = UIFont.SystemFontOfSize((nfloat)baseFontSize);
+            scaledSize = UIFontMetrics.DefaultMetrics.GetScaledFont(font).PointSize;
+        }
+
+        return scaledSize;
+    }
 }

From e5babc8a6f4c6522f52d22cb9b1cf6c673ea0ab6 Mon Sep 17 00:00:00 2001
From: Tom Edwards <tom.edwards@chaos.com>
Date: Sun, 21 Dec 2025 13:10:07 +0100
Subject: [PATCH 4/5] Added TextScaling static class with configuration
 properties Added ITextScaler to support custom text scaling Calculate a font
 scale factor and use this to adjust height and spacing values Fixed TextBox
 not updating when LineHeight changes and MaxLines or MinLines are active

---
 samples/ControlCatalog/MainView.xaml          |   2 +-
 src/Avalonia.Base/ITextScaler.cs              |  16 ++
 .../Platform/DefaultPlatformSettings.cs       |   2 +-
 .../Platform/IPlatformSettings.cs             |  12 +-
 .../Documents/IInlineHost.cs                  |   2 +-
 src/Avalonia.Controls/Documents/Inline.cs     |   2 +-
 .../Documents/TextElement.cs                  |  32 +---
 .../IPlatformTextScaleable.cs                 |  17 ---
 src/Avalonia.Controls/ITextScaleable.cs       |  13 ++
 .../Presenters/TextPresenter.cs               |  57 +++----
 .../Primitives/TextSelectionCanvas.cs         |   6 +-
 src/Avalonia.Controls/SelectableTextBlock.cs  |   9 +-
 src/Avalonia.Controls/TextBlock.cs            |  46 ++----
 src/Avalonia.Controls/TextBox.cs              |  29 +++-
 src/Avalonia.Controls/TextScaling.cs          | 139 ++++++++++++++++++
 src/Avalonia.Controls/TopLevel.cs             |   9 +-
 .../Avalonia.Win32/Win32PlatformSettings.cs   |   4 +-
 src/iOS/Avalonia.iOS/PlatformSettings.cs      |   2 +-
 18 files changed, 256 insertions(+), 143 deletions(-)
 create mode 100644 src/Avalonia.Base/ITextScaler.cs
 delete mode 100644 src/Avalonia.Controls/IPlatformTextScaleable.cs
 create mode 100644 src/Avalonia.Controls/ITextScaleable.cs
 create mode 100644 src/Avalonia.Controls/TextScaling.cs

diff --git a/samples/ControlCatalog/MainView.xaml b/samples/ControlCatalog/MainView.xaml
index 401d96fad2..5d6b5c6c86 100644
--- a/samples/ControlCatalog/MainView.xaml
+++ b/samples/ControlCatalog/MainView.xaml
@@ -7,7 +7,7 @@
              xmlns:pages="using:ControlCatalog.Pages"
              xmlns:viewModels="using:ControlCatalog.ViewModels"
              x:DataType="viewModels:MainWindowViewModel"
-             TextElement.IsPlatformTextScalingEnabled="True">
+             TextScaling.IsEnabled="True">
   <Grid>
     <Grid.Styles>
       <Style Selector="TextBlock.h2">
diff --git a/src/Avalonia.Base/ITextScaler.cs b/src/Avalonia.Base/ITextScaler.cs
new file mode 100644
index 0000000000..624a47d0e2
--- /dev/null
+++ b/src/Avalonia.Base/ITextScaler.cs
@@ -0,0 +1,16 @@
+using System;
+
+namespace Avalonia;
+
+/// <summary>
+/// Represents an object which can algoritmically scale text.
+/// </summary>
+public interface ITextScaler
+{
+    double GetScaledFontSize(Visual target, double baseFontSize);
+
+    /// <summary>
+    /// Raised when the text scaling algorithm has changed. Indicates that all text should be rescaled.
+    /// </summary>
+    event EventHandler<EventArgs>? TextScalingChanged;
+}
diff --git a/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs b/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs
index 6c07484aa0..7888b3c534 100644
--- a/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs
+++ b/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs
@@ -57,6 +57,6 @@ namespace Avalonia.Platform
 
         protected virtual void OnTextScaleChanged() => Dispatcher.UIThread.Send(_ => TextScalingChanged?.Invoke(this, EventArgs.Empty));
 
-        public virtual double GetScaledFontSize(double baseFontSize) => baseFontSize;
+        public virtual double GetScaledFontSize(Visual target, double baseFontSize) => baseFontSize;
     }
 }
diff --git a/src/Avalonia.Base/Platform/IPlatformSettings.cs b/src/Avalonia.Base/Platform/IPlatformSettings.cs
index e94c765593..077db569dd 100644
--- a/src/Avalonia.Base/Platform/IPlatformSettings.cs
+++ b/src/Avalonia.Base/Platform/IPlatformSettings.cs
@@ -10,7 +10,7 @@ namespace Avalonia.Platform
     /// Some of these settings might be changed by used globally in the OS in runtime.
     /// </summary>
     [NotClientImplementable]
-    public interface IPlatformSettings
+    public interface IPlatformSettings : ITextScaler
     {
         /// <summary>
         /// The size of the rectangle around the location of a pointer down that a pointer up
@@ -52,15 +52,5 @@ namespace Avalonia.Platform
         /// Raises when current system color values are changed. Including changing of a dark mode and accent colors.
         /// </summary>
         event EventHandler<PlatformColorValues>? ColorValuesChanged;
-
-        /// <summary>
-        /// Raised when the system text scaling changes.
-        /// </summary>
-        event EventHandler<EventArgs>? TextScalingChanged;
-
-        /// <summary>
-        /// Scales a font size according to the current system text scaling rules.
-        /// </summary>
-        double GetScaledFontSize(double baseFontSize);
     }
 }
diff --git a/src/Avalonia.Controls/Documents/IInlineHost.cs b/src/Avalonia.Controls/Documents/IInlineHost.cs
index 3fa6140bbe..167e186721 100644
--- a/src/Avalonia.Controls/Documents/IInlineHost.cs
+++ b/src/Avalonia.Controls/Documents/IInlineHost.cs
@@ -3,7 +3,7 @@ using Avalonia.LogicalTree;
 
 namespace Avalonia.Controls.Documents
 {
-    internal interface IInlineHost : ILogical, IPlatformTextScaleable
+    internal interface IInlineHost : ILogical, ITextScaleable
     {
         void Invalidate();
 
diff --git a/src/Avalonia.Controls/Documents/Inline.cs b/src/Avalonia.Controls/Documents/Inline.cs
index d89cdc9cf9..62bc429352 100644
--- a/src/Avalonia.Controls/Documents/Inline.cs
+++ b/src/Avalonia.Controls/Documents/Inline.cs
@@ -83,7 +83,7 @@ namespace Avalonia.Controls.Documents
             return new GenericTextRunProperties(
                 typeface,
                 FontFeatures, 
-                InlineHost?.GetScaledFontSize(FontSize) ?? FontSize,
+                InlineHost is Visual hostVisual ? TextScaling.GetScaledFontSize(hostVisual, FontSize) : FontSize,
                 TextDecorations, 
                 Foreground,
                 parentOrSelfBackground,
diff --git a/src/Avalonia.Controls/Documents/TextElement.cs b/src/Avalonia.Controls/Documents/TextElement.cs
index 245d4fd7bf..46fc3f1518 100644
--- a/src/Avalonia.Controls/Documents/TextElement.cs
+++ b/src/Avalonia.Controls/Documents/TextElement.cs
@@ -14,15 +14,6 @@ namespace Avalonia.Controls.Documents
         public static readonly StyledProperty<IBrush?> BackgroundProperty =
             Border.BackgroundProperty.AddOwner<TextElement>();
 
-        /// <summary>
-        /// Defines the <see cref="IsPlatformTextScalingEnabled"/> property.
-        /// </summary>
-        public static readonly AttachedProperty<bool> IsPlatformTextScalingEnabledProperty =
-            AvaloniaProperty.RegisterAttached<TextElement, Control, bool>(
-                nameof(IsPlatformTextScalingEnabled),
-                defaultValue: false,
-                inherits: true);
-
         /// <summary>
         /// Defines the <see cref="FontFamily"/> property.
         /// </summary>
@@ -111,17 +102,6 @@ namespace Avalonia.Controls.Documents
             set => SetValue(BackgroundProperty, value);
         }
 
-        /// <summary>
-        /// Gets or sets whether <see cref="FontSize"/>, <see cref="LetterSpacing"/>, <see cref="TextBlock.LineHeight"/>, and 
-        /// <see cref="TextBlock.LineSpacing"/> should be scaled according to platform text scaling rules when measuring and rendering this control.
-        /// </summary>
-        /// <remarks>Text scaling is typically not uniform. Smaller text scales up faster than larger text.</remarks>
-        public bool IsPlatformTextScalingEnabled
-        {
-            get => GetValue(IsPlatformTextScalingEnabledProperty);
-            set => SetValue(IsPlatformTextScalingEnabledProperty, value);
-        }
-
         /// <summary>
         /// Gets or sets the font family.
         /// </summary>
@@ -194,9 +174,6 @@ namespace Avalonia.Controls.Documents
             set => SetValue(LetterSpacingProperty, value);
         }
 
-        public static bool GetIsPlatformTextScalingEnabled(Control control) => control.GetValue(IsPlatformTextScalingEnabledProperty);
-        public static void SetIsPlatformTextScalingEnabled(Control control, bool value) => control.SetValue(IsPlatformTextScalingEnabledProperty, value);
-
         /// <summary>
         /// Gets the value of the attached <see cref="FontFamilyProperty"/> on a control.
         /// </summary>
@@ -377,17 +354,22 @@ namespace Avalonia.Controls.Documents
         {
             base.OnPropertyChanged(change);
 
+            if (change.Property.OwnerType == typeof(TextScaling))
+            {
+                InlineHost?.Invalidate();
+                return;
+            }
+
             switch (change.Property.Name)
             {
                 case nameof(Background):
                 case nameof(FontFamily):
                 case nameof(FontSize):
-                case nameof(IsPlatformTextScalingEnabled):
                 case nameof(FontStyle):
                 case nameof(FontWeight):
                 case nameof(FontStretch):
                 case nameof(Foreground):
-                    InlineHost?.Invalidate();
+                InlineHost?.Invalidate();
                     break;
             }
         }
diff --git a/src/Avalonia.Controls/IPlatformTextScaleable.cs b/src/Avalonia.Controls/IPlatformTextScaleable.cs
deleted file mode 100644
index 6cf6c1b742..0000000000
--- a/src/Avalonia.Controls/IPlatformTextScaleable.cs
+++ /dev/null
@@ -1,17 +0,0 @@
-namespace Avalonia.Controls;
-
-/// <summary>
-/// Represents an object which particpates in platform text scaling. This is an accessibility feature
-/// which allows the user to request that text be drawn larger (or on some platforms smaller) than normal,
-/// without altering other UI elements.
-/// </summary>
-public interface IPlatformTextScaleable
-{
-    bool IsPlatformTextScalingEnabled { get; }
-    void OnPlatformTextScalingChanged();
-
-    /// <summary>
-    /// Scales a font size according to the current system text scaling rules and the value of <see cref="IsPlatformTextScalingEnabled"/>.
-    /// </summary>
-    double GetScaledFontSize(double baseFontSize);
-}
diff --git a/src/Avalonia.Controls/ITextScaleable.cs b/src/Avalonia.Controls/ITextScaleable.cs
new file mode 100644
index 0000000000..7dd5512ae4
--- /dev/null
+++ b/src/Avalonia.Controls/ITextScaleable.cs
@@ -0,0 +1,13 @@
+namespace Avalonia.Controls;
+
+/// <summary>
+/// Represents an object which particpates in <see cref="TextScaling"/>.
+/// </summary>
+/// <seealso cref="ITextScaler"/>
+public interface ITextScaleable
+{
+    /// <summary>
+    /// Called when the active text scaling algorithm for this object changes.
+    /// </summary>
+    void OnTextScalingChanged();
+}
diff --git a/src/Avalonia.Controls/Presenters/TextPresenter.cs b/src/Avalonia.Controls/Presenters/TextPresenter.cs
index 847da4f390..948228f1a6 100644
--- a/src/Avalonia.Controls/Presenters/TextPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/TextPresenter.cs
@@ -1,9 +1,7 @@
 using System;
 using System.Collections.Generic;
-using System.Data;
 using Avalonia.Controls.Documents;
 using Avalonia.Controls.Primitives;
-using Avalonia.Interactivity;
 using Avalonia.Layout;
 using Avalonia.Media;
 using Avalonia.Media.Immutable;
@@ -15,7 +13,7 @@ using Avalonia.VisualTree;
 
 namespace Avalonia.Controls.Presenters
 {
-    public class TextPresenter : Control, IPlatformTextScaleable
+    public class TextPresenter : Control, ITextScaleable
     {
         public static readonly StyledProperty<bool> ShowSelectionHighlightProperty =
             AvaloniaProperty.Register<TextPresenter, bool>(nameof(ShowSelectionHighlight), defaultValue: true);
@@ -47,12 +45,6 @@ namespace Avalonia.Controls.Presenters
         public static readonly StyledProperty<int> SelectionEndProperty =
             TextBox.SelectionEndProperty.AddOwner<TextPresenter>(new(coerce: TextBox.CoerceCaretIndex));
 
-        /// <summary>
-        /// Defines the <see cref="IsPlatformTextScalingEnabled"/> property.
-        /// </summary>
-        public static readonly StyledProperty<bool> IsPlatformTextScalingEnabledProperty =
-            TextElement.IsPlatformTextScalingEnabledProperty.AddOwner<TextPresenter>();
-
         /// <summary>
         /// Defines the <see cref="Text"/> property.
         /// </summary>
@@ -64,7 +56,7 @@ namespace Avalonia.Controls.Presenters
         /// </summary>
         public static readonly StyledProperty<string?> PreeditTextProperty =
             AvaloniaProperty.Register<TextPresenter, string?>(nameof(PreeditText));
-        
+
         /// <summary>
         /// Defines the <see cref="PreeditText"/> property.
         /// </summary>
@@ -130,13 +122,6 @@ namespace Avalonia.Controls.Presenters
             set => SetValue(BackgroundProperty, value);
         }
 
-        /// <inheritdoc cref="TextElement.IsPlatformTextScalingEnabled"/>
-        public bool IsPlatformTextScalingEnabled
-        {
-            get => GetValue(IsPlatformTextScalingEnabledProperty);
-            set => SetValue(IsPlatformTextScalingEnabledProperty, value);
-        }
-
         /// <summary>
         /// Gets or sets a value that determines whether the TextPresenter shows a selection highlight.
         /// </summary>
@@ -161,7 +146,7 @@ namespace Avalonia.Controls.Presenters
             get => GetValue(PreeditTextProperty);
             set => SetValue(PreeditTextProperty, value);
         }
-        
+
         public int? PreeditTextCursorPosition
         {
             get => GetValue(PreeditTextCursorPositionProperty);
@@ -194,12 +179,6 @@ namespace Avalonia.Controls.Presenters
             get => TextElement.GetFontSize(this);
             set => TextElement.SetFontSize(this, value);
         }
-        
-        /// <inheritdoc cref="IPlatformTextScaleable.GetScaledFontSize(double)"/>
-        protected double GetScaledFontSize(double baseFontSize) => !double.IsNaN(baseFontSize) && IsPlatformTextScalingEnabled && 
-            TopLevel.GetTopLevel(this) is { PlatformSettings: { } platformSettings } ? platformSettings.GetScaledFontSize(baseFontSize) : baseFontSize;
-
-        double IPlatformTextScaleable.GetScaledFontSize(double baseFontSize) => GetScaledFontSize(baseFontSize);
 
         /// <summary>
         /// Gets or sets the font style.
@@ -354,13 +333,7 @@ namespace Avalonia.Controls.Presenters
 
         internal TextSelectionHandleCanvas? TextSelectionHandleCanvas { get; set; }
 
-        void IPlatformTextScaleable.OnPlatformTextScalingChanged()
-        {
-            if (IsPlatformTextScalingEnabled)
-            {
-                InvalidateMeasure();
-            }
-        }
+        void ITextScaleable.OnTextScalingChanged() => InvalidateMeasure();
 
         /// <summary>
         /// Creates the <see cref="TextLayout"/> used to render the text.
@@ -377,9 +350,12 @@ namespace Avalonia.Controls.Presenters
             var maxWidth = MathUtilities.IsZero(constraint.Width) ? double.PositiveInfinity : constraint.Width;
             var maxHeight = MathUtilities.IsZero(constraint.Height) ? double.PositiveInfinity : constraint.Height;
 
-            var textLayout = new TextLayout(text, typeface, FontFeatures, GetScaledFontSize(FontSize), foreground, TextAlignment,
+            var effectiveFontSize = TextScaling.GetScaledFontSize(this, FontSize);
+            var fontScaleFactor = effectiveFontSize / FontSize;
+
+            var textLayout = new TextLayout(text, typeface, FontFeatures, effectiveFontSize, foreground, TextAlignment,
                 TextWrapping, maxWidth: maxWidth, maxHeight: maxHeight, textStyleOverrides: textStyleOverrides,
-                flowDirection: FlowDirection, lineHeight: GetScaledFontSize(LineHeight), letterSpacing: GetScaledFontSize(LetterSpacing));
+                flowDirection: FlowDirection, lineHeight: LineHeight * fontScaleFactor, letterSpacing: LetterSpacing * fontScaleFactor);
 
             return textLayout;
         }
@@ -568,7 +544,7 @@ namespace Avalonia.Controls.Presenters
             var preeditText = PreeditText;
             var text = GetCombinedText(Text, caretIndex, preeditText);
             var typeface = new Typeface(FontFamily, FontStyle, FontWeight, FontStretch);
-            var effectiveFontSize = GetScaledFontSize(FontSize);
+            var effectiveFontSize = TextScaling.GetScaledFontSize(this, FontSize);
             var selectionStart = SelectionStart;
             var selectionEnd = SelectionEnd;
             var start = Math.Min(selectionStart, selectionEnd);
@@ -775,7 +751,7 @@ namespace Avalonia.Controls.Presenters
 
             CaretChanged();
         }
-        
+
         private void EnsureCaretTimer()
         {
             if (_caretTimer == null)
@@ -801,7 +777,7 @@ namespace Avalonia.Controls.Presenters
                 _caretTimer = null;
             }
 
-            if (CaretBlinkInterval.TotalMilliseconds > 0) 
+            if (CaretBlinkInterval.TotalMilliseconds > 0)
             {
                 _caretTimer = new DispatcherTimer { Interval = CaretBlinkInterval };
                 _caretTimer.Tick += CaretTimerTick;
@@ -998,7 +974,7 @@ namespace Avalonia.Controls.Presenters
                 _caretTimer.Tick -= CaretTimerTick;
             }
         }
-        
+
         private void OnPreeditChanged(string? preeditText, int? cursorPosition)
         {
             if (string.IsNullOrEmpty(preeditText))
@@ -1029,7 +1005,7 @@ namespace Avalonia.Controls.Presenters
             {
                 OnPreeditChanged(change.NewValue as string, PreeditTextCursorPosition);
             }
-            
+
             if(change.Property == PreeditTextCursorPositionProperty)
             {
                 OnPreeditChanged(PreeditText, PreeditTextCursorPosition);
@@ -1056,6 +1032,11 @@ namespace Avalonia.Controls.Presenters
                 ResetCaretTimer();
             }
 
+            if (change.Property.OwnerType == typeof(TextScaling))
+            {
+                InvalidateTextLayout();
+            }
+
             switch (change.Property.Name)
             {
                 case nameof(PreeditText):
diff --git a/src/Avalonia.Controls/Primitives/TextSelectionCanvas.cs b/src/Avalonia.Controls/Primitives/TextSelectionCanvas.cs
index 1911c34926..eaac5db7d8 100644
--- a/src/Avalonia.Controls/Primitives/TextSelectionCanvas.cs
+++ b/src/Avalonia.Controls/Primitives/TextSelectionCanvas.cs
@@ -154,7 +154,7 @@ namespace Avalonia.Controls.Primitives
                 }
 
                 var point = ToPresenter(handle.IndicatorPosition);
-                point = point.WithY(point.Y - ((IPlatformTextScaleable)_presenter).GetScaledFontSize(_presenter.FontSize) / 2);
+                point = point.WithY(point.Y - TextScaling.GetScaledFontSize(_presenter, _presenter.FontSize) / 2);
                 var hit = _presenter.TextLayout.HitTestPoint(point);
                 var position = hit.CharacterHit.FirstCharacterIndex + hit.CharacterHit.TrailingLength;
 
@@ -327,9 +327,6 @@ namespace Avalonia.Controls.Primitives
             {
                 if (_textBox.ContextFlyout is PopupFlyoutBase flyout)
                 {
-                    var verticalOffset = ((IPlatformTextScaleable)_textBox).GetScaledFontSize(double.IsNaN(_textBox.LineHeight) ? _textBox.FontSize : _textBox.LineHeight) +
-                                         ContextMenuPadding;
-
                     TextSelectionHandle? handle = null;
 
                     if (_textBox.SelectionStart != _textBox.SelectionEnd)
@@ -349,6 +346,7 @@ namespace Avalonia.Controls.Primitives
 
                     if (handle != null)
                     {
+                        var verticalOffset = (_textBox.GetLineHeight() ?? 0) + ContextMenuPadding;
                         var topLeft = ToTextBox(handle.GetTopLeft());
                         flyout.VerticalOffset = topLeft.Y - verticalOffset;
                         flyout.HorizontalOffset = topLeft.X;
diff --git a/src/Avalonia.Controls/SelectableTextBlock.cs b/src/Avalonia.Controls/SelectableTextBlock.cs
index 78c533f0e5..b27486b853 100644
--- a/src/Avalonia.Controls/SelectableTextBlock.cs
+++ b/src/Avalonia.Controls/SelectableTextBlock.cs
@@ -183,8 +183,9 @@ namespace Avalonia.Controls
         protected override TextLayout CreateTextLayout(string? text)
         {
             var typeface = new Typeface(FontFamily, FontStyle, FontWeight, FontStretch);
-            var effectiveFontSize = GetScaledFontSize(FontSize);
-            
+            var effectiveFontSize = TextScaling.GetScaledFontSize(this, FontSize);
+            var fontScaleFactor = effectiveFontSize / FontSize;
+
             var defaultProperties = new GenericTextRunProperties(
                 typeface,
                 FontFeatures,
@@ -193,9 +194,9 @@ namespace Avalonia.Controls
                 Foreground);
 
             var paragraphProperties = new GenericTextParagraphProperties(FlowDirection, TextAlignment, true, false,
-                defaultProperties, TextWrapping, GetScaledFontSize(LineHeight), 0, GetScaledFontSize(LetterSpacing))
+                defaultProperties, TextWrapping, LineHeight * fontScaleFactor, 0, LetterSpacing * fontScaleFactor)
             {
-                LineSpacing = GetScaledFontSize(LineSpacing),
+                LineSpacing = LineSpacing * fontScaleFactor,
             };
 
             List<ValueSpan<TextRunProperties>>? textStyleOverrides = null;
diff --git a/src/Avalonia.Controls/TextBlock.cs b/src/Avalonia.Controls/TextBlock.cs
index 1be9b43e00..253beef00b 100644
--- a/src/Avalonia.Controls/TextBlock.cs
+++ b/src/Avalonia.Controls/TextBlock.cs
@@ -15,7 +15,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// A control that displays a block of text.
     /// </summary>
-    public class TextBlock : Control, IInlineHost, IPlatformTextScaleable
+    public class TextBlock : Control, IInlineHost, ITextScaleable
     {
         /// <summary>
         /// Defines the <see cref="Background"/> property.
@@ -23,12 +23,6 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<IBrush?> BackgroundProperty =
             Border.BackgroundProperty.AddOwner<TextBlock>();
 
-        /// <summary>
-        /// Defines the <see cref="IsPlatformTextScalingEnabled"/> property.
-        /// </summary>
-        public static readonly StyledProperty<bool> IsPlatformTextScalingEnabledProperty =
-            TextElement.IsPlatformTextScalingEnabledProperty.AddOwner<TextBlock>();
-
         /// <summary>
         /// Defines the <see cref="Padding"/> property.
         /// </summary>
@@ -198,13 +192,6 @@ namespace Avalonia.Controls
         /// </summary>
         public TextLayout TextLayout => _textLayout ??= CreateTextLayout(Text);
 
-        /// <inheritdoc cref="TextElement.IsPlatformTextScalingEnabled"/>
-        public bool IsPlatformTextScalingEnabled
-        {
-            get => GetValue(IsPlatformTextScalingEnabledProperty);
-            set => SetValue(IsPlatformTextScalingEnabledProperty, value);
-        }
-
         /// <summary>
         /// Gets or sets the padding to place around the <see cref="Text"/>.
         /// </summary>
@@ -250,12 +237,6 @@ namespace Avalonia.Controls
             set => SetValue(FontSizeProperty, value);
         }
 
-        /// <inheritdoc cref="IPlatformTextScaleable.GetScaledFontSize(double)"/>
-        protected double GetScaledFontSize(double baseFontSize) => !double.IsNaN(baseFontSize) && IsPlatformTextScalingEnabled && 
-            TopLevel.GetTopLevel(this) is { PlatformSettings: { } platformSettings } ? platformSettings.GetScaledFontSize(baseFontSize) : baseFontSize;
-        
-        double IPlatformTextScaleable.GetScaledFontSize(double baseFontSize) => GetScaledFontSize(baseFontSize);
-
         /// <summary>
         /// Gets or sets the font style used to draw the control's text.
         /// </summary>
@@ -671,13 +652,7 @@ namespace Avalonia.Controls
             }
         }
 
-        void IPlatformTextScaleable.OnPlatformTextScalingChanged()
-        {
-            if (IsPlatformTextScalingEnabled)
-            {
-                InvalidateMeasure();
-            }
-        }
+        void ITextScaleable.OnTextScalingChanged() => InvalidateMeasure();
 
         /// <summary>
         /// Creates the <see cref="TextLayout"/> used to render the text.
@@ -690,14 +665,16 @@ namespace Avalonia.Controls
             var defaultProperties = new GenericTextRunProperties(
                 typeface,
                 FontFeatures,
-                GetScaledFontSize(FontSize),
+                TextScaling.GetScaledFontSize(this, FontSize),
                 TextDecorations,
                 Foreground);
 
+            var fontScaleFactor = defaultProperties.FontRenderingEmSize / FontSize;
+
             var paragraphProperties = new GenericTextParagraphProperties(FlowDirection, IsMeasureValid ? TextAlignment : TextAlignment.Left, true, false,
-                defaultProperties, TextWrapping, GetScaledFontSize(LineHeight), 0, GetScaledFontSize(LetterSpacing))
+                defaultProperties, TextWrapping, LineHeight * fontScaleFactor, 0, LetterSpacing * fontScaleFactor)
             {
-                LineSpacing = GetScaledFontSize(LineSpacing),
+                LineSpacing = LineSpacing * fontScaleFactor,
             };
 
             ITextSource textSource;
@@ -762,7 +739,7 @@ namespace Avalonia.Controls
                 //Force arrange so text will be properly aligned.
                 InvalidateArrange();
             }
-           
+
             var inlines = Inlines;
 
             if (HasComplexContent)
@@ -862,10 +839,15 @@ namespace Avalonia.Controls
                 }
             }
 
+            if (change.Property.OwnerType == typeof(TextScaling))
+            {
+                InvalidateTextLayout();
+                return;
+            }
+
             switch (change.Property.Name)
             {
                 case nameof(FontSize):
-                case nameof(IsPlatformTextScalingEnabled):
                 case nameof(FontWeight):
                 case nameof(FontStyle):
                 case nameof(FontFamily):
diff --git a/src/Avalonia.Controls/TextBox.cs b/src/Avalonia.Controls/TextBox.cs
index 52f2900662..ca9cf5c9db 100644
--- a/src/Avalonia.Controls/TextBox.cs
+++ b/src/Avalonia.Controls/TextBox.cs
@@ -824,6 +824,20 @@ namespace Avalonia.Controls
             return this._presenter?.TextLayout.TextLines.Count ?? -1;
         }
 
+        /// <summary>
+        /// Gets the height of each line in the <see cref="TextBox"/>, or null if no layout information is available.
+        /// </summary>
+        /// <returns></returns>
+        public double? GetLineHeight()
+        {
+            if (_presenter == null)
+                return null;
+
+            var scaledFontSize = TextScaling.GetScaledFontSize(_presenter, _presenter.FontSize);
+
+            return double.IsNaN(LineHeight) ? scaledFontSize : LineHeight * (scaledFontSize / _presenter.FontSize);
+        }
+
         /// <summary>
         /// Raised when content is being copied to the clipboard
         /// </summary>
@@ -985,6 +999,10 @@ namespace Avalonia.Controls
             {
                 InvalidateMeasure();
             }
+            else if (change.Property == LineHeightProperty)
+            {
+                InvalidateMeasure();
+            }
             else if (change.Property == UndoLimitProperty)
             {
                 OnUndoLimitChanged(change.GetNewValue<int>());
@@ -2392,9 +2410,14 @@ namespace Avalonia.Controls
         /// <returns>Height of <paramref name="numLines"/> lines of text in device-independent pixels.</returns>
         private double CalculateLineDIPHeight(int numLines)
         {
-            var textScaler = _presenter as IPlatformTextScaleable;
-            var effectiveFontSize = textScaler?.GetScaledFontSize(FontSize) ?? FontSize;
-            var effectiveLineHeight = textScaler?.GetScaledFontSize(LineHeight) ?? LineHeight;
+            var effectiveFontSize = FontSize;
+            var effectiveLineHeight = LineHeight;
+
+            if (_presenter != null)
+            { 
+                effectiveFontSize = TextScaling.GetScaledFontSize(_presenter, effectiveFontSize);
+                effectiveLineHeight = effectiveFontSize / _presenter.FontSize * LineHeight;
+            }
 
             var typeface = new Typeface(FontFamily, FontStyle, FontWeight, FontStretch);
             var paragraphProperties = TextLayout.CreateTextParagraphProperties(typeface, effectiveFontSize, null, default, default, null, default, effectiveLineHeight, default, FontFeatures);
diff --git a/src/Avalonia.Controls/TextScaling.cs b/src/Avalonia.Controls/TextScaling.cs
new file mode 100644
index 0000000000..6aa68d7f3a
--- /dev/null
+++ b/src/Avalonia.Controls/TextScaling.cs
@@ -0,0 +1,139 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using Avalonia.Controls.Documents;
+using Avalonia.Threading;
+
+namespace Avalonia.Controls;
+
+/// <summary>
+/// Configures and computes text scaling. This is an accessibility feature which allows the user to request that text be 
+/// drawn at a different size than normal, without altering other UI elements. The default scaling algorithm is determined 
+/// by the platform and may make text smaller as well as larger.
+/// </summary>
+/// <remarks>
+/// Text scaling is applied when text is measured. It does not modify the value of <see cref="TextElement.FontSize"/>.
+/// </remarks>
+/// <seealso cref="ITextScaleable"/>
+/// <seealso cref="ITextScaler"/>
+public static class TextScaling
+{
+    private static readonly ConditionalWeakTable<ITextScaler, HashSet<Visual>> s_customTextScalerSubscribers = [];
+
+    /// <summary>
+    /// Determines whether <see cref="TextElement.FontSize"/> (along with <see cref="TextElement.LetterSpacing"/>, <see cref="TextBlock.LineHeight"/>, and 
+    /// <see cref="TextBlock.LineSpacing"/>) should be scalled by calling <see cref="GetScaledFontSize"/> when measuring text content. The value is inherited.
+    /// </summary>
+    /// <remarks>Text scaling is typically not uniform. Smaller text scales up faster than larger text.</remarks>
+    public static readonly AttachedProperty<bool> IsEnabledProperty =
+        AvaloniaProperty.RegisterAttached<Visual, bool>("IsEnabled", typeof(TextScaling), inherits: true);
+
+    /// <summary>
+    /// Determines the minimum size (in em units) to which text will be scaled by <see cref="GetScaledFontSize"/>. The value is inherited.
+    /// </summary>
+    /// <remarks>This value is used only when <see cref="IsEnabledProperty"/> is true.</remarks>
+    public static readonly AttachedProperty<double> MinFontSizeProperty =
+        AvaloniaProperty.RegisterAttached<Visual, double>("MinFontSize", typeof(TextScaling), inherits: true, validate: size => size >= 0);
+
+    /// <summary>
+    /// Determines the maximum size (in em units) to which text will be scaled by <see cref="GetScaledFontSize"/>. The value is inherited.
+    /// </summary>
+    /// <remarks>This value is used only when <see cref="IsEnabledProperty"/> is true.</remarks>
+    public static readonly AttachedProperty<double> MaxFontSizeProperty =
+        AvaloniaProperty.RegisterAttached<Visual, double>("MaxFontSize", typeof(TextScaling), defaultValue: double.PositiveInfinity, inherits: true,
+            validate: size => size > 0);
+
+    /// <summary>
+    /// Determines a user-defined text scaling algorithm, which overrides platform text scaling in <see cref="GetScaledFontSize"/>. The value is inherited.
+    /// </summary>
+    /// <remarks>This value is used only when <see cref="IsEnabledProperty"/> is true.</remarks>
+    public static readonly AttachedProperty<ITextScaler?> CustomTextScalerProperty =
+        AvaloniaProperty.RegisterAttached<Visual, ITextScaler?>("CustomTextScaler", typeof(TextScaling), inherits: true);
+  
+    /// <inheritdoc cref="IsEnabledProperty"/> <see cref="IsEnabledProperty"/>
+    public static bool GetIsEnabled(Visual visual) => visual.GetValue(IsEnabledProperty);
+    /// <inheritdoc cref="IsEnabledProperty"/> <see cref="IsEnabledProperty"/>
+    public static void SetIsEnabled(Visual visual, bool value) => visual.SetValue(IsEnabledProperty, value);
+    /// <inheritdoc cref="MinFontSizeProperty"/> <see cref="MinFontSizeProperty"/>
+    public static double GetMinFontSize(Visual visual) => visual.GetValue(MinFontSizeProperty);
+    /// <inheritdoc cref="MinFontSizeProperty"/> <see cref="MinFontSizeProperty"/>
+    public static void SetMinFontSize(Visual visual, double value) => visual.SetValue(MinFontSizeProperty, value);
+    /// <inheritdoc cref="MaxFontSizeProperty"/> <see cref="MaxFontSizeProperty"/>
+    public static double GetMaxFontSize(Visual visual) => visual.GetValue(MaxFontSizeProperty);
+    /// <inheritdoc cref="MaxFontSizeProperty"/> <see cref="MaxFontSizeProperty"/>
+    public static void SetMaxFontSize(Visual visual, double value) => visual.SetValue(MaxFontSizeProperty, value);
+    /// <inheritdoc cref="CustomTextScalerProperty"/> <see cref="CustomTextScalerProperty"/>
+    public static ITextScaler? GetCustomTextScaler(Visual visual) => visual.GetValue(CustomTextScalerProperty);
+    /// <inheritdoc cref="CustomTextScalerProperty"/> <see cref="CustomTextScalerProperty"/>
+    public static void SetCustomTextScaler(Visual visual, ITextScaler? value) => visual.SetValue(CustomTextScalerProperty, value);
+
+    static TextScaling()
+    {
+        CustomTextScalerProperty.Changed.AddClassHandler<Visual>(OnCustomTextScalerChanged);
+    }
+
+    private static void OnCustomTextScalerChanged(Visual visual, AvaloniaPropertyChangedEventArgs args)
+    {
+        if (visual is not ITextScaleable)
+        {
+            return;
+        }
+
+        var (oldScaler, newScaler) = args.GetOldAndNewValue<ITextScaler?>();
+
+        if (oldScaler != null && s_customTextScalerSubscribers.TryGetValue(oldScaler, out var oldSubscribers))
+        {
+            oldSubscribers.Remove(visual);
+        }
+
+        if (newScaler != null)
+        {
+            if (s_customTextScalerSubscribers.TryGetValue(newScaler, out var newSubscribers))
+            {
+                newSubscribers.Add(visual);
+            }
+            else
+            {
+                s_customTextScalerSubscribers.Add(newScaler, [visual]);
+                newScaler.TextScalingChanged += OnCustomTextScalingChanged;
+            }
+        }
+    }
+
+    private static void OnCustomTextScalingChanged(object? sender, EventArgs e)
+    {
+        Dispatcher.UIThread.VerifyAccess();
+
+        if (sender is ITextScaler scaler && s_customTextScalerSubscribers.TryGetValue(scaler, out var subscribers))
+        {
+            foreach (var visual in subscribers)
+            {
+                if (GetIsEnabled(visual))
+                {
+                    ((ITextScaleable)visual).OnTextScalingChanged();
+                }
+            }
+        }
+    }
+
+    /// <summary>
+    /// Scales <paramref name="baseFontSize"/> according to either the current platform text scaling rules, or the rules
+    /// defined by the object assigned to <see cref="CustomTextScalerProperty"/> for <paramref name="visual"/>.
+    /// </summary>
+    /// <remarks>The values of <see cref="IsEnabledProperty"/>, <see cref="MinFontSizeProperty"/>, and <see cref="MaxFontSizeProperty"/>
+    /// are enforced, even when <see cref="CustomTextScalerProperty"/> is in use.</remarks>
+    public static double GetScaledFontSize(Visual visual, double baseFontSize)
+    {
+        if (double.IsNaN(baseFontSize) || baseFontSize <= 0 || !GetIsEnabled(visual) || 
+            (GetCustomTextScaler(visual) ?? TopLevel.GetTopLevel(visual)?.PlatformSettings) is not { } scaler)
+        {
+            return baseFontSize;
+        }
+
+        // Extend min/max to encompass the base size. Conveniently, this means that min > max is not possible.
+        var min = Math.Min(GetMinFontSize(visual), baseFontSize);
+        var max = Math.Max(GetMaxFontSize(visual), baseFontSize);
+
+        return Math.Clamp(scaler.GetScaledFontSize(visual, baseFontSize), min, max);
+    }
+}
diff --git a/src/Avalonia.Controls/TopLevel.cs b/src/Avalonia.Controls/TopLevel.cs
index 5156830d4f..40569cdee5 100644
--- a/src/Avalonia.Controls/TopLevel.cs
+++ b/src/Avalonia.Controls/TopLevel.cs
@@ -347,9 +347,14 @@ namespace Avalonia.Controls
 
         private void OnPlatformTextScalingChanged(object? sender, EventArgs e)
         {
-            foreach (var scaleable in this.GetVisualDescendants().OfType<IPlatformTextScaleable>())
+            foreach (var visual in this.GetVisualDescendants())
             {
-                scaleable.OnPlatformTextScalingChanged();
+                if (visual is not ITextScaleable scaleable || !TextScaling.GetIsEnabled(visual) || TextScaling.GetCustomTextScaler(visual) != null)
+                {
+                    continue;
+                }
+
+                scaleable.OnTextScalingChanged();
             }
         }
 
diff --git a/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs b/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
index cac4191ed7..35a8c41a4f 100644
--- a/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
+++ b/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
@@ -110,9 +110,9 @@ internal class Win32PlatformSettings : DefaultPlatformSettings
     /// <summary>
     /// The algorithm used is undocumented, but <see href="https://github.com/microsoft/microsoft-ui-xaml/blob/5788dee271452753d5b2c70179f976c3e96a45c7/src/dxaml/xcp/core/text/common/TextFormatting.cpp#L181-L204">defined in Microsoft's source code</see>.
     /// </summary>
-    public override double GetScaledFontSize(double baseFontSize)
+    public override double GetScaledFontSize(Visual target, double baseFontSize)
     {
-        if (baseFontSize <= 0)
+        if (baseFontSize <= 0 || _textScaleFactor == 1)
         {
             return baseFontSize;
         }
diff --git a/src/iOS/Avalonia.iOS/PlatformSettings.cs b/src/iOS/Avalonia.iOS/PlatformSettings.cs
index a6114da363..dfd57a1dd4 100644
--- a/src/iOS/Avalonia.iOS/PlatformSettings.cs
+++ b/src/iOS/Avalonia.iOS/PlatformSettings.cs
@@ -83,7 +83,7 @@ internal class PlatformSettings : DefaultPlatformSettings
         }
     }
 
-    public override double GetScaledFontSize(double baseFontSize)
+    public override double GetScaledFontSize(Visual target, double baseFontSize)
     {
         if (baseFontSize <= 0)
         {

From 0fcf8acea723aedcd92c44ed8ab6046a197fe9e6 Mon Sep 17 00:00:00 2001
From: Tom Edwards <tom.edwards@chaos.com>
Date: Fri, 6 Feb 2026 21:57:16 +0100
Subject: [PATCH 5/5] Fix _fontScaleCache not ever being populated

---
 src/iOS/Avalonia.iOS/PlatformSettings.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/iOS/Avalonia.iOS/PlatformSettings.cs b/src/iOS/Avalonia.iOS/PlatformSettings.cs
index dfd57a1dd4..71ba1c8144 100644
--- a/src/iOS/Avalonia.iOS/PlatformSettings.cs
+++ b/src/iOS/Avalonia.iOS/PlatformSettings.cs
@@ -93,7 +93,7 @@ internal class PlatformSettings : DefaultPlatformSettings
         if (!_fontScaleCache.TryGetValue(baseFontSize, out var scaledSize))
         {
             var font = UIFont.SystemFontOfSize((nfloat)baseFontSize);
-            scaledSize = UIFontMetrics.DefaultMetrics.GetScaledFont(font).PointSize;
+            scaledSize = _fontScaleCache[baseFontSize] = UIFontMetrics.DefaultMetrics.GetScaledFont(font).PointSize;
         }
 
         return scaledSize;