Added CaretBlinkInterval to TextPresenter (#13685)

* Added CaretBlinkInterval to TextPresenter

* TextPresenter CaretBlinkInterval property exposed through TextBox

* Added PropertyChanged handler for CaretBlinkInterval

* CaretBlinkInterval datatype changed from int to TimeSpan

* Added CaretBlinkInterval comments

* TextBox.CaretBlinkInterval comment changed to inherit from TextPresenter.CaretBlinkInterval

* AddOwner given to CaretBlinkInterval in TextPresenter

---------

Co-authored-by: Benedikt Stebner <Gillibald@users.noreply.github.com>

src/Avalonia.Controls/Presenters/TextPresenter.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Data;
 using Avalonia.Controls.Documents;
 using Avalonia.Controls.Primitives;
 using Avalonia.Interactivity;
@@ -34,6 +35,9 @@ namespace Avalonia.Controls.Presenters
         public static readonly StyledProperty<IBrush?> CaretBrushProperty =
             AvaloniaProperty.Register<TextPresenter, IBrush?>(nameof(CaretBrush));
 
+        public static readonly StyledProperty<TimeSpan> CaretBlinkIntervalProperty =
+            TextBox.CaretBlinkIntervalProperty.AddOwner<TextPresenter>();
+
         public static readonly StyledProperty<int> SelectionStartProperty =
             TextBox.SelectionStartProperty.AddOwner<TextPresenter>(new(coerce: TextBox.CoerceCaretIndex));
 
@@ -88,7 +92,7 @@ namespace Avalonia.Controls.Presenters
         public static readonly StyledProperty<IBrush?> BackgroundProperty =
             Border.BackgroundProperty.AddOwner<TextPresenter>();
 
-        private readonly DispatcherTimer _caretTimer;
+        private DispatcherTimer? _caretTimer;
         private bool _caretBlink;
         private TextLayout? _textLayout;
         private Size _constraint;
@@ -104,10 +108,7 @@ namespace Avalonia.Controls.Presenters
             AffectsRender<TextPresenter>(CaretBrushProperty, SelectionBrushProperty, TextElement.ForegroundProperty);
         }
 
-        public TextPresenter()
-        {
-            _caretTimer = new DispatcherTimer { Interval = TimeSpan.FromMilliseconds(500) };
-        }
+        public TextPresenter() { }
 
         public event EventHandler? CaretBoundsChanged;
 
@@ -288,6 +289,15 @@ namespace Avalonia.Controls.Presenters
             set => SetValue(CaretBrushProperty, value);
         }
 
+        /// <summary>
+        /// Gets or sets the caret blink rate
+        /// </summary>
+        public TimeSpan CaretBlinkInterval
+        {
+            get => GetValue(CaretBlinkIntervalProperty);
+            set => SetValue(CaretBlinkIntervalProperty, value);
+        }
+
         public int SelectionStart
         {
             get => GetValue(SelectionStartProperty);
@@ -443,7 +453,7 @@ namespace Avalonia.Controls.Presenters
         public void ShowCaret()
         {
             _caretBlink = true;
-            _caretTimer.Start();
+            _caretTimer?.Start();
             InvalidateVisual();
         }
 
@@ -454,7 +464,7 @@ namespace Avalonia.Controls.Presenters
             {
                 TextSelectionHandleCanvas.ShowHandles = false;
             }
-            _caretTimer.Stop();
+            _caretTimer?.Stop();
             InvalidateVisual();
         }
 
@@ -465,18 +475,18 @@ namespace Avalonia.Controls.Presenters
                 return;
             }
 
-            if (_caretTimer.IsEnabled)
+            if (_caretTimer?.IsEnabled ?? false)
             {
                 _caretBlink = true;
-                _caretTimer.Stop();
-                _caretTimer.Start();
+                _caretTimer?.Stop();
+                _caretTimer?.Start();
                 InvalidateVisual();
             }
             else
             {
-                _caretTimer.Start();
+                _caretTimer?.Start();
                 InvalidateVisual();
-                _caretTimer.Stop();
+                _caretTimer?.Stop();
             }
 
             if (IsMeasureValid)
@@ -716,6 +726,33 @@ namespace Avalonia.Controls.Presenters
             CaretChanged();
         }
 
+        private void ResetCaretTimer()
+        {
+            bool isEnabled = false;
+
+            if (_caretTimer != null)
+            {
+                _caretTimer.Tick -= CaretTimerTick;
+
+                if (_caretTimer.IsEnabled)
+                {
+                    _caretTimer.Stop();
+                    isEnabled = true;
+                }
+
+                _caretTimer = null;
+            }
+
+            if (CaretBlinkInterval.TotalMilliseconds > 0) 
+            {
+                _caretTimer = new DispatcherTimer { Interval = CaretBlinkInterval };
+                _caretTimer.Tick += CaretTimerTick;
+
+                if (isEnabled)
+                    _caretTimer.Start();
+            }
+        }
+
         public CharacterHit GetNextCharacterHit(LogicalDirection direction = LogicalDirection.Forward)
         {
             if (Text is null)
@@ -855,7 +892,7 @@ namespace Avalonia.Controls.Presenters
         {
             base.OnAttachedToVisualTree(e);
 
-            _caretTimer.Tick += CaretTimerTick;
+            ResetCaretTimer();
 
             if (TextSelectionHandleCanvas is { } canvas && _layer != null && !_layer.Children.Contains(canvas))
                 _layer?.Add(TextSelectionHandleCanvas);
@@ -882,9 +919,11 @@ namespace Avalonia.Controls.Presenters
                 c.SetPresenter(null);
             }
 
-            _caretTimer.Stop();
-
-            _caretTimer.Tick -= CaretTimerTick;
+            if (_caretTimer != null)
+            {
+                _caretTimer.Stop();
+                _caretTimer.Tick -= CaretTimerTick;
+            }
         }
         
         private void OnPreeditChanged(string? preeditText, int? cursorPosition)
@@ -939,6 +978,11 @@ namespace Avalonia.Controls.Presenters
                 }
             }
 
+            if (change.Property == CaretBlinkIntervalProperty)
+            {
+                ResetCaretTimer();
+            }
+
             switch (change.Property.Name)
             {
                 case nameof(PreeditText):

src/Avalonia.Controls/TextBox.cs

@@ -92,6 +92,12 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<IBrush?> CaretBrushProperty =
             AvaloniaProperty.Register<TextBox, IBrush?>(nameof(CaretBrush));
 
+        /// <summary>
+        /// Defines the <see cref="CaretBlinkInterval"/> property
+        /// </summary>
+        public static readonly StyledProperty<TimeSpan> CaretBlinkIntervalProperty =
+            AvaloniaProperty.Register<TextBox, TimeSpan>(nameof(CaretBlinkInterval), defaultValue: TimeSpan.FromMilliseconds(500));
+
         /// <summary>
         /// Defines the <see cref="SelectionStart"/> property
         /// </summary>
@@ -443,6 +449,13 @@ namespace Avalonia.Controls
             set => SetValue(CaretBrushProperty, value);
         }
 
+        /// <inheritdoc cref="TextPresenter.CaretBlinkInterval"/>
+        public TimeSpan CaretBlinkInterval
+        {
+            get => GetValue(CaretBlinkIntervalProperty);
+            set => SetValue(CaretBlinkIntervalProperty, value);
+        }
+
         /// <summary>
         /// Gets or sets the starting position of the text selected in the TextBox
         /// </summary>

src/Avalonia.Themes.Fluent/Controls/TextBox.xaml

@@ -155,6 +155,7 @@
                               VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                       <TextPresenter Name="PART_TextPresenter"
                                     Text="{TemplateBinding Text, Mode=TwoWay}"
+                                    CaretBlinkInterval="{TemplateBinding CaretBlinkInterval}"
                                     CaretIndex="{TemplateBinding CaretIndex}"
                                     SelectionStart="{TemplateBinding SelectionStart}"
                                     SelectionEnd="{TemplateBinding SelectionEnd}"

src/Avalonia.Themes.Simple/Controls/TextBox.xaml

@@ -143,6 +143,7 @@
                                TextAlignment="{TemplateBinding TextAlignment}"
                                TextWrapping="{TemplateBinding TextWrapping}" />
                     <TextPresenter Name="PART_TextPresenter"
+                                   CaretBlinkInterval="{TemplateBinding CaretBlinkInterval}"
                                    CaretBrush="{TemplateBinding CaretBrush}"
                                    CaretIndex="{TemplateBinding CaretIndex}"
                                    LineHeight="{TemplateBinding LineHeight}"