How to customize a caret of TextBox in UWP?

Question

How to customize a caret of TextBox in UWP?

水知 165

I want to make customized TextBox and I don't know how to customize the caret in UWP.

I thought of these ways to make it:

Change the style of the original caret directly
Use a rectangle and let it blink, but how to hide the original caret or how to make the new one blink at the same time as the orignal one?
Remake a TextBox, but how to do it and make it support IME?

Please help!

Junjie Zhu - MSFT 21,646 Reputation points

2024-09-30T07:33:45.47+00:00

Hello,

Welcome to Microsoft Q&A!

What kind of caret do you want to achieve?

In this document Custom text input, it seems that only simple modifications can be achieved in UWP.

Thank you.
水知 165 Reputation points

2024-09-30T07:40:27.71+00:00

Hello Junjie Zhu,

I'm considering using a vertical line as the caret but it's wider and has round edges at the top and bottom, I still can't achive it! Is that possible in UWP?

Thanks,

Shimizu
Junjie Zhu - MSFT 21,646 Reputation points

2024-09-30T07:48:40.64+00:00

Sorry, there is no public API in UWP that can achieve your needs.
水知 165 Reputation points

2024-09-30T07:53:08.75+00:00

Thanks, is that possible to use a ContentPresenter to get input from keyboard and IME, and locate the position of a character? Now I'm considering to remake a TextBox.
Junjie Zhu - MSFT 21,646 Reputation points

2024-10-01T08:01:41.41+00:00

I think it is difficult to achieve caret with rounded edges on the top and bottom in UWP. I searched the official documentation and couldn't find any clues.

水知 165

Hello Junjie Zhu,

Sorry for disturbing you again, I've just wrote a comment but I can't found it, so I rewrite it. since you mentioned there's no public API, is the way 2.(Use a rectangle and let it blink) or 3.(Remake a TextBox) possible? I was working on way 2 and finally can make a fake caret not blinking, it can move with the system caret. But how can we keep it syncing blink with system caret? I found the system caret dosen't just blink, it will keep highlighting in some cases such as typing. I don't know how to make it.

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:CustomCaret">

    <Style TargetType="local:CustomCaretTextBox" >
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="local:CustomCaretTextBox">
                    <Border
                        Background="{TemplateBinding Background}"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="{TemplateBinding BorderThickness}">
                        <Canvas>
                            <TextBox x:Name="MyTextBox"
                 TextChanged="MyTextBox_TextChanged"
                 GotFocus="MyTextBox_GotFocus"
                 LostFocus="MyTextBox_LostFocus"
                 HorizontalAlignment="Stretch"
                 VerticalAlignment="Center"
                                     AcceptsReturn="True"/>

                            <Rectangle x:Name="CaretRectangle"
                   Fill="Black"
                   Width="4"
                   Height="20"
                   Visibility="Collapsed"
                   VerticalAlignment="Center"
                                       Margin="10,5,0,0"
                                       RadiusX="2"
                                       RadiusY="2"/>
                        </Canvas>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Documents;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Shapes;

// The Templated Control item template is documented at https://go.microsoft.com/fwlink/?LinkId=234235

namespace CustomCaret
{
    public sealed class CustomCaretTextBox : Control
    {
        private Rectangle caretRectangle;
        private TextBox textBox;
        private bool isCaretVisible;

        public CustomCaretTextBox()
        {
            DefaultStyleKey = typeof(CustomCaretTextBox);
        }

        protected override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            caretRectangle = GetTemplateChild("CaretRectangle") as Rectangle;
            textBox = GetTemplateChild("MyTextBox") as TextBox;

            // Add event handlers
            this.GotFocus += OnGotFocus;
            this.LostFocus += OnLostFocus;
            textBox.TextChanged += OnTextChanged;
            this.KeyDown += OnKeyDown;
        }

        private void OnGotFocus(object sender, RoutedEventArgs e)
        {
            StartCaretBlinking();
            UpdateCaretPosition();
        }

        private void OnLostFocus(object sender, RoutedEventArgs e)
        {
            StopCaretBlinking();
        }

        private void StartCaretBlinking()
        {
            isCaretVisible = true;
            caretRectangle.Visibility = Visibility.Visible;
            // Implement a timer for blinking if desired
        }

        private void StopCaretBlinking()
        {
            isCaretVisible = false;
            caretRectangle.Visibility = Visibility.Collapsed;
        }

        private void OnTextChanged(object sender, TextChangedEventArgs e)
        {
            // Update caret position logic here
            UpdateCaretPosition();
        }

        private void OnKeyDown(object sender, KeyRoutedEventArgs e)
        {
            // Update caret position on key press
            UpdateCaretPosition();
        }

        private void UpdateCaretPosition()
        {
            if (textBox.SelectionStart > 0 && textBox.SelectionStart <= textBox.Text.Length)
            {
                Rect rectLast;
                int lastIndex = textBox.SelectionStart + textBox.SelectionLength;
                if (lastIndex == textBox.Text.Length)
                {
                    rectLast = textBox.GetRectFromCharacterIndex(lastIndex - 1, true);
                }
                else
                {
                    rectLast = textBox.GetRectFromCharacterIndex(lastIndex, false);
                }


                    // Set the caret rectangle's position
                    Canvas.SetLeft(caretRectangle, rectLast.X);
                    Canvas.SetTop(caretRectangle, rectLast.Y);
                

                    // Show the caret
                    caretRectangle.Visibility = Visibility.Visible;
            }
            else
            {
                // Hide the caret if the index is invalid
                caretRectangle.Visibility = Visibility.Collapsed;
            }
        }
    }
}

And... as for the way 3, is there any possible ways to make a control get input from an IME?

Thanks!

Accepted answer

0 additional answers

Your answer

Junjie Zhu - MSFT 21,646 Reputation points

2024-09-30T07:33:45.47+00:00

Hello,

Welcome to Microsoft Q&A!

What kind of caret do you want to achieve?

In this document Custom text input, it seems that only simple modifications can be achieved in UWP.

Thank you.
水知 165 Reputation points

2024-09-30T07:40:27.71+00:00

Hello Junjie Zhu,

I'm considering using a vertical line as the caret but it's wider and has round edges at the top and bottom, I still can't achive it! Is that possible in UWP?

Thanks,

Shimizu
Junjie Zhu - MSFT 21,646 Reputation points

2024-09-30T07:48:40.64+00:00

Sorry, there is no public API in UWP that can achieve your needs.
水知 165 Reputation points

2024-09-30T07:53:08.75+00:00

Thanks, is that possible to use a ContentPresenter to get input from keyboard and IME, and locate the position of a character? Now I'm considering to remake a TextBox.
Junjie Zhu - MSFT 21,646 Reputation points

2024-10-01T08:01:41.41+00:00

I think it is difficult to achieve caret with rounded edges on the top and bottom in UWP. I searched the official documentation and couldn't find any clues.

Answer 1

Junjie Zhu - MSFT 21,646

Hello @水知 ,

To summarize this question. Currently, there is no public API in UWP that can achieve caret with rounded edges on the top and bottom, only simple modifications can be implemented in UWP.

Thank you.

水知 165

Hello Junjie Zhu,

Thanke for that and finnally I got this, if we can't modify the caret directly, how about we use a rectangle to make a fake caret to cover that? If that's a possible solvation, how can we make the caret sync blinking with the system caret? Since the system caret is not just simply blinking, it will keep highlighting while typing and keeping highlighting after blinked 6 (or 7?) times.

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:CustomCaret">
    <Style TargetType="local:CustomCaretTextBox" >
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="local:CustomCaretTextBox">
                    <Border
                        Background="{TemplateBinding Background}"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="{TemplateBinding BorderThickness}">
                        <Canvas>
                            <TextBox x:Name="MyTextBox"
                 TextChanged="MyTextBox_TextChanged"
                 GotFocus="MyTextBox_GotFocus"
                 LostFocus="MyTextBox_LostFocus"
                 HorizontalAlignment="Stretch"
                 VerticalAlignment="Center"/>
                            <Rectangle x:Name="CaretRectangle"
                   Fill="Black"
                   Width="4"
                   Height="20"
                   Visibility="Collapsed"
                   VerticalAlignment="Center"
                                       Margin="10,5,0,0"
                                       RadiusX="2"
                                       RadiusY="2"/>
                        </Canvas>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Documents;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Shapes;
// The Templated Control item template is documented at https://go.microsoft.com/fwlink/?LinkId=234235
namespace CustomCaret
{
    public sealed class CustomCaretTextBox : Control
    {
        private Rectangle caretRectangle;
        private TextBox textBox;
        private bool isCaretVisible;
        public CustomCaretTextBox()
        {
            DefaultStyleKey = typeof(CustomCaretTextBox);
        }
        protected override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            caretRectangle = GetTemplateChild("CaretRectangle") as Rectangle;
            textBox = GetTemplateChild("MyTextBox") as TextBox;
            // Add event handlers
            this.GotFocus += OnGotFocus;
            this.LostFocus += OnLostFocus;
            textBox.TextChanged += OnTextChanged;
            this.KeyDown += OnKeyDown;
        }
        private void OnGotFocus(object sender, RoutedEventArgs e)
        {
            StartCaretBlinking();
            UpdateCaretPosition();
        }
        private void OnLostFocus(object sender, RoutedEventArgs e)
        {
            StopCaretBlinking();
        }
        private void StartCaretBlinking()
        {
            isCaretVisible = true;
            caretRectangle.Visibility = Visibility.Visible;
            // Implement a timer for blinking if desired
        }
        private void StopCaretBlinking()
        {
            isCaretVisible = false;
            caretRectangle.Visibility = Visibility.Collapsed;
        }
        private void OnTextChanged(object sender, TextChangedEventArgs e)
        {
            // Update caret position logic here
            UpdateCaretPosition();
        }
        private void OnKeyDown(object sender, KeyRoutedEventArgs e)
        {
            // Update caret position on key press
            UpdateCaretPosition();
        }
        private void UpdateCaretPosition()
        {
            if (textBox.SelectionStart > 0 && textBox.SelectionStart <= textBox.Text.Length)
            {
                Rect rectLast;
                int lastIndex = textBox.SelectionStart + textBox.SelectionLength;
                if (lastIndex == textBox.Text.Length)
                {
                    rectLast = textBox.GetRectFromCharacterIndex(lastIndex - 1, true);
                }
                else
                {
                    rectLast = textBox.GetRectFromCharacterIndex(lastIndex, false);
                }
                    // Set the caret rectangle's position
                    Canvas.SetLeft(caretRectangle, rectLast.X);
                    Canvas.SetTop(caretRectangle, rectLast.Y);
                
                    // Show the caret
                    caretRectangle.Visibility = Visibility.Visible;
            }
            else
            {
                // Hide the caret if the index is invalid
                caretRectangle.Visibility = Visibility.Collapsed;
            }
        }
    }
}


```Thank you.

Junjie Zhu - MSFT 21,646

Hello @水知 ,

This is a great workaround.

I added a blinking animation that repeats for 7 seconds to your code, hope that helps.

<Style TargetType="local:CustomCaretTextBox" >
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="local:CustomCaretTextBox">
                <Border
                    Background="{TemplateBinding Background}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    BorderThickness="{TemplateBinding BorderThickness}">
                    <Canvas>
                        <Canvas.Resources>
                            <Storyboard x:Name="CaretRectangleStoryboard" BeginTime="00:00:00" 
                                        RepeatBehavior="00:00:07">
                                <DoubleAnimation
                                    Storyboard.TargetName="CaretRectangle"
                                    Storyboard.TargetProperty="Opacity"
                                    From="0.0" To="1.0" Duration="0:0:1"/>
                            </Storyboard>
                        </Canvas.Resources>
                            
  
                        <TextBox x:Name="MyTextBox"
             TextChanged="MyTextBox_TextChanged"
             GotFocus="MyTextBox_GotFocus"
             LostFocus="MyTextBox_LostFocus"
             HorizontalAlignment="Stretch"
             VerticalAlignment="Center"/>
                        
                        <Rectangle x:Name="CaretRectangle"
               Fill="Black"
               Width="4"
               Height="20"
               Visibility="Collapsed"
               VerticalAlignment="Center"
                                   Margin="10,5,0,0"
                                   RadiusX="2"
                                   RadiusY="2"/>
                    </Canvas>
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

 public sealed class CustomCaretTextBox : Control
 {
     private Rectangle caretRectangle;
     private TextBox textBox;
     private bool isCaretVisible;
     private Storyboard storyboard;
     public CustomCaretTextBox()
     {
         DefaultStyleKey = typeof(CustomCaretTextBox);
     }
     protected override void OnApplyTemplate()
     {
         base.OnApplyTemplate();
         caretRectangle = GetTemplateChild("CaretRectangle") as Rectangle;
         textBox = GetTemplateChild("MyTextBox") as TextBox;
         storyboard= GetTemplateChild("CaretRectangleStoryboard") as Storyboard;
         // Add event handlers
         textBox.TextChanged += OnTextChanged;
         textBox.SelectionChanged += TextBox_SelectionChanged;
     }
     private void TextBox_SelectionChanged(object sender, RoutedEventArgs e)
     {
         UpdateCaretPosition();
         storyboard.Begin();
     }
     private void OnTextChanged(object sender, TextChangedEventArgs e)
     {
         // Update caret position logic here
         UpdateCaretPosition();
         storyboard.Begin();
     }
     private void UpdateCaretPosition()
     {
         if (textBox.SelectionStart > 0 && textBox.SelectionStart <= textBox.Text.Length)
         {
             Rect rectLast;
             int lastIndex = textBox.SelectionStart + textBox.SelectionLength;
             if (lastIndex == textBox.Text.Length)
             {
                 rectLast = textBox.GetRectFromCharacterIndex(lastIndex - 1, true);
             }
             else
             {
                 rectLast = textBox.GetRectFromCharacterIndex(lastIndex, false);
             }
             // Set the caret rectangle's position
             Canvas.SetLeft(caretRectangle, rectLast.X);
             Canvas.SetTop(caretRectangle, rectLast.Y);
             // Show the caret
             caretRectangle.Visibility = Visibility.Visible;
         }
         else
         {
             // Hide the caret if the index is invalid
             caretRectangle.Visibility = Visibility.Collapsed;
         }
     }
 }

水知 165 Reputation points

2024-10-11T00:21:23.31+00:00

Hi Junjie Zhu,

That inspired me on modifying the caret! and I made this. It looks woring perfectry while in a single line, but whem I set AcceptsReturn true and press enter at the end of the Text, the position of customized caret is not sync with the system caret. here's my code:

水知 165

Hi Junjie Zhu,

Thanks for your inspiring code! I modified the caret more and met 2 new problems:

1. When AcceptReturn=True and the caret is at the end of the string, if press Enter, the position of the moified caret is not same with the system caret.
2. When AccrptReturn=True, if we press Enter too quickly, the position of the caret will be out of the TextBox.

Here's my code:

xaml
<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:CustomCaret">

    <Style TargetType="local:CustomCaretTextBox" >
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="local:CustomCaretTextBox">
                    <Border
                    Background="{TemplateBinding Background}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    BorderThickness="{TemplateBinding BorderThickness}">
                        <Canvas>
                            <Canvas.Resources>
                                <Storyboard x:Name="CaretRectangleStoryboard" BeginTime="00:00:00" 
                                        RepeatBehavior="Forever">
                                    <DoubleAnimationUsingKeyFrames
                                        Duration="0:0:1"
                                        Storyboard.TargetName="CaretRectangle"
                                        Storyboard.TargetProperty="Opacity">
                                        <DiscreteDoubleKeyFrame KeyTime="0:0:0.7" Value="1"/>
                                        <EasingDoubleKeyFrame KeyTime="0:0:0.99" Value="0">
                                            <EasingDoubleKeyFrame.EasingFunction>
                                                <QuarticEase EasingMode="EaseOut"/>
                                            </EasingDoubleKeyFrame.EasingFunction>
                                        </EasingDoubleKeyFrame>
                                        <DiscreteDoubleKeyFrame KeyTime="0:0:1" Value="1"/>
                                    </DoubleAnimationUsingKeyFrames>

                                </Storyboard>
                            </Canvas.Resources>


                            <TextBox x:Name="MyTextBox"
             TextChanged="MyTextBox_TextChanged"
             GotFocus="MyTextBox_GotFocus"
             LostFocus="MyTextBox_LostFocus"
             HorizontalAlignment="Stretch"
             VerticalAlignment="Center"
                                     CornerRadius="4"
                                     AcceptsReturn="True"/>
                            <Rectangle x:Name="CaretCoverRectangle"
                                       IsHitTestVisible="False"
                                       Fill="White"
                                       Height="21"
                                       Width="2"
                                       Visibility="Collapsed"
                                       VerticalAlignment="Center"
                                   Margin="11,4,0,0"
                                   RadiusX="2"
                                   RadiusY="2"/>
                            <Rectangle x:Name="CaretRectangle"
                                       IsHitTestVisible="False"
                                       Fill="Black"
                                       Width="3"
                                       Height="16"
                                       Visibility="Collapsed"
                                       VerticalAlignment="Center"
                                       Margin="12,8,0,0"
                                       RadiusX="2"
                                       RadiusY="2"/>

                        </Canvas>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

</ResourceDictionary>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.System;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Documents;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Media.Animation;
using Windows.UI.Xaml.Shapes;

// The Templated Control item template is documented at https://go.microsoft.com/fwlink/?LinkId=234235

namespace CustomCaret
{
    public sealed class CustomCaretTextBox : Control
    {
        private Rectangle caretRectangle;
        private Rectangle caretCoverRectangle;
        private TextBox textBox;
        private bool isCaretVisible;
        private Storyboard storyboard;
        public CustomCaretTextBox()
        {
            DefaultStyleKey = typeof(CustomCaretTextBox);
        }



        protected override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            caretRectangle = GetTemplateChild("CaretRectangle") as Rectangle;
            caretCoverRectangle = GetTemplateChild("CaretCoverRectangle") as Rectangle;
            textBox = GetTemplateChild("MyTextBox") as TextBox;
            storyboard = GetTemplateChild("CaretRectangleStoryboard") as Storyboard;
            // Add event handlers
            textBox.TextChanged += OnTextChanged;
            textBox.SelectionChanged += TextBox_SelectionChanged;
            textBox.GettingFocus += TextBox_GettingFocus;
            textBox.LostFocus += TextBox_LostFocus;
            textBox.KeyDown += MyTextBox_KeyDown;
        }

        private void TextBox_LostFocus(object sender, RoutedEventArgs e)
        {
            caretRectangle.Visibility = Visibility.Collapsed;
            caretCoverRectangle.Visibility = Visibility.Collapsed;
            storyboard?.Stop();
        }

        private void TextBox_GettingFocus(UIElement sender, GettingFocusEventArgs args)
        {
            caretRectangle.Visibility = Visibility.Visible;
            caretCoverRectangle.Visibility = Visibility.Visible;
            UpdateCaretPosition();
            storyboard?.Stop();
            storyboard.Begin();
        }

        private void TextBox_SelectionChanged(object sender, RoutedEventArgs e)
        {
            //Selecting characters
            if (textBox.SelectedText.Length > 0)
            {
                UpdateCaretPosition();
                if (textBox.SelectedText.Length < textBox.Text.Length)
                {
                    caretRectangle.Visibility = Visibility.Collapsed;
                    storyboard?.Stop();
                }
                else
                {
                    caretCoverRectangle.Visibility = Visibility.Collapsed;
                    caretRectangle.Visibility = Visibility.Collapsed;
                    storyboard?.Stop();
                }
            }
            else
            {
                caretRectangle.Visibility = Visibility.Visible;
                caretCoverRectangle.Visibility = Visibility.Visible;
                UpdateCaretPosition();
                storyboard?.Stop();
                storyboard.Begin();
            }

        }

        private void OnTextChanged(object sender, TextChangedEventArgs e)
        {
            // Update caret position logic here
            caretRectangle.Visibility = Visibility.Visible;
            caretCoverRectangle.Visibility = Visibility.Visible;
            UpdateCaretPosition();
            storyboard?.Stop();
            storyboard.Begin();
        }

        private void MyTextBox_KeyDown(object sender, KeyRoutedEventArgs e)
        {
            UpdateCaretPosition();
        }

        private void UpdateCaretPosition()
        {
            if (textBox.Text.Length > 0)
            {
                if (textBox.SelectionStart > 0 && textBox.SelectionStart <= textBox.Text.Length)
                {
                    Rect rectLast;
                    int lastIndex = textBox.SelectionStart + textBox.SelectionLength;
                    if (lastIndex == textBox.Text.Length)
                    {
                        rectLast = textBox.GetRectFromCharacterIndex(lastIndex - 1, true);
                    }
                    else
                    {
                        rectLast = textBox.GetRectFromCharacterIndex(lastIndex, false);
                    }
                    // Set the caret rectangle's position
                    Canvas.SetLeft(caretCoverRectangle, rectLast.X);
                    Canvas.SetTop(caretCoverRectangle, rectLast.Y);
                    Canvas.SetLeft(caretRectangle, rectLast.X);
                    Canvas.SetTop(caretRectangle, rectLast.Y);
                    // Show the caret
                    caretRectangle.Visibility = Visibility.Visible;
                }
                else
                {
                    // Hide the caret if the index is invalid
                    caretRectangle.Visibility = Visibility.Collapsed;
                }
            }
            else
            {
                // Set the caret rectangle's position
                Canvas.SetLeft(caretCoverRectangle, 0);
                Canvas.SetTop(caretCoverRectangle, 0);
                Canvas.SetLeft(caretRectangle, 0);
                Canvas.SetTop(caretRectangle, 0);
                // Show the caret
                caretRectangle.Visibility = Visibility.Visible;
            }
        }
    }

}

Thanks!

Junjie Zhu - MSFT 21,646

Hello @水知 ,

Try this, force the rectangle to the next line when the last character is a carriage return.

 private void UpdateCaretPosition()
 {
     if (textBox.Text.Length > 0)
     {
         if (textBox.SelectionStart >= 0 && textBox.SelectionStart <= textBox.Text.Length)
         {
             Rect rectLast;
             int lastIndex = textBox.SelectionStart + textBox.SelectionLength;
            
powershell
         if (lastIndex > 0)
         {
             if (textBox.Text[lastIndex - 1] == 13) // Special treatment for return characters
             {
                 rectLast = textBox.GetRectFromCharacterIndex(lastIndex - 1, false);
                 Canvas.SetLeft(caretCoverRectangle, 0);
                 Canvas.SetTop(caretCoverRectangle, rectLast.Y + 19);
                 Canvas.SetLeft(caretRectangle, 0);
                 Canvas.SetTop(caretRectangle, rectLast.Y + 19);
             }
             else
             {
                 if (lastIndex == textBox.Text.Length)
                 {
                     rectLast = textBox.GetRectFromCharacterIndex(lastIndex - 1, true);
                 }
                 else
                 {
                     rectLast = textBox.GetRectFromCharacterIndex(lastIndex, false);
                 }
                 // Set the caret rectangle's position
                 Canvas.SetLeft(caretCoverRectangle, rectLast.X);
                 Canvas.SetTop(caretCoverRectangle, rectLast.Y);
                 Canvas.SetLeft(caretRectangle, rectLast.X);
                 Canvas.SetTop(caretRectangle, rectLast.Y);
             }
         }
         else
         {
             // Set the caret rectangle's position
             Canvas.SetLeft(caretCoverRectangle, 0);
             Canvas.SetTop(caretCoverRectangle, 0);
             Canvas.SetLeft(caretRectangle, 0);
             Canvas.SetTop(caretRectangle, 0);
             // Show the caret
             caretRectangle.Visibility = Visibility.Visible;
         }
         caretRectangle.Visibility = Visibility.Visible;
     }
     else
     {
         // Hide the caret if the index is invalid
         caretRectangle.Visibility = Visibility.Collapsed;
     }
 }
 else
 {
     // Set the caret rectangle's position
     Canvas.SetLeft(caretCoverRectangle, 0);
     Canvas.SetTop(caretCoverRectangle, 0);
     Canvas.SetLeft(caretRectangle, 0);
     Canvas.SetTop(caretRectangle, 0);
     // Show the caret
     caretRectangle.Visibility = Visibility.Visible;
 }
 }

水知 165

Hello Junjie Zhu,

Thanks, That works! But when I further tested the control, I found these problems, when I tried to solve them, I failed to solve these problems

The TextBox dosen't react to the FontSize value in MainPage.xaml, if I add these code, it will react to that, but if we try to set the FontSize of it again, it'll never change its value successfully. Also the size of the carets.

Plus, since Canvas.SetTop(caretCoverRectangle, rectLast.Y + 19); is using a constant value, it won't fit when the FontSize is not the defalut value.

        protected override void OnApplyTemplate()
        {
			//...
            textBox.Loaded += TextBox_Loaded;
        }
        private void TextBox_Loaded(object sender, RoutedEventArgs e)
        {
            textBox.FontSize = FontSize;
        }

When the caret is at the end of the string, if we input spaces, the TextBox won't resize to contain them in. This problem dosen't appear in original TextBox.
The caret will be out of the TextBox while pressing enter since the TextBox has a motion, I've tried to use a Storyboard to solve that but failed, I don't know how to operate on that.

And here's my new code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.System;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Documents;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Media.Animation;
using Windows.UI.Xaml.Shapes;

// The Templated Control item template is documented at https://go.microsoft.com/fwlink/?LinkId=234235

namespace CustomCaret
{
    public sealed class CustomCaretTextBox : Control
    {
        private Rectangle caretRectangle;
        private Rectangle caretCoverRectangle;
        private TextBox textBox;
        private bool isCaretVisible;
        private Storyboard storyboard;
        public CustomCaretTextBox()
        {
            DefaultStyleKey = typeof(CustomCaretTextBox);
        }

        public static new readonly DependencyProperty FontSizeProperty
            =DependencyProperty.Register(
                nameof(FontSize),
                typeof(CustomCaretTextBox),
                typeof(double),
                new PropertyMetadata(null));

        public new double FontSize
        {
            get => (double)GetValue(FontSizeProperty);
            set
            {
                UpdateElementSize();
                SetValue(FontSizeProperty, value);

            }
        }


        protected override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            caretRectangle = GetTemplateChild("CaretRectangle") as Rectangle;
            caretCoverRectangle = GetTemplateChild("CaretCoverRectangle") as Rectangle;
            textBox = GetTemplateChild("MyTextBox") as TextBox;
            storyboard = GetTemplateChild("CaretRectangleStoryboard") as Storyboard;
            // Add event handlers
            textBox.TextChanged += OnTextChanged;
            textBox.SelectionChanged += TextBox_SelectionChanged;
            textBox.GettingFocus += TextBox_GettingFocus;
            textBox.LostFocus += TextBox_LostFocus;
            textBox.KeyDown += MyTextBox_KeyDown;
        }

        private void TextBox_LostFocus(object sender, RoutedEventArgs e)
        {
            caretRectangle.Visibility = Visibility.Collapsed;
            caretCoverRectangle.Visibility = Visibility.Collapsed;
            storyboard?.Stop();
        }

        private void TextBox_GettingFocus(UIElement sender, GettingFocusEventArgs args)
        {
            UpdateElementSize();
            caretRectangle.Visibility = Visibility.Visible;
            caretCoverRectangle.Visibility = Visibility.Visible;
            UpdateCaretPosition();
            storyboard?.Stop();
            storyboard.Begin();
        }

        private void TextBox_SelectionChanged(object sender, RoutedEventArgs e)
        {
            //Selecting characters
            if (textBox.SelectedText.Length > 0)
            {
                UpdateCaretPosition();
                if (textBox.SelectedText.Length < textBox.Text.Length)
                {
                    caretRectangle.Visibility = Visibility.Collapsed;
                    storyboard?.Stop();
                }
                else
                {
                    caretCoverRectangle.Visibility = Visibility.Collapsed;
                    caretRectangle.Visibility = Visibility.Collapsed;
                    storyboard?.Stop();
                }
            }
            else
            {
                caretRectangle.Visibility = Visibility.Visible;
                caretCoverRectangle.Visibility = Visibility.Visible;
                UpdateCaretPosition();
                storyboard?.Stop();
                storyboard.Begin();
            }

        }

        private void OnTextChanged(object sender, TextChangedEventArgs e)
        {
            // Update caret position logic here
            caretRectangle.Visibility = Visibility.Visible;
            caretCoverRectangle.Visibility = Visibility.Visible;
            UpdateCaretPosition();
            storyboard?.Stop();
            storyboard.Begin();
        }

        private void MyTextBox_KeyDown(object sender, KeyRoutedEventArgs e)
        {
            UpdateCaretPosition();
        }

        private void UpdateCaretPosition()
        {
            if (textBox.Text.Length > 0)
            {
                if (textBox.SelectionStart >= 0 && textBox.SelectionStart <= textBox.Text.Length)
                {
                    Rect rectLast;
                    int lastIndex = textBox.SelectionStart + textBox.SelectionLength;

                    if (lastIndex > 0)
                    {
                        if (textBox.Text[lastIndex - 1] == 13) // Special treatment for return characters
                        {
                            rectLast = textBox.GetRectFromCharacterIndex(lastIndex - 1, false);
                            Canvas.SetLeft(caretCoverRectangle, 0);
                            Canvas.SetTop(caretCoverRectangle, rectLast.Y + 19);
                            Canvas.SetLeft(caretRectangle, 0);
                            Canvas.SetTop(caretRectangle, rectLast.Y + 19);
                        }
                        else
                        {
                            if (lastIndex == textBox.Text.Length)
                            {
                                rectLast = textBox.GetRectFromCharacterIndex(lastIndex - 1, true);
                            }
                            else
                            {
                                rectLast = textBox.GetRectFromCharacterIndex(lastIndex, false);
                            }
                            // Set the caret rectangle's position
                            Canvas.SetLeft(caretCoverRectangle, rectLast.X);
                            Canvas.SetTop(caretCoverRectangle, rectLast.Y);
                            Canvas.SetLeft(caretRectangle, rectLast.X);
                            Canvas.SetTop(caretRectangle, rectLast.Y);
                        }
                    }
                    else
                    {
                        // Set the caret rectangle's position
                        Canvas.SetLeft(caretCoverRectangle, 0);
                        Canvas.SetTop(caretCoverRectangle, 0);
                        Canvas.SetLeft(caretRectangle, 0);
                        Canvas.SetTop(caretRectangle, 0);
                        // Show the caret
                        caretRectangle.Visibility = Visibility.Visible;
                    }
                    caretRectangle.Visibility = Visibility.Visible;
                }
                else
                {
                    // Hide the caret if the index is invalid
                    caretRectangle.Visibility = Visibility.Collapsed;
                }
            }
            else
            {
                // Set the caret rectangle's position
                Canvas.SetLeft(caretCoverRectangle, 0);
                Canvas.SetTop(caretCoverRectangle, 0);
                Canvas.SetLeft(caretRectangle, 0);
                Canvas.SetTop(caretRectangle, 0);
                // Show the caret
                caretRectangle.Visibility = Visibility.Visible;
            }
        }

        private void UpdateElementSize()
        {
            if (textBox != null)
            {
                textBox.FontSize = FontSize;
            }
            if (caretRectangle != null && caretCoverRectangle != null)
            {
                caretRectangle.Height = 1.35 * FontSize;
                caretCoverRectangle.Height = 1.38 * FontSize;
            }
        }
    }

}

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:CustomCaret">
    <ResourceDictionary.ThemeDictionaries>
        <ResourceDictionary x:Key="Default">
            <SolidColorBrush x:Key="TextBoxDefaultBackground" Color="#202020"/>
            <SolidColorBrush x:Key="TextBoxPointerOverBackground" Color="#303030"/>
            <SolidColorBrush x:Key="TextBoxEditingBackground" Color="#252525"/>
            <SolidColorBrush x:Key="TextBoxDisabledBackground" Color="#101010"/>
            <SolidColorBrush x:Key="TextBoxEnabledForeground" Color="#FEFEFE"/>
            <SolidColorBrush x:Key="textBoxDisabledForeground" Color="#AEAEAE"/>
            <SolidColorBrush x:Key="TextBoxNotOnFocusInnerBorderColor" Color="Transparent"/>
            <SolidColorBrush x:Key="TextBoxNotOnFocusOuterBorderBackground" Color="Transparent"/>
            <SolidColorBrush x:Key="TextBoxOnFocusInnerBorderBrush" Color="#FFAAAAAA"/>
            <SolidColorBrush x:Key="TextBoxOnFocusOuterBorderBrush" Color="Transparent"/>
            <SolidColorBrush x:Key="TextBoxCaretBrush" Color="#FFFFFF"/>
        </ResourceDictionary>
        <ResourceDictionary x:Key="Dark">
            <SolidColorBrush x:Key="TextBoxDefaultBackground" Color="#202020"/>
            <SolidColorBrush x:Key="TextBoxPointerOverBackground" Color="#303030"/>
            <SolidColorBrush x:Key="TextBoxEditingBackground" Color="#252525"/>
            <SolidColorBrush x:Key="TextBoxDisabledBackground" Color="#101010"/>
            <SolidColorBrush x:Key="TextBoxEnabledForeground" Color="#FEFEFE"/>
            <SolidColorBrush x:Key="textBoxDisabledForeground" Color="#AEAEAE"/>
            <SolidColorBrush x:Key="TextBoxNotOnFocusInnerBorderColor" Color="Transparent"/>
            <SolidColorBrush x:Key="TextBoxNotOnFocusOuterBorderBackground" Color="Transparent"/>
            <SolidColorBrush x:Key="TextBoxOnFocusInnerBorderBrush" Color="#FFAAAAAA"/>
            <SolidColorBrush x:Key="TextBoxOnFocusOuterBorderBrush" Color="Transparent"/>
            <SolidColorBrush x:Key="TextBoxCaretBrush" Color="#FFFFFF"/>
        </ResourceDictionary>
        <ResourceDictionary x:Key="Light">
            <SolidColorBrush x:Key="TextBoxDefaultBackground" Color="#F5F5F5"/>
            <SolidColorBrush x:Key="TextBoxPointerOverBackground" Color="#EAEAEA"/>
            <SolidColorBrush x:Key="TextBoxEditingBackground" Color="#F0F0F0"/>
            <SolidColorBrush x:Key="TextBoxDisabledBackground" Color="#E0E0E0"/>
            <SolidColorBrush x:Key="TextBoxEnabledForeground" Color="#000000"/>
            <SolidColorBrush x:Key="textBoxDisabledForeground" Color="#2E2E2E"/>
            <SolidColorBrush x:Key="TextBoxNotOnFocusInnerBorderColor" Color="Transparent"/>
            <SolidColorBrush x:Key="TextBoxNotOnFocusOuterBorderBackground" Color="Transparent"/>
            <SolidColorBrush x:Key="TextBoxOnFocusInnerBorderBrush" Color="#FF3B3B3B"/>
            <SolidColorBrush x:Key="TextBoxOnFocusOuterBorderBrush" Color="Transparent"/>
            <SolidColorBrush x:Key="TextBoxCaretBrush" Color="#000000"/>
        </ResourceDictionary>
    </ResourceDictionary.ThemeDictionaries>
    <Style TargetType="local:CustomCaretTextBox">
        <Setter Property="Background" Value="{ThemeResource TextBoxDefaultBackground}"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="local:CustomCaretTextBox">
                    <Border
                    Background="{TemplateBinding Background}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    BorderThickness="{TemplateBinding BorderThickness}">
                        <Canvas>
                            <Canvas.Resources>
                                <Storyboard x:Name="CaretRectangleStoryboard" BeginTime="00:00:00" 
                                        RepeatBehavior="Forever">
                                    <DoubleAnimationUsingKeyFrames
                                        Duration="0:0:1"
                                        Storyboard.TargetName="CaretRectangle"
                                        Storyboard.TargetProperty="Opacity">
                                        <DiscreteDoubleKeyFrame KeyTime="0:0:0.7" Value="1"/>
                                        <EasingDoubleKeyFrame KeyTime="0:0:0.99" Value="0">
                                            <EasingDoubleKeyFrame.EasingFunction>
                                                <QuarticEase EasingMode="EaseOut"/>
                                            </EasingDoubleKeyFrame.EasingFunction>
                                        </EasingDoubleKeyFrame>
                                        <DiscreteDoubleKeyFrame KeyTime="0:0:1" Value="1"/>
                                    </DoubleAnimationUsingKeyFrames>
                                </Storyboard>
                            </Canvas.Resources>

                            <TextBox x:Name="MyTextBox"
                                     FontSize="{Binding FontSize,RelativeSource={RelativeSource TemplatedParent}}"
                                     TextChanged="MyTextBox_TextChanged"
                                     GotFocus="MyTextBox_GotFocus"
                                     LostFocus="MyTextBox_LostFocus"
                                     HorizontalAlignment="Stretch"
                                     VerticalAlignment="Center"
                                     CornerRadius="4"
                                     AcceptsReturn="True"
                                     Background="#202020"/>
                            <Rectangle x:Name="CaretCoverRectangle"
                                       IsHitTestVisible="False"
                                       Fill="White"
                                       Height="21"
                                       Width="2"
                                       Visibility="Collapsed"
                                       VerticalAlignment="Center"
                                       Margin="11,4,0,0"
                                       RadiusX="2"
                                       RadiusY="2"/>
                            <Rectangle x:Name="CaretRectangle"
                                       IsHitTestVisible="False"
                                       Fill="Black"
                                       Width="3"
                                       Height="16"
                                       Visibility="Collapsed"
                                       VerticalAlignment="Center"
                                       Margin="12,8,0,0"
                                       RadiusX="2"
                                       RadiusY="2"/>
                        </Canvas>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

</ResourceDictionary>

Please help me solve these problems

Thanks a lot.

Junjie Zhu - MSFT 21,646 Reputation points

2024-10-14T08:12:36.91+00:00

Plus, since Canvas.SetTop(caretCoverRectangle, rectLast.Y + 19); is using a constant value, it won't fit when the FontSize is not the defalut value.

This problem can be solved by collecting multiple fontsize values(X) to find the appropriate offset value(Y), and then using the XY function to express it. like Y=aX+b, use functions to express the change curve of fontsize and offset.

When the caret is at the end of the string, if we input spaces, the TextBox won't resize to contain them in. This problem dosen't appear in original TextBox.

As for the space problem, we can only add another check to handle the situation where both Space and Carriage return characters appear at the same time.

I have no idea about other problems, because we cannot directly get the cursor object or its position in UWP. This will be a difficult project.
水知 165 Reputation points

2024-10-15T06:29:10.6133333+00:00

Thanks Junjie Zhu,

I'll have a try to fix that!

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How to customize a caret of TextBox in UWP?

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