WPF TextBox slowness with spellcheck enabled on Windows 10

Question

We're seeing significant lag while typing into a WPF TextBox that has SpellCheck enabled on Windows 10. We see this with just a simple application containing a TextBox:

<Window x:Class="TestSpellCheck.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:TestSpellCheck"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
            <TextBox x:Name="textBox" TextWrapping="Wrap" Text="TextBox" AcceptsReturn="True" 
                     HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto"
                     SpellCheck.IsEnabled="True"/>
    </Grid>
</Window>

When I paste a section of text with a number of spelling errors (say, some Lorem Ipsum text), subsequent typing sees a lag of a few seconds between when I type a character and when it appears on the screen. This doesn't happen if the text I paste doesn't have spelling errors, or if I do this on Windows 7.

Answer 1

Please check global dictionary registration key in the Registry Editor at:

HKEY_CURRENT_USER\Software\Microsoft\Spelling\Dictionaries
Key: Global

Like the below picture shown:

Is there any temp dictionaries in the Value data? If there are, please delete them.then check your slowness resolved or not.

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Answer 2

I am having a similar issue, in my case happens when I press the space bar, the control gets stuck while typing and start to drop letters, any update on your issue so far?

Answer 3

Our users have also reported the same issue. Interestingly enough, they say it started in early September. Prior to that there were no issues. As with @John Restrepo Bedoya , it seems to start after pressing the spacebar. (I suspect that's because the space signals to the spell checker that it's time to check a word.) As we continue to type, the textbox it begins to drop characters forcing corrections which slow it down even further.

This is not so much an issue for simple fields, but for comments this is really causing a problem. The textbox can't keep up with even reasonably fast typing.

I have tried the registry solution mentioned above. There was definitely a value in the global tag, but removing it had no effect. OS version is 1909