Crash in TextBoxView.cs related to wrapping.

[katedsouza]

Description

I created this small application so that I could report the problem (see the reproduction steps). The callstack is different in this particular case to the crash that I am having in my real application, but the origin is the same:

• Text in a TextBox that consists of a single space followed by a long word so that the text wrapping results in a top line with a single space and 2 more lines.
• Type a space at the beginning of the 3rd line so that the text wrapping will now result in 2 lines, the 1st line consisting of a space followed by the characters that were previously on the 2nd line, and the 2nd line consisting of the characters that were previously on the 3rd line.

The crashes are always in TextBoxView.cs.

What seems to happen is that the space gets positioned at the end of the 2nd line, so we have a 1st line with a single space, a 2nd line with o's then a space, then a 3rd line with the remaining o's. If the wrapping algorithm was applied to the whole text then we would have a 1st line with a space following by o's, then a 2nd line with the remaining o's. When something happens that uses the wrapping algorithm on the beginning of the text, the result does not match the current line metrics causing a crash.

Is it possible to have a fix for this problem?

Thanks.

Reproduction Steps

Create a WPF application with this MainWindow:

<Window x:Class="MyTestApp.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:MyTestApp" mc:Ignorable="d" Title="MainWindow" Height="200" Width="200"> <Grid> <Grid.RowDefinitions> <RowDefinition Height="Auto" /> </Grid.RowDefinitions> <TextBox x:Name="MyTextBox" Grid.Row="1" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" VerticalContentAlignment="Top" FontSize="14.0" TextAlignment="Left" TextWrapping="Wrap"> </TextBox> </Grid> </Window>

1. Run application (and DO NOT resize the window).
2. Paste the text that is within the quotes here " oooooooooooooooooooooooo". (The result is 3 lines: first line has a single space, the second has lots of o characters and the last has 3 o characters.
3. Place the cursor at the start of the third line and type a single space.
4. Move the mouse cursor around the window (specifically over the first line).
5. Application crashes with a FatalExecutionEngineError.

Expected behavior

No crash.

Actual behavior

In our application, the problem is a hard crash and our application simply disappears with no message.

Regression?

No response

Known Workarounds

We have no good workaround. It may seem that the workaround would be to not allow users to enter a second space in the TextBox, but the bug occurs in other circumstances i.e. if we have a mix of Arabic and Latin text, the crash can occur by entering a Latin character within the Arabic text.

Impact

No response

Configuration

No response

Other information

For your information, this particular TextBox is used to enter a character set for the creation of a font file. So in this case it is normal to have a long 'word' without spaces in between.

[miloush]

You didn't mention OS version or .NET version. Are you expecting font fallback to be involved?

[katedsouza]

Hello!

I am on Windows 11 Enterprise, OS build 26100.7840. In my small test app the Target Framework is .NET Framework 4.8.1. In our real application the Target Framework is .NET 9.0. Does that answer your question?

I'm not sure what you mean by a font fallback. I don't think the font is related to the problem. It seems to be purely a wrapping problem. However, the font will affect the repro for the bug because it will change when the wrapping occurs. Please let me know if you need any extra information to reproduce the problem.

Thanks!

[lindexi]

@katedsouza I can not repro your isseus

You can find my demo code in : https://github.com/lindexi/lindexi_gd/tree/06c36313e89171f6f52948936bd83898728072cc/WPFDemo/HehehelcereleeBenawlairfoho

Reference: #8827 (comment) #10333

[miloush]

@katedsouza yes that answers my question, if it repros on both .NET FW and .NET 9 for you then that rules out some possible causes. Font fallback happens when the font you use to display the glyphs does not have the glyphs, you mentioned creating a font, and the fallback font might have different metrics which affects wrapping.

I think it would be helpful if you could provide a repro project, and note your DPI too.

[katedsouza]

For the repro, you just need to resize the window a bit. Basically, the window has to be of a width that it fits 1 space + n x letter, but does not fit (n + 1) x letter. For example, I am attaching a screenshot with the window at 2 different sizes.

In this example, to produce the crash, type more Ws, then put the cursor at the beginning of the 3rd line and type a space then move the mouse around over the top line and wait for a few seconds.

(Sorry, I forgot in my image to start the test with: Type 1 space). :)

[katedsouza]

Sorry, I don't know how to find my DPI. I have attached a zip with my whole project directory.

MyTestApp.zip

[lindexi]

@katedsouza Can I know what the Crash you means?

I try your code in MyTestApp.zip , but I can not find any crash.

[katedsouza]

It looks like you didn't understand my repro. In your gif, you have the situation in my screenshot that is "Crash does NOT happen". You need to resize the window slightly so that you get the situation in my screenshot that "Crash happens". In your gif:

• Type space
• Type lots of w's that fill the first line
• Type another w - all the w's fit on the second line - in this case the crash will not happen

You need the following case:

• Type space
• Type lots of w's that fill the first line
• Type another w - not all the w's fit on the second line and so you have 3 lines: 1st with a space, 2nd with lots of w's and 3rd with a single w.
• Place the cursor at the beginning of the 3rd line
• Type space
• Move the cursor around the window over the top line and wait a few seconds
• Crash and the application disappears

[lindexi]

@katedsouza Thank you. And it sounds like the Accessibility 's issues. Could you re-test your application after close the Accessibility in Windows Settings?

Reference: #8827

[laxmikanth-msft]

@katedsouza Does disabling the accessibility resolve this issue?

[katedsouza]

Hello!

Sorry I've been busy. I already had this option set to false, so no it is not connected. Can you still not reproduce the issue? It is not connected to the mouse at all. I can make another application if you like and try to get you a different repro. I just used this mouse manner of reproducing it so that I could send you a really simple application.

I'm not sure what I am missing in my explanation to you. I'll try to explain again...

There are probably many ways of reproducing the problem, but the way that I know of is specifically if the start of your text is a space, then the rest of your text contains no spaces. It also requires that the TextBox has a width that results in the following wrapping situation:

• Type a space then lots of characters and no more spaces.
• The width of the TextBox is wide enough to fit the space + n x characters. The (n + 1)th character is wider than a space and when it is typed, the n characters move to the 2nd line and the (n+1)th character appears on the 3rd line (this is where the width of the TextBox must be sized so that the (n+1)th characters appears on the 3rd line).
• All is fine at this point.
• Type many more characters without spaces so that you have at least 3 lines.
• Type a space at the beginning of the 3rd line - the error occurs at this point:
  • Displayed in the TextBox you have line 1 (single space), line 2 (n+1 chars), line 3 (more chars) and the space is between line 2 and line 3 - this is incorrect.
  • What should be displayed is line 1 (single space + n chars), line 2 (more chars).
• When another action occurs that results in the TextBox passing by the wrapping algorithm there is a crash - this is because the currrent line metrics do not match the results of the wrapping algorithm.

[czdietrich]

I'm able to reproduce reliably on 100% DPI even without resizing the window. (see GIF)
[Space] > 14 [W] > [Backspace] > [Arrow Up] > Crash

It's also reproducible on .NET Framework.
Just a simple <TextBox TextWrapping="Wrap" /> is enough to cause the exception.

[lindexi]

@katedsouza Your attached picture is extremely important. It has enabled me to see the most crucial information.

I found the same problem: #2314

The application crash in:

wpf/src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/documents/TextBoxView.cs

Line 1696 in cb00b41

Invariant.Assert(metrics.Length == line.Length, "Line is out of sync with metrics!");

Could you add the exception info to here?