App Crashes When Setting `MathML` in `RichEditBox`

[Zakariathr22]

Describe the bug

When setting the MathOnly mode for a RichEditBox and then assigning a MathML expression, the application crashes.

Steps to reproduce the bug

1. Add a RichEditBox to the XAML:

<RichEditBox x:Name="REBox" />

2. In the code-behind, attempt to set the math mode and apply a MathML expression:

REBox.Document.SetMathMode(RichEditMathMode.MathOnly);
REBox.Document.SetMathML("a^2");

3. Run the application.

Expected behavior

The RichEditBox should correctly display the given MathML expression without causing a crash.
If the input is invalid, an exception should be handled gracefully instead of causing an application crash.

Screenshots

No response

NuGet package version

Windows App SDK 1.7.0: 1.7.250310001

Packaging type

Packaged (MSIX)

Windows version

Windows 11 version 23H2 (22631, November 2023 Update)

IDE

Visual Studio 2022

Additional context

I found this in the documentation, but I'm not sure if it's the main cause since I don't receive an "access denied" message.

[Hemantxk]

Hello @Zakariathr22, Once you set the RichEditMathMode to MathOnly, then user can type in text in Unicode Math (https://www.unicode.org/notes/tn28/UTN28-PlainTextMath-v3.1.pdf) syntax that will be converted to math expression of input.

Using SetMathML API - App needs to supply a valid XML based MathML string (https://www.w3.org/TR/MathML3/). SetMathML API will parse the string and place math expression of that string in the RichEditBox.

"a^2" is not a MathML content, it's in UnicodeMath, so it's not supposed to work with SetMathML API, though you can type it directly in math mode enabled RichEditBox. The notice that you see in the documentation will be removed soon.

[Zakariathr22]

@Hemantxk
Thank you for the clarification! I would truly appreciate a simple and valid example of how to use SetMathML?

[Hemantxk]

First app needs enable math mode by calling SetMathMode with MathOnly mode and then provide xml formatted mathml content in SetMathML API to show math expression in the RichEditBox.
Example:
Passing below string in SetMathML will render to -

<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="block">
    <mml:msup>
        <mml:mrow>
            <mml:mi mathcolor="#000000">x</mml:mi>
        </mml:mrow>
        <mml:mrow>
            <mml:mn mathcolor="#000000">3</mml:mn>
        </mml:mrow>
    </mml:msup>
    <mml:mo mathcolor="#000000">+</mml:mo>
    <mml:mi mathcolor="#000000">y</mml:mi>
    <mml:mo mathcolor="#000000">&#x3E;</mml:mo>
    <mml:mn mathcolor="#000000">5</mml:mn>
</mml:math>

You can use GetMathML API to get MathML content for existing text in math mode enabled RichEditBox. You can save it for later purpose or replace it in another math mode enabled RichEditBox.

[Zakariathr22]

First app needs enable math mode by calling SetMathMode with MathOnly mode and then provide xml formatted mathml content in SetMathML API to show math expression in the RichEditBox. Example: Passing below string in SetMathML will render to -

<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="block">
    <mml:msup>
        <mml:mrow>
            <mml:mi mathcolor="#000000">x</mml:mi>
        </mml:mrow>
        <mml:mrow>
            <mml:mn mathcolor="#000000">3</mml:mn>
        </mml:mrow>
    </mml:msup>
    <mml:mo mathcolor="#000000">+</mml:mo>
    <mml:mi mathcolor="#000000">y</mml:mi>
    <mml:mo mathcolor="#000000">&#x3E;</mml:mo>
    <mml:mn mathcolor="#000000">5</mml:mn>
</mml:math>

You can use GetMathML API to get MathML content for existing text in math mode enabled RichEditBox. You can save it for later purpose or replace it in another math mode enabled RichEditBox.

Thanks!