Very low Text Rendering Performance due native C++ interop

• .NET Core Version: 5.0.6
• Windows version: 21H1 (Build 19043.928)
• Does the bug reproduce also in WPF for .NET Framework 4.8?: Yes
• Is this bug related specifically to tooling in Visual Studio (e.g. XAML Designer, Code editing, etc…)?: No

Problem description: UIElement.Measure this very slow

Actual behavior:

Expected behavior: Fast measuring for WPF rendering. If there is nothing more that can be optimized in the measure method, it might make sense to cache the measures according to certain parameters, since this is very slow with large visual trees. Compared to Windows Forms, Windows Forms is superior in terms of performance here.

Would it not make sense to write the measure method in native C++ somehow to optimize the performance accordingly or is the overhead here too large?

Minimal repro:

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <!-- ... Many column definitions -->
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition Heigth="*"/>
        <!-- ... Many row definitions -->
    </Grid.RowDefinitions>
    <Button Grid.Row="0" Grid.Column="0">Test</Button>
    <Button Grid.Row="1" Grid.Column="0">Test</Button>
    <Button Grid.Row="0" Grid.Column="2">Test</Button>
    <Button Grid.Row="2" Grid.Column="3">Test</Button>
    <Button Grid.Row="12" Grid.Column="0">Test</Button>
    <Button Grid.Row="7" Grid.Column="8">Test</Button>
    <!-- ... big visual tree -->
</Grid>

[deeprobin]

@IAmTheCShark This is exactly what I meant in DataGrid and this makes scrolling very unperformant. And it shouldn’t be like that. Thank you for providing the example 😃.

[IAmTheCShark]

@deeprobin I wrote a small hack that uses reflection to turn on some optimizations. Just out of curiosity, can you give it a try and see if there are any improvements?

Obviously, this is nothing for productoin enivronment and only for testing purposes. This might have weird consequences so use with cuaiton.

The hack will make Typeface.CheckFastPathNominalGlyphs (https://referencesource.microsoft.com/#PresentationCore/Core/CSharp/System/Windows/Media/Typeface.cs,550) return true alot more often

Paste the following code into your MainWindow constructor before InitializeComponent or before you create all the TextBlocks. The first line creates a Typeface. If you have different FontFamilies, Styles and so on, you might need to call this multiple times. `

        Typeface typeFace = new Typeface(FontFamily, FontStyle, FontWeight, FontStretch);

        var tryGetGlyphTypeFaceMethod =
            typeof(Typeface).GetMethod("TryGetGlyphTypeface", BindingFlags.Instance | BindingFlags.NonPublic);

        GlyphTypeface glyphTypeFace = tryGetGlyphTypeFaceMethod.Invoke(typeFace, null) as GlyphTypeface;

        var fontFaceLayoutInfoProperty =
            typeof(GlyphTypeface).GetProperty("FontFaceLayoutInfo", BindingFlags.Instance | BindingFlags.NonPublic);

        var fontFaceLayoutInfo = fontFaceLayoutInfoProperty.GetValue(glyphTypeFace);
        var fontFaceLayoutInfoType = fontFaceLayoutInfo.GetType();
        var typographyAvailabilitiesField = fontFaceLayoutInfoType
            .GetField("_typographyAvailabilities", BindingFlags.NonPublic | BindingFlags.Instance);

        var typographyAvailabilitiesProperty
            = fontFaceLayoutInfoType
                .GetProperty("TypographyAvailabilities", BindingFlags.Instance | BindingFlags.NonPublic);

        // forces initialization of a few things
        typographyAvailabilitiesProperty.GetValue(fontFaceLayoutInfo);
        
        // the actual hack, fake some enum value that is suitable
        typographyAvailabilitiesField.SetValue(fontFaceLayoutInfo, 16);

`