fix: explicit content in markdowntextblock

[JulesEmond]

Fixes

PR Type

What kind of change does this PR introduce?

What is the current behavior?

What is the new behavior?

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• New component
  • Pull Request has been submitted to the documentation repository instructions. Link:
  • Added description of major feature to project description for NuGet package (4000 total character limit, so don't push entire description over that)
  • If control, added to Visual Studio Design project
• Sample in sample app has been added / updated (for bug fixes / features)
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• New major technical changes in the toolkit have or will be added to the Wiki e.g. build changes, source generators, testing infrastructure, sample creation changes, etc...
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Header has been added to all new source files (run build/UpdateHeaders.bat)
• Contains NO breaking changes

Other information

[jeromelaban]

I don't think this will do. The RootElement is likely manipulated from the code behind, so this is unlikely to fix the issue (this control is not a ContentPresenter).

[JulesEmond]

I guess you are right. I think I found where the rendering actually happens

Uno.WindowsCommunityToolkit/CommunityToolkit.WinUI.UI.Controls.Markdown/MarkdownTextBlock/MarkdownTextBlock.Methods.cs

Lines 85 to 163 in 47a040a

	renderer.Background = Background;
	renderer.BorderBrush = BorderBrush;
	renderer.BorderThickness = BorderThickness;
	renderer.CharacterSpacing = CharacterSpacing;
	renderer.FontFamily = FontFamily;
	renderer.FontSize = FontSize;
	renderer.FontStretch = FontStretch;
	renderer.FontStyle = FontStyle;
	renderer.FontWeight = FontWeight;
	renderer.Foreground = Foreground;
	renderer.IsTextSelectionEnabled = IsTextSelectionEnabled;
	renderer.Padding = Padding;
	renderer.CodeBackground = CodeBackground;
	renderer.CodeBorderBrush = CodeBorderBrush;
	renderer.CodeBorderThickness = CodeBorderThickness;
	renderer.InlineCodeBorderThickness = InlineCodeBorderThickness;
	renderer.InlineCodeBackground = InlineCodeBackground;
	renderer.InlineCodeBorderBrush = InlineCodeBorderBrush;
	renderer.InlineCodePadding = InlineCodePadding;
	renderer.InlineCodeFontFamily = InlineCodeFontFamily;
	renderer.InlineCodeForeground = InlineCodeForeground;
	renderer.CodeForeground = CodeForeground;
	renderer.CodeFontFamily = CodeFontFamily;
	renderer.CodePadding = CodePadding;
	renderer.CodeMargin = CodeMargin;
	renderer.EmojiFontFamily = EmojiFontFamily;
	renderer.Header1FontSize = Header1FontSize;
	renderer.Header1FontWeight = Header1FontWeight;
	renderer.Header1Margin = Header1Margin;
	renderer.Header1Foreground = Header1Foreground;
	renderer.Header2FontSize = Header2FontSize;
	renderer.Header2FontWeight = Header2FontWeight;
	renderer.Header2Margin = Header2Margin;
	renderer.Header2Foreground = Header2Foreground;
	renderer.Header3FontSize = Header3FontSize;
	renderer.Header3FontWeight = Header3FontWeight;
	renderer.Header3Margin = Header3Margin;
	renderer.Header3Foreground = Header3Foreground;
	renderer.Header4FontSize = Header4FontSize;
	renderer.Header4FontWeight = Header4FontWeight;
	renderer.Header4Margin = Header4Margin;
	renderer.Header4Foreground = Header4Foreground;
	renderer.Header5FontSize = Header5FontSize;
	renderer.Header5FontWeight = Header5FontWeight;
	renderer.Header5Margin = Header5Margin;
	renderer.Header5Foreground = Header5Foreground;
	renderer.Header6FontSize = Header6FontSize;
	renderer.Header6FontWeight = Header6FontWeight;
	renderer.Header6Margin = Header6Margin;
	renderer.Header6Foreground = Header6Foreground;
	renderer.HorizontalRuleBrush = HorizontalRuleBrush;
	renderer.HorizontalRuleMargin = HorizontalRuleMargin;
	renderer.HorizontalRuleThickness = HorizontalRuleThickness;
	renderer.ListMargin = ListMargin;
	renderer.ListGutterWidth = ListGutterWidth;
	renderer.ListBulletSpacing = ListBulletSpacing;
	renderer.ParagraphMargin = ParagraphMargin;
	renderer.ParagraphLineHeight = ParagraphLineHeight;
	renderer.QuoteBackground = QuoteBackground;
	renderer.QuoteBorderBrush = QuoteBorderBrush;
	renderer.QuoteBorderThickness = QuoteBorderThickness;
	renderer.QuoteForeground = QuoteForeground;
	renderer.QuoteMargin = QuoteMargin;
	renderer.QuotePadding = QuotePadding;
	renderer.TableBorderBrush = TableBorderBrush;
	renderer.TableBorderThickness = TableBorderThickness;
	renderer.YamlBorderBrush = YamlBorderBrush;
	renderer.YamlBorderThickness = YamlBorderThickness;
	renderer.TableCellPadding = TableCellPadding;
	renderer.TableMargin = TableMargin;
	renderer.TextWrapping = TextWrapping;
	renderer.LinkForeground = LinkForeground;
	renderer.ImageStretch = ImageStretch;
	renderer.ImageMaxHeight = ImageMaxHeight;
	renderer.ImageMaxWidth = ImageMaxWidth;
	renderer.WrapCodeBlock = WrapCodeBlock;
	renderer.FlowDirection = FlowDirection;
	_rootElement.Child = renderer.Render();

I looked at Microsoft's documentation and MarkDownTextBlock doesn't have a content attribute