This may or may not be a specific RichTextBox problem so I’m going to treat it like it is not.

The situation is that I’m displaying a document with text that can specify any font that it desires.  Of course, you cannot display text in a font that isn’t installed.  Silverlight 4 does not give any kind of font list by font name.

Wait! Fonts.SystemFontFaces will give you a list of all fonts installed on the local system.  It will give you a list of font FILE NAMES.  Not a list of actual font names.  There does not seem to be anyway to translate a font file name to a font name.  So that’s a big fat dead end.

Supposedly, Silverlight should just fall back on the system default which is “Portable User Interface” which is a best effort on Silverlight’s part to display text.  That ought to be fine for me when I’m trying to display a font that isn’t installed.

However, that isn’t what happens for the RichTextBox.  What does happen is that the RichTextBox decides to have a CATASTROPHIC FAILURE in it’s MeasureOverride method when trying to size up the box.  What seemingly happens is that the fallback mechanism just doesn’t work.  I’ve specified a font that doesn’t exist and Silverlight blows up.  Actually, it loops the exception for a while then throws up an unhandled crash box thing.  If I try to manually handle the error and give a reasonable size back, then it’s an infinite loop :)

The solution is to manually specify a fallback font when I’m setting the FontFamily through code:

new FontFamily(formatting.FontName + “, ” + TextFormatting.DefaultFontName);

DefaultFontName currently spits out “Arial” which is no good for non-latin languages.  So I’ll have to solve that later.  I had hoped I could simply put “Portable User Interface” to be the default but that doesn’t work at all.

If anyone knows of anything better, please comment.

Posted via email from Adam Hathcock’s Life in Software | Comment »