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One of the exceptions I see with a reasonable frequency (usually in Gif Animator) is Only TrueType fonts are supported. This is not a TrueType font.

System.ArgumentException: Only TrueType fonts are supported. This is not a TrueType font.
  at System.Drawing.Font.FromLogFont(Object lf, IntPtr hdc)
  at System.Windows.Forms.FontDialog.UpdateFont(LOGFONT lf)
  at System.Windows.Forms.FontDialog.RunDialog(IntPtr hWndOwner)
  at System.Windows.Forms.CommonDialog.ShowDialog(IWin32Window owner)

This exception is thrown when using the System.Windows.Forms.FontDialog component and you select an invalid font. And you can't do a thing about it*, as this exception is buried in a private method of the FontDialog that isn't handled.

As the bug has been there for years without being fixed, and given that fact that Windows Forms isn't exactly high on the list of priorities for Microsoft, I suspect it will never be fixed. This is one wheel I'd prefer not to reinvent, but... here it is anyway.

The Cyotek.Windows.Forms.FontDialog component is a drop in replacement for the original System.Windows.Forms.FontDialog, but without the crash that occurs when selecting a non-True Type font.

This version uses the native Win32 dialog via ChooseFont - the hook procedure to handle the Apply event and hiding the colour combobox has been taken directly from the original component. As I'm inheriting from the same base component and have replicated the API completely, you should simply be able to replace System.Windows.Forms.FontDialog with Cyotek.Windows.Forms.FontDialog and it will work.

There's also a fully managed solution buried in one of the branches of the repository. It is incomplete, mainly because I wasn't able to determine which fonts are hidden by settings, and how to combine families with non standard styles such as Light. It's still interesting in its own right, showing how to use EnumFontFamiliesEx and other interop calls, but for now it is on hold as a work in progress.

I haven't actually managed to find a font that causes this type of crash, although I have quite a few automated error reports from users who experience it. If you know of such a font that is (legally!) available for download, please let me know so that I can test this myself. I assume my version fixes the problem but at this point I don't actually know for sure.

The source is available from GitHub.

A NuGet package is available.

Install-Package Cyotek.Windows.Forms.FontDialog

The FontDialog component is licensed under the MIT License. See LICENSE.txt for the full text.

* You might be able to catch it in Application.ThreadException or AppDomain.CurrentDomain.UnhandledException (or even by just wrapping the call to ShowDialog in a try ... catch block), but as I haven't been able to reproduce this crash I have no way of knowing for sure. Plus I have no idea if it will leave the Win32 dialog open or destabilize it in some way

• 2015-08-15 - First published
• 2020-11-21 - Updated formatting

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