bug#38442: 27.0.50; segmentation fault switching to cairo

[Robert Pluim]

>>>>> On Mon, 2 Dec 2019 00:55:29 +0100, Juanma Barranquero <lekktu@gmail.com> 
>>>>> said:

    Juanma> I'm reluctant to filtering it out unconditionally, because the 
font-backend
    Juanma> is something the users can specify for themselves, perhaps to fix 
some
    Juanma> problem with their installation.

    Juanma> The "right" fix, I think, would be either:

    Juanma> - To filter it out when saving, if it is the default (i.e., 
'(harfbuzz gdi)
    Juanma> on Windows, currently), or
    Juanma> - To filter it out when loading, if the saved value is not 
supported on the
    Juanma> running instance of Emacs.

The latter makes sense.

    Juanma> The problem is, there's no way to get a list of supported font 
backends
    Juanma> from elisp, there is?

No, but we could add one, or you could compare on load to
(frame-parameter nil 'font-backend)

Robert