pick a named instance of a variation font without installed it first

[typemytype]

installFonts(...) is deprecated in favour of providing a font path... but for a variation font a script must be able to select a named instance, now the fontName is a path and not a PS font name.

I would like to propose something similar to fontNumber

font(path, namedInstance="myCool-Regular")

https://github.com/typemytype/drawbot/blob/master/drawBot/drawBotDrawingTools.py#L1312

this should raise an error when the current font is not a variation font and warn when the name instance is not available

[justvanrossum]

It could also be a variant of fontVariations(). In a way, named instances are just shortcuts for designspace locations.

[justvanrossum]

    def fontVariations(self, namedInstance=None, **axes):
        if namedInstance is not None:
            assert not axes
            ...select named instance...
        else:
            ...select location from axes...

[typemytype]

True, only those named instances have already their own listFontVariations and named instances are not listed there.

So to make it similar it could also be fontNamedInstance(name)

[justvanrossum]

fontNamedInstance(name) is fine with me, too.

We'd need to ensure this also works with installed fonts.

[typemytype]

we store the fontNameOrPath in self._font, see

if this is not a path then fontNamedInstance(Name) would just redirect to font(name)

[justvanrossum]

if this is not a path then fontNamedInstance(Name) would just redirect to font(name)

Hm, so this would "work"?:

font("Helvetica")
fontNamedInstance("A-Named-Instance-From-An-Unrelated-VF-That-Is-Installed")

Either we provide something that works transparently (and intuititely) for both installed and path-based fonts, or we need to make clear this funtionality is specific to path-based fonts. The latter is not something we currently have I think.

[typemytype]

It should test if the font has an instance with that name, otherwise raise or warn (redirect wasnt the smartest plan :) )

[typemytype]

oke, proposal:

from drawBot.misc import DrawBotError

def fontNamedInstance(name):
    instances = listNamedInstances()
    if name in instances:
        fontVariations(**instances[name])    
    else:
        raise DrawBotError(f"Can not find instance with name: '{name}'.")

font("Skia", 200)        
fontNamedInstance("Skia-Regular_Black-Extended")
fontNamedInstance("Skia-Regular_Light-Extended")

text("abc", (50, 50))