> From: Stefan Monnier <monnier@iro.umontreal.ca> > Cc: emacs-devel@gnu.org > Date: Tue, 29 Nov 2022 22:31:26 -0500 > > >> I'm trying to write a test for our font choice code (bug#59347) > > Is it useful? > > We've had a fair bit of regressions in our font-selection code over the > years, and some of those have happened several times, so I think it > would be useful, yes. I was asking whether the particular approach you've chosen to implement such tests was useful. Not whether having tests about font selection in general would be useful (which has a trivial answer). > > This test will work only on your platform and maybe on a few > > other lucky ones. > > Sounds like a good reason to add more tests to cover other cases. Not if all of them will have the same disadvantage. > [ FWIW, Dejavu Sans is very widespread under GNU/Linux, AFAIK, and > misc-fixed used to be very widespread as well, so there's a chance > I'm not the only one where this test can run. ] A useful test should be runnable by more than just a handful. From where I stand, any test that I cannot run on my system is useless as a test. > > I suggest to defer coding of the test until we fully understand the > > problem, and then try to write the test in some generic way > > independent of specific font families. > > Writing tests for the font code is not super easy, so I'd rather we get > started earlier than wait for some hypothetical future. It's much > easier to improve/extend existing tests than trying to figure out how > the hell can we test GUI code in batch mode. My point is that without understanding that problem fully, we don't know what should be the expected results of a correctly-working Emacs. > > ...why do you need to go to these obscure entities, when you have the font's > > name as a string to begin with? So you should be able to: > > > > . use face-font, which returns the font's name as a string > > I'm not sure `face-font` will faithfully reproduce the result I'll see > on my screen. > > > . compare that string with what you wanted it to be > > I'd rather not hard code any specific font name, actually, which is why > my code was written to just check that we get one of the available fonts > from the "DejaVu Sans" family. > > > . and/or use find-font to check whether the font is in fact installed on > > the system > > How does that compare to `list-fonts`? It avoids the problems you said got in your way. Anyway, you asked for help in overcoming practical difficulties, and I tried to do my best to help. If my suggestions aren't useful, feel free to ignore them (but know that I did base them on running and well-tested code which needed to overcome similar obstacles while I was writing it).
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