ConTeXt: specify a path to font in \definefontfamily

Question

I'm very new to ConTeXt, so please excuse the newbie question. I'm trying to load a font from a file. The .otf files are stored in a directory named fonts/ which is in the directory of the .tex file I'm trying to compile.

This code does not work, and reverts to the default font:

\definefontfamily [mainface][serif] [My Font]
                  [tf=file:./fonts/MyFont.otf,
                   it=file:./fonts/MyFont-It.otf,
                   bf=file:./fonts/MyFont-Bd.otf,
                   bi=file:./fonts/MyFont-BdIt.otf]

\setupbodyfont[mainface]                   

\starttext
\title{Hello, world!}

Hello World! \emph{Hi!}

\stoptext

However, if I copy the .otf files into the same directory as the .tex file, and write tf=file:MyFont.otf etc, then everything works fine.

How do I specify a relative path to the font, inside the .tex file?

In LaTeX, I would use fontspec package and do the following:

\setmainfont {MyFont.otf}
             [Path        =./fonts/,
              ItalicFont  = MyFont-It.otf]

However, I couldn't find the equivalent syntax for \definefontfamily in ConTeXt.

Just to mention, I am using ConTeXt version: 2019.03.21 21:39 as part of TeX Live, on Manjaro Linux.

Answer 1

Following the advice in the comments, I asked this question on the ConTeXt mailing list and got a reply from Hans Hagen. The solution is to add:

\ctxlua{os.setenv("RUNTIMEFONTS","./fonts")}

After that

\definefontfamily [mainface][serif] [My Font]
                  [tf=file:MyFont.otf,
                   it=file:MyFont-It.otf,
                   bf=file:MyFont-Bd.otf,
                   bi=file:MyFont-BdIt.otf]

works as expected.

However, I was also warned that this leaves garbage in the cache that can affect other projects that use different fonts with the same name, so the solution is to either clear the cache or rename the fonts to have a unique name. Ideally, however, fonts should be installed in texmf/fonts/ directory, but when that is not possible (e.g. for portability reasons), the above should work.