[BUG] Cannot proceed without the font: [...].woff2 problem

[Nikolay Shaplov]

Some users (me included) reports getting error message

xdvipdfmx:fatal: Cannot proceed without the font: /home/nataraj/.local/share/
fonts/Gilroy-Regular.woff2

wile running xelatex utility. File /home/nataraj/.local/share/fonts/Gilroy-
Regular.woff2 actually exists, and this confuses most of all.

Users at https://bbs.archlinux.org/viewtopic.php?id=263072 also report same 
thing.

I managed to figure out how to reproduce it, and how to work it around. But I 
am not able to fix it. I hope you will do it.

How to reproduce:

1. Take test.tex from the attachment.
2. Download  Gilroy font from  https://xfonts.pro/font-family/gilroy (Or find 
it in ant other place. We need .woff2 format here)
3. Put all content of font.zip into ~/.local/share/fonts or where ever user's 
font should be placed in your system
4. Run fc-cache -f -v to make sure fonts are properly indexed (Or similar 
thing for non-debian systems)
5. Run 
   xelatex test
6. Get an error 

xdvipdfmx:fatal: Cannot proceed without the font: /home/nataraj/.local/share/
fonts/Gilroy-Regular.woff2

This /home/nataraj/.local/share/fonts/Gilroy-Regular.woff2 file actually exists  
and this confuses a lot.

What Causes The Bug:

texk/dvipdfm-x/dvi.c has a code

  if ((path = dpx_find_dfont_file(filename)) != NULL &&                         
      (fp = MFOPEN(path, "rb")) != NULL)                                        
    is_dfont = 1;                                                               
  else if ((path = dpx_find_type1_file(filename)) != NULL)                      
    is_type1 = 1;                                                               
  else if (((path = dpx_find_opentype_file(filename)) == NULL                   
         && (path = dpx_find_truetype_file(filename)) == NULL)                  
         || (fp = MFOPEN(path, "rb")) == NULL) {                                
    ERROR("Cannot proceed without the font: %s", filename);                     
  }      

It tries to open font file this way or that way and if there is no success it 
throws an error. 

Suggestion how to fix it:

1. I guess .woff2 fonts should be ignored at all, if they can't be properly 
loaded. (I actually do not know what is woff2 and how it should work, the only 
thing I know: it does not work)

2. If there is still font file that can't be loaded, you should have different 
error texts for cases: "can't open a font file", and "Font file format is not 
supported", so people were not confused anymore if they have some broken font 
file, or font-file with unsupported version or something.

Since I do not understand many things here I will dare not suggesting a patch.

Workaround:

I've just deleted all .woff and .woff2 files from ~/.local/share/fonts and 
everything started working for me.

I hope somebody will manage to fix that, and there won't be any problems with 
that strange error message

-- 
Nikolay Shaplov aka Nataraj
Fuzzing Engineer at Postgres Professional
Matrix IM: @dhyan:nataraj.su
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