pdfs with boxes instead of letters

[Michael Green <merely.ridiculous@gmail.com>]

On Oct 30, 2009, Oliver Buerschaper wrote:

> > I seem to have spoken too soon. The very next document I prepared
> > had the same boxes-rather-than-letters problem.
> >
> > That said, I cleared the font caches again and, after restarting,
> > the document looked correct. Perhaps this is a coincidence. Or
> > perhaps there is something amiss with the way my computers are
> > caching fonts. Sigh.
>
> Well, if your engine is pdftex (from an unpatched TeXLive 2008) then
> chances are you're running into the nasty (TM) font cache bug:
>
> http://www.tug.org/mactex/fontcache/
>
> Oliver

The symptoms seem right: strange, unpredictable display problems with  
Apple's pdf software but not Adobe's. And it's not just pdftex,  
apparently. They say that luatex is affected too. That's primarily  
what I use. So we have both known symptoms (sort of - they're vague)  
and an allegedly known cause. Perhaps we have a diagnosis.

Here is Dick Koch, "A Fix for the Corrupt Font Cache Bug"

http://www.tug.org/mactex/fontcache/Font-Cache-Bugfix.pdf

> The “corrupt font cache bug” on OS X has been traced by Melissa  
> O’Neill to a bug in  pdftex, present in that program since 2004.  
> The incorrect code is also used in other  programs, notably dvips,  
> luatex, and metapost.  …
>
> The code containing the pdftex bug was used with little change in  
> modern versions of  dvips, so fixing the bug in dvips was not  
> difficult. However, it wasn’t so easy to find the  corresponding  
> code in luatex and metapost. Instead of waiting for decisive fixes  
> in these  programs, we decided to just release the fixed pdftex and  
> dvips. This should fix the bug  for most users. Notice that pdftex  
> is used when typesetting in “pdftex” mode and dvips  is used when  
> typesetting in “TeX and DVI” mode. XeTeX does not have the bug.

And in another document, "Looking over the Debugger’s Shoulders ",  
Koch summarizes what they discovered this way:

http://www.tug.org/mactex/fontcache/Debugging.pdf

> Two bugs contributed to the problem. First, pdftex, dvips, luatex,  
> and metapost were  not correctly subsetting certain fonts. And  
> second, a large number of fonts contained  subroutines which did not  
> conclude with a RETURN command. Many of these were  created with the  
> utility mmpfb, which has been patched.

Question: is this still a problem for luatex 0.44? (Please say no).

If not, perhaps I should clean my caches and use only MkII/XeTeX.

Even then, I gather that old documents created with luatex will still  
be little time bombs (see Appendix, below). I guess I have to delete  
all pdfs made by luatex and regenerate them as needed. That's a lot of  
documents.

"Nasty" is right. Oy.

mjg

Appendix: Koch's explanation of why the font cache might become  
corrupt seemingly for no reason at all.

http://www.tug.org/mactex/fontcache/Font-Cache-Bugfix.pdf

> When GUI programs display pdf files,  they call Apple’s internal  
> pdf routines. In turn, these routines call Apple’s font routines  
> to  construct bitmaps for the outline fonts. These Apple routines  
> store the bitmaps in a font  cache to speed up future display. For  
> reasons unknown until recently, this font cache can  become corrupt;  
> this is “triggered” by displaying a defective pdf file. After  
> that trigger,  display problems persist for all files. To fix the  
> problem, the font cache needs to be rebuilt,  as happens when the  
> machine is rebooted. Adobe Acrobat does not use Apple’s pdf  
> display  routines, so it is immune to the bug. ...
>
> Once you install the repaired pdftex and dvips binaries, pdf files  
> created by these programs  will not contain damaged fonts and thus  
> won’t trigger the bug. But unfortunately, your old pdf files may  
> still be damaged. In addition, users on other platforms won’t have  
> the  repaired binaries for some time, so pdf files sent by  
> colleagues may still be damaged and  trigger the bug. That is why  
> you may still experience the bug from time to time until the  TeX  
> world catches up.
>
> It isn’t even necessary to display an old damaged pdf file to  
> trigger the bug, because Apple’s  QuickLook software and the  
> software in Finder which gives a miniature version of the first   
> page in the file browser can trigger it. If you keep experiencing  
> the bug after applying the  fix, you may need to retypeset files  
> which you often open.

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