[OS X TeX] Computer Modern in a Mac program

Doug McKenna doug at mathemaesthetics.com
Sun Oct 28 23:18:58 CET 2012

All -

I made a fair amount of progress before reading your latest round of 
helpful responses, so here's my summary of reality.

I found the Latin Modern and Latin Modern Math fonts on the GUST website, 
downloaded them, and got them installed in my ~/Library/Fonts folder, and 
they show up on FontBook.

Using Get Info on them in FontBook, I determined their official 
PostScript names.  Using these names, one can then use Core Graphics 
calls in one's source code to make one of the Latin Modern fonts the 
current font, and then draw a single glyph at a given position on the 
screen.  E.g., 

 CGContextSelectFont(context, "LatinModern-Regular", 10.0, 
kCGEncodingMacRoman );
 CGGlyph chCode = 'x';
 CGContextShowGlyphsAtPoint(g.context, x, y, &chCode, 1);

places an 'x' at the given coordinates (x,y).  So far so good!

I then found a discussion on the web that explained that Latin Modern 
were Unicode fonts, and eventually determined at


that the official Unicode code point for the summation symbol is, as 
Peter Dyballa also explained, U+2211.  Which led to this code snippet for 
testing the math font:

 CGContextSelectFont(context, "LModernMath-Regular", 10.0, 
kCGEncodingFontSpecific );
 CGGlyph chCode = 0x2211;
 CGContextShowGlyphsAtPoint(g.context, x, y, &chCode, 1);

(note that the math font name doesn't include the prefix "Latin" in its 
official PostScript name, just a single "L", which---unlike the text 
fonts---definitely makes it next-to-impossible to guess what its official 
name might be).

But setting |chCode| in the above to 0x2211 didn't work.  Nothing drew on 
the screen.

I then found the utility |ttfdump| on my Mac, and tried using it in 
Terminal to look at information inside the Latin Modern Math font file:

 ttfdump lmodern-math.otf

ttfdump is not very good, crashing with a segmentation fault just after 
it tried to dump an area called the 'loca' table.  But fortunately prior 
to that crash there's a fair amount of information to peruse.  In 
particular, searching the dump text for "2211" finds a mapping to an 
index 2822 (decimal, not hex).  So I tried that in my code above and 
voila, the sigma summation sign appeared on the screen!

So that solved my immediate problem, but now I've got one more: the 
glyph's baseline is obviously not the same as it is in the "lmex10.tfm" 
(or "cmex10.tfm") metrics files, where I determined that the glyph is 
(peculiarly) nearly all below the baseline (15 times as much below as 
above).  In Latin Modern, the baseline of the summation symbol appears to 
be about a quarter of the way up the glyph, with 3/4s of the glyph above 
the baseline.

In my various searches and researches, there are statements saying that 
Latin Modern is, with a few exceptions, the same as Computer Modern.  It 
seems I unluckily chose one of the few symbols that are an exception.

Does anyone know of an official (stable?) compendium of what (precisely) 
these metric differences are?

Doug McKenna

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