[dev-context] Difference between LM and CM font size

Aditya Mahajan adityam at umich.edu
Mon Feb 11 19:22:03 CET 2013


On Mon, 11 Feb 2013, Hans Hagen wrote:

> On 2/11/2013 2:18 AM, Aditya Mahajan wrote:
>> Hi,
>> 
>> While checking my context article for tugboat, Karl Berry found that
>> typewriter fonts were coming out a bit smaller than expected. The
>> following test file shows this:
>> 
>> \starttext
>> {\font\myfont = cmtt9 \myfont externalfigure[logo.pdf][width=1cm]}
>> 
>> {\font\myfont = ec-lmtt9 \myfont externalfigure[logo.pdf][width=1cm]}
>> \stoptext
>> 
>> With ConTeXt MkIV 2013.01.27 (and also with ConTeXt TL), I get the
>> attached output. Notice that the first and second line are of different
>> height.
>> 
>> Both lines are of the same height and width with MkII and with plain TeX.
>
> In context it all depends on how the lineheight (ratio ht/dp) is defined 
> which is:
>
> \setupinterlinespace
>  [height=.72,
>   depth=.28,
>   line=2.8ex]
>
> Also, in the opentype fonts we don't have the limitations of tfm with respect 
> to the number of different heights and depths - in fact, the ht/dp can be 
> derived from either the boundingbox or from the line properties defined in 
> the font.

I don't think that this has anything to do with height/depth radio. The 
physical size of the glyphs is smaller.

> So, as soon as one uses opentype fonts one is also incompatible with respect 
> to spacing (and even with type one there can be differences as one can decide 
> to overload dimensions in the afm -> tfm conversion, although in mkii we 
> always stuck to these automatically generated ones, and not the hand-tweaked 
> ones).
>
>> Any ideas on what is happening here? And more specifically, how can I
>> get a typing environment whose font size is the same as that of cmtt9.
>> Using
>
> Maybe tweak the interlinespace related settings as they also dictate the 
> struts (that are often put in front of verbatim lines).
>
>> \setuptyping[bodyfont=9pt]
>> 
>> switches to font size that is the same as ec-lmtt9 in the above example.
>
> (I found out that I couldn't test the cmtt9 because I haven't installed these 
> pfb files any longer. I'm surprised that I still did have some cmtt9 tfm 
> file, but that one gets mapped onto an lm counterpart visa the map file.)

FWIW, the size of lmtt10.tfm (or lmmono10-regular.otf) matches that of 
cmtt9! At least that suggests a workaround.

@Karl: Does,

\setuptyping[bodyfont=10pt]

or

\setuptyping[bodyfont=small, style=\tta]

give the right size, visually?

Aditya


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