Hagen - Pragma ADE

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3.1 Introduction
In traditional T E X a font is defined by referring to its filename. A definition looks like
this:
\font \MyFontA = lmr10
\font \MyFontB = lmr10 at 20pt
\font \MyFontC = lmr10 scaled 1500
The first definition defines the command MyFontA as a reference to the font stored in the
file lmx10. No scaling takes place so the natural size is taken. This so called designsize
is in no way standardized. Just look at these three specimen:
Design Size (Dejavu)
Design Size (Cambria)
Design Size (Latin Modern)
The designsize is normally 10 point, but as there is no real reference for this a designer
decides how to translate this into a visual representation. As a consequence the
20pt in the second line of the example definitions only means that the font is scaled to
(normally) twice the designsize. The third line scaled by a factor 1.5 and the reason for
using a value thousand times larger is that T E X’s numbers are integers.
The next three lines are typical for Latin Modern (derived from Computer Modern)
because this family comes in different design sizes.
\font \MyFontD = lmr12
\font \MyFontE = lmr12 at 20pt
\font \MyFontF = lmr12 scaled 1500
Because the designsize is part of the font metrics the second line (\MyFontE) is of similar
size as \MyFontB although the 12 point variant is visually better suited for scaling up.
These definitions refer to files, but what file? What gets loaded is the file with name
name.tfm. Eventually for embedding in the (let’s assume pdf) file the outlines are taken
from name.pfb. At that stage, when present, a name.vf is consulted in order to resolve
characters that are combinations of others (potentially from other pfb files). The mapping
from name.tfm to name.pfb filename happens in the so called map file. This means
that one can also refer to another file, for instance name.ttf.
All this logic is hard coded in the engine and because the virtual font mechanism was
introduced later without extending the tfm format, it can be hard at times to figure out
issues when a (maybe obsolete) virtual file is present (this can be the case if you have
generated the tfm file from an afm file that comes with the pfb file when you buy one.
But, in LuaT E X we no longer use traditional fonts and as a consequence we have more
options open. Before we move on to them, we mention yet another definition:
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