Does anyone know of any reason why it would be difficult/impossible to build an interactive user interface for Metafont ?

I'm not talking about a "drawing" interface where you drag control points around the screen (like Fontographer, etc). But, rather, a system that would allow interactive adjustment of the font parameter values, with near-real-time display of some sort of preview (a single character, or some chosen group of characters).

Some conceivable reasons why this might be impossible are:

(1) MF rasterization is too slow to support this type of interactive work

(2) The internal architecture of the system is essentially "batch job" oriented, and can not support this sort of "incremental" editing

(3) The code is impossible to understand

Are these reasons valid? Any other known roadblocks?

Edit: I found a thing called metaflop modulator. http://www.metaflop.com/modulator. Its name is puzzling, but it's roughly the kind of thing I had in mind. It has a client-server architecture, rather than the rich desktop app I envisioned. Also, the fonts shown only have about 14 parameters, which is fewer than I expected. But, it seems to work OK, so this seems to indicate that there are no fundamental barriers.

  • 4
    I think the usefulness of such an interface would be rather limited, because (a) a metafont definition is essentially a computer program, even a highly modularized one. The number and influence of parameters which can be adjusted by an interactive interface would be extremely limited, and (b) the idea of creating fonts with a system whose only output option are bitmap graphics is really outdated. Commented Nov 18, 2012 at 5:38
  • Especially the 3rd point that @StephanLehmke mentions. Metafont was very good program when Knuth introduced it (produced fonts at any dpi from a text file, so it had small disk usage and still allowed all the fonts needed). Now, most of the fonts are stored as curves allowing unlimited scalability, and Metafont is not capable of producing such fonts AFAIK.
    – yo'
    Commented Nov 18, 2012 at 9:00
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    @tohecz -- it is possible to produce outline fonts from Metafont, though the process is roundabout and problematic (as far as I know). So, the whole point of the "previewer" I described is to make sure you have the parameter values correct before you go through all the trouble of creating an outline font. But, again, this is a discussion of usefulness, and what I asked about was feasibility.
    – bubba
    Commented Nov 18, 2012 at 9:18
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    None of the three reasons you mention is valid. The main problem I see is that users are free to set any number of parameters that control the font appearance. The second problem is, as I have already commented, that Metafont's model is different from drawing programs: its best feature is the ability of solving linear equations. It's not "point and click".
    – egreg
    Commented Nov 18, 2012 at 10:58
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    @egreg -- as I said in the question, I'm not talking about a "drawing" interface where you drag control points around the screen. The metaflop program I mentioned is not point and click, and, as I said, it's fairly close to what I had in mind.
    – bubba
    Commented Nov 18, 2012 at 12:30

2 Answers 2


There is a thing called metaflop modulator http://www.metaflop.com/modulator, which is roughly the kind of thing I had in mind. It seems to work OK, so this seems to indicate that there are no fundamental barriers.


Since Metafont outputs bitmap fonts, you are not restricted to using only lines, arcs, and quadratic and cubic curves to describe the shapes of the glyphs. But the subsequent vectorization (which can give pretty messy results; also I assumed you were interested in generating vector fonts) clearly renders useless all the efforts one may have made polishing their Metafont source. So if you want to see useful interactive counterpart of Metafont, you have to forget about erasing, exquisite pens and so on. As far as other features of Metafont are concerned, it's actually not that hard create Metafont with some sort of GUI. I've created one myself recently, just for fun - http://www.epilib.com/mf.

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    At first glance the links seems to be a 'commercial' one, this is not the case. A screenshot of the gui would be nice, such that other users reading this answer can decide whether they should follow the link. Welcome to TeX.SX!
    – user31729
    Commented Sep 22, 2014 at 18:55
  • Nice seeing everyone here, too. Sorry, did not intend it to look like a commercial, if that's what you mean. Commented Sep 22, 2014 at 19:01
  • That's why I wrote 'at first glance' ;-)
    – user31729
    Commented Sep 22, 2014 at 19:07
  • The epilib.com site seems to be off-line --- anyone know of an updated URL or other source for the code?
    – WillAdams
    Commented Aug 23, 2019 at 14:22

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