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Re: [Texmacs-dev] TeXmacs source prerequisites

From: David Allouche
Subject: Re: [Texmacs-dev] TeXmacs source prerequisites
Date: Thu, 19 Jun 2003 10:39:21 +0200
User-agent: Mutt/1.5.4i

On Wed, Jun 18, 2003 at 11:52:05PM -0700, Salman Khilji wrote:
> I'd like to know what should be considered as prerequisites before a
> developer tries to understand/maintain/modify/enhance TeXmacs. I am
> talking about the kind of developer that has at least some sort of
> understanding about every asepct of TeXmacs and could possible say
> port TeXmacs to using Qt or GTK library. Or perhaps I am talking
> about Joris---everything that he had to learn before he started the
> project.

As you pointed out you need C++. Mostly the basics: classes, simple
inheritance, simple templates.

You need not know anything about the STL or other standard libraries
since TeXmacs implements its own fundation classes.

If you are aiming at a global understanding of the whole mess, Scheme
is also a prerequiste since a lot of the application logic (and more
in the future) is written in Scheme. Important parts currently include
the keymaps and menu definitions, a lot of GUI and editor policy, the
plugins and some conversion filters.

Depending on what you want to do, you might not need it at all. At the
moment, I think it may be possible to port texmacs to a new GUI
toolkit without touching the scheme code at all. Still, it is a good
idea to know the basics of Scheme (things like cons lists or sexps)
because it is likely to help you understand a lot of the C++ code.

> According to TeXmacs WiKi "TeXmacs dependancy on TeX is limited to fonts, 
> font 
> rendering and BibTeX".  Considering that I have never done "font rendering", 
> I would consider this as a prerequisite.  I studied:
> http://freetype.sourceforge.net/freetype2/docs/glyphs/index.html

Nice link. I would have to read it sometime.

> I went thru the above link to gain an understanding of what kinda of issues 
> are involved in font rendering.  So is there any documentation that I could 
> read that explains TeX fonts in detail?  FreeType does not seem to address 
> TeX fonts.  Where is the screen font rendering code in the source?  I'd like 
> to go through it and see how such beautiful rendering is implemented.

Font rendering is handled in two steps:

  1. Ask METAFONT to rasterize a font, then load the rasterized font
     file (.pk).

     It is important to understant that TeX fonts are fundamentally a
     different technology than PostScript/TrueType fonts. TeX fonts
     are brush-and-stroke based while TrueType fond are outline based.

     If you are interested in METAFONT, you should dig in the Don
     Knuth's litterature. Ther should be a "METAFONT Book" available
     near you.

     Check for source code in src/Resources/Fonts and

  2. Automatically hint the character bitmaps for the current
     shrinking factor in order to provide.

     The magic is done in src/Resources/Bitmap_fonts/shrink.cc.

     It is very likely that FreeType have better/faster/smarter hint
     and display features, but texmacs hinting generally does a decent

> Again, from TeXmacs Wiki, "MetaPost was a pain to implement (Joris' words)".  
> Having not ever used MetaPost in the past, I got from the homepage that 
> MetaPost is some sort of graphics language.  To me it seems like MetaPost is 
> implemented in TeXmacs (although I don't see anywhere it could have been used 
> since TeXmacs does not do graphics).  So is MetaPost a prerequisite.

Weird quote (from Alvaro)... there was some discussion on the mailing
list recently about how texmacs does not support MetaPOST... Or maybe
I misunderstood.

> Would anybody like to recommend a set of links and references that I can 
> consult to gain a better understanding of the theory behind the design of 
> TeXmacs.

The basics you have already: the developper mailing list and the
source code of texmacs.

As I said before, it would be a good thing to get familiar with Scheme
in order to better understand TeXmacs (even the C++ part). A good book
to start in Scheme is "The Structure and Interpretation of Computer
Programs". A html version is freely available.

Also, a very good book to read is "Design Patterns". It will present a
number of high-level constructs that will see in several places in
texmacs C++ code.

For the rest... well... read code, experiment and write code.

                                                            -- ddaa

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