Re: [Plplot-devel] How do you specify special symbols and Greek letters with TrueType fonts?

[Rafael L. <rla...@us...>]

* Andrew Roach <aro...@ya...> [2004-05-18 22:05]:

> I agree with Rafael, and believe unicode is the way to go long term - it's 
> only an accident of 1980s 8 bit architecture we are stuck with ASCII's 256 
> characters. Translating between the Hershey fonts, unicode, then finding 
> freetype compatible fonts with the symbols would be the interesting part of
> the exercise.

In practical terms, we will have to make the functions pllab, plmtex, and
plptex become Unicode-aware. (N.B. : the remaining problem is with plsym,
which retains the semantics of the Hershey encoding.) This should not be
very complicated.  For instance, the following call in x03c.c:

    plmtex("t", 2.0, 0.5, 0.5, "#frPLplot Example 3 - r(#gh)=sin 5#gh");
    
would become:

    plmtex("t", 2.0, 0.5, 0.5, "#frPLplot Example 3 - r(θ)=sin 5θ");

where the funny sequence of 8-bit characters "θ" means "the lower-case
greek letter theta".  (Just cut & paste the line above, put it into a file
and open the file in a Web browser with character coding set to Unicode and
you will see a nice "theta"; at least, it works with my Mozilla 1.6.)

Of course, the old method would still be valid, and escaped sequences #g*
would be converted to the equivalent Unicode sequences.

To prove that it is really simple to use Unicode nowadays, I prepared a C
program using libunicode that decodes the string above.  It is attached
below along with its Makefile.  If you have the libunicode-dev package
installed (in Debian, at least), just type make and you will see:

$ make
gcc `unicode-config --libs --cflags` plunicode.c -o plunicode
./plunicode

UTF-8 decoding of string: "#frPLplot Example 3 - r(θ)=sin 5θ"

  1: 35
  2: 102
  3: 114
  4: 80
  5: 76
  6: 112
  7: 108
  8: 111
  9: 116
 10: 32
 11: 69
 12: 120
 13: 97
 14: 109
 15: 112
 16: 108
 17: 101
 18: 32
 19: 51
 20: 32
 21: 45
 22: 32
 23: 114
 24: 40
 25: 952
 26: 41
 27: 61
 28: 115
 29: 105
 30: 110
 31: 32
 32: 53
 33: 952

 
The characters at positions 25 and 33 have the code number 952.  This is
indeed the code for the lower-case greek theta (0x03B8), according to the
Unicode chart for the Greek glyphs
(http://www.unicode.org/charts/PDF/U0370.pdf).

The PLplot core routines would do different things with the Unicode
characters: either sending it directly to be plotted when using an
Unicode-aware driver (like gd with Unicode fonts), or lookup into a table
Unicode->Hershey and proceed with the plotting as it is the case today.

-- 
Rafael