Explore the internal font table

Explore an internal font table

Let us define a macro

\def\studyfont#1{\directlua0{
function printtable (ind,tableau,prof)
local k,l
texio.write_nl(string.rep("...",prof) .. ind .. " -> {")
prof=prof+1
for k,l in pairs(tableau) do 
if (type(l)=="table") then
printtable(k,l,prof)
else
texio.write_nl(string.rep("...",prof) .. k .. " -> " .. tostring(l))
end
end
texio.write_nl(string.rep("...",prof-1) .. "}")
end

for i,f in font.each() do
  if (f.name=="#1") then
    printtable("#1",f,0)
  end
end
}}

and apply it to cmr10 for example. (The font.each() has been added by Taco in checkout 573.) Here is what we get:

cmr10 -> {
...checksum -> 1274110073
...type -> real
...characters -> {
......1 -> {
.........italic -> 0
.........height -> 447828
.........depth -> 0
.........used -> false
.........width -> 546135
......}
......2 -> {
.........italic -> 0
.........height -> 447828
.........depth -> 0
.........used -> false
.........width -> 509726
......}
......3 -> {
.........italic -> 0
.........height -> 447828
.........depth -> 0
.........used -> false
.........width -> 455111
......}
......4 -> {
.........italic -> 0
.........height -> 447828
.........depth -> 0
.........used -> false
.........width -> 436908
......}
......5 -> {
.........italic -> 0
.........height -> 447828
.........depth -> 0
.........used -> false
.........width -> 491521
......}
......6 -> {
.........italic -> 0
.........height -> 447828
.........depth -> 0
.........used -> false
.........width -> 473316
......}
......7 -> {
.........italic -> 0
.........height -> 447828
.........depth -> 0
.........used -> false
.........width -> 509726
......}
......8 -> {
.........italic -> 0
.........height -> 447828
.........depth -> 0
.........used -> false
.........width -> 473316
......}
......9 -> {
.........italic -> 0
.........height -> 447828
.........depth -> 0
.........used -> false
.........width -> 509726
......}
......10 -> {
.........italic -> 0
.........height -> 447828
.........depth -> 0
.........used -> false
.........width -> 473316
......}
......11 -> {
.........kerns -> {
............63 -> 50973
............93 -> 50973
............39 -> 50973
............33 -> 50973
............41 -> 50973
.........}
.........italic -> 50973
.........ligatures -> {
............105 -> {
...............char -> 14
...............type -> 0
............}
............108 -> {
...............char -> 15
...............type -> 0
............}
.........}
.........height -> 455111
.........depth -> 0
.........used -> false
.........width -> 382295
......}

Glyph 11, namely the "ff" ligature has several kernings as well as two ligatures: one with i and one with l.

...another 1095 lines...

......127 -> {
.........italic -> 0
.........height -> 437688
.........depth -> 0
.........used -> false
.........width -> 327681
......}
......0 -> {
.........italic -> 0
.........height -> 447828
.........depth -> 0
.........used -> false
.........width -> 409601
......}
...}
...parameters -> {
......x_height -> 282168
......space_stretch -> 109226
......extra_space -> 0
......space -> 218453
......quad -> 655361
......space_shrink -> 72818
......slant -> 0
...}
...embedding -> unknown
...encodingbytes -> 0
...direction -> -1
...name -> cmr10
...size -> 655360
...used -> false
...format -> unknown
...designsize -> 655360
...area -> 
}

If you want to explore the internal font table you have just defined but not yet used, then do not forget to write a \relax after the font definition:

\font\x=something
\studyfont{something}

will NOT WORK. But:

\font\x=something\relax
\studyfont{something}

will work. (Thanks Taco for the hint!)