This is a follow-up question to Restriction of a function: the subscript seems too low.
Typesetting the following math formulas with kpfonts
\documentclass{article}
\usepackage{kpfonts-otf}
\begin{document}
$\left.g\right\vert, \left.g\right\Vert$
\end{document}
produces a vertical bar that does not go sufficiently low to cover the descender of g
. By contrast, the double vertical bar goes low enough.
The single bar is a single character:
\TU/KpMath-Regular.otf(1)/m/n/10 ๐
\vbox(8.85+0.0)x3.09, shifted 1.925, direction TLT
.\hbox(7.13+1.72)x3.09, direction TLT
..\TU/KpMath-Regular.otf(1)/m/n/10 |
The double bar is a constructed from an extensible character:
\TU/KpMath-Regular.otf(1)/m/n/10 ๐
\vbox(12.0+0.0)x5.18, shifted 3.5, direction TLT
.\hbox(0.11+4.61)x5.18, direction TLT
..\TU/KpMath-Regular.otf(1)/m/n/10 ๎ฉ
.\glue -1.57 plus 1.37001
.\hbox(7.13+1.72)x5.18, direction TLT
..\TU/KpMath-Regular.otf(1)/m/n/10 โ
When typesetting the same with Computer Modern instead of kpfonts, both vertical bars behave the same (a single character in both cases):
\OML/cmm/m/it/10 g
\kern0.35878 (italic)
\hbox(7.5+2.5)x2.77779, direction TLT
.\OMS/cmsy/m/n/10 j
\OML/cmm/m/it/10 g
\kern0.35878 (italic)
\hbox(7.5+2.5)x5.00002, direction TLT
.\OMS/cmsy/m/n/10 k
Why does the single vertical bar in kpfonts not behave in the same way as the double vertical bar?
Additional remark after reading the answer
The answer says
\vert
is not extended (this is a bug)
But the vertical bar after a taller formula
$$\left.g\over h\right\vert$$
is extended:
\hbox(11.48+6.96)x7.62999, direction TLT
.\hbox(0.0+0.0)x1.2, shifted -2.5, direction TLT
.\vbox(11.48+6.96)x5.23, direction TLT
..\hbox(4.64+2.59)x5.23, glue set 0.28fil, direction TLT
...\glue 0.0 plus 1.0fil minus 1.0fil
...\TU/KpMath-Regular.otf(1)/m/n/10 ๐
...\glue 0.0 plus 1.0fil minus 1.0fil
..\kern1.5 (font)
..\rule(0.5+0.0)x*
..\kern1.89 (font)
..\hbox(7.22+0.1)x5.23, direction TLT
...\TU/KpMath-Regular.otf(1)/m/n/10 โ
.\hbox(0.0+0.0)x1.2, shifted -2.5, direction TLT
\vbox(17.03398+0.0)x3.09, glue set 0.68758, shifted 6.017, direction TLT
.\hbox(0.11+4.61)x3.09, direction TLT
..\TU/KpMath-Regular.otf(1)/m/n/10 ๎
.\glue -1.57 plus 1.37001
.\hbox(0.11+4.61)x3.09, direction TLT
..\TU/KpMath-Regular.otf(1)/m/n/10 ๎
.\glue -1.57 plus 1.37001
.\hbox(7.13+1.72)x3.09, direction TLT
..\TU/KpMath-Regular.otf(1)/m/n/10 |
\left.g\right\vert
and\left.g\right\Vert
having different sizes. Instead, it appears to be with the fact that the bar drawn by\left.g\right\vert
"does not go sufficiently low to cover the descender ofg
", i.e., it's too short. The height of the vertical bars is a choice variable for the font designer. It's well known that the\vert
and\Vert
symbols drawn by Palatino-type math fonts are quite short -- and, in particular, "do not go sufficiently low to cover the descender ofg
".\Vert
does go low enough, thus behaving differently from\vert
.\Vert
does go low enough, thus behaving differently from\vert
". Sorry, but that's false: Both\vert
and\Vert
draw bars that have the exact same depth -- which you have criticized as as being "too short", since they don't cover the descender ofg
. What you have come across is that\left.g\right\vert
and\left.g\right\Vert
create symbols of different heights. To me, the question is not why the symbol drawn by\left.g\right\vert
is too short; instead, it shoud be why the symbol drawn by\left.g\right\Vert
is needlessly tall.