You might try
\documentclass[a4paper]{article}
\usepackage{ifxetex,ifluatex}
\newif\ifunicode
\ifxetex\unicodetrue\else\ifluatex\unicodetrue\fi\fi
\ifunicode
\usepackage{unicode-math}
\setmainfont[Ligatures=TeX,Fractions=On]{XITS}
\setmathfont{XITS Math}
\makeatletter
\let\@@@frac\frac
\def\frac#1#2{\sbox0{#1/#2}\sbox2{#1\phantom{/}#2}%
\ifdim\wd0=\wd2 % no corresponding character
\@@@frac{#1}{#2}%
\else
\mbox{#1/#2}%
\fi}
\makeatother
\fi
\begin{document}
1/2$\frac{1}{2}\frac{12}{11}$
\end{document}
Here I assume that a vulgar fraction width is different than the width of the slashed form, which seems rather likely to happen.
However I would advise not to use vulgar fractions in a mathematical context.
I got it working with a lua script. Your minimal example becomes:
\documentclass{minimal}
\usepackage{unicode-math}
\setmathfont{XITS Math}
\AtBeginDocument{\directlua{require("combining_preprocessor.lua")}}
\newcommand{\⃗}[1]{\ensuremath{\vec{#1}}}
\begin{document}
$v⃗$
\end{document}
The idea is that it's difficult to make LaTeX handle a command or macro that comes after its argument, which is how Unicode combining characters work, so we use would like a preprocessor to move the accent so it comes before its argument. That is, map v⃗ to \⃗{v} in a script, and then define whatever action you want \⃗ to have. (That's a backslash followed by a combining arrow, which should be printed above the backslash.)
My lua script does most (all?) of the combining characters, so you just need to define what they should do in the .tex file. Many accents on the same character is possible. Example:
\documentclass{minimal}
\usepackage{unicode-math}
\setmathfont{XITS Math}
\AtBeginDocument{\directlua{require("combining_preprocessor.lua")}}
\newcommand{\̂}[1]{\ensuremath{\hat{#1}}}
\newcommand{\⃑}[1]{\ensuremath{\vec{#1}}}
\newcommand{\̱}[1]{\ensuremath{\underline{#1}}}
\newcommand{\́}[1]{\ensuremath{\acute{#1}}}
\usepackage{stackrel}
\newcommand{\᷽}[1]{\ensuremath{\stackrel[\approx]{}{#1}}}
\begin{document}
Hello
$ℂ̂$ is hat on $ℂ$, more on $ℂ̂⃑$ (stress test)
$ℂ̂ x̂$
Many combining accents on $x᷽̱̂́⃑$ is cool.
\end{document}
(My browser doesn't do the many combining characters justice here, but it looks nice in the PDF file.)
Not sure if this is the ideal way of doing things, but for what it's worth, here is combining_preprocessor.lua:
function minornil(a, b)
if a == nil and b == nil then
return nil
elseif a == nil then
return b
elseif b == nil then
return a
else
return math.min(a, b)
end
end
function findfirstcombining(line, n)
local a = string.find(line, "\204[\128-\191]", n) -- From U0300,
local b = string.find(line, "\205[\128-\175]", n) -- to U036F.
a = minornil(a, b)
b = string.find(line, "\226\131[\144-\176]", n) -- U20D0 to U20F0
a = minornil(a, b)
b = string.find(line, "\225\183[\128-\191]", n) -- U1DC0 to U1DFF
a = minornil(a, b)
return a
end
function is_utf8_continuation(byte)
return byte < 191 and byte > 127
end
function find_next_utf8_char(str, n)
while str:byte(n) ~= nil and is_utf8_continuation(str:byte(n)) do
n = n + 1
end
return n
end
function combining_iter(str)
local n = 0
return function ()
n = (n ~= nil) and findfirstcombining(str, n + 1)
return n
end
end
function dobuffer(line)
local n1 = 0
local t = {}
for n2 in combining_iter(line) do
if n2 > n1 then
local n3 = n2
repeat
n3 = n3 - 1
until not is_utf8_continuation(line:byte(n3))
table.insert(t, string.sub(line, n1, n3 - 1))
n1 = find_next_utf8_char(line, n2 + 1)
local comb = {}
table.insert(comb, "\\" .. string.sub(line, n2, n1 - 1) .. "{")
table.insert(comb, string.sub(line, n3, n2 - 1) .. "}")
n2 = findfirstcombining(line, n1)
while n2 == n1 do
n1 = find_next_utf8_char(line, n2 + 1)
table.insert(comb, 1, "\\" .. line:sub(n2, n1 - 1) .. "{")
table.insert(comb, "}")
n2 = findfirstcombining(line, n1)
end
table.insert(t, table.concat(comb))
end
end
table.insert(t, string.sub(line, n1))
return table.concat(t)
end
luatexbase.add_to_callback("process_input_buffer",
dobuffer, "combining_preprocessor", 1)
Best Answer
You might use the
old-arrowspackage that provides arrows with smaller tips. However, using the package would change all arrows in the document, which is possibly not desired, so we can fetch just the necessary bits:The definitions for
\smallrightarrowand\smallleftarroware not required, but they make no harm.