Microtype protrusion doesn't work with hyperref in XeTeX

Question

See this basic MWE. Protrusion works beautifully.

\documentclass{article}
\usepackage[hidelinks]{hyperref}
\usepackage{microtype}
\begin{document}
Lorem ipsum dolor sit amet, consectetuer adipiscing elit. 
Ut purus elit, vestibulum ut, 
placerat ac, adipiscing vitae, felis. 
Curabitur dictum gravida mauris. Nam arcu libero, 
nonummy eget, consectetuer id, vulputate a, magna. Donec vehicula 
augue eu neque. Pellentesque habitant morbi 
tristique senectus et netus et malesuada fames ac turpis egestas. 
Mauris ut leo. Cras viverra metus rhoncus sem. 
\end{document}

Now, I add some \href{}{} command to the protruded comma and period:

\documentclass{article}
\usepackage[hidelinks]{hyperref}
\usepackage{microtype}
\begin{document}
Lorem ipsum dolor sit amet, consectetuer adipiscing elit. 
Ut purus \href{http://tex.stackexchange.com}{elit,} vestibulum ut, 
placerat ac, adipiscing vitae, felis. 
Curabitur dictum gravida mauris. Nam arcu libero, 
nonummy eget, consectetuer id, vulputate a, \href{http://tex.stackexchange.com}{magna.} Donec vehicula 
augue eu neque. Pellentesque habitant morbi 
tristique senectus et netus et malesuada fames ac turpis egestas. 
Mauris ut leo. Cras viverra metus rhoncus sem. 
\end{document}

As you can see when you compile the code above, protrusion stops working with hyperlinked characters.

• I discovered this issue is engine-specific. When I compile this with LaTeX or LuaLaTex, protrusion works. But when I compile this with XeLaTeX, protrusion doesn't work. Can I make it work with XeLaTeX?

Answer 1

Links in xelatex are done with a \special, a "whatsit" and they seem not to be transparent for protrusion. You can see a similar problem with \label. Imho it is a deficiency or a bug of the engine but the author of microtype could say something more definitive.

\documentclass{article}
\usepackage{microtype,tikz}
\begin{document}
\tikz[overlay]\draw[red](\textwidth-\parindent,0.5)--++(0,-20cm);%
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
Ut purus {elit,} vestibulum ut,
placerat ac, adipiscing vitae, felis.
Curabitur dictum gravida mauris. Nam arcu libero,
nonummy eget, consectetuer id, vulputate a, magna. Donec vehicula
augue eu neque. Pellentesque habitant morbi
tristique senectus et netus et malesuada fames ac turpis egestas.
Mauris ut leo. Cras viverra metus rhoncus sem.


Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
Ut purus \special{}{elit,}\special{} vestibulum ut,
placerat ac, adipiscing vitae, felis.
Curabitur dictum gravida mauris. Nam arcu libero,
nonummy eget, consectetuer id, vulputate a, \special{}magna.\special{} Donec vehicula
augue eu neque. Pellentesque habitant morbi
tristique senectus et netus et malesuada fames ac turpis egestas.
Mauris ut leo. Cras viverra metus rhoncus sem.

Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
Ut purus {elit,}\label{a} vestibulum ut,
placerat ac, adipiscing vitae, felis.
Curabitur dictum gravida mauris. Nam arcu libero,
nonummy eget, consectetuer id, vulputate a, magna.\label{b} Donec vehicula
augue eu neque. Pellentesque habitant morbi
tristique senectus et netus et malesuada fames ac turpis egestas.
Mauris ut leo. Cras viverra metus rhoncus sem.
\end{document}