\SetTracking in the math environment

Question

I have been trying to use the \SetTracking option in microtype to shrink a paragraph that has some text and math. However, I notice that only the text - and not the math fonts - are being adjusted. The MWE below samples one such scenario:

    % START PREAMBLE
    \documentclass[12pt]{report}
    \usepackage[margin=1.25in]{geometry}

    %Required math packages
    \usepackage{amsmath}
    \usepackage{bm}
    \newcommand\vect[1]{\bm{#1}}%bm{#1}

    %Document and typesetting
    \usepackage{setspace}
    \linespread{1.5}
    \setlength{\parindent}{0in}

    %Microtyping
    \usepackage{microtype}

    % END PREAMBLE

    \begin{document}

    This is without any tracking:

    $
    {{\vect{\varphi }}_{{qj}}} = ({\Psi _{qj1,{m_{qj1}} - 1,}} {\Psi _{qj2,{m_{qj2}} - 1,}},\dots, {\Psi _{qjS,{m_{qjS}} - 1}}),
    {{\vect{\varphi }}_{q}} = ({{\vect{\varphi }}_{{q1}}}, {{\vect{\varphi }}_{{q2}}},\dots, {{\vect{\varphi }}_{{qJ}}}),$
    and 
    ${\vect{\varphi}} = ({{\vect{\varphi}}_{1}}, {{\vect{\varphi}}_{2}},\dots, {{\vect{\varphi}}_{Q}})$
    and 
    ${{\vect{\vartheta}}_{qj}}{\rm{ }} = {\rm{ (}}{\Psi _{qj1,{m_{qj1}},{\rm{ }}}}{\rm{ }}{\Psi _{qj2,{m_{qj2}},{\rm{ }}}},\dots,{\rm{ }}{\Psi _{qjS,{m_{qjS}}}}){\rm{, }}
    {\vect{\vartheta }_{q}} = {\rm{(}}{\vect{\vartheta }_{{q1}}}, {\vect{\vartheta }_{{q2}}}{\rm{ , }}\dots{\rm{, }}{\vect{\vartheta }_{{qJ}}})$
    and 
    $\vect{\vartheta } = {\rm{ (}}{\vect{\vartheta }_{1}}, {\vect{\vartheta }_{2}},\dots, {\vect{\vartheta }_{Q}}).
    $

    \vspace{7mm}

    This is with tracking:

    \SetTracking[spacing={-50*,0*,50*}]{encoding={OT1,T1,TS1,OML,OMS,OMX,U}}{-30}
    \textls{${{\vect{\varphi }}_{{qj}}} = ({\Psi _{qj1,{m_{qj1}} - 1,}} {\Psi _{qj2,{m_{qj2}} - 1,}},\dots, {\Psi _{qjS,{m_{qjS}} - 1}}),
    {{\vect{\varphi }}_{q}} = ({{\vect{\varphi }}_{{q1}}}, {{\vect{\varphi }}_{{q2}}},\dots, {{\vect{\varphi }}_{{qJ}}}),$
    and 
    ${\vect{\varphi}} = ({{\vect{\varphi}}_{1}}, {{\vect{\varphi}}_{2}},\dots, {{\vect{\varphi}}_{Q}})$
    and 
    ${{\vect{\vartheta}}_{qj}}{\rm{ }} = {\rm{ (}}{\Psi _{qj1,{m_{qj1}},{\rm{ }}}}{\rm{ }}{\Psi _{qj2,{m_{qj2}},{\rm{ }}}},\dots,{\rm{ }}{\Psi _{qjS,{m_{qjS}}}}){\rm{, }}
    {\vect{\vartheta }_{q}} = {\rm{(}}{\vect{\vartheta }_{{q1}}}, {\vect{\vartheta }_{{q2}}}{\rm{ , }}\dots{\rm{, }}{\vect{\vartheta }_{{qJ}}})$
    and 
    $\vect{\vartheta } = {\rm{ (}}{\vect{\vartheta }_{1}}, {\vect{\vartheta }_{2}},\dots, {\vect{\vartheta }_{Q}}).
    $
    }

    \end{document}

We can clearly discern that only the and within the paragraph is being changed - the math fonts remains the same. How can I get around this issue?

Answer 1

This is a similar bug in microtype as the one you stumbled upon in pdfTeX font expansion error - \SetExpansion in microtype package. Fix it by adding the following lines to the preamble:

\makeatletter
\DeclareRobustCommand\lsstyle{%
  \not@math@alphabet\lsstyle\textls
  \let\glb@currsize\@empty % <- added
  \def\MT@feat{tr}%
  \let\MT@tracking\MT@set@tr@codes
  \selectfont
}
\makeatother

It seems like I should take a closer look at math font setup again.