Bdtjtk

The attached example (not really an MWE) explains the problem better than I probably can here:

% !TeX program = xelatex

documentclass{scrreprt}

usepackage{siunitx}

    sisetup{%

%       detect-mode,

%       detect-all,

%       detect-display-math,

%       math-rm=mathnormal,

            }%

usepackage{unicode-math}

    setmainfont[Numbers=OldStyle,Color=2244FF]{TeX Gyre Pagella}

    setmathfont[Numbers=Lining,Color=FF4422]{TeX Gyre Pagella Math}%lining as 'opposite' of OldStyle



linespread{1.3}



begin{document}

    Wanted behaviour:



    Text-Style numbers: 123456789.  Math-Style numbers: (123456789).



    In Display-Math, only the math font should be used. This works:

    begin{equation}

        f(x) = 23.1(2) times 10^{-2} x^2

    end{equation}

    However, textit{siunitx} does not detect the (surrounding) math font and sets its digits using the text font. Triggering textit{detect-all} does not change this either:



%   sisetup{detect-all}



    begin{equation}

        f(x) = num{23.1(2)e-2} x^2 

    end{equation}

    Even explicitly requesting math-font does not seem to work:

    begin{equation}

        num{10} quad SI{20}{newton} quad SI[mode=text]{30}{newton} quad SI[mode=math]{40}{newton} quad SI[number-mode=math]{50}{newton}.   

    end{equation}



    Does not work outside of math mode either. These are expected to use math mode:



    SI[mode=math]{40}{newton} quad SI[number-mode=math]{50}{newton}.



    This approach seems to work, since it will always use the math-font for its numbers and picks the text-font for its units, textbf{as long as we are in math-mode}:



    sisetup{number-math-rm=mathnormal,unit-math-rm=mathrm,detect-mode}



    (SI{40}{newton}) quad SI{40}{newton} quad (num{45.2(1)e-2}) quad num{45.32(12)e-27}



    However, if we try to replicate the same for text-mode, an error is thrown:



%   sisetup{number-text-rm=mathnormal,unit-text-rm=textrm}



%   (SI{40}{newton}) quad SI{40}{newton} quad (num{45.2(1)e-2}) quad num{45.32(12)e-27}



    vspace{2baselineskip}



    Also, if we use textit{mathrm} instead of textit{mathnormal}, it no longer works, and textit{siunitx} picks the text-font for its numbers again. I do not know the difference here and why it does this:



    sisetup{number-math-rm=mathrm}



    (SI{40}{newton}) quad SI{40}{newton} quad (num{45.2(1)e-2}) quad num{45.32(12)e-27}    

end{document}

These two (Number 1 and Number 2) questions are similiar, but mode=text does not do the trick, since then the numbers are set in OldStyle. Inversely, mode=math sets the units in (italic) math font.

This solution is looking for the same thing, but it seems different, since they don't use fontspec / unicode-math.

I can stick with

        sisetup{number-math-rm=mathnormal}

and it works for now, but it seems to be a very narrow solution that will fall apart quickly, once more sophisticated typesetting occurs. Is there a better solution?

You can define a new font family for the text mode (here in green):

documentclass{scrreprt}

usepackage{siunitx}

    sisetup{%

     number-text-rm=unitnumberfont,

     detect-mode,

            }%

usepackage{unicode-math}

    setmainfont[Numbers=OldStyle,Color=2244FF]{TeX Gyre Pagella}

    newfontfamilyunitnumberfont{TeX Gyre Pagella Math}[Color=00FF00]

    setmathfont[Color=FF4422,mathrm=sym]{TeX Gyre Pagella Math}%



linespread{1.3}



begin{document}

    Wanted behaviour:



    Text-Style numbers: 123456789.  Math-Style numbers: (123456789).



    In Display-Math, only the math font should be used. This works:

    begin{equation}

        f(x) = 23.1(2) times 10^{-2} x^2

    end{equation}



    begin{equation}

        f(x) = num{23.1(2)e-2} x^2

    end{equation}



    begin{equation}

        num{10} quad SI{20}{newton} quad SI{30}{newton} quad SI{40}{newton} quad SI{50}{newton}.

    end{equation}



    SI{40}{newton} quad SI{50}{newton}.

end{document}