Define SizeFeatures for my own font face with fontspec

Question

I use a large family of fonts, containing a lot of fontfaces. Besides standart Upright, Bold, Italic, and BoldItalic I need to use, e. g. Semibold.

I define the new face with

FontFace        =   {semibold}{n}{*Semibold},
FontFace        =   {semibold}{it}{*SemiboldIt},

And I need something similar to

UprightFeatures =   {
                        SizeFeatures={
                            {Size={-8.9},       Font    =   *Capt},
                            {Size={8.4-12.9},   Font    =   *Regular},
                            {Size={13.0-22.9},  Font    =   *Subh},
                            {Size={22.9-},      Font    =   *Disp}
                        }
},

But for the semibold.

How can I do this?

LuaLaTeX MWE:

\documentclass{article}

\newcommand{\MyPath}{} % Your Path to the fonts here

\usepackage{polyglossia}
\usepackage{mathtools}
\usepackage{tabularx}
\usepackage{booktabs}

\setmainlanguage{english}

\setmainfont{WarnockPro-}[%
    Extension       =   .otf,
    UprightFont     =   *Regular,
    ItalicFont      =   *It,
    BoldFont        =   *Bold,
    BoldItalicFont  =   *BoldIt,
    FontFace        =   {semibold}{n}{*Semibold},
    FontFace        =   {semibold}{it}{*SemiboldIt},
    Path            =   \MyPath,
    Ligatures       =   {TeX,Rare,Common},
    Contextuals     =   {Swash},
    Numbers         =   {Uppercase},
    Style           =   {Historic},
    Kerning         =   {On},
    UprightFeatures =   {
                            SizeFeatures={
                                {Size={-8.9},       Font    =   *Capt},
                                {Size={8.4-12.9},   Font    =   *Regular},
                                {Size={13.0-22.9},  Font    =   *Subh},
                                {Size={22.9-},      Font    =   *Disp}
                            }
    },
    ItalicFeatures  =   {
                            SizeFeatures={
                                {Size={-8.9},       Font    =   *ItCapt},
                                {Size={8.4-12.9},   Font    =   *It},
                                {Size={13.0-22.9},  Font    =   *ItSubh},
                                {Size={22.9-},      Font    =   *ItDisp}
                            }
    },
    BoldFeatures    =   {
                            SizeFeatures={
                                {Size={-8.9},       Font    =   *BoldCapt},
                                {Size={8.4-12.9},   Font    =   *Bold},
                                {Size={13.0-22.9},  Font    =   *BoldSubh},
                                {Size={22.9-},      Font    =   *BoldDisp}
                            }
    },
    BoldItalicFeatures  =   {
                            SizeFeatures={
                                {Size={-8.9},       Font    =   *BoldItCapt},
                                {Size={8.4-12.9},   Font    =   *BoldIt},
                                {Size={13.0-22.9},  Font    =   *BoldItSubh},
                                {Size={22.9-},      Font    =   *BoldItDisp}
                            }
    },
]

\makeatletter

\DeclareRobustCommand\semiboldseries % Defines SEMIBOLD series
{\not@math@alphabet\semiboldseries\mathbf
    \fontseries{semibold}\selectfont
}

\makeatother 

\newcommand{\GO}{ % Typesets dummy text
    \resizebox{!}{12pt}{\fontsize{7}{7}\selectfont Test Word}

    \resizebox{!}{12pt}{\fontsize{10}{10}\selectfont Test Word}

    \resizebox{!}{12pt}{\fontsize{16}{16}\selectfont Test Word}

    \resizebox{!}{12pt}{\fontsize{40}{40}\selectfont Test Word}
}

\begin{document}


\begin{tabularx}{\textwidth}{ X X X X }
    \toprule
           & Regular              & Semibold                   & Bold                 \\ \midrule
    Italic & \itshape\mdseries\GO & \itshape\semiboldseries\GO & \itshape\bfseries\GO \\[3mm]
    Up     & \mdseries\GO         & \semiboldseries\GO         & \bfseries\GO         \\ \bottomrule
\end{tabularx}


\end{document}

Works for italic and bold just as expected:

Answer 1

The "official" NFSS identifier for semibold is sb (see LaTeX 2e font selection), so I will use this instead of semibold. You can pass font features, including SizeFeatures, to FontFace with

FontFace        =   {sb}{n}{
                        Font = *Semibold,
                        SizeFeatures = {
                          {Size= -8.9,   Font    =   *CaptSemibold},
                          {Size=8.9-22.9}, % No Font=, so *Semibold is used
                          {Size=22.9- ,   Font    =   *DispSemibold},
                        }
                    },

For more information you can look at the fontspec documentation, section 2.3