這個問題已經被問過這裡，但接受的答案恢復為 pdflatex，這不適用於該項目。
我最初指定 Palatino 字體為\usepackage[sc, osf]{mathpazo}，但是我有學到了由於polyglossia，我需要各種國際語言，隱式加載fontspec，我改為使用\setmainfont{TeX Gyre Pagella}，我手動安裝在（OS X）系統上的字體CTAN下載。
TeX Gyre Pagella似乎不包括小型大寫字母，所以我下載並安裝Palatino Small Caps & Old Style Figures.ttf如下所示：
fc-list | grep Palatino
/Users/mikekilmer/Library/Fonts/Palatino Small Caps & Old Style Figures.ttf: Palatino Small Caps & Old Style,Palatino:style=Regular,Small Caps & Old Style Figures
/System/Library/Fonts/Palatino.ttc: Palatino:style=Bold
/System/Library/Fonts/Palatino.ttc: Palatino:style=Regular
/System/Library/Fonts/Palatino.ttc: Palatino:style=Bold Italic
/System/Library/Fonts/Palatino.ttc: Palatino:style=Italic
根據我從以下字體資訊可以看出，Palatino-SC 將是參考使用的名稱：
otfinfo -i '~/Library/Fonts/Palatino Small Caps & Old Style Figures.ttf'
Family: Palatino Small Caps & Old Style
Subfamily: Regular
Full name: Palatino-SC
PostScript name: Palatino-SC
Version: 001.001
Unique ID: Palatino Small Caps & Old Style Figures:1178633258
Copyright: Copyright (c) 1985, 1987, 1989, 1990, 1991 Adobe Systems Incorporated. All Rights Reserved.Palatino is a trademark of Linotype AG and/or its subsidiaries.
但在此範例中，沒有顯示小型大寫字母：
\documentclass[a5paper,twoside,11pt]{extbook}
\usepackage{polyglossia}
\setdefaultlanguage{english}
\defaultfontfeatures{Mapping=tex-text}
\setmainfont[Numbers=OldStyle,
SmallCapsFont={Palatino-SC},
SmallCapsFeatures={Letters=SmallCaps}
]{TeX Gyre Pagella}
\begin{document}
\textsc{Once upon a time} we had a story. Once upon a time.
\end{document}
有效的是以下fontspec字體系列替換：
\newfontfamily\scshape[Letters=SmallCaps,Scale=1.15]{Palatino-SC}
有人可以解釋一下 1. 為什麼setmainfont參數不起作用以及 2. 如何讓 OldStyleNums 顯示？
答案1
在 XeLaTeX 中定義字型取決於您安裝它們的方式。
如果 TeX Gyre Pagella 可用作系統字體，則
\documentclass{article}
\usepackage{fontspec}
\usepackage{polyglossia}
\setdefaultlanguage{english}
\setmainfont{TeX Gyre Pagella}[
Numbers=OldStyle,
]
\begin{document}
\textsc{Once upon a time} we had a story. Once upon a time.
1234567890
\end{document}
就足夠了。否則，您需要使用 TeX Live 發行版中的字體，方法稍微複雜一些。
如果我使用 運行該範例xelatex -output-driver="xdvipdfmx -vv"，我會在終端上得到以下輸出：
DVI Comment: XeTeX output 2017.01.29:2158
<AGL:texglyphlist.txt><AGL:pdfglyphlist.txt><AGL:glyphlist.txt>[1</Library/Fonts/tex-gyre/[email protected]<NATIVE-FONTMAP:/Library/Fonts/tex-gyre/texgyrepagella-regular.otf/0/H/65536/0/0>
fontmap: /Library/Fonts/tex-gyre/texgyrepagella-regular.otf/0/H/65536/0/0 -> /Library/Fonts/tex-gyre/texgyrepagella-regular.otf(Identity-H)
pdf_font>> Input encoding "Identity-H" requires at least 2 bytes.
pdf_font>> The -m <00> option will be assumed for "/Library/Fonts/tex-gyre/texgyrepagella-regular.otf".
(CID:TeXGyrePagella-Regular)
pdf_font>> Type0 font "/Library/Fonts/tex-gyre/texgyrepagella-regular.otf" cmap_id=<Identity-H,0> opened at font_id=</Library/Fonts/tex-gyre/texgyrepagella-regular.otf/0/H/65536/0/0,0>.
></Library/Fonts/tex-gyre/[email protected]>]
otf_cmap>> Creating ToUnicode CMap for "/Library/Fonts/tex-gyre/texgyrepagella-regular.otf"...
(CID:/Library/Fonts/tex-gyre/texgyrepagella-regular.otf[SMRJXI+TeXGyrePagella-Regular][CIDFontType0][39 glyphs][5175 bytes])
這表明我安裝了 TeX Gyre 字體，/Library/Fonts並且這些字體被xdvipdfmx.
稍微複雜一點的版本是
\documentclass{article}
\usepackage{fontspec}
\usepackage{polyglossia}
\setdefaultlanguage{english}
\setmainfont{texgyrepagella}[
Extension=.otf,
UprightFont=*-regular,
ItalicFont=*-italic,
BoldFont=*-bold,
BoldItalicFont=*-bolditalic,
Numbers=OldStyle,
]
\begin{document}
\textsc{Once upon a time} we had a story. Once upon a time.
1234567890
\end{document}
詳細輸出變成
DVI Comment: XeTeX output 2017.01.29:2202
<AGL:texglyphlist.txt><AGL:pdfglyphlist.txt><AGL:glyphlist.txt>[1</usr/local/texlive/2016/texmf-dist/fonts/opentype/public/tex-gyre/[email protected]<NATIVE-FONTMAP:/usr/local/texlive/2016/texmf-dist/fonts/opentype/public/tex-gyre/texgyrepagella-regular.otf/0/H/65536/0/0>
fontmap: /usr/local/texlive/2016/texmf-dist/fonts/opentype/public/tex-gyre/texgyrepagella-regular.otf/0/H/65536/0/0 -> /usr/local/texlive/2016/texmf-dist/fonts/opentype/public/tex-gyre/texgyrepagella-regular.otf(Identity-H)
pdf_font>> Input encoding "Identity-H" requires at least 2 bytes.
pdf_font>> The -m <00> option will be assumed for "/usr/local/texlive/2016/texmf-dist/fonts/opentype/public/tex-gyre/texgyrepagella-regular.otf".
(CID:TeXGyrePagella-Regular)
pdf_font>> Type0 font "/usr/local/texlive/2016/texmf-dist/fonts/opentype/public/tex-gyre/texgyrepagella-regular.otf" cmap_id=<Identity-H,0> opened at font_id=</usr/local/texlive/2016/texmf-dist/fonts/opentype/public/tex-gyre/texgyrepagella-regular.otf/0/H/65536/0/0,0>.
></usr/local/texlive/2016/texmf-dist/fonts/opentype/public/tex-gyre/[email protected]>]
otf_cmap>> Creating ToUnicode CMap for "/usr/local/texlive/2016/texmf-dist/fonts/opentype/public/tex-gyre/texgyrepagella-regular.otf"...
(CID:/usr/local/texlive/2016/texmf-dist/fonts/opentype/public/tex-gyre/texgyrepagella-regular.otf[KRFMAA+TeXGyrePagella-Regular][CIDFontType0][39 glyphs][5175 bytes])
顯示使用了 TeX Live 目錄。
兩種情況下的輸出是相同的。
如您所見，小型大寫字母受到尊重。