No bold, italic and small caps with XeLaTeX

Question

I switched my working document from pdfLaTeX to XeLaTeX. I have a problem with the font, because now Computer Modern Roman doesn't display bold, italic and small caps text (it works only in one page if I say \usefont{T1}{cmr}{m}{n}\selectfont).

Ex in my images caption, I've said in preamble labelfont={sc,color=blue}, textfont={small,it}, labelsep=endash what is working except for it and sc. And \textit, \textbf, \textsc are not working in all the document :

This is a MWE :

%%Classe du document
\documentclass[11pt,oneside]{book}

\usepackage[labelfont={sc,color=blue}, textfont={small,it}, labelsep=endash]{caption}
\usepackage{subcaption}

\usepackage[cm-default]{fontspec}
\usepackage{xunicode}
\DeclareTextCommandDefault{\nobreakspace}{\leavevmode\nobreak\ } 

%%Pour insérer des images
\usepackage{graphicx} 

%%Le document est en français
\usepackage{polyglossia}
\setdefaultlanguage{french}

\usepackage{cmlgc}

\begin{document}
{\huge\textsc{Sans la liberté de blâmer, il n'est point d'éloge flatteur. }}

\begin{figure}
\includegraphics{image.png}
\caption{Beaumarchais}
\end{figure}

\end{document}

Answer 1

It looks like cmlgc package is not compatible with Unicode fonts as used by xetex, if I remove that the font warnings go and you get small caps output

\documentclass[11pt,oneside]{book}

\usepackage[labelfont={sc,color=blue}, textfont={small,it}, labelsep=endash]{caption}
\usepackage{subcaption}

\usepackage{fontspec}

\DeclareTextCommandDefault{\nobreakspace}{\leavevmode\nobreak\ } 

%%Pour insérer des images
\usepackage{graphicx} 

%%Le document est en français
\usepackage{polyglossia}
\setdefaultlanguage{french}

%\usepackage{cmlgc}

\begin{document}
{\huge\textsc{Sans la liberté de blâmer, il n'est point d'éloge flatteur. }}

\begin{figure}
\includegraphics{image.png}
\caption{Beaumarchais}
\end{figure}

\end{document}