Strange distancing when starting with a bulleted enviroment. about xsim

[muzimuzhi]

With the default setting exercise/template=default, exercise title is typeset by \subsection*{<title>}, which takes care of vertical spacing between following list (like enumerate) automatically, through \@afterheading.

With exercise/template=centered, the same exercise title is now typeset manually, by \hfil\textbf{<title>}...\hfil\par\noindent. This time the vertical space \topsep inserted by a list environment (between it and the previous text) is not ignored automatically any more.

Implementations of exercise templates default and centered

xsim/code/xsim.sty

Lines 5509 to 5533 in 06e3dba

	\DeclareExerciseEnvironmentTemplate {default}
	{
	\GetExerciseHeadingF { \subsection* }
	{
	\XSIMmixedcase { \GetExerciseName } \nobreakspace
	\GetExerciseProperty {counter}
	\IfInsideSolutionF
	{
	\IfExercisePropertySetT {subtitle}
	{ ~ { \normalfont \itshape \GetExerciseProperty {subtitle} } }
	}
	}
	\GetExercisePropertyT {points}
	{
	\marginpar
	{
	\IfInsideSolutionF { \rule {1.2cm} {1pt} \slash }
	\printgoal {\PropertyValue}
	\GetExercisePropertyT {bonus-points}
	{ \nobreakspace ( + \printgoal {\PropertyValue} ) }
	\nobreakspace\XSIMtranslate {point-abbr}
	}
	}
	}
	{ \par }

xsim/code/xsim.style.layouts.code.tex

Lines 95 to 115 in 06e3dba

	\DeclareExerciseEnvironmentTemplate{centered}
	{%
	\par\vspace{\baselineskip}
	\Needspace*{2\baselineskip}
	\noindent
	\hfil\textbf{\XSIMmixedcase{\GetExerciseName}~\GetExerciseProperty{counter}}%
	\GetExercisePropertyT{subtitle}{ \textit{#1}}\hfil
	\par\noindent
	\IfInsideSolutionF{%
	\GetExercisePropertyT{points}{%
	\marginpar{%
	\printgoal{\PropertyValue}%
	\GetExercisePropertyT{bonus-points}{+\printgoal{\PropertyValue}}%
	\,\IfExerciseGoalSingularTF{points}
	{\XSIMtranslate{point}}
	{\XSIMtranslate{points}}%
	}%
	}%
	}%
	}
	{}

Adding back \@afterheading (manually or by patching the centered template) solves the problem, partially. Note with exercise/template=centered, if exercise property points is given for an exercise starting with a list environment, the value of points will be typeset in its own paragraph, as a marginal note. You may need to manually adjust the vertical spacing.

\documentclass{article}
\usepackage{lipsum}

% to show distances between baseline heights
\usepackage{lineno}
\renewcommand{\thelinenumber}{\arabic{linenumber}\rlap{\rule{.4pt}{11pt}}}
\linenumbers

%\usepackage{cmbright}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

\usepackage[clear-aux]{xsim}
\xsimsetup{
	load-style=layouts,
	exercise/template=centered,
}

\makeatletter
% cheat `xsim` as if `centered` template is undefined
\ExpandArgs{cc}\relax {cs_undefine:N} {l__xsim_template_begin_centered_setup_tl}
\ExpandArgs{cc}\relax {cs_undefine:N} {l__xsim_template_end_centered_setup_tl}

\DeclareExerciseEnvironmentTemplate{centered}
  {%
    \par\vspace{\baselineskip}
    \Needspace*{2\baselineskip}
    \noindent
    \hfil\textbf{\XSIMmixedcase{\GetExerciseName}~\GetExerciseProperty{counter}}%
    \GetExercisePropertyT{subtitle}{ \textit{#1}}\hfil
    \par\noindent\@afterheading % <<< changed
    \IfInsideSolutionF{%
      \GetExercisePropertyT{points}{%
          \marginpar{%
            \printgoal{\PropertyValue}%
            \GetExercisePropertyT{bonus-points}{+\printgoal{\PropertyValue}}%
            \,\IfExerciseGoalSingularTF{points}
                {\XSIMtranslate{point}}
                {\XSIMtranslate{points}}%
          }%
      }%
    }%
  }
  {}
\makeatother

\begin{document}
\begin{exercise}[subtitle={no points + plain text}]
  Normal distance between header and text!
\end{exercise}

\begin{exercise}[subtitle={no points + list}]
  \begin{enumerate}
  	\item Greater distance between header and text!
  \end{enumerate}
\end{exercise}

\begin{exercise}[points=2, subtitle={points + plain text}]
  Normal distance between header and text!
\end{exercise}

\begin{exercise}[points=3, subtitle={points + list}]
  \begin{enumerate}
  	\item Greater distance between header and text!
  \end{enumerate}
\end{exercise}

\begin{exercise}[points=4, subtitle={points + list + manual adjustment}]
  \vspace{-\baselineskip}
  \begin{enumerate}
  	\item Greater distance between header and text!
  \end{enumerate}
\end{exercise}

\section*{Emulation}
\subsection*{EnvironmentTemplate=default}
\lipsum[2][1]

\subsection*{EnvironmentTemplate=default}
\begin{enumerate}
  \item \lipsum[2][1]
\end{enumerate}

\hfil\textbf{EnvironmentTemplate=centered}\hfil \par
\lipsum[2][1]

\hfil\textbf{EnvironmentTemplate=centered}\hfil \par
\begin{enumerate}
  \item \lipsum[2][1]
\end{enumerate}

\hfil\textbf{EnvironmentTemplate=centered, patched}\hfil \par
\UseName{@afterheading}%
\begin{enumerate}
  \item \lipsum[2][1]
\end{enumerate}
\end{document}