下划线公式

beamer 中的公式实现下划线的标识

发布于 2023-05-23 08:44:40

正如您已经发现的那样，有几种技术可以实现下划线，但没有一种（我知道的）能够满足您所有的要求。

因此，我编写了一个包装器 \myul，在这种情况下基于上下文（数学模式或普通模式）选择一种技术来使用。通过可选参数，您可以手动指定颜色、厚度、深度和技术。您可以使用命令 \setmyul 为当前组中的整个设置更改这些设置。对于某些选项，数学模式或文本模式可能需要指定不同的值。有关更多详细信息，请参见代码中的注释。

\documentclass{beamer}

\usepackage{soul}
\usepackage{pgfkeys}
\usepackage{mathstyle}
\usepackage{transparent}

\makeatletter

% ---------- key=value options ----------

\newif\if@myul@math@usedistance@
\newif\if@myul@text@usedistance@

\newcommand\@myul@text@depth{\SOUL@uldepth}
\newcommand\@myul@math@depth{\SOUL@uldepth}

\pgfqkeys{/myul}{
    % thickness of the rule
    thickness/.code={\setul{}{#1}},
    %
    % distance from baseline where to place the top of the rule
    depth/.style={%
        math depth=#1,
        text depth=#1,
    },
    math depth/.code={%
        \@myul@math@usedistance@false
        \def\@myul@math@depth{#1}%
    },
    text depth/.code={%
        \@myul@text@usedistance@false
        \setul{#1}{}%
    },
    %
    % distance from bottom edge of box where to place the top of the rule
    % works only with command = box
    distance/.style={%
        math distance=#1,
        text distance=#1,
    },
    math distance/.code={%
        \@myul@math@usedistance@true
        \def\@myul@math@distance{#1}%
    },
    text distance/.code={%
        \@myul@text@usedistance@true
        \def\@myul@text@distance{#1}%
    },
    %
    % color in which to draw the rule (not the text)
    color/.code={\setulcolor{#1}},
    %
    % which implementation technique to use
    command/.style={%
        text command=#1,
        math command=#1,
    },
    %
    text command/.is choice,
    text command/soul/.code     ={\let\@myul@text@do=\@myul@soul},
    text command/box/.code      ={\let\@myul@text@do=\@myul@box},
    text command/primitive/.code={\let\@myul@text@do=\@myul@primitive},
    %
    math command/.is choice,
    math command/soul/.code     ={\let\@myul@math@do=\@myul@soul},
    math command/box/.code      ={\let\@myul@math@do=\@myul@box},
    math command/primitive/.code={\let\@myul@math@do=\@myul@primitive},
    %
    % what to do if key is none of the above defined
    .unknown/.code={%
        % only process keys for which no full path has been provided
        % TikZ documentation, page 900
        \ifpgfkeysaddeddefaultpath
            \let\@myul@currentname=\pgfkeyscurrentname
            \pgfkeysalso{%
                command/\@myul@currentname/.try,
                color/.lastretry=\@myul@currentname,
            }%
        \else
            \def\pgfutilnext{\pgfkeysvalueof {/handlers/.unknown/.@cmd}#1\pgfeov}%
            \pgfutilnext
        \fi
    },
}


% ---------- user interface ----------

\newcommand{\setmyul}[1]{%
    \pgfqkeys{/myul}{#1}%
}

\newcommand<>{\myul}[2][black]{%
    \begingroup
        \setmyul{#1}%
        \ifmmode
            \expandafter \@myul@math@do
        \else
            \expandafter \@myul@text@do
        \fi
        #3{#2}%
    \endgroup
}

% for auto completion in TeXstudio
\providecommand{\myul}[1]{}


% ---------- using soul package ----------
% based on soul package
% supports line break
% the text to be underlined can *not* be arbitrary TeX code
% see soul package documentation [November 17, 2003] page 5
% does *not* work in math mode

\newcommand<>{\@myul@soul}[1]{%
    %https://tex.stackexchange.com/a/41693/120953
    \let\set@color=\beamerorig@set@color
    \let\reset@color=\beamerorig@reset@color
    \alt#2{%
        \ul{#1}%
    }{%
        \def\SOUL@ulcolor{\texttransparent{0.0}}%
        \ul{#1}%
    }%
}


% ---------- using boxes ----------
% based on:
% https://tex.stackexchange.com/a/9472/120953
% https://tex.stackexchange.com/a/1236/120953
% does *not* support line breaks

\newsavebox\@myul@box@tmpbox

\newcommand<>{\@myul@box}[1]{%
    \ifmmode
        \sbox\@myul@box@tmpbox{$\m@th \currentmathstyle #1$}%
        \if@myul@math@usedistance@
            \def\@myul@box@useddepth{\dimexpr-\dp\@myul@box@tmpbox-\@myul@math@distance-\SOUL@ulthickness}%
        \else
            \def\@myul@box@useddepth{\dimexpr-\@myul@math@depth-\SOUL@ulthickness}%
        \fi
    \else
        \sbox\@myul@box@tmpbox{#1}%
        \if@myul@text@usedistance@
            \def\@myul@box@useddepth{\dimexpr-\dp\@myul@box@tmpbox-\@myul@text@distance-\SOUL@ulthickness}%
        \else
            \def\@myul@box@useddepth{\dimexpr-\@myul@text@depth-\SOUL@ulthickness}%
        \fi
    \fi
    \usebox\@myul@box@tmpbox%
    \alt#2{%
        \llap{%
            % \SOUL@ulcolor = \textcolor{<color>}
            \SOUL@ulcolor{%
                \rule[\@myul@box@useddepth]{\wd\@myul@box@tmpbox}{\SOUL@ulthickness}%
            }%
        }%
    }{%
        \rule[\@myul@box@useddepth]{0pt}{\SOUL@ulthickness}%
    }%
}


% ---------- using TeX primitive ----------
% In plain TeX \underline is a primitive 
% which can be used in math mode only.
% In LaTeX \underline is overridden 
% so that it can be used outside of math mode, too.
% Either way, it does *not* support line breaks.
% Thickness and depth are *not* freely adjustable.
% thickness = $\theta$, distance to underline = $3\theta$
% where $\theta=\xi_8$ default rule thickness
% [The TeXbook, page 443, rule 10]
% default rule thickness can be changed with:
% \fontdimen8\textfont3=5pt
% default rule thickness is 0.4pt
% https://tex.stackexchange.com/a/167957/25264
% Changing the default rule thickness 
% changes the thickness of fraction bars, too.
% Therefore this command ignores the thickness and depth options.
% You should avoid this method to avoid inconsistencies.

% based on https://gist.github.com/lucaswerkmeister/3f7672ee522f7e823cec63fdc85fd7aa
\newcommand<>{\@myul@primitive}[1]{%
    % colored underline: https://tex.stackexchange.com/a/9477/25264
    % transparent underline: https://tex.stackexchange.com/a/45601/25264
    % switch between colored and transparent: http://mirrors.ibiblio.org/CTAN/macros/latex/contrib/beamer/doc/beameruserguide.pdf sections 9.3 and 9.6.1
    % \SOUL@ulcolor = \textcolor{<color>}
    \let\textcolor=\color
    \alt#2%
        {\SOUL@ulcolor\underline{{\color{black}#1}}\color{black}}%
        {\transparent{0.0}\underline{{\transparent{1.0}#1}}\transparent{1.0}}%
}

\makeatother


% ---------- default settings ----------

\setmyul{
    text command=soul,
    math command=box,
}



% ---------- test ----------

\setmyul{math distance=.5ex}

\useinnertheme{default}
\beamertemplatenavigationsymbolsempty


% based on https://tex.stackexchange.com/questions/14821/whats-the-proper-way-to-typeset-a-differential-operator
\newcommand{\dif}{\ensuremath{\operatorname{d}\!}}


\begin{document}

\begin{frame}{Coloured Underlining}

    Different parts of text can be underlined, using colours such as \myul[color=green]{green}, \myul[red]{red}. 
    The \myul[thickness=2pt]{thickness} of the underline can be set.
    Additionally, the \myul[depth=1pt]{depth} of the underline can be set, too.

    \vfill

    Underlining is consistent with \myul<2->{Beamer} \myul<3->[thickness=5pt]{overlays}.

    \vfill

    Underlining works as well in equations such
    as $f(x) = \lambda\, e^x$ and


    \begin{align*}
        \mu = \myul<2->[red]{\frac{1}{2} \int_0^1 x \, f_{P_{ij}}(x) \dif x} 
            + \frac{1}{2} \int_0^1 f_{P_{ij}}(x) 
              \int_0^1 \myul<3->[red, thickness=5pt]{y \,f_{P_{ji}\vert P_{ij}}(y \mid x)} \dif y \dif x.
    \end{align*}

    \vfill


    Underlining longer expressions doesn't lead to \myul{lines breaking early, but rather the underline} stretches across two lines of text.

\end{frame}
\end{document}