对于已编辑的部分

Question

tikz当文本长度超过要装饰的路径时，我有几个关于文本装饰的问题：

1. 为什么装饰不从行首开始（而在行尾正确截断）？
2. raise如果使用负片，为什么当文本弯曲时字母之间的水平空间太多/太小？

看这里：

\documentclass[a4paper]{book}
\usepackage{tikz}
\usetikzlibrary{decorations.text,shapes}
\usetikzlibrary{matrix}
\begin{document}
    \begin{tikzpicture}
    \matrix[column sep=7em,row sep=7ex]{%
    \draw[postaction={decorate,decoration={text along path,text align=center,
        text={Why doesn't this begin at the beginning of the line?}}}]
        (0,0) to (1,0);
        &
    \draw[postaction={decorate,decoration={text along path,text align=center,
        text={Idem as the previous one}}}]
        (0,0) to[bend right] (1,0);
        &
    \draw[postaction={decorate,decoration={text along path,text align=center,
        text={Idem as the previous one}}}]
        (0,0) to[bend left] (1,0);
        \\
    \draw[postaction={decorate,decoration={text along path,text align=center,raise=-3ex,
        text={Idem as the previous one}}}]
        (0,0) to (1,0);
        &
    \draw[postaction={decorate,decoration={text along path,text align=center,raise=-3ex,
        text={Moreover, why is there so much space between the bended letters?}}}]
        (0,0) to[bend right] (1,0);
        &
    \draw[postaction={decorate,decoration={text along path,text align=center,raise=-3ex,
        text={Moreover, why is there so little space between the bended letters?}}}]
        (0,0) to[bend left] (1,0);
        \\
    };
    \end{tikzpicture}
\end{document}

编辑：

符号 1 解释了为什么会发生这种情况，但我仍然不明白原因。

下面的行为难道不是更加连贯吗？

甚至是下面这个？

仅仅是因为自动完成这件事太难了吗？

PS = 之所以出现这个问题，是因为我想解释一下我在这篇文章的评论中使用“水平挤压”的意思cfr 的答案。

Answer 1

1.

如果文本太长，PGF 将插入负左缩进（和/或右缩进，取决于align=right// center）left。因此看起来文本开始得更早。

然而，PGF 保持一个长度，\pgfdecoratedremainingdistance称为输入路径上的剩余距离. （手册第 1001 页）根据装饰的设计，它是一个有限状态自动机，如果\pgfdecoratedremainingdistance小于 1pt，它将终止。（pgfmoduledecorations.code.tex第 789 行）

一旦自动机终止，PGF 将确定此路径，并且没有机会打印剩余的文本。（也许您可以通过使此长度为正来欺骗 PGF。但真正的问题是：您要去哪里？）

2.

因为间距/位置是相对于 x 轴为路径本身的坐标系进行的。无论您降低或升高角色，它们的宽度都保持不变。

对于已编辑的部分

1

添加此

\makeatletter
\pgfutil@namedef{pgf@decorate@@text along path@left indent@options}{
    width={max(\pgf@lib@dec@text@indent@left,0)},next state=scan
}

2

添加这个

\makeatletter
\pgfkeys{
    /pgf/decoration automaton/width/.code={
        \ifx\pgf@lib@dec@text@indent@left\undefined
            \def\pgf@decorate@width{#1}\pgf@decorate@switch@if#1 to final\pgf@stop
        \else
            % deceive the automaton by making the remaining distance longer
            \advance\pgfdecoratedremainingdistance-\pgf@lib@dec@text@indent@left
            \def\pgf@decorate@width{#1}\pgf@decorate@switch@if#1 to final\pgf@stop
            \advance\pgfdecoratedremainingdistance\pgf@lib@dec@text@indent@left
        \fi
    }
}
\def\pgf@decorate@@movealongpath{%
  \advance\pgfdecoratedinputsegmentcompleteddistance\pgf@decorate@distancetomove%
  \advance\pgfdecoratedinputsegmentremainingdistance-\pgf@decorate@distancetomove%
  \ifdim\pgfdecoratedinputsegmentremainingdistance>0pt\relax%
    \let\pgf@next\pgf@decorate@@@movealongpath%
  \else%
    \begingroup
      % check if we are at the last path
      \pgf@decorate@processnextinputsegmentobject%
      \ifx\pgf@decorate@currentinputsegmentobjects\pgfutil@empty%
        % if yes, then insist to keep decorating on this path
        \let\pgf@next\pgf@decorate@@@@movealongpath%
      \else%
        % if no, process the next segment again outside the group
        \def\pgf@next{
          \pgf@decorate@processnextinputsegmentobject
          \pgf@decorate@@movealongpath
        }
      \fi%
      \pgfmath@smuggleone\pgf@next
    \endgroup
  \fi%
  \pgf@next%
}
\def\pgf@decorate@@@@movealongpath{
  \pgf@decorate@movealonginputsegment{\the\pgf@decorate@distancetomove}%
  \pgf@decorate@distancetomove0pt\relax
}

3

我认为这很明显