树：一个子节点被线穿过，其他子节点没有被穿过

Question

在该示例中，第四个子节点与线相交，但其他节点（例如第二个节点）没有。我如何才能使第四个子节点的线也“位于”框下方？

\documentclass{article}
\usepackage{geometry}
\geometry{textwidth=126mm, textheight=192mm}
\usepackage{color}

\usepackage{tikz}

\begin{document}
\begin{tikzpicture}[sibling distance=7em,
 every node/.style = {shape=rectangle, rounded corners,
 draw, align=center,
 top color=white, bottom color=blue!20}]
 \node {Top}
 child { node {A\\B\\C\\D} }
 child { node {A\\B\\C\\D} }
 child { node {A\\B\\C\\D} }
 child { node {A\\B\\C\\D} }
 child { node {A\\B\\C\\D} };
 \end{tikzpicture}
 \end{document}

Answer 1

使用来自的代码https://tex.stackexchange.com/a/20426/2388：

\documentclass{article}
\usepackage{geometry}
\geometry{textwidth=126mm, textheight=192mm}
\usepackage{color}

\usepackage{tikz}
\pgfdeclarelayer{back}
\pgfsetlayers{back,main}

\makeatletter
\pgfkeys{%
  /tikz/on layer/.code={
    \pgfonlayer{#1}\begingroup
    \aftergroup\endpgfonlayer
    \aftergroup\endgroup
  },
}
\makeatother
\begin{document}

\begin{tikzpicture}[sibling distance=7em,
 edge from parent/.style={draw,on layer=back},
 every node/.style = {shape=rectangle, rounded corners,
 draw, align=center,
 top color=white, bottom color=blue!20}]
 \node {Top}
 child { node {A\\B\\C\\D} }
 child { node {A\\B\\C\\D} }
 child { node {A\\B\\C\\D} }
 child { node {A\\B\\C\\D} }
 child { node {A\\B\\C\\D} };
 \end{tikzpicture}
 \end{document}