The contents of a node are drawn in text mode. Is there a way, short of introducing a tikzpicture environment, to draw a picture inside a node?
Nesting tikzpicture environments is problematic, also because the inner environment inherits all TikZ attributes from the surrounding tikzpicture environment.
You need to take precautions to use nesting tikzpicture but but it is doable.
You need to also take certain precautions to work with tikzpicture inside tikzpicture or with scope inside tikzpicture. Everything depends on circumstances and what you want to do but I think there is always a way to deal.
I work on the next document for another question. The problem here is to place automatically the heart and I need to use an extern node '(txt)' to place a node inside the tikzpicture inside a node. Well Tikz is magic and do that without problem
\documentclass{scrartcl}
\usepackage[paperwidth=8cm,
paperheight=8cm,
margin=0cm,
left=0cm,
bottom=0mm]{geometry}
%\PassOptionsToPackage{dvipsnames,svgnames}{xcolor}
\usepackage{tikz}
\begin{document}
\pagestyle{empty}
\setlength{\parindent}{0em}
\tikzset{text style/.style={align = center,
text width = \textwidth}}
\newcommand\mytext{The life that I have \\
Is all that I have \\
And the life that I have \\
Is yours. \\
The love that I have \\
Of the life that I have \\
Is yours and yours and yours. \\
A sleep I shall have \\
A rest I shall have \\
Yet death will be but a pause.\\
For the peace of my years \\
In the long green grass \\
Will be yours and yours and yours.}
\null\vfill
\begin{tikzpicture}[remember picture]
\node[text style,color=red] (txt) {\mytext};
\node at (txt.center)
{\begin{tikzpicture}[fill = red]
\pgftransformscale{.025}
\pgfpathmoveto{\pgfqpoint{3600 pt}{3350 pt}}
\pgfpathcurveto{\pgfqpoint{3580 pt}{4270 pt}}
{\pgfqpoint{870 pt}{6400 pt}}
{\pgfqpoint{990 pt}{7860 pt}}%
\pgfpathcurveto{\pgfqpoint{1040 pt}{8430 pt}}
{\pgfqpoint{1590 pt}{9060 pt}}
{\pgfqpoint{2200 pt}{9060 pt}}%
\pgfpathcurveto{\pgfqpoint{3610 pt}{9050 pt}}
{\pgfqpoint{3600 pt}{7720 pt}}
{\pgfqpoint{3600 pt}{7720 pt}}%
\pgfpathcurveto{\pgfqpoint{3600 pt}{7720 pt}}
{\pgfqpoint{3580 pt}{9050 pt}}
{\pgfqpoint{4990 pt}{9060 pt}}%
\pgfpathcurveto{\pgfqpoint{5600 pt}{9060 pt}}
{\pgfqpoint{6150 pt}{8430 pt}}
{\pgfqpoint{6200 pt}{7860 pt}}%
\pgfpathcurveto{\pgfqpoint{6320 pt}{6400 pt}}
{\pgfqpoint{3610 pt}{4270 pt}}
{\pgfqpoint{3600 pt}{3350 pt}}%
\pgfpathclose
\pgfusepath{clip,fill,stroke}%
%
\node[white,
anchor = north west,
text style] at (txt.north west) {\mytext};
\end{tikzpicture}};
\end{tikzpicture}
\vfill
\end{document}
Update I added inside a new tikpicture inside a node inside a tikzpicture inside a node inside the first tikzpicture with opacity , filling.
I created the ant.pgf from the ant of the pst-fun with some difficulties because original picture use rlineto and rcurveto and I don't know if it's possible with pgf.
% http://altermundus.com/SandBox/ant1.pgf
\documentclass{scrartcl}
\usepackage[paperwidth=8cm,
paperheight=8cm,
margin=0cm,
left=0cm,
bottom=0mm]{geometry}
\PassOptionsToPackage{dvipsnames,svgnames}{xcolor}
\usepackage{tikz}
\makeatletter
\newcommand{\callornament}[1]{%
\begingroup
\def\i{\pgfusepath{clip}}%
\let\o\pgfpathclose
\let\s\pgfusepathqfillstroke
\def\p ##1##2{\pgfqpoint{##1bp}{##2bp}}%
\def\m ##1 ##2 {\pgfpathmoveto{\p{##1}{##2}}}%
\def\l ##1 ##2 {\pgfpathlineto{\p{##1}{##2}}}%
\def\r ##1 ##2 ##3 ##4 {\pgfpathrectangle{\p{##1}{##2}}{\p{##3}{##4}}}%
\def\c ##1 ##2 ##3 ##4 ##5 ##6 {%
\pgfpathcurveto{\p{##1}{##2}}{\p{##3}{##4}}{\p{##5}{##6}}}%
\@@input #1\relax
\endgroup}
\makeatother
\begin{document}
\pagestyle{empty}
\setlength{\parindent}{0em}
\tikzset{text style/.style={align = center,
text width = \textwidth}}
\newcommand\mytext{The life that I have \\
Is all that I have \\
And the life that I have \\
Is yours. \\
The love that I have \\
Of the life that I have \\
Is yours and yours and yours. \\
A sleep I shall have \\
A rest I shall have \\
Yet death will be but a pause.\\
For the peace of my years \\
In the long green grass \\
Will be yours and yours and yours.}
\null\vfill
\begin{tikzpicture}[remember picture]
\node[text style,color=red] (txt) {\mytext};
\node (h) at (txt.center)
{\begin{tikzpicture}[fill = red]
\pgftransformscale{.025}
\pgfpathmoveto{\pgfqpoint{3600 pt}{3350 pt}}
\pgfpathcurveto{\pgfqpoint{3580 pt}{4270 pt}}
{\pgfqpoint{870 pt}{6400 pt}}
{\pgfqpoint{990 pt}{7860 pt}}%
\pgfpathcurveto{\pgfqpoint{1040 pt}{8430 pt}}
{\pgfqpoint{1590 pt}{9060 pt}}
{\pgfqpoint{2200 pt}{9060 pt}}%
\pgfpathcurveto{\pgfqpoint{3610 pt}{9050 pt}}
{\pgfqpoint{3600 pt}{7720 pt}}
{\pgfqpoint{3600 pt}{7720 pt}}%
\pgfpathcurveto{\pgfqpoint{3600 pt}{7720 pt}}
{\pgfqpoint{3580 pt}{9050 pt}}
{\pgfqpoint{4990 pt}{9060 pt}}%
\pgfpathcurveto{\pgfqpoint{5600 pt}{9060 pt}}
{\pgfqpoint{6150 pt}{8430 pt}}
{\pgfqpoint{6200 pt}{7860 pt}}%
\pgfpathcurveto{\pgfqpoint{6320 pt}{6400 pt}}
{\pgfqpoint{3610 pt}{4270 pt}}
{\pgfqpoint{3600 pt}{3350 pt}}%
\pgfpathclose
\pgfusepath{clip,fill,stroke}%
%
\node[white,
anchor = north west,
text style] at (txt.north west) {\mytext};
\node at (txt.center){\tikz \pgftransformscale{.0125}%
\pgfsetfillcolor{MidnightBlue}%
\pgfsetfillopacity{.5}%
\callornament{ant1.pgf} ;};
\end{tikzpicture}};
\end{tikzpicture}
\vfill
\end{document}
