TikZ Positioning Nodes Relative to Other Nodes in Command

Question

So I am a new user to TeX. I have extensive experience in HTML and CSS, and boy is this a whole different ball game.

I have the following command:

\newcommand{\header}[4]{
  \begin{tikzpicture}[remember picture, overlay]
    \node [below right, fill=#1, minimum height=\hdrheight, minimum width=\paperwidth, outer sep=0] (name) at (current page.north west) {};
    \node[text=white, anchor=east, xshift=-10mm] (nametext) at (name.east) {
      \fontsize{40pt}{32pt}\color{white}
      {\titlefont #2}
    };
  \end{tikzpicture}
}

It works well enough. However, say I wanted to reuse it. If I called \header again, it would write right over the top of the previous one. How do I properly position it so it will draw under the previous node? Each of these is like a header for a section on a flyer or whatever. Under it would be proper text for the section. So then it would follow that the element be positioned where the last ends.

Thanks

Answer 1

To place nodes relatively to each other in tikz use \usetikzlibrary{positioning}:

\node (a) {node a};
\node (b) [above=of a] {node b};

where in front of the of the distance can be given.

The following code places the headers below each other, because that is easier than above each other:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning}

\newlength{\hdrheight}
\setlength{\hdrheight}{1cm}
\newcounter{headercounter}
\setcounter{headercounter}{0}

\newcommand{\header}[4]{%
    \begin{tikzpicture}[remember picture, overlay]
        \ifnum \theheadercounter=0
            \def\positionKey{at}
            \def\positionVal{(current page.north)}
        \else
            \def\positionKey{below}
            \def\positionVal{0em of header-\number\numexpr\theheadercounter-1\relax}
        \fi
        \node[anchor=north, fill=#1, minimum height=\hdrheight, minimum width=\paperwidth, outer sep=0, \positionKey=\positionVal] (header-\theheadercounter) {};
        \node[text=white, anchor=east, xshift=-10mm, text=white, font=\fontsize{40pt}{32pt}] at (header-\theheadercounter.east) {#2};
    \end{tikzpicture}%
    \stepcounter{headercounter}%
}


\begin{document}
\header{yellow}{hello world}{arg3}{arg4}%
\header{green}{hello again}{arg3}{arg4}%
\header{orange}{and a third one}{arg3}{arg4}%
content...
\end{document}

Note how I have used % characters to comment out line breaks in order to avoid undesired spaces. (Spaces inside of a tikzpicture are ignored - that's why I have not done it there.)

Also, please note that this is for one page only. If you want to use this on another page again you need to reset the counter with \setcounter{headercounter}{0}.

The usual way to set headings in LaTeX is using the fancyhdr package. For a simple example see page 5 of it's documentation.

---

The following code places the headers above each other. In order to do that the \header command now merely saves the header in different commands and when all headers have been specified the \setheaders command loops over all of them and places them below each other in reversed order.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning}

\newlength{\hdrheight}
\setlength{\hdrheight}{1cm}
\newcounter{headercounter}
\setcounter{headercounter}{0}
\newif\ifFirstHeader

\newcommand{\header}[4]{% #1: background color, #2: text, #3: ?, #4: ?
    \def\saveheader##1{%
        \expandafter\def\csname header\theheadercounter\endcsname{%
            \begin{tikzpicture}[remember picture, overlay]
                \ifFirstHeader
                    \def\positionKey{at}
                    \def\positionVal{(current page.north)}
                    \global\FirstHeaderfalse
                \else
                    \def\positionKey{below}
                    \def\positionVal{0em of header-\number\numexpr##1+1\relax}
                \fi
                \node[anchor=north, fill=#1, minimum height=\hdrheight, minimum width=\paperwidth, outer sep=0, \positionKey=\positionVal] (header-##1) {};
                \node[text=white, anchor=east, xshift=-10mm, text=white, font=\fontsize{40pt}{32pt}] at (header-##1.east) {#2};
            \end{tikzpicture}%
        }%
    }%
    \expandafter\saveheader\expandafter{\theheadercounter}%
    \stepcounter{headercounter}%
}
\newcommand{\setheaders}{%
    \FirstHeadertrue
    \loop
        \addtocounter{headercounter}{-1}%
        \csname header\theheadercounter\endcsname
    \ifnum\theheadercounter>0
    \repeat
}


\begin{document}
\header{yellow}{hello world}{arg3}{arg4}%
\header{green}{hello again}{arg3}{arg4}%
\header{orange}{and a third one}{arg3}{arg4}%
\setheaders
content...

\newpage
\header{blue!30}{new page}{arg3}{arg4}%
\header{green!70!blue!30}{new header}{arg3}{arg4}%
\setheaders
content...
\end{document}

---

EDIT: If you want to customize \section command and friends titlesec is the way to go:

\documentclass{article}
\usepackage{titlesec}
\usepackage{tikz}
\usetikzlibrary{positioning}

\newlength{\hdrheight}
\setlength{\hdrheight}{1cm}
\newcounter{headercounter}
\setcounter{headercounter}{0}

\newcommand{\lastPageWithHeader}{-1}
\newcommand{\header}[4]{%
    \ifnum\thepage=\lastPageWithHeader
    \else
        \setcounter{headercounter}{0}%
    \fi
    \xdef\lastPageWithHeader{\thepage}%
    \begin{tikzpicture}[remember picture, overlay]
        \ifnum \theheadercounter=0
            \def\positionKey{at}
            \def\positionVal{(current page.north)}
        \else
            \def\positionKey{below}
            \def\positionVal{0em of header-\number\numexpr\theheadercounter-1\relax}
        \fi
        \node[anchor=north, fill=#1, minimum height=\hdrheight, minimum width=\paperwidth, outer sep=0, \positionKey=\positionVal] (header-\theheadercounter) {};
        \node[text=white, anchor=east, xshift=-10mm, text=white, font=\fontsize{40pt}{32pt}] at (header-\theheadercounter.east) {#2};
    \end{tikzpicture}%
    \stepcounter{headercounter}%
}

\newcommand{\setTitleBackgroundColor}[1]{%
    \def\theTitleBackgroundColor{#1}%
    \ignorespaces
}
\setTitleBackgroundColor{black}

\newcommand{\sectionformat}[1]{%
    \header{\theTitleBackgroundColor}{#1}{arg3}{arg4}%
    #1%
}

% default values copied from titlesec documentation page 23
% parameters of \titleformat command are explained on page 4
\titleformat%
    {\section}% <command> is the sectioning command to be redefined, i. e., \part, \chapter, \section, \subsection, \subsubsection, \paragraph or \subparagraph.
    {\normalfont\Large\bfseries}% <format>
    {}% <label> the number
    {0em}% <sep> length. horizontal separation between label and title body
    {\sectionformat}% code preceding the title body  (title body is taken as argument)

\usepackage{blindtext}
\begin{document}
\tableofcontents
\newpage

\setTitleBackgroundColor{yellow}
\section{Section~1}
\blindtext
\setTitleBackgroundColor{green}
\section{Section~2}
\Blindtext
\setTitleBackgroundColor{orange}
\section{Section~3}
\Blindtext
\setTitleBackgroundColor{brown}
\section{Section~4}
\blindtext
\setTitleBackgroundColor{blue!30}
\section{Section~5}
\blindtext
\setTitleBackgroundColor{green!70!blue!30}
\section{Section~6}
\blindtext
\setTitleBackgroundColor{rgb,255:red,255; green,194; blue,0}
\section{Section~7}
\blindtext
\end{document}

If you want to customize the spacing of \section you can use \titlespacing{\section}{<left-margin>}{<space-above-the-heading>}{<space-below-the-heading>}.

If you want to know more about how to specify colors see the xcolor package documentation and this answer.