Redraw a kernel scheme diagram

Question

I'm trying to redraw a kernel scheme diagram for a university lecture note. This is how far I got:

\documentclass{article}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[magyar]{babel}

\usepackage{tikz}
\usetikzlibrary{positioning,fit}

\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}


\begin{document}

\begin{tikzpicture}[font=\sffamily]
    \tikzstyle{title}=[rectangle]
    \tikzstyle{wrapper}=[anchor=west, draw]
    \tikzstyle{bigblock}=[rectangle, minimum width=10cm, minimum height=1cm, anchor=west, draw]
    \tikzstyle{Nbigblock}=[rectangle, minimum width=10cm, minimum height=1cm, anchor=north, draw]
    \tikzstyle{Sbigblock}=[rectangle, minimum width=10cm, minimum height=1cm, anchor=south, draw]
    \tikzstyle{medblock}=[rectangle, minimum width=6cm, minimum height=1cm, anchor=south, draw]
    \tikzstyle{smallblock}=[rectangle, minimum width=3cm, minimum height=1cm, anchor=west, draw]

    \node (kernel) [title] {Kernel};
    \node (syscalls) [bigblock, below=of kernel] {Rendszerhívások};
    \node (filesystems) [smallblock, below=of syscalls.west] {Fájlrendszerek};
    \node (networklayer) [smallblock, below=of filesystems] {Hálózati réteg};

    \node (processhandling) [title,below=of syscalls.east] {Processzkezelés};
    \node (scheduler) [smallblock, below=of processhandling] {Ütemező};
    \node (memhandling) [smallblock, below=of scheduler] {Memóriakezelés};
    \node (IPC) [smallblock, below=of memhandling] {IPC};

    \node (processhandlingwrapper) [wrapper, fit={(processhandling) (scheduler) (memhandling) (IPC)}] {};

    \node (periphhandling) [bigblock, below=of processhandlingwrapper.south east] {Perifériák kezelése};

    \node (kernelwrapper) [wrapper, fit={(kernel) (filesystems) (syscalls) (networklayer) (processhandling) (periphhandling)}] {};

    \node (hardver) [below=of kernelwrapper.south, Nbigblock] {Hardver};

    \node (syslibs) [above=of kernelwrapper, medblock] {Rendszerkönyvtárak};

    \node (usrprocesses) [above=of syslibs, Sbigblock] {Felhasználói processzek};
\end{tikzpicture}

\end{document}

On the left you can see the diagram I want to redraw using TikZ, on the right side is my approach, where you can see wrong positioning and the lack of arrows.

Could you help me correct the positioning and draw the arrows to the right places? Thanks!

Answer 1

The reason why the positioning in your example doesn't work as expected, is that there is a difference in whether one specifies the anchor of a node before or after the relative position (e.g., below=of). Take this simple example:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}[demo/.style={anchor=west,draw}]
\node (A) [draw] {lorem};
\node [below=of A.south east,demo] {ipsum};
\node [yshift=-2em,demo,below=of A.south east] {ipsum};
\end{tikzpicture}
\end{document}

As you can see, when the anchor is specified after the relative position (top "ipsum"), the result is what one might expect. The reason it doesn't work for the opposite case, is that the anchor is set automatically when you use something like below=of somenode. Hence, when your anchor=west parameter is before the positioning, it will be overwritten.

Below then is code that more or less reproduces your diagram. A little hackish, as there is some manually shifting of nodes. Also, the top and bottom node aren't as wide as kernelwrapper. You could simply increase the minimum width for those a little, I don't know of a better way.

I added the arrows as well. Not the prettiest way perhaps, Stefan's way might be better. Instead of shifting the start point of the arrow, I used the <node name>.<angle> syntax. Probably not the best for rectangular nodes, though it works.

\documentclass{article}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[magyar]{babel}

\usepackage{tikz}
\usetikzlibrary{positioning,fit}

\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}


\begin{document}

\begin{tikzpicture}[font=\sffamily]
    \tikzstyle{title}=[rectangle]
    \tikzstyle{wrapper}=[anchor=west, draw]
    \tikzstyle{bigblock}=[rectangle,minimum width=10cm, minimum height=1cm, anchor=west, draw]
    \tikzstyle{Nbigblock}=[rectangle, minimum width=10cm, minimum height=1cm, anchor=north, draw]
    \tikzstyle{Sbigblock}=[rectangle, minimum width=10cm, minimum height=1cm, anchor=south, draw]
    \tikzstyle{medblock}=[rectangle, minimum width=6cm, minimum height=1cm, draw]
    \tikzstyle{smallblock}=[rectangle, minimum width=3cm, minimum height=1cm, anchor=west, draw,node distance=.2cm]

    \node (kernel) [title,below=of syslibs] {Kernel};
    \node (syscalls) [bigblock, below=of kernel] {Rendszerhívások};
    \node (filesystems) [below=of syscalls.south west,smallblock] {Fájlrendszerek};
    \node (networklayer) [smallblock, below right=of filesystems,anchor=north,yshift=-1cm] {Hálózati réteg};

    \node (processhandling) [title,below=of syscalls.south east,anchor=east,xshift=-2.5ex] {Processzkezelés};
    \node (scheduler) [smallblock, below=of processhandling] {Ütemező};
    \node (memhandling) [smallblock, below=of scheduler] {Memóriakezelés};
    \node (IPC) [smallblock, below=of memhandling] {IPC};

    \node (processhandlingwrapper) [wrapper, fit={(processhandling) (scheduler) (memhandling) (IPC)}] {};

    \node (periphhandling) [below=of processhandlingwrapper.south east,bigblock,anchor=east] {Perifériák kezelése};

    \node (kernelwrapper) [wrapper, fit={(kernel) (filesystems) (syscalls) (networklayer) (processhandling) (periphhandling)}] {};

    \node (hardver) [below=of kernelwrapper, Nbigblock] {Hardver};
    \node (usrprocesses) [Sbigblock,above=2cm of kernelwrapper] {Felhasználói processzek};
    \node (syslibs) [above=of kernelwrapper.north west, medblock,anchor=west] {Rendszerkönyvtárak};

    \begin{scope}[latex-latex]
        \draw (usrprocesses.350) -- (usrprocesses.350 |- processhandlingwrapper.north);
        \draw (syslibs) -- (syslibs |- usrprocesses.south);
        \draw (syslibs) -- (syslibs |- syscalls.north);
        \draw (filesystems) -- (filesystems |- syscalls.south);
        \draw (filesystems) -- (filesystems -| processhandlingwrapper.west);
        \draw (filesystems.240) -- (filesystems.240 |- periphhandling.north);
        \draw (networklayer) -- (networklayer -| processhandlingwrapper.west);
        \draw (networklayer.150) -- (networklayer.150 |- filesystems.south);
        \draw (networklayer.60) -- (networklayer.60 |- syscalls.south);
        \draw (networklayer) -- (networklayer |- periphhandling.north);
        \draw (hardver) -- (periphhandling);
    \end{scope}
\end{tikzpicture}
\end{document}

Answer 2

You could use

• \draw with optional arrow argument, such as \draw[<->], perhaps define a style for it
• specify the nodes with anchors such as syslibs.north for connection
• use |- in node specifications to get orthogonal arrows
• use xshift for shifting arrows horizontally

For example:

\tikzstyle{doublearrow}=[draw, thick, latex-latex] 
...
\draw[doublearrow] (syslibs.north)--(usrprocesses.south);
\draw[doublearrow] (syslibs.south) --(syscalls.north-|syslibs.south);
\draw[doublearrow] ([xshift=-1.5cm]syscalls.north) -- 
                   ([xshift=-1.5cm]usrprocesses.south-|syscalls);