[Tex/LaTex] creating a fifo symbol with pgfdeclareshape

nodespgf-corepgfkeystikz-pgf

I'm compiling with:

  • pdfTeX, Version 3.1415926-2.3-1.40.12 (MiKTeX 2.9 64-bit) (preloaded format=pdflatex 2011.7.8)
  • pgf 2008/01/15 v2.10 (rcs-revision 1.12)
  • tikz 2010/10/13 v2.10 (rcs-revision 1.76)

I'm trying to create two new shapes for use with the PGF/TikZ environment for my final thesis in embedded engineering. The purpose with the symbols are a task diagram, which is kinda like a UML diagram.
The first symbol, which I think could be a template for the second is a simple FIFO queue symbol.Simple FIFO queue symbol FIFO queue with a semaphore

These are figures from a previous course in embedded programming I've taken. So I'm free to create my own ones. But these seem to be the standard at my school, so I would like to not deviate too much.

I've figured out by reading this answer ( What is the easiest way to draw 3D cube with TikZ? and thank you Matthew Leingang for that answer) that I could copy the rectangle shape and remove the west and east sides, like this:

\makeatletter
\pgfkeys{/pgf/.cd,
  fifo offset x/.initial=20pt,
  fifo offset y/.initial=20pt
}

\pgfdeclareshape{fifo}
{
    \inheritsavedanchors[from=rectangle] % this is nearly a rectangle
    \inheritanchorborder[from=rectangle]
    \inheritanchor[from=rectangle]{north}
    \inheritanchor[from=rectangle]{north west}
    \inheritanchor[from=rectangle]{north east}
    \inheritanchor[from=rectangle]{center}
    \inheritanchor[from=rectangle]{west}
    \inheritanchor[from=rectangle]{east}
    \inheritanchor[from=rectangle]{mid}
    \inheritanchor[from=rectangle]{mid west}
    \inheritanchor[from=rectangle]{mid east}
    \inheritanchor[from=rectangle]{base}
    \inheritanchor[from=rectangle]{base west}
    \inheritanchor[from=rectangle]{base east}
    \inheritanchor[from=rectangle]{south}
    \inheritanchor[from=rectangle]{south west}
    \inheritanchor[from=rectangle]{south east}
  \backgroundpath{
    % store lower right in xa/ya and upper right in xb/yb
    \southwest \pgf@xa=\pgf@x \pgf@ya=\pgf@y
    \northeast \pgf@xb=\pgf@x \pgf@yb=\pgf@y
    \pgfmathsetlength\pgfutil@tempdima{\pgfkeysvalueof{/pgf/fifo offset x}}%
    \pgfmathsetlength\pgfutil@tempdimb{\pgfkeysvalueof{/pgf/fifo offset y}}%
    \def\ppd@offset{\pgfpoint{\pgfutil@tempdima}{\pgfutil@tempdimb}}%
    \pgfpathmoveto{\pgfqpoint{\pgf@xa}{\pgf@ya}}%
    \pgfpathlineto{\pgfqpoint{\pgf@xb}{\pgf@ya}}%
    \pgfpathclose%
    \pgfpathmoveto{\pgfqpoint{\pgf@xb}{\pgf@yb}}%
    \pgfpathlineto{\pgfqpoint{\pgf@xa}{\pgf@yb}}%
    \pgfpathclose
  }
}
\makeatother

That give me this:

Rectangle without sides

I could live with that, having the text in the center also opens for a lot more connection points for arrows to other nodes. But I still need to have a FIFO with a semaphore symbol and semaphore name. For the life of me, I can't crack that one. I'm thinking that I should do a multipart node so I'd have a field for both the queue name and the semaphore name.

I tried to create the internal vertical lines, but only got as far as the first one, then the next ones crashed the compilation. I went about it by first defining the offset between them:

By adding:

\pgfkeys{/pgf/.cd,
internal_displacement x/.initial=5pt,
internal_displacement y/.initial=5pt
}

Between the first \pgfkeys and \pgfdeclareshape and then I defined new x axis values for the vertical lines with:

\pgf@xc=\pgf@xb \advance\pgf@xc by-\pgfkeysvalueof{/pgf/internal_displacement x}%

and added the path:

\pgfpathmoveto{\pgfqpoint{\pgf@xc}{\pgf@ya}}
\pgfpathlineto{\pgfqpoint{\pgf@xc}{\pgf@yb}}
\pgfpathclose

this gave me this:

FIFO with one vertical line

NICE! right?!? But then I want to define some more vertical lines, so I add this right after I have declared \pgf@xc:

\pgf@xd=\pgf@xc \advance\pgf@xd by-\pgfkeysvalueof{/pgf/internal_displacement x}%
\pgf@xe=\pgf@xd \advance\pgf@xe by-\pgfkeysvalueof{/pgf/internal_displacement x}%
\pgf@xf=\pgf@xe \advance\pgf@xf by-\pgfkeysvalueof{/pgf/internal_displacement x}%

I'm thinking that this should shift the x value left by internal_displacement x, but instead I get a whole lot of errors along the likes of:

\pgf@sh@bg@fifo ...nternal_displacement x}\pgf@xe 
                                              =\pgf@xd \advance \pgf@xe ...
l.10 ...idth=2cm,align=center] (fifo1)  {Node One};

I'm guessing internal_displacement x is cleared after being read the first time? This seems rather counter productive. There must be another way of doing this.

So is there somebody who has an idea of:

  1. getting the semaphore symbol added with a multipart node (so I'll have to text fields)
  2. what I'm doing wrong in the vertical lines? I'm thinking if I could get this question nailed, I would not have trouble making the distance between the vertical and horizontal lines.

Best Answer

You can also place your node with a pattern fill and decorate it if the shape declaration turns out to be difficult. 

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{patterns}
\makeatletter
\tikzset{
    mynode/.style={outer sep=1mm,
    pattern=vertical lines,
    minimum width=2cm,
    minimum height=1cm,
    append after command={
        \pgfextra{
        \draw(\tikzlastnode.north east) -- (\tikz@last@fig@name.north west);
        \draw(\tikz@last@fig@name.south east) -- (\tikz@last@fig@name.south west);
        \node[anchor=north] at (\tikz@last@fig@name.south) {#1};}
        }
    },
    with flag/.style={append after command={
        \pgfextra{
        \draw[fill=white](\tikzlastnode.135) circle (3mm);
        \draw[fill,line width=1mm,line cap=round,line join=round]
        ([xshift=-1pt]\tikzlastnode.135) +(0,-2mm) -- ++(0,2mm) --++(-35:2mm) --++(-145:2mm);
        }
        },
    }
}
\makeatother


\begin{document}

\begin{tikzpicture}
\node[mynode={Queue Name}] (a) at (0,0) {};
\node[mynode={Another Queue}, with flag] (b) at (1,2) {};
\end{tikzpicture}

\end{document}

enter image description here

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