# Draw dotted line with circled dots and automatic spacing

I'm trying to create dotted lines with where every dot has a defined size and a circle around it, with also a defined size.

First I applied this answer to create a dash pattern:

\tikzset{
dot diameter/.store in=\dot@diameter,
dot diameter=3pt,
dot spacing/.store in=\dot@spacing,
dot spacing=10pt,
dots/.style={
line width=\dot@diameter,
line cap=round,
dash pattern=on 0pt off \dot@spacing
}
}


Then I plot these dotted lines in black - white - black on top of each other to achieve the desired effect. How can I change the tikzset to get this in one step?

The next problem is that it requires a defined dot-spacing which is fine if I'd knew the distance between the endpoints of my line, which I usually don't, so I'm fiddling around with the spacing manually. But I'd like to have a circled dot at the beginning and end node and the rest of the dots equally spaced inbetween. How can I achieve that equal distribution? Is it possible to define, say, exactly 11 dots on that line, equally distributed?

Thank you!

## MWE

\documentclass{article}
\usepackage{tikz}

\makeatletter
\tikzset{
dot diameter/.store in=\dot@diameter,
dot diameter=3pt,
dot spacing/.store in=\dot@spacing,
dot spacing=10pt,
dots/.style={
line width=\dot@diameter,
line cap=round,
dash pattern=on 0pt off \dot@spacing
}
}
\makeatother

\begin{document}
\begin{tikzpicture}

\coordinate (A1) at (1,1);
\coordinate (B1) at (5,1);
\coordinate (A2) at (1,1.5);
\coordinate (B2) at (5,1.5);

% for reference frame
\draw [black, thick]   (A1.center) -- (B1.center) -- (B2.center) -- (A2.center) -- (A1.center);

% three dot layers #1
\draw [black, dot diameter=3mm, dot spacing=3.8mm, dots]   (A1.center) -- (B1.center);
\draw [white, dot diameter=2.5mm, dot spacing=3.8mm, dots]  (A1.center) -- (B1.center);
\draw [black, dot diameter=1mm, dot spacing=3.8mm, dots]    (A1.center) -- (B1.center);

% three dot layers #2
\draw [black, dot diameter=3mm, dot spacing=4mm, dots]   (A2.center) -- (B2.center);
\draw [white, dot diameter=2.5mm, dot spacing=4mm, dots]  (A2.center) -- (B2.center);
\draw [black, dot diameter=1mm, dot spacing=4mm, dots]    (A2.center) -- (B2.center);

\end{tikzpicture}
\end{document}


The solid line is just for orientation, there shouldn't be a connect between the dots. The upper dotted line is manually adjusted to get the correct spacing.

This answer proposes to use preaction and|or postaction to define a style which draws all three layers in one command but doesn't solve the problem about equally distributed 11 dots between two points.

\documentclass{article}
\usepackage{tikz}

\makeatletter
\tikzset{
dot diameter/.store in=\dot@diameter,
dot diameter=3pt,
dot spacing/.store in=\dot@spacing,
dot spacing=10pt,
dots/.style={
line width=\dot@diameter,
line cap=round,
dash pattern=on 0pt off \dot@spacing
},
mydots/.style={
dot spacing=3.8mm,
preaction={draw=black,
dot diameter=3mm,
dots},
draw = white,
dot diameter=2.5mm,
dots,
postaction={draw=black,
dot diameter=1mm,
dots},
}
}
\makeatother

\begin{document}
\begin{tikzpicture}

\draw [mydots]   (0,0) -- (4,0);

\draw [mydots]   (0,1) .. controls (3,1) and (4,2).. (3,3);

\end{tikzpicture}
\end{document}


Update: Parametric version: \mydots={dot dimension}{distance}

\documentclass[tikz,border=2mm]{standalone}

\makeatletter
\tikzset{
dot diameter/.store in=\dot@diameter,
dot diameter=3pt,
dot spacing/.store in=\dot@spacing,
dot spacing=10pt,
dots/.style={
line width=#1,
line cap=round,
dash pattern=on 0pt off \dot@spacing
},
mydots/.style 2 args={
dot spacing=#2,
preaction={draw=black,
dots=#1},
draw = white,
dots=.8*#1,
postaction={draw=black,
dots=.333*#1},
}
}
\makeatother

\begin{document}
\begin{tikzpicture}

\draw [mydots={3mm}{3.8mm}]   (0,0) -- (4,0);

\draw [mydots={2mm}{5mm}]   (0,1) .. controls (3,1) and (4,2).. (3,3);

\end{tikzpicture}
\end{document}


• But it seems that I can just predefine the dot diameters of pre- and post-action, right? The creating of the variable dot innerdiameter/.store in=\dot@innerdiameter, and use it with pre- and post-action does not seem to work. Also preaction={draw=black, dot diameter=\dot@diameter, dots}, does not work. Somehow the size of the dots must be controllable, either relative to each other by specifying just one of the dot sizes or all three absolute. – thewaywewalk Nov 24 '15 at 12:12
• @thewaywewalk I'm sorry but I don't understand your question. In any case I've updated the answer with a parametric dots style. Is something like this what you want? – Ignasi Nov 24 '15 at 17:31
• you haven't updated the answer like mentioned in you comment as there is no edit, have you? – thewaywewalk Dec 4 '15 at 6:44
• @thewaywewalk: Sorry, I did it, but probably forgot to click save button. Now it's ok. – Ignasi Dec 4 '15 at 7:50
• This works great. But the automatic sapcing is not trivial to realize, is it? – thewaywewalk Dec 4 '15 at 11:23