# How to draw a box around a certain part of the page?

I'm using a0poster package to create a poster of dimensions 90x100 cm^2. To place text on the page I use \textblock command. Now, there are several blocks I want to frame together. The obvious choice is to use tikz. This, however, fail miserably. For example, Consider the following

\begin{tikzpicture}
\node (a) at (0,0) {a};
\node (b) [left=50cm of a] {b};
\node (c) [right=10cm of a] {c};
\end{tikzpicture}

a and c doesn't appear on the page when I apply this inside a textblock. When I use it outside a textblock, the nodes positions change in an unpredictable way. If I try to use

\begin{tikzpicture}
\node (a) at (current page) {a};
\node (b) [left=50cm of a] {b};
\node (c) [right=10cm of a] {c};
\end{tikzpicture}

The results are pretty much the same with the main feature that the position is not constant. Event using current page.center isn't constant, which is buffering to me.

How can I, then, draw a line between two fixed points on the poster?

• Is it just about drawing a line from some foxed point to another fixed point? I didn't follow! – user11232 Jan 16 '14 at 12:37
• Yes, drawing from point (a) on the poster to point (b) on the poster. – Yotam Jan 16 '14 at 12:50

I don't think it is so complicated. You have to use proper coordinates and remember picture,overlay options:

\documentclass{a0poster}
\usepackage{tikz}
\usetikzlibrary{calc}
\usepackage{blindtext}
\begin{document}
\begin{tikzpicture}[remember picture,overlay]
\draw[red,line width=5pt] (20,-20) -- (40,-20);  %% one line
\draw[green,line width=5pt] (50,-40) -- (50,-80);  %% another line
\draw[blue,line width=5pt] ($(current page.north west)+(40cm,-50cm)$) -- ($(current page.north west)+(80cm,-50cm)$);  %% one more line
\end{tikzpicture}
\Blinddocument
\end{document}

Another example:

\documentclass{a0poster}
\usepackage{tikz}
\usetikzlibrary{calc,positioning}
\usepackage{blindtext}
\begin{document}
\begin{tikzpicture}[remember picture,overlay]
\node (a) at ($(current page.north west)+(90cm,-50cm)$) {a};
\node (b) [left=50cm of a] {b};
\node (c) [right=10cm of a] {c};
\draw[red,line width=5pt] (a) -- (b);  %% one line
\draw[green,line width=10pt] (a) -- (c);  %% one line
\end{tikzpicture}
\Blinddocument
\end{document}