# Using intersecting coordinates in tikz with the current coordinate

I've learned these tricks:

\draw (X) -- ++(1,1);        % relative positioning
\draw (X) -- (P1 |- P2);
% intersecting coordinates: the x-coordinate of P1 and the y-coordinate of P2


Is there a way to replace P1 in the second \draw command above with something that designates the current position?

Similar complete example:

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{calc}

\begin{document}
\begin{tikzpicture}[font=\sffamily]

\node[draw, circle](C1) at (2,2){Hey dude!};
\node[draw, circle](C2) at (3,4){C2};
\draw[thick] (C1.east) -- ++(1,1) -- (4,0 |- C2.south);

\coordinate(X) at ($(C1.east) + (1,1)$);
\draw[red,thick](X) -- (X |- C2.south);
\end{tikzpicture}
\end{document} The red vertical line is what I want (but I had to manually calculate it and define a coordinate); the black diagonal line next to it is the line drawn by -- (4,0 |- C2.south) and I want to replace 4,0 with something representing the current position.

You know how to use coordinates. So you could just say \draw[thick] (C1.east) -- ++(1,1) coordinate (y) -- (y |- C2.south);. I left the red line in the code as thin and dashed for comparison.

\documentclass[border=3mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{calc}

\begin{document}
\begin{tikzpicture}[font=\sffamily]

\node[draw, circle](C1) at (2,2){Hey dude!};
\node[draw, circle](C2) at (3,4){C2};
\draw[thick] (C1.east) -- ++(1,1) coordinate (y) -- (y |- C2.south);

\coordinate(X) at ($(C1.east) + (1,1)$);
\draw[red,thin, dashed](X) -- (X |- C2.south);
\end{tikzpicture}
\end{document} • what does the coordinate (y) do? I don't understand. – Jason S Apr 27 '16 at 19:54
• I am just assigning to the relative point (C1.east) -- ++(1,1) the coordinate (which is just a node without physical size) of name y. Then I am able to reference this point afterwards. You make use of this by calculating the coordinate at the intersection (y |- C2.south). Basically I do nothing else than you, when you say \coordinate(X) at ($(C1.east) + (1,1)$); \draw[red,thin, dashed](X) -- (X |- C2.south); but in a little different syntax being more compact. – JMP Apr 27 '16 at 19:59