[Tex/LaTex] TikZ grid and remember picture, overlay

tikz-pgf

In A package to help with layout generation? Graph paper in the background? the question was asked in the comments as to why it was necessary to shift the whole picture in order to line up the grid properly. It never had a satisfactory answer.

Unfortunately, it appears that the position as well as the grid generation routine are influenced by the paragraph indentation.

Consider the MWE below and run it with both commented as well as un-commented lines.

\documentclass{article}
\usepackage{tikz}
\begin{document}
%\null
%\noindent
\begin{tikzpicture}[remember picture, overlay]
     \draw[line width=1pt,color=teal,step=1cm] (current page.south west) grid ++(5cm,5cm);
  \end{tikzpicture}
XXXX
\end{document}

This produces the following:

enter image description here

If you un-comment the lines you get a different layout. If you add a shift of 7.8mm it results in integral squares

\draw[line width=1pt,color=teal,step=1cm,xshift=-7.8mm,yshift=-7.8mm] (current page.south west) grid ++(5cm,5cm);

What is the right way to compensate and why does the algorithm does not produce integral squares? How can I enforce integral squares?

Best Answer

I guess the trick is to shift the grid slightly. The required shift is defined in the .aux file, which defines a point called pgfid<x>, where <x> is refers to the index of the tikzpicture. In general, this number is given by \pgfpictureid. The following code seems to work (after compiling twice) for all pages.

\documentclass{article}
\usepackage{tikz}
\usepackage{lipsum}

\begin{document}

\newlength\shiftx
\newlength\shifty

\makeatletter
\newcommand\calcshift{%
   \pgfsys@getposition{\pgfpictureid}\@basepoint%
   \pgf@process{\pgfpointorigin\@basepoint}%
   \setlength\shiftx\pgf@x%
   \setlength\shifty\pgf@y%
}
\makeatother

\begin{tikzpicture}[remember picture, overlay]
    \calcshift
    \draw [line width=1pt,color=teal,step=1cm,xshift=-\shiftx, yshift=-\shifty] 
         (current page.south west) grid ++(5cm,5cm);
\end{tikzpicture}

\lipsum{4}

% --- just some other tikz picture
\begin{tikzpicture}
  \draw (0, 0) rectangle (1, 1);
\end{tikzpicture}

\begin{tikzpicture}[remember picture, overlay]
    \calcshift
    \draw [line width=1pt,color=teal,step=1cm,xshift=-\shiftx, yshift=-\shifty] 
         (current page.south west) grid ++(5cm,5cm);
\end{tikzpicture}

\end{document}

Related Solutions

[Tex/LaTex] Using tikz overlay / remember picture option with forest trees

As @cfr suggested in the comment section, this can be done by making use of the tikzmark library.

You need to add \usetikzlibrary{tikzmark} to your preamble. Then, you can put a \subnode in each forest environment and then add a tikzpicture after that with the options overlay and remember picture.

When you issue the \draw command, you can prefix the names of the subnodes with pic cs:, if you want to treat that subnode as a coordinate point (otherwise don't use the pic cs: prefix). Note that you will also need to compile the document twice.

I've also moved the starting point and ending point of the arrow up and over a bit by using the ($()+()$) syntax for specifying a coordinate position.

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{tikzmark}
\newcommand{\false}{\mathbf{f}}
\usetikzlibrary{calc, positioning}
\usetikzlibrary{arrows}
\usepackage{forest}
\setbeamercovered{transparent}
\begin{document}

\begin{frame}{}  

% Tree 1
\begin{forest}
    [$\sigma$, calign=last
        [$a$]
        [\subnode{replaceNode}{$\langle\sigma, \{1,2\},\false \rangle$}, calign=first, baseline, draw=blue, ellipse
            [$\sigma_*$]
            [$a$]
        ]
    ]
  \node at (current bounding box.east)
        [anchor=west]
        {$\Rightarrow_G$};
\end{forest}
%
% Tree 2
\begin{forest}
    [$\sigma$, calign=last
        [$a$]
        [$\sigma$, calign=last
            [$b$]
            [\subnode{t1}{$\langle\sigma, \{1,2\},\false \rangle$}, calign=first, baseline
                [$\sigma$, calign=first
                    [$\sigma_*$]
                    [$a$]
                ]
                [$b$]
            ]
        ]
    ]
\end{forest}
%
% This arrow should connect two nodes of both trees.
\begin{tikzpicture}[overlay,remember picture]
\draw[->, black, dashed, bend angle=45, bend left] ($(pic cs:replaceNode)+(0.25,.2)$) to ($(pic cs:t1)+(0.25,.2)$);
\end{tikzpicture}

\end{frame}

\end{document}

enter image description here

[Tex/LaTex] Tikzpicture with remember picture and overlay inserting vertical space

The problem

The problem is, like in the questions you link to, that using TikZ switches TeX from vertical to horizontal mode. So if your document starts with a TikZ picture, this picture will be part of the first paragraph of your document, which in your case is the title.

When you use \vspace in horizontal mode, this space will be inserted after the current line. Here is a little demonstration:

\documentclass{article}
\usepackage{tikz}

\begin{document}

\fbox{\begin{minipage}[t]{2cm} %% no vspace
    ab cd ef gh ij kl mn op qr st uv wx yz
\end{minipage}}
%
\fbox{\begin{minipage}[t]{2cm} %% vspace in vertical mode
    \vspace{1ex}ab cd ef gh ij kl mn op qr st uv wx yz
\end{minipage}}
%
\fbox{\begin{minipage}[t]{2cm} %% vspace mid paragraph
    ab \vspace{1ex} cd ef gh ij kl mn op qr st uv wx yz
\end{minipage}}
%
\fbox{\begin{minipage}[t]{2cm} %% vspace at the start of a paragraph, in horizontal mode
    \leavevmode\vspace{1ex}ab cd ef gh ij kl mn op qr st uv wx yz
\end{minipage}}
%
\fbox{\begin{minipage}[t]{2cm} %% vspace after a tikz environment
    \begin{tikzpicture}\end{tikzpicture}\vspace{1ex}ab cd ef gh ij kl mn op qr st uv wx yz
\end{minipage}}

\end{document}

(Note that the Tikz picture will reside in a paragraph of its own if it is separated from other content by paragraph breaks, in which case it will probably introduce more vertical space than expected or desired.)

A solution

I think the safer way to include an overlay TikZ environment on a given page is to not have it be part of the running text at all and to draw it when the page is being shipped. That way it is guaranteed not to mess up any spacing.

This can be done by using the atbegshi package. The following code is mostly identical to yours: I've added five lines and removed one empty line. The changes are indicated by comments.

\documentclass{article}
\usepackage{showframe}
\usepackage{xparse}
\usepackage{tikz}
\usepackage{layout}

\usepackage{atbegshi} %% <-- I added this line

\usepackage[textwidth=5.0cm]{geometry}

\newcommand*{\Text}{%
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
Ut purus elit, vestibulum ut, placerat ac, adipiscing vitae, felis.%
}%

\newcommand*{\MyAboveSkip}{5pt}
\newcommand*{\MyBotSkip}{5pt}
\newcommand*{\TypesetTitle}[1]{%
    %% See comments in https://tex.stackexchange.com/q/7676/4301
    \hbox{}\kern-\topskip  
    \vspace*{\MyAboveSkip}
    {\bfseries\centering#1\par}%
    \vspace*{\MyBotSkip}%
}%

\NewDocumentCommand{\TikzDecorations}{%
    O{2}% #1 = Number of lines for title
}{%
  \AtBeginShipoutNext{% %% <-- I added this line
    \AtBeginShipoutUpperLeftForeground{% %% <-- I added this line
      \begin{tikzpicture}[remember picture,overlay]
        \coordinate (X) at ([
              xshift=1.0in+\hoffset+\oddsidemargin,
              yshift=-1.0in-\voffset-\topmargin-\headheight-\headsep%
          ]current page.north west);
        % %% <-- Deleted blank line here
        \draw [red] ([yshift=-2\baselineskip-\MyAboveSkip-\MyBotSkip]X) -- ++ (\linewidth,0);
      \end{tikzpicture}%
    }% %% <-- I added this line
  }% %% <-- I added this line
}

\begin{document}%\layout
\TikzDecorations[2]
\sloppy\parskip0pt\relax
\TypesetTitle{A Long Title That Requires Two Lines}%
\noindent\Text

\end{document}

Some remarks

I had to delete an empty line in your TikZ environment because \AtBeginShipoutNext and \AtBeginShipoutUpperLeftForeground are not defined \long and their arguments are therefore not allowed to contain paragraph breaks. (See e.g. this answer.)

The TikZ environment inside \AtBeginShipoutUpperLeftForeground{…} is placed in the top left corner of the page, so it actually has coordinates (0,0). You can therefore replace current page.north west by 0,0 and leave out the remember picture option. The following thus works just as well:

\NewDocumentCommand{\TikzDecorations}{%
    O{2}% #1 = Number of lines for title
}{%
  \AtBeginShipoutNext{%
    \AtBeginShipoutUpperLeftForeground{%
      \begin{tikzpicture}[overlay] %% <-- removed remember picture
        \coordinate (X) at ([
              xshift=1.0in+\hoffset+\oddsidemargin,
              yshift=-1.0in-\voffset-\topmargin-\headheight-\headsep%
          ]0,0); %% <-- 0,0 instead of current page.north west
        \draw [red] ([yshift=-2\baselineskip-\MyAboveSkip-\MyBotSkip]X) -- ++ (\linewidth,0);
      \end{tikzpicture}%
    }%
  }%
}

(In fact, you won't even need to run LaTeX twice for this line to show up at the right spot. Note that the opposite corner of the page has coordinates (\paperwidth,-\paperheight), with a minus sign.)

If you replace AtBeginShipoutUpperLeftForeground by AtBeginShipoutUpperLeft, then the tikz picture will be drawn behind your text rather than on top of it.