Kdjykuj

please, consider the following mwe:

documentclass[tikz, margin=3mm]{standalone}

usetikzlibrary{matrix}



begin{document}

begin{tikzpicture}

matrix (m) [matrix of math nodes,

            nodes={draw, font=footnotesize, minimum size=1em,

                   anchor=center,inner sep=0pt},

                   column sep=-pgflinewidth,

                   row sep=-pgflinewidth,

                   every even column/.style={column sep=2pt},

                   every even row/.style={row sep=2pt},% doesn't insert row separation

                   inner sep=1pt,

                   left delimiter={[},right delimiter={]},

             ]

{

alpha  & beta   & gamma  & delta    \

alpha  & beta   & gamma  & delta    \

alpha  & beta   & gamma  & delta    \

alpha  & beta   & gamma  & delta    \

};

end{tikzpicture}

end{document}

meanwhile every even column/.style={column sep=2pt}, gives expected result, i.e. introduce additional column separation after each second column, the every even row/.style={row sep=2pt}, not. do i did something wrong or i misunderstand how it can work or this is bug in TikZ v3.1 (i never test this before, so i don't know if the same happen in v3.0.1)?

edit:

the same happens with for example

row 2/.style = {row sep=2pt} 

thus it might means, that every even row/.style=... and row <row number> works fine only when one like to change some properties of cells inside row, for example color of nodes borders:

every even row/.style={draw red},

but not when one like to change row separation (see @AndréC comment below). However it is interesting, that this is possible to do in every column sep ...

of course, as (temporary) work around is terminate each second row in matrix with for example [2pt], but his is annoying when matrix is huge, for example as is here.

The issue is with scopes. In order to make sure that the style code for the current row only applies to the current row, the style code is executed inside of a scope that is local to the current row. This scope is closed prior to ending the row and adding the row separation, so the value is reverted before it is applied. The solution is to make the change to the row sep global. The key row sep stores the value in pgfmatrixrowsep so we globally define this to be the updated value. Because this change is global, it applies to all rows going forward, so we need an every odd row key setting the row sep to zero to switch it back.

documentclass[tikz, margin=3mm]{standalone}

usetikzlibrary{matrix}



begin{document}

begin{tikzpicture}

matrix (m) [matrix of math nodes,

            nodes={draw, font=footnotesize, minimum size=1em,

                   anchor=center,inner sep=0pt},

                   column sep=-pgflinewidth,

                   every even column/.style={column sep=2pt},

                   every even row/.style={/utils/exec=gdefpgfmatrixrowsep{2pt}},

                   every odd row/.style={/utils/exec=gdefpgfmatrixrowsep{-pgflinewidth}},

                   inner sep=1pt,

                   left delimiter={[},right delimiter={]},

             ]

{

alpha  & beta   & gamma  & delta    \

alpha  & beta   & gamma  & delta    \

alpha  & beta   & gamma  & delta    \

alpha  & beta   & gamma  & delta    \

};

end{tikzpicture}

end{document}