%D \module
%D   [       file=spac-grd,
%D        version=2009.10.16, % 1998.03.10, was core-grd.tex
%D          title=\CONTEXT\ Spacing Macros,
%D       subtitle=Grid Snapping,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

%D This module will be merged into spac-ver.mkiv.

\writestatus{loading}{ConTeXt Spacing Macros / Grid Snapping}

\unprotect

%D A rather crappy macro that we need to avoid and as such it will probably
%D disappear:

\installcorenamespace{lastnodepusher}

\let\poplastnode\relax

\unexpanded\def\pushlastnode
  {\csname\??lastnodepusher
     \ifcsname\??lastnodepusher\the\lastnodetype\endcsname
       \the\lastnodetype
     \else
       \s!unknown
     \fi
   \endcsname}

\setvalue{\??lastnodepusher\number\kernnodecode}%
  {\unexpanded\edef\poplastnode{\kern\the\lastkern\relax}%
   \kern-\lastkern}

\setvalue{\??lastnodepusher\number\gluenodecode}%
  {\unexpanded\edef\poplastnode{\vskip\the\lastskip\relax}%
   \vskip-\lastskip}

\setvalue{\??lastnodepusher\number\penaltynodecode}%
  {\unexpanded\edef\poplastnode{\penalty\the\lastpenalty\relax}%
   \nobreak}

\setvalue{\??lastnodepusher\s!unknown}%
  {\let\poplastnode\relax}

%D Moved from supp-box:

%D \macros
%D  {startbaselinecorrection,baselinecorrection,
%D   showbaselinecorrection,offbaselinecorrection}
%D
%D Spacing around ruled boxes can get pretty messed up. The
%D next macro tries as good as possible to fix this.
%D
%D \startbuffer[1]
%D \startbaselinecorrection
%D \ruledhbox{Rule Brittanica}
%D \stopbaselinecorrection
%D \stopbuffer
%D
%D \typebuffer[1]
%D
%D The macros put some white space around the box:
%D
%D \getbuffer[1]
%D
%D A simple alternative is \type {\baselinecorrection}, which
%D only looks at the previous line.
%D
%D \startbuffer[2]
%D \baselinecorrection
%D \ruledhbox{Rule Brittanica}
%D \baselinecorrection
%D \stopbuffer
%D
%D \typebuffer[2]
%D
%D This time the last preceding line gets a correction,%
%D dependant on the depth.
%D
%D \getbuffer[2]
%D
%D One can make the correction visible by saying \type
%D {\showbaselinecorrection}. Part of the correction is
%D calculated from the dimensions of a~(. One can disble the
%D correction by calling \type {\offbaselinecorrection}.
%D
%D When visualize the first example looks like:
%D
%D {\showbaselinecorrection\getbuffer[1]}
%D
%D and the second one comes out as:
%D
%D {\showbaselinecorrection\getbuffer[2]}

% \definecolor[GridLineColor][red]
% \definecolor[GridTextColor][blue]

\newdimen\d_spac_lines_correction_before
\newdimen\d_spac_lines_correction_after

\newbox  \b_spac_lines_correction_before
\newbox  \b_spac_lines_correction_after

\def\spac_lines_initialize_corrections
  {\setbox\b_spac_lines_correction_before\hpack{\setstrut\strut}%
   \setbox\b_spac_lines_correction_after \hbox {(}%
   \d_spac_lines_correction_before\dimexpr\ht\b_spac_lines_correction_before-\ht\b_spac_lines_correction_after\relax
   \d_spac_lines_correction_after \dimexpr\dp\b_spac_lines_correction_before-\dp\b_spac_lines_correction_after\relax
   \ifdim\d_spac_lines_correction_before<\zeropoint\d_spac_lines_correction_before\zeropoint\fi
   \ifdim\d_spac_lines_correction_after <\zeropoint\d_spac_lines_correction_after \zeropoint\fi}

%unexpanded\def\dotopbaselinecorrection{\kern\d_spac_lines_correction_before}
%unexpanded\def\dobotbaselinecorrection{\kern\d_spac_lines_correction_after }

% experiment, todo: proper mkiv mechanism
%
% \input ward \par
% \startframedtext test  \stopframedtext
% \input ward \par
% \startlinecorrection \framed{xxx} \stoplinecorrection
% \input ward \par
%
% \setupwhitespace[big]
%
% \input ward \par
% \startframedtext test  \stopframedtext
% \input ward \par
% \startlinecorrection \framed{xxx} \stoplinecorrection
% \input ward \par

% to be redone:

\unexpanded\def\dotopbaselinecorrection{\expandafter\blank\expandafter[\the\d_spac_lines_correction_before]}
\unexpanded\def\dobotbaselinecorrection{\expandafter\blank\expandafter[\the\d_spac_lines_correction_after ]}

\def\showbaselinecorrection
  {\def\dobaselinecorrection % visualization is not watertight!
     {\bgroup
      \ifdim\prevdepth>\zeropoint
        \kern-\prevdepth
      \fi
      \setbox\scratchbox\emptyhbox
      \wd\scratchbox\hsize
      \dp\scratchbox\strutdp
      \nointerlineskip
      \forgetall
      \ruledvpack{\box\scratchbox}%
      \egroup
      \prevdepth\strutdp}%
   \def\dotopbaselinecorrection
     {\hrule\s!height\d_spac_lines_correction_before}%
   \def\dobotbaselinecorrection
     {\hrule\s!height\d_spac_lines_correction_after}}

\def\dobaselinecorrection % beware, this one is redefined / used locally elsewhere
  {\ifdim\prevdepth>\zeropoint\kern-\prevdepth\fi
   \kern\strutdp
   \prevdepth\strutdp}

\def\baselinecorrection
  {\endgraf
   \ifvmode
     \ifdim\prevdepth<\maxdimen
       \ifdim\prevdepth<\zeropoint \else
         \ifdim\prevdepth<\strutdepth \relax
           \pushlastnode
           \dobaselinecorrection
           \poplastnode
         \fi
       \fi
     \fi
   \fi}

\def\pagebaselinecorrection
  {\ifdim\pagegoal<\maxdimen
     \ifdim\pagetotal>\lineheight % or \topskip
       \scratchdimen\pagetotal
       \advance\scratchdimen\lineheight
       \ifdim\scratchdimen<\pagegoal
         \baselinecorrection
       \fi
     \fi
   \fi}

\unexpanded\def\startbaselinecorrection
  {\bgroup
   \let\stopbaselinecorrection\egroup
   \ifcase\baselinecorrectionmode
   \or % normal
     \baselinecorrection
     \ifvmode
       \setbox\scratchbox\vbox\bgroup\ignorespaces
       \let\stopbaselinecorrection\donormalstopbaselinecorrection
     \fi
   \or % off
   \or % force
     \baselinecorrection
     \ifvmode
       \setbox\scratchbox\vbox\bgroup\ignorespaces
       \let\stopbaselinecorrection\doforcedstopbaselinecorrection
     \fi
   \fi}

\let\stopbaselinecorrection\relax

\def\donormalstopbaselinecorrection % I have to check columns yet.
  {\egroup
   \topbaselinecorrection
   \box\scratchbox
   \botbaselinecorrection
   \egroup}

\def\doforcedstopbaselinecorrection % I have to check columns yet.
  {\egroup
   \forcedtopbaselinecorrection
   \box\scratchbox
   \forcedbotbaselinecorrection
   \egroup}

%D We do a bit more checking than needed. The pageborder check
%D is not needed, but I want to look the visualization as good
%D as possible too.

\setnewconstant\baselinecorrectionmode\plusone

\def\onbaselinecorrection   {\baselinecorrectionmode\plusone  }
\def\offbaselinecorrection  {\baselinecorrectionmode\plustwo  }
\def\forcebaselinecorrection{\baselinecorrectionmode\plusthree}

%D \macros
%D  {topbaselinecorrection,botbaselinecorrection}
%D
%D The actual top and bottom corrections are implemented as:

\def\topbaselinecorrection
  {\ifvmode \ifdim\pagegoal<\maxdimen
     \forcedtopbaselinecorrection
   \fi \fi}

\def\forcedtopbaselinecorrection
  {\ifvmode
     \bgroup
     \spac_lines_initialize_corrections
     \whitespace % no longer ok
     \nointerlineskip
     \dotopbaselinecorrection
     \egroup
   \fi}

\def\botbaselinecorrection
  {\ifvmode
     \bgroup
     \spac_lines_initialize_corrections
     \dobotbaselinecorrection
     \allowbreak % new, otherwise problems when many in a row
     \prevdepth\strutdp
     \egroup
   \fi}

\let\forcedbotbaselinecorrection\botbaselinecorrection

% nointerlineskip
%
% startpacked
%     \startlinecorrection \framed{test} \stoplinecorrection
%     \startlinecorrection \framed{test} \stoplinecorrection
% \stoppacked

\def\forcedtopbaselinecorrection
  {\ifvmode
     \bgroup
     \spac_lines_initialize_corrections
     \vspacing[\v!white]
%      \nointerlineskip %
     \dotopbaselinecorrection
     \egroup
\fi}

\def\dobaselinecorrection
  {\ifdim\prevdepth>\zeropoint
     \vspacing[\the\dimexpr-\prevdepth+\strutdp\relax]%
   \else
     \vspacing[\the\dimexpr\strutdp\relax]%
   \fi
   \prevdepth\strutdp}

\let\normalstartbaselinecorrection\startbaselinecorrection

\unexpanded\def\startbaselinecorrection
  {\ifgridsnapping
     \snaptogrid[\v!normal]\vbox\bgroup
     \let\stopbaselinecorrection\egroup
   \else
     \normalstartbaselinecorrection
   \fi}

%D Different in LMTX, maybe here we can use this in \MKIV:
%D
%D \let\checkprevdepth\forcestrutdepth % mlv only
%D
%D as we have sync issues that makes it not work otherwise.

\let\checkprevdepth\baselinecorrection

% This is new (and experimental) and might replace some of the above. beware it doesn't always work
% out well, e.g. when used grouped and such (e.g. before display math doesn't work out well).

% \unexpanded\def\fakenextstrutline
%   {\par
%    \begingroup
%    \reseteverypar
%    \dontleavehmode\hpack to \zeropoint{\page_sides_anchor\hss\strut}% just a tracer
%    \vskip-\parskip
%    \vskip-\struttotal
%    \endgroup}

% \unexpanded\def\fakenextstrutline
%   {\par
%    \begingroup
%    \reseteverypar
%    \dontleavehmode\hpack{\strut}\par
%    \clf_fakenextstrutline
%    \ifdim\pagetotal>\lineheight
%      \pagetotal\dimexpr\pagetotal-\lineheight\relax
%    \fi
%    \endgroup}

% \unexpanded\def\fakenextstrutline
%   {\par
%    \begingroup
%    \reseteverypar
%    \forgetall
%    \dontleavehmode\hpack{\strut}\par
%    \clf_removelastline
%    \endgroup}

\protect \endinput