% This is part of OpTeX project, see http://petr.olsak.net/optex

\_codedecl \slideshow {Slides style for OpTeX <2020-03-19>} % loaded on demand by \slides

   \_doc -----------------------------
   Default margins and design is declared here. 
   Note that `\_ttfont` is scaled by `mag1.15` in order to balance the
   ex height of Helvetica (Heros) and LM fonts Typewriter.
   The `\begtt`...`\endtt` verbatim is printed by smaller text.
   \_cod -----------------------------

\_margins/1 a5l (14,14,10,3)mm  % landscape A5 format
\_def\_wideformat{\_margins/1 (263,148) (16,16,10,3)mm } % 16:9 format

\_fontfam[Heros]
\_typosize[16/19]
\_famvardef\_ttfont{\_setfontsize{mag1.15}\_tt}
\_def\_urlfont{}
\_everytt={\_typosize[13/16] \advance\hsize by10mm}
\_fontdef\_fixbf{\_bf}

\_nopagenumbers
\_parindent=0pt
\_ttindent=5mm
\_parskip=5pt plus 4pt minus2pt
\_rightskip=0pt plus 1fil
\_ttindent=10pt
\_def\_ttskip{\_smallskip}

\_onlyrgb   % RGB color space is better for presentations

   \_doc -----------------------------
   The bottom margin is set to 3\,mm. If we use 1\,mm, then baseline of
   `\footline` is 2\,mm from the bottom page. This is depth of the `\Grey`
   rectange used for page numbers. It is rlapped to `\hoffset` because left
   margin = `\hoffset` = right margin. It is 14\,mm for narrow pages or
   16\,mm for wide pages. 
   \_cod -----------------------------

\_footlinedist=1mm
\_footline={\_hss \_rlap{%
   \_rlap{\Grey\_kern.2\_hoffset\_vrule height6mm depth2mm width.8\_hoffset}%
                      \_hbox to\_hoffset{\White\_hss\_folio\_kern3mm}}}

   \_doc -----------------------------
   The `\subtit` is defined analogicaly like `\tit`.
   \_cod -----------------------------

\_eoldef\_subtit#1{\_vskip20pt {\_leftskip=0pt plus1fill \_rightskip=\_leftskip
   \_subtitfont #1\_nbpar}}

   \_doc -----------------------------
   The `\pshow<num>` is implemented by printing the text in invisible
   (transparent) font when `\layernum<<num>`. 
   The color font feature is used for this transparency.
   \_cod -----------------------------

\_famvardef\Transparent{\_setfontcolor{FF000000}\_currvar}
\_def\_use#1#2{\_ifnum\_layernum#1\_relax#2\_fi}
\_def\_pshow#1{\_use{=#1}\Red \_use{<#1}\Transparent \_ignorespaces}

   \_doc -----------------------------
   The main level list is activated here. The `\_item:X` and 
   `\_item:x` are used and are re-defined here.
   If we are in nested level of items and `\pg+` is used then
   `\egroups` macro xepands to the right number of `\egroup`s
   in order to close page correctly. The level of nested item lists
   is saved to the `\_ilevel` register and used when we start again 
   the next text after `\pg+`. 
   \_cod -----------------------------

\_newcount\_ilevel  \_newcount\_gilevel
\_def\*{*}
\_adef*{\_startitem}
\_sdef{_item:X}{\Blue\_raise.2ex\_fullrectangle{.8ex}\_kern.5em}
\_sdef{_item:x}{\Blue\_raise.3ex\_fullrectangle{.6ex}\_kern.4em}
\_style X
\_addto\_begitems{\_style x }\public \begitems ;
\_def\_egroups{\_par\_global\_gilevel=\_ilevel \_egroup}
\_everybegitems={\_advance\_ilevel by1 \_addto\_egroups{\_egroup}}

   \_doc -----------------------------
   The default values of `\pg;`, `\pg+` and `\pg.` are very simple.
   They are used when `\showslides` is not specified.
   \_cod -----------------------------

\_def\_pg#1{\_cs{_spg:#1}}
\_sdef{_spg:;}{\_vfil\_break \_lfnotenumreset}
\_sdef{_spg:.}{\_end}
\_sdef{_spg:+}{\_par}

   \_doc -----------------------------
   We need no numbers and no table of contents when using slides.
   The `\_printsec` macro is redefined in order the title is centered
   and typeset in `\Blue`. 
   \_cod -----------------------------

\_def\_titfont{\_typosize[42/60]\_bf \Blue}
\_def\_subtitfont{\_typosize[20/30]\_bf}
\_def\_secfont{\_typosize[25/30]\_bf \Blue}

\_nonum \_notoc \_let\_resetnonumnotoc=\_relax
\_def\_printsec#1{\_par 
   \_abovetitle{\_penalty-400}\_bigskip
   {\_secfont \_noindent \_leftskip=0pt plus1fill \_rightskip=\_leftskip 
     \_printrefnum[@\_quad]#1\_nbpar}\_insertmark{#1}%
   \_nobreak \_belowtitle{\_medskip}% 
}

   \_doc -----------------------------
   When `\slideshow` is active then each page is opened (roughly speaking) 
   by `\setbox\_slidepage=\vbox\bgroup` and closed by `\egroup`. The material is
   `\unvbox`ed and saved for the usage in the next usage if `\pg+` is in process.
   The `\_slidelayer` is inceremnted instead `\pageno` if `\pg+`.
   This counter is equal to `\count1`, so it is printed to the terminal and
   log file next to `\pageno`. 

   The code is somewhat more complicated when `\layers` is used. Then
   <layered-text> is saved to the `\_layertext` macro, the material before
   it is in `\_sidepage` box and the material after it is in `\_slidepageB`
   box. The pages are completrd in the `\loop` which increments the
   `\layernum` register.   
   \_cod -----------------------------

\_newbox\_slidepage  \_newbox\_slidepageB
\_countdef\_slidelayer=1
\_def\_decr#1{\_global\_advance#1 by-1 }

\_def\_slideshow{\_slidelayer=1 \_slideshowactive \_setbox\_slidepage=\_vbox\_bgroup}

\_def\_slideshowactive{%
   \_sdef{_spg:;}{\_closepage \_global\_slidelayer=1 \_resetpage \_openslide}
   \_sdef{_spg:.}{\_closepage \_end}
   \_sdef{_spg:+}{\_closepage \_incr\_slidelayer \_decr\_pageno \_openslide}
   \_def\bye     {\_closepage \_end}
   \_let\_layers=\_layersactive
   \_def\_destbox[##1:##2]{\_isequal{##1}{ref}\_iffalse \_destboxori[##1:##2]\_fi}%
}
\_def\_openslide{\_setbox\_slidepage=\_vbox\_bgroup \_setilevel 
   \_ifvoid\_slidepage \_else \_unvbox\_slidepage \_nointerlineskip\_lastbox \_fi}
\_def\_setilevel{\_loop \_decr\_gilevel \_ifnum\_gilevel<0 \_else \_begitems \_repeat}

\_def\_closepage{\_egroups  
   \_ifnum \_maxlayers=0 \_unvcopy\_slidepage \_vfil\_break
   \_else \_begingroup \_setwarnslides \_layernum=0 
      \_loop 
         \_ifnum\_layernum<\_maxlayers \_advance\_layernum by1
            \_printlayers \_vfil\_break
            \_ifnum\_layernum<\_maxlayers \_incr\_slidelayer \_decr\_pageno \_fi 
      \_repeat
      \_global\_maxlayers=0
      \_incr\_layernum \_global\_setbox\_slidepage=\_vbox{\_printlayers}%  
      \_endgroup
   \_fi}
\_def\_resetpage{%
   \_global\_setbox\_slidepage=\_box\_voidbox \_global\_setbox\_slidepageB=\_box\_voidbox
   \_lfnotenumreset
}
\_def\_setwarnslides{%
   \_def\pg##1{\_opwarning{\_string\pg##1 \_layersenv}\_def\pg####1{}}%
   \_def\layers##1 {\_opwarning{\_string\layers\_space \_layersenv}\_def\layers####1{}}%
}
\_def\_layersenv{cannot be inside \_string\layers...\_string\endlayers, ignored}

\_def\_printlayers{\_unvcopy\_slidepage \_nointerlineskip\_lastbox
   \_layertext \_endgraf
   \_ifdim\_prevdepth>-1000pt \_kern-\_prevdepth \_kern\_dp\_strutbox \_fi
   \_vskip\_parskip
   \_unvcopy\_slidepageB
}
\_let\_destboxori=\_destbox

\_newcount\_layernum \_newcount\_maxlayers
\_maxlayers=0

\_long\_def\_layersactive #1 #2\endlayers{%
   \_par\_egroup
   \_gdef\_layertext{#2}%
   \_global\_maxlayers=#1
   \_setbox\_slidepageB=\_vbox\_bgroup
}

   \_doc -----------------------------
   Default `\layers <num>` macro (when `\slideshow` is not activated) is simple.
   It prints the <layered-text> with `\layernum=<num>+1` because we need the
   result after last layer is processed.
   \_cod -----------------------------

\_def\_layers #1 {\_par\_layernum=\_numexpr#1+1\_relax}
\_let\endlayers=\_relax

\_def\layers{\_layers}
\_public \subtit \slideshow \pg \wideformat \use \pshow ;

   \_doc -----------------------------
   We must to redefine `\fnotenumpages` because the data from `.ref` file
   are less usable for implementing such feature: the
   footnote should be in more layers repeatedly. But we can suppose that 
   each page starts by `\pg;` macro, so we can reset the footnote counter by
   this macro. 
   \_cod -----------------------------

\_def \_fnotenumpages {\def\_fnotenum{\_the\_lfnotenum}\_pgfnotefalse
   \_def\_lfnotenumreset{\_global\_lfnotenum=0 }}
\_let \_lfnotenumreset=\_relax
\_public \fnotenumpages ;

\_endcode % ----------------------------------------------

The user manual of \OpTeX/ slides are in `op-slides.tex` file.