Automatic vertical skip in margin notes in Optex

Question

The image below shows the result for the second page of the following code:

\fontfam[Myriad]
\margins/2 a4 (2,6,2,2)cm 
\mnotesize=4.5cm
\newcount\notenum 
%\fixmnotes\right 
\def\note#1{\global\advance\notenum by 1 
   \fnmark{\the\notenum}% 
   \mnote{\fnmark{\the\notenum}\kern.3em #1}% 
}
\def\fnmark#1{\leavevmode\raise.7ex\hbox{\setfontsize{mag.6}\setff{+lnum}\setff{-onum}\currvar #1}}
%and use:
%
%Text\fnmark{69} text.
%
%If you want to use this in footnotes, try to define:
\def_printfnotemark{\fnmark{_fnotenum}}
\onum\rm
ASDF1234567890\note{asdf}
ASDF\note{asdf} And this note will be above the next one \mnoteskip -\baselineskip\note{asdf}
\mnoteskip =-\baselineskip
ASDF\note{asdf}
\lipsum[1]\note{asdf}
\vfill \eject
ASDF1234567890\note{This is a very long note to check out if we’re going to need more space below.}
ASDF \mnoteskip-2\baselineskip \note{asdf} And this note will be above the next one. \mnoteskip-3\baselineskip \note{asdf}\mnoteskip-4\baselineskip\note{asdf}
ASDF\mnoteskip-5\baselineskip \note{asdf}
\lipsum[1]\note{asdf}
\bye

The worrisome part is that we have to adjust the vertical space manually with \mnoteskip whenever there is more than one note or a long note. Is there a way to set this space according to the space of the previous note?

Answer 1

If we add the sidenotes at shipout time using Lua, we can make sure that nothing collides. With this mechanism, we only need a single pass, and we don't need to write to any .aux or .ref files.

sidenote-test.tex

\fontfam[lm]
\margins/2 letter (1,3,2,2)in
\parindent=0pt
\parskip=1ex
\addto_begoutput{%
    \ifodd\pageno%
        \sidenote_side\right%
    \else%
        \sidenote_side\left%
    \fi%
}
\load[sidenote]
\lorem[1.]\sidenote{\lorem[1.]}
\lorem[2.]\sidenote{\lorem[2.]}
\def_par{\let_par=\par}
\lorem[3]\sidenote{\lorem[3.]}
\lorem[4.]\sidenote{\lorem[4.]}
\lorem[5.]\sidenote{\lorem[5.]}
\lorem[6.]\sidenote{\lorem[6.]}
\lorem[7.]\sidenote{\lorem[7.]}
\vfill\eject
\sidenote_number=199
\def\sidenote_makemark{%
    \leavevmode%
    \raise 0.7ex%
    \hbox{\typosize[8/8]\romannumeral\sidenote_number}%
}
\def\sidenote_makeleft#1{%
    \hsize=2in\relax%
    \leftskip=0pt plus 1fill\relax%
    \rightskip=1in\relax%
    \it%
    \sidenote_makemark%
    #1%
    \vskip 1cm\relax%
}
\lorem[1.]\sidenote{\lorem[1.]}
\lorem[2.]\sidenote{\lorem[2.]}
\def_par{\let_par=\par}
\lorem[3]\sidenote{\lorem[3.]}
\lorem[4.]\sidenote{\lorem[4.]}
\lorem[5.]\sidenote{\lorem[5.]}
\lorem[6.]\sidenote{\lorem[6.]}
\lorem[7.]\sidenote{\lorem[7.]}
\bye

sidenote.opm

%% Initialize namespace
\_namespace{sidenote}
%% Initialize some variables
_newcount\sidenote_number
_newbox.left
_newbox.right
%% We just want a unique attribute number, but to get at the number
%% itself, we need this hack.
_newattribute.attr__
_chardef.attr=_attributealloc
%% Load the Lua module
_directlua{require "sidenote"}
%% Add some redefinable styling commands
%% Make the sidenote mark in the text.
%%     out --> Something to be typeset in the current paragraph
%%             (will be placed in an \hbox)
%% (redefine this if you want a different style)
_newpublic_def\sidenote_makemark{%
    _unskip$^{_the\sidenote_number}$%
}
%% Make the sidenote variant for the left margin.
%%     #1  --> The text of the sidenote
%%     out --> The contents of the sidenote (will be placed in a \vbox)
%% (redefine this if you want a different style)
_newpublic_def\sidenote_makeleft#1{%
    _hsize=2in_relax%%  Width of the sidenote
    _leftskip=0pt plus 1fill_relax%%  Ragged left
    _rightskip=1em_relax%%  1em separation from the paragraphs
    \sidenote_makemark%%  Print the sidenote number
    #1%%  Sidenote text
    _vskip 1ex_relax%%  Make sure succesive sidenotes are 1ex apart
}
%% Make the sidenote variant for the left margin.
%%     #1  --> The text of the sidenote
%%     out --> The contents of the sidenote (will be placed in a \vbox)
%% (redefine this if you want a different style)
_newpublic_def\sidenote_makeright#1{%
    _hsize=2in_relax%%  Width of the sidenote
    _rightskip=0pt plus 1fill_relax%%  Ragged right
    _leftskip=1em_relax%%  1em separation from the paragraphs
    \sidenote_makemark%%  Print the sidenote number
    #1%%  Sidenote text
    _vskip 1ex_relax%%  Make sure succesive sidenotes are 1ex apart
}
%% Define the sidenote command
%%     #1  --> The text of the sidenote
%%     out --> Typesets the sidenote number with \sidenote_makemark,
%%             and records the sidenote text to be included at shipout.
_newpublic_def\sidenote#1{%
    _incr\sidenote_number%%  Increment the sidenote number
    _setbox.left=_vbox{%%  Save the left sidenote contents
        \sidenote_makeleft{#1}%
    }%
    _setbox.right=_vbox{%%  Save the right sidenote contents
        \sidenote_makeright{#1}%
    }%
    %
    %% Make the sidenote mark and mark it with an attribute so we can
    %% find it from Lua
    _hbox attr .attr=\sidenote_number {\sidenote_makemark}%
    %
    .savenote%% Run the Lua function
}
%% Set the page side
_newcount.side
%% Sets the side to typeset the sidenotes on
%%     #1  --> \left'' or\right''
%%     out --> (nothing)
_newpublic_def\sidenote_side#1{%
    \ifx#1_left%
        _global.side=0%
    \else%
        _global.side=1%
    \fi%
}
%% Set the default sidenote side
\sidenote_side\left
%% Switch sides automatically for each page
% \addto_begoutput{%
%     \ifodd\pageno%
%         \sidenote_side\right%
%     \else%
%         \sidenote_side\left%
%     \fi%
% }
_endnamespace

sidenote.lua

-- Initialize some constants
local glue_id = node.id("glue")
local hlist_id = node.id("hlist")
local vlist_id = node.id("vlist")
local attribute = token.create("_sidenote_attr").mode
local LEFT = 0
-- Make an \hss now so that we can copy and reuse it later
local hss = node.new("glue")
hss.stretch = 1
hss.stretch_order = 1
hss.shrink = 1
hss.shrink_order = 1
-- Store the sidenote contents
local lefts = {}
local rights = {}
-- Save the sidenote contents in Lua so we can access them later
define_lua_command(
    "_sidenote_savenote",
    function()
        local number = tex.count.sidenote_number
        lefts[number] = node.copy_list(tex.box._sidenote_left)
        rights[number] = node.copy_list(tex.box._sidenote_right)
    end
)
-- Typeset the sidenote contents
callback.add_to_callback("pre_shipout_filter", function(head)
    -- Should we place the sidenotes on the left or on the right?
    local side = tex.count._sidenote_side
-- The minimum height to place the sidenote at
local min_height = 0
local max_height = (tex.voffset or 0) + tex.vsize

-- Recursively traverse the page
local function recurse(n, height, parent)
    for m in node.traverse(n) do
        -- Set the height of the current node
        local self_height = 0
        if m.id == glue_id and parent.id == vlist_id then
            -- Glue is only vertical if it's in a \vbox
            self_height = node.effective_glue(m, parent)
        elseif (m.height or m.depth) and parent.id == vlist_id then
            self_height = (m.height or 0) + (m.depth or 0)
        end

        -- A node's "shift" attribute is vertical only if the parent is
        -- an \hbox. This corresponds to the primitive \raise.
        local vshift = 0
        if m.shift and
           (parent.id == hlist_id or
            not node.is_node(parent))
        then
            vshift = m.shift
        end

        -- Set the current height
        height = height + self_height

        -- The number of this node's corresponding sidenote
        local attr = node.get_attribute(m, attribute)

        -- We've found a sidenote node
        if attr then
            -- Get the sidenote contents
            local note
            if side == LEFT then
                note = lefts[attr]
            else
                note = rights[attr]
            end

            local note_height = note.height + note.depth

            if min_height + note_height > max_height then
                texio.write_nl(
                    "Warning: sidenote " .. attr .. " is too tall!!!\n"
                )
            end

            -- Zero out the note's height
            note.height = 0
            note.depth = 0

            -- Add any necessary vertical space to prevent collisions
            local offset = math.max(min_height - height, 0)
            local vskip = node.new("glue")
            vskip.width = offset
            note.list = node.insert_before(note.list, note.list, vskip)

            local hss = node.copy(hss)

            -- Create a zero-width \hbox to hold the sidenote
            local box
            if side == LEFT then
                hss.next = note
                box = node.hpack(hss, 0, "exactly")

                lefts[attr] = nil
                node.free(rights[attr])
                rights[attr] = nil
            else
                local offset = node.new("glue")
                offset.width = parent.width

                offset.next = note
                note.next = hss
                box = node.hpack(offset, 0, "exactly")

                rights[attr] = nil
                node.free(lefts[attr])
                lefts[attr] = nil
            end

            -- Inject the \hbox into the page
            parent.prev.next = box
            box.next = parent
            node.slide(parent.prev)

            -- Update the minimum height
            min_height = height + note_height + offset

        -- Not a sidenote, so we need to recurse
        elseif m.list then
            recurse(
                m.list,
                height - self_height + vshift,
                m
            )
        end
    end
end

-- Start at the root of the page
recurse(head.list, tex.voffset or 0, {})

return true

end, "sidenote")