--- /dev/null
+\documentclass[10ptj]{ltjsarticle}
+\usepackage[width=40\zw, lines=40,centering]{geometry}
+\usepackage{amsmath,luacode,xcolor}
+\begin{luacode}
+ lineskip = {}
+do
+ local insert = table.insert
+ local rangedimensions, max = node.rangedimensions, math.max
+ function lineskip.p_profile(before, after)
+ local t = {}
+ do
+ local w_acc, d_before = 0, 0
+ local x = before.head; local xn = x.next
+ while x do
+ local w, d
+ if xn then w, _, d= rangedimensions(before,x,xn)
+ else w, _, d= rangedimensions(before,x) end
+ if d~=d_before then
+ d_before = d; t[w_acc] = t[w_acc] or {}
+ if t[w_acc][1] then t[w_acc][1]=max(t[w_acc][1],d)
+ else t[w_acc][1]=d end
+ end
+ w_acc = w_acc + w
+ x = xn; if x then xn = x.next end
+ end
+ end
+ do
+ local w_acc, h_before = 0, 0
+ local x = after.head; local xn = x.next
+ while x do
+ local w, h
+ if xn then w, h = rangedimensions(after,x,xn)
+ else w, h = rangedimensions(after,x) end
+ if h~=h_before then
+ h_before = h; t[w_acc] = t[w_acc] or {}
+ if t[w_acc][2] then t[w_acc][2]=max(t[w_acc][2],h)
+ else t[w_acc][2]=h end
+ end
+ w_acc = w_acc + w
+ x = xn; if x then xn = x.next end
+ end
+ end
+ local t2 = {}
+ for i,v in pairs(t) do insert(t2, { i, v[1], v[2] } ) end
+ table.sort(t2, function(a,b) return a[1]<b[1] end)
+ do
+ local bls = tex.baselineskip.width
+ local dmax, d, hmax, h, lmin = 0, 0, 0, 0, 1/0
+ for i,v in ipairs(t2) do
+ d, h = (v[2] or d), (v[3] or h)
+ if d>dmax then dmax=d end
+ if h>hmax then hmax=h end
+ if (bls-h-d)<lmin then lmin=bls-h-d end
+ --print(v[1], d, h, bls-h-d)
+ end
+ return lmin, bls - lmin - (before.depth+after.height)
+ end
+ end
+ function lineskip.p_dummy(before, after)
+ local bls = tex.baselineskip.width
+ return nil, 0
+ end
+end
+do
+ local setglue = node.setglue
+ local floor, min = math.floor, math.min
+ function lineskip.l_dummy(dist, g, adj, normal)
+ if dist < tex.lineskiplimit then
+ local ng = tex.lineskip; g.subtype=2
+ setglue(g, ng.width + adj, ng.stretch, ng.shrink, ng.stretch_order, ng.shrink_order)
+ else
+ local ng = tex.baselineskip; g.subtype=2
+ setglue(g, normal, ng.stretch, ng.shrink, ng.stretch_order, ng.shrink_order)
+ end
+ end
+ function lineskip.l_fixed(dist, g, adj, normal)
+ local ng = tex.baselineskip; local f = ng.width*lineskip.fixed_factor
+ g.subtype=2
+ setglue(g,
+ normal - f * floor((dist-lineskip.fixed_mindist)/f),
+ ng.stretch, ng.shrink, ng.stretch_order, ng.shrink_order)
+ end
+end
+
+ local l_profiler, l_skip = lineskip.p_dummy, lineskip.l_dummy
+ function lineskip.setting(profiler, skip_method)
+ l_profiler = lineskip['p_'..tostring(profiler)] or lineskip.p_dummy
+ l_skip = lineskip['l_'..tostring(skip_method)] or lineskip.l_dummy
+ end
+
+ luatexbase.add_to_callback('post_linebreak_filter',
+ function(h)
+ for x in node.traverse_id(12, h) do
+ if (x.subtype==1)or(x.subtype==2)then
+ local p, n = x.prev, x.next
+ if p then
+ while ((p.id==14)or(p.id==12)or(p.id==13)) and p.prev do p = p.prev end
+ if p.id==0 and n.id==0 then
+ local normal = tex.baselineskip.width - p.depth - n.height
+ local lmin, adj; lmin, adj = l_profiler(p,n)
+ l_skip(lmin or normal,x,adj, normal)
+ print(p.depth, x.width, n.height, p.depth+x.width+n.height)
+ end
+ end
+ end
+ end
+ return true
+ end, 'test', 10000
+ )
+\end{luacode}
+\begin{document}
+\directlua{%
+ lineskip.fixed_mindist = tex.lineskip.width
+ lineskip.fixed_factor = 0.5
+}
+
+
+\def\R#1#2{\directlua{lineskip.setting('#1','#2')}%
+\noindent\fbox{\parbox{25\zw}{%
+\baselineskip14pt\noindent
+\setbox2=\vtop{\noindent\hsize20\zw\textcolor{cyan!30!white}{%
+ □□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■
+ □□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■
+ □□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■
+ □□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■
+ □□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■
+ □□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■
+ □□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■□□□□■
+ □□□□■□□□□■□□□□■□□□□■
+}}\dp2=0pt\rlap{\copy2}\par\vspace*{-\baselineskip}
+\textbf{#1, #2}\\
+\the\baselineskip あああああああああああああああ\\
+あああああああああ$X_{X_{X_X}}$ああああああ\\
+ああああああああああああああああああ\\
+……であるから$b=\dfrac1{X_2}$となる.\\
+一方$\dfrac{A^A}{B_B}=21$なので……\\
+……であるから$b=\dfrac1{X_2}$となる.\vadjust{あああああ$\dfrac34$}\\
+一方$\dfrac{A^A}{B_B}=21$なので……
+
+……であるから$b=\dfrac1{X_2}$となる.\\
+一方$\dfrac{A^A}{B_B}=21$なので……
+}}\par}
+
+
+\R{null}{null}
+\R{profile}{null}
+\R{null}{fixed}
+\R{profile}{fixed}
+
+\end{document}