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|
--[[
lua-widow-control
https://github.com/gucci-on-fleek/lua-widow-control
SPDX-License-Identifier: MPL-2.0+
SPDX-FileCopyrightText: 2022 Max Chernoff
]]
--- Tell the linter about node attributes
--- @class node
--- @field prev node
--- @field next node
--- @field id integer
--- @field subtype integer
--- @field penalty integer
--- @field height integer
--- @field depth integer
-- Set some default variables
lwc = lwc or {}
lwc.name = "lua-widow-control"
lwc.nobreak_behaviour = "keep"
-- Locals for `debug_print`
local write_nl = texio.write_nl
local string_rep = string.rep
local write_log
if status.luatex_engine == "luametatex" then
write_log = "logfile"
else
write_log = "log"
end
--- Prints debugging messages to the log, only if `debug` is set to `true`.
--- @param title string The "title" to use
--- @param text string? The "content" to print
--- @return nil
local function debug_print(title, text)
if not lwc.debug then return end
-- The number of spaces we need
local filler = 15 - #title
if text then
write_nl(write_log, "LWC (" .. title .. string_rep(" ", filler) .. "): " .. text)
else
write_nl(write_log, "LWC: " .. string_rep(" ", 18) .. title)
end
end
--[[
\lwc/ is intended to be format-agonistic. It only runs on Lua\TeX{},
but there are still some slight differences between formats. Here, we
detect the format name then set some flags for later processing.
]]
local format = tex.formatname
local context, latex, plain, optex, lmtx
if format:find("cont") then -- cont-en, cont-fr, cont-nl, ...
context = true
if status.luatex_engine == "luametatex" then
lmtx = true
end
elseif format:find("latex") then -- lualatex, lualatex-dev, ...
latex = true
elseif format == "luatex" then -- Plain
plain = true
elseif format == "optex" then -- OpTeX
optex = true
end
--[[
Save some local copies of the node library to reduce table lookups.
This is probably a useless micro-optimization, but it can't hurt.
]]
-- Node ID's
local baselineskip_subid = 2
local glue_id = node.id("glue")
local glyph_id = node.id("glyph")
local hlist_id = node.id("hlist")
local line_subid = 1
local linebreakpenalty_subid = 1
local par_id = node.id("par") or node.id("local_par")
local penalty_id = node.id("penalty")
-- Local versions of globals
local copy = node.copy_list or node.copylist
local find_attribute = node.find_attribute or node.findattribute
local flush_list = node.flush_list or node.flushlist
local free = node.free
local getattribute = node.get_attribute or node.getattribute
local insert_token = token.put_next or token.putnext
local last = node.slide
local new_node = node.new
local node_id = node.is_node or node.isnode
local set_attribute = node.set_attribute or node.setattribute
local string_char = string.char
local traverse = node.traverse
local traverseid = node.traverse_id or node.traverseid
-- Misc. Constants
local iffalse = token.create("iffalse")
local iftrue = token.create("iftrue")
local INFINITY = 10000
local min_col_width = tex.sp("250pt")
local SINGLE_LINE = 50
local PAGE_MULTIPLE = 100
--[[
Package/module initialization
]]
local attribute,
contrib_head,
emergencystretch,
info,
max_cost,
pagenum,
stretch_order,
warning
if lmtx then
-- LMTX has removed underscores from most of the Lua parts
debug_print("LMTX")
contrib_head = "contributehead"
stretch_order = "stretchorder"
else
contrib_head = "contrib_head"
stretch_order = "stretch_order"
end
if context then
debug_print("ConTeXt")
warning = logs.reporter(lwc.name, "warning")
local _info = logs.reporter(lwc.name, "info")
info = function (text)
logs.pushtarget("logfile")
_info(text)
logs.poptarget()
end
attribute = attributes.public(lwc.name)
pagenum = function() return tex.count["realpageno"] end
-- Dimen names
emergencystretch = "lwc_emergency_stretch"
max_cost = "lwc_max_cost"
elseif plain or latex or optex then
pagenum = function() return tex.count[0] end
-- Dimen names
if tex.isdimen("g__lwc_emergencystretch_dim") then
emergencystretch = "g__lwc_emergencystretch_dim"
max_cost = "g__lwc_maxcost_int"
else
emergencystretch = "lwcemergencystretch"
max_cost = "lwcmaxcost"
end
if plain or latex then
debug_print("Plain/LaTeX")
luatexbase.provides_module {
name = lwc.name,
date = "2022/05/14", --%%dashdate
version = "2.1.0", --%%version
description = [[
This module provides a LuaTeX-based solution to prevent
widows and orphans from appearing in a document. It does
so by increasing or decreasing the lengths of previous
paragraphs.]],
}
warning = function(str) luatexbase.module_warning(lwc.name, str) end
info = function(str) luatexbase.module_info(lwc.name, str) end
attribute = luatexbase.new_attribute(lwc.name)
elseif optex then
debug_print("OpTeX")
warning = function(str) write_nl(lwc.name .. " Warning: " .. str) end
info = function(str) write_nl("log", lwc.name .. " Info: " .. str) end
attribute = alloc.new_attribute(lwc.name)
end
else -- This shouldn't ever happen
error [[Unsupported format.
Please use LaTeX, Plain TeX, ConTeXt or OpTeX.]]
end
local paragraphs = {} -- List to hold the alternate paragraph versions
--- Gets the current paragraph and page locations
--- @return string
local function get_location()
return "At " .. pagenum() .. "/" .. #paragraphs
end
--[[
Function definitions
]]
--- Prints the initial glyphs and glue of an hlist
--- @param head node
--- @return nil
local function get_chars(head)
if not lwc.debug then return end
local chars = ""
for n in traverse(head) do
if n.id == glyph_id then
if n.char < 127 then -- Only ASCII
chars = chars .. string_char(n.char)
else
chars = chars .. "#" -- Replacement for an unknown glyph
end
elseif n.id == glue_id then
chars = chars .. " " -- Any glue goes to a space
end
if #chars > 25 then
break
end
end
debug_print(get_location(), chars)
end
--- The "cost function" to use. See the manual.
--- @param demerits number The demerits of the broken paragraph
--- @param lines number The number of lines in the broken paragraph
--- @return number The cost of the broken paragraph
function lwc.paragraph_cost(demerits, lines)
return demerits / math.sqrt(lines)
end
--- Checks if the ConTeXt "grid snapping" is active
--- @return boolean
local function grid_mode_enabled()
-- Compare the token "mode" to see if `\\ifgridsnapping` is `\\iftrue`
return token.create("ifgridsnapping").mode == iftrue.mode
end
--- Gets the next node of a type/subtype in a node list
--- @param head node The head of the node list
--- @param id number The node type
--- @param args table?
--- subtype: number = The node subtype
--- reverse: bool = Whether we should iterate backwards
--- @return node
local function next_of_type(head, id, args)
args = args or {}
if lmtx or not args.reverse then
for n, subtype in traverseid(id, head, args.reverse) do
if (subtype == args.subtype) or (args.subtype == nil) then
return n
end
end
else -- Only LMTX has the built-in backwards traverser
while head do
if head.id == id and
(head.subtype == args.subtype or args.subtype == nil)
then
return head
end
head = head.prev
end
end
end
--- Saves each paragraph, but lengthened by 1 line
---
--- Called by the `pre_linebreak_filter` callback
---
--- @param head node
--- @return node
function lwc.save_paragraphs(head)
if (head.id ~= par_id and context) or -- Ensure that we were actually given a par
status.output_active -- Don't run during the output routine
then
return head
end
-- Prevent the "underfull hbox" warnings when we store a potential paragraph
local renable_box_warnings
if (context or optex) or
#luatexbase.callback_descriptions("hpack_quality") == 0
then -- See #18 and michal-h21/linebreaker#3
renable_box_warnings = true
lwc.callbacks.disable_box_warnings.enable()
end
-- We need to return the unmodified head at the end, so we make a copy here
local new_head = copy(head)
-- Prevent ultra-short last lines (\TeX{}Book p. 104), except with narrow columns
-- Equivalent to \\parfillskip=0pt plus 0.8\\hsize
local parfillskip
if lmtx or last(new_head).id ~= glue_id then
-- LMTX does not automatically add the \\parfillskip glue
parfillskip = new_node("glue", "parfillskip")
else
parfillskip = last(new_head)
end
if tex.hsize > min_col_width then
parfillskip[stretch_order] = 0
parfillskip.stretch = 0.8 * tex.hsize -- Last line must be at least 20% long
end
if lmtx or last(new_head).id ~= glue_id then
last(new_head).next = parfillskip
end
-- Break the paragraph 1 line longer than natural
local long_node, long_info = tex.linebreak(new_head, {
looseness = 1,
emergencystretch = tex.getdimen(emergencystretch),
})
-- Break the natural paragraph so we know how long it was
nat_head = copy(head)
if lmtx then
parfillskip = new_node("glue", "parfillskip")
parfillskip[stretch_order] = 1
parfillskip.stretch = 1 -- 0pt plus 1fil
last(nat_head).next = parfillskip
end
local natural_node, natural_info = tex.linebreak(nat_head)
flush_list(natural_node)
if renable_box_warnings then
lwc.callbacks.disable_box_warnings.disable()
end
if not grid_mode_enabled() then
-- Offset the accumulated \\prevdepth
local prevdepth = new_node("glue")
prevdepth.width = natural_info.prevdepth - long_info.prevdepth
last(long_node).next = prevdepth
end
local long_cost = lwc.paragraph_cost(long_info.demerits, long_info.prevgraf)
if long_info.prevgraf == natural_info.prevgraf + 1 and
long_cost > 10 -- Any paragraph that is "free" to expand is suspicious
then
table.insert(paragraphs, {
cost = long_cost,
node = next_of_type(long_node, hlist_id, { subtype = line_subid })
})
end
-- Print some debugging information
get_chars(head)
debug_print(get_location(), "nat lines " .. natural_info.prevgraf)
debug_print(
get_location(),
"nat cost " ..
lwc.paragraph_cost(natural_info.demerits, natural_info.prevgraf)
)
debug_print(get_location(), "long lines " .. long_info.prevgraf)
debug_print(
get_location(),
"long cost " ..
lwc.paragraph_cost(long_info.demerits, long_info.prevgraf)
)
-- \ConTeXt{} crashes if we return `true`
return head
end
--- Tags the beginning and the end of each paragraph as it is added to the page.
---
--- We add an attribute to the first and last node of each paragraph. The ID is
--- some arbitrary number for \lwc/, and the value corresponds to the
--- paragraphs index, which is negated for the end of the paragraph. Called by the
--- `post_linebreak_filter` callback.
---
--- @param head node
--- @return node
function lwc.mark_paragraphs(head)
if not status.output_active then -- Don't run during the output routine
-- Get the start and end of the paragraph
local top_para = next_of_type(head, hlist_id, { subtype = line_subid })
local bottom_para = last(head)
if top_para ~= bottom_para then
set_attribute(
top_para,
attribute,
#paragraphs + (PAGE_MULTIPLE * pagenum())
)
set_attribute(
bottom_para,
attribute,
-1 * (#paragraphs + (PAGE_MULTIPLE * pagenum()))
)
else
-- We need a special tag for a 1-line paragraph since the node can only
-- have one attribute value
set_attribute(
top_para,
attribute,
#paragraphs + (PAGE_MULTIPLE * pagenum()) + SINGLE_LINE
)
end
end
return head
end
--- A "safe" version of the last/slide function.
---
--- Sometimes the node list can form a loop. Since there is no last element
--- of a looped linked-list, the `last()` function will never terminate. This
--- function provides a "safe" version of the `last()` function that will break
--- the loop at the end if the list is circular. Called by the `pre_output_filter`
--- callback.
---
--- @param head node The start of a node list
--- @return node The last node in a list
local function safe_last(head)
local ids = {}
local prev
while head.next do
local id = node_id(head)
if ids[id] then
warning [[Circular node list detected!
This should never happen. I'll try and
recover, but your output may be corrupted.
(Internal Error)]]
prev.next = nil
debug_print("safe_last", node.type(head.id) .. " " .. node.type(prev.id))
return prev
end
ids[id] = true
head.prev = prev
prev = head
head = head.next
end
return head
end
--- Checks to see if a penalty matches the widow/orphan/broken penalties
--- @param penalty number
--- @return boolean
function is_matching_penalty(penalty)
local widowpenalty = tex.widowpenalty
local clubpenalty = tex.clubpenalty
local displaywidowpenalty = tex.displaywidowpenalty
local brokenpenalty = tex.brokenpenalty
--[[
We only need to process pages that have orphans or widows. If `paragraphs`
is empty, then there is nothing that we can do.
The list of penalties is from:
https://tug.org/TUGboat/tb39-3/tb123mitt-widows-code.pdf#subsection.0.2.1
]]
penalty = penalty - tex.interlinepenalty
return penalty ~= 0 and
penalty < INFINITY and (
penalty == widowpenalty or
penalty == displaywidowpenalty or
penalty == clubpenalty or
penalty == clubpenalty + widowpenalty or
penalty == clubpenalty + displaywidowpenalty or
penalty == brokenpenalty or
penalty == brokenpenalty + widowpenalty or
penalty == brokenpenalty + displaywidowpenalty or
penalty == brokenpenalty + clubpenalty or
penalty == brokenpenalty + clubpenalty + widowpenalty or
penalty == brokenpenalty + clubpenalty + displaywidowpenalty
)
end
--- Remove the widows and orphans from the page, just after the output routine.
---
--- This function holds the "meat" of the module. It is called just after the
--- end of the output routine, before the page is shipped out. If the output
--- penalty indicates that the page was broken at a widow or an orphan, we
--- replace one paragraph with the same paragraph, but lengthened by one line.
--- Then, we can push the bottom line of the page to the next page.
---
--- @param head node
--- @return node
function lwc.remove_widows(head)
local head_save = head -- Save the start of the `head` linked-list
debug_print("outputpenalty", tex.outputpenalty .. " " .. #paragraphs)
if not is_matching_penalty(tex.outputpenalty) or
#paragraphs == 0
then
paragraphs = {}
return head_save
end
info("Widow/orphan/broken hyphen detected. Attempting to remove")
--[[
Find the paragraph on the page with the least cost.
]]
local paragraph_index = 1
local best_cost = paragraphs[paragraph_index].cost
local last_paragraph
local head_last = last(head)
-- Find the last paragraph on the page, starting at the end, heading in reverse
while head_last do
local value = getattribute(head_last, attribute)
if value then
last_paragraph = value % PAGE_MULTIPLE
break
end
head_last = head_last.prev
end
local first_paragraph
-- Find the first paragraph on the page, from the top
local first_attribute_val, first_attribute_head = find_attribute(head, attribute)
if first_attribute_val // 100 == pagenum() - 1 then
-- If the first complete paragraph on the page was initially broken on the
-- previous page, then we can't expand it here so we need to skip it.
first_paragraph = find_attribute(
first_attribute_head.next,
attribute
) % PAGE_MULTIPLE
else
first_paragraph = first_attribute_val % PAGE_MULTIPLE
end
-- We find the current "best" replacement, then free the unused ones
for i, paragraph in pairs(paragraphs) do
if paragraph.cost < best_cost and
i < last_paragraph and
i >= first_paragraph
then
-- Clear the old best paragraph
flush_list(paragraphs[paragraph_index].node)
paragraphs[paragraph_index].node = nil
-- Set the new best paragraph
paragraph_index, best_cost = i, paragraph.cost
elseif i > 1 then
-- Not sure why `i > 1` is required?
flush_list(paragraph.node)
paragraph.node = nil
end
end
debug_print(
"selected para",
pagenum() ..
"/" ..
paragraph_index ..
" (" ..
best_cost ..
")"
)
if best_cost > tex.getcount(max_cost) or
paragraph_index == last_paragraph
then
-- If the best replacement is too bad, we can't do anything
warning("Widow/Orphan/broken hyphen NOT removed on page " .. pagenum())
paragraphs = {}
return head_save
end
local target_node = paragraphs[paragraph_index].node
-- Start of final paragraph
debug_print("remove_widows", "moving last line")
-- Here we check to see if the widow/orphan was preceded by a large penalty
head = last(head_save).prev
local big_penalty_found, last_line, hlist_head
while head do
if head.id == glue_id then
-- Ignore any glue nodes
elseif head.id == penalty_id and head.penalty >= INFINITY then
-- Infinite break penalty
big_penalty_found = true
elseif big_penalty_found and head.id == hlist_id then
-- Line before the penalty
if lwc.nobreak_behaviour == "keep" then
hlist_head = head
big_penalty_found = false
elseif lwc.nobreak_behaviour == "split" then
head = last(head_save)
break
elseif lwc.nobreak_behaviour == "warn" then
warning("Widow/Orphan/broken hyphen NOT removed on page " .. pagenum())
paragraphs = {}
return head_save
end
else
-- Not found
if hlist_head then
head = hlist_head
else
head = last(head_save)
end
break
end
head = head.prev
end
local potential_penalty = head.prev.prev
if potential_penalty and
potential_penalty.id == penalty_id and
potential_penalty.subtype == linebreakpenalty_subid and
is_matching_penalty(potential_penalty.penalty)
then
warning("Making a new widow/orphan/broken hyphen on page " .. pagenum())
end
last_line = copy(head)
last(last_line).next = copy(tex.lists[contrib_head])
head.prev.prev.next = nil
-- Move the last line to the next page
tex.lists[contrib_head] = last_line
local free_next_nodes = false
-- Loop through all of the nodes on the page with the lwc attribute
head = head_save
while head do
local value
value, head = find_attribute(head, attribute)
if not head then
break
end
debug_print("remove_widows", "found " .. value)
-- Insert the start of the replacement paragraph
if value == paragraph_index + (PAGE_MULTIPLE * pagenum()) or
value == paragraph_index + (PAGE_MULTIPLE * pagenum()) + SINGLE_LINE
then
debug_print("remove_widows", "replacement start")
safe_last(target_node) -- Remove any loops
-- Fix the `\\baselineskip` glue between paragraphs
height_difference = (
next_of_type(head, hlist_id, { subtype = line_subid }).height -
next_of_type(target_node, hlist_id, { subtype = line_subid }).height
)
local prev_bls = next_of_type(
head,
glue_id,
{ subtype = baselineskip_subid, reverse = true }
)
if prev_bls then
prev_bls.width = prev_bls.width + height_difference
end
head.prev.next = target_node
free_next_nodes = true
end
-- Insert the end of the replacement paragraph
if value == -1 * (paragraph_index + (PAGE_MULTIPLE * pagenum())) or
value == paragraph_index + (PAGE_MULTIPLE * pagenum()) + SINGLE_LINE
then
debug_print("remove_widows", "replacement end")
local target_node_last = safe_last(target_node)
if grid_mode_enabled() then
-- Account for the difference in depth
local after_glue = new_node("glue")
after_glue.width = head.depth - target_node_last.depth
target_node_last.next = after_glue
after_glue.next = head.next
else
target_node_last.next = head.next
end
break
end
if free_next_nodes then
head = free(head)
else
head = head.next
end
end
info(
"Widow/orphan/broken hyphen successfully removed at paragraph "
.. paragraph_index
.. " on page "
.. pagenum()
)
paragraphs = {} -- Clear paragraphs array at the end of the page
return head_save
end
--- Create a table of functions to enable or disable a given callback
--- @param t table Parameters of the callback to create
--- callback: string = The \LuaTeX{} callback name
--- func: function = The function to call
--- name: string = The name/ID of the callback
--- category: string = The category for a \ConTeXt{} "Action"
--- position: string = The "position" for a \ConTeXt{} "Action"
--- lowlevel: boolean = If we should use a lowlevel \LuaTeX{} callback instead of a
--- \ConTeXt{} "Action"
--- @return table t Enablers/Disablers for the callback
--- enable: function = Enable the callback
--- disable: function = Disable the callback
local function register_callback(t)
if plain or latex then -- Both use \LuaTeX{}Base for callbacks
return {
enable = function()
luatexbase.add_to_callback(t.callback, t.func, t.name)
end,
disable = function()
luatexbase.remove_from_callback(t.callback, t.name)
end,
}
elseif context and not t.lowlevel then
return {
-- Register the callback when the table is created,
-- but activate it when `enable()` is called.
enable = nodes.tasks.appendaction(t.category, t.position, "lwc." .. t.name)
or function()
nodes.tasks.enableaction(t.category, "lwc." .. t.name)
end,
disable = function()
nodes.tasks.disableaction(t.category, "lwc." .. t.name)
end,
}
elseif context and t.lowlevel then
--[[
Some of the callbacks in \ConTeXt{} have no associated "actions". Unlike
with \LuaTeX{}base, \ConTeXt{} leaves some \LuaTeX{} callbacks unregistered
and unfrozen. Because of this, we need to register some callbacks at the
engine level. This is fragile though, because a future \ConTeXt{} update
may decide to register one of these functions, in which case
\lwc/ will crash with a cryptic error message.
]]
return {
enable = function() callback.register(t.callback, t.func) end,
disable = function() callback.register(t.callback, nil) end,
}
elseif optex then -- Op\TeX{} is very similar to luatexbase
return {
enable = function()
callback.add_to_callback(t.callback, t.func, t.name)
end,
disable = function()
callback.remove_from_callback(t.callback, t.name)
end,
}
end
end
-- Add all of the callbacks
lwc.callbacks = {
disable_box_warnings = register_callback({
callback = "hpack_quality",
func = function() end,
name = "disable_box_warnings",
lowlevel = true,
}),
remove_widows = register_callback({
callback = "pre_output_filter",
func = lwc.remove_widows,
name = "remove_widows",
lowlevel = true,
}),
save_paragraphs = register_callback({
callback = "pre_linebreak_filter",
func = lwc.save_paragraphs,
name = "save_paragraphs",
category = "processors",
position = "after",
}),
mark_paragraphs = register_callback({
callback = "post_linebreak_filter",
func = lwc.mark_paragraphs,
name = "mark_paragraphs",
category = "finalizers",
position = "after",
}),
}
local enabled = false
--- Enable the paragraph callbacks
function lwc.enable_callbacks()
debug_print("callbacks", "enabling")
if not enabled then
lwc.callbacks.save_paragraphs.enable()
lwc.callbacks.mark_paragraphs.enable()
enabled = true
else
info("Already enabled")
end
end
--- Disable the paragraph callbacks
function lwc.disable_callbacks()
debug_print("callbacks", "disabling")
if enabled then
lwc.callbacks.save_paragraphs.disable()
lwc.callbacks.mark_paragraphs.disable()
--[[
We do \emph{not} disable `remove_widows` callback, since we still want
to expand any of the previously-saved paragraphs if we hit an orphan
or a widow.
]]
enabled = false
else
info("Already disabled")
end
end
function lwc.if_lwc_enabled()
debug_print("iflwc")
if enabled then
insert_token(iftrue)
else
insert_token(iffalse)
end
end
--- Mangles a macro name so that it's suitable for a specific format
--- @param name string The plain name
--- @param args table<string> The TeX types of the function arguments
--- @return string The mangled name
local function mangle_name(name, args)
if plain then
return "lwc@" .. name:gsub("_", "@")
elseif optex then
return "_lwc_" .. name
elseif context then
return "lwc_" .. name
elseif latex then
return "__lwc_" .. name .. ":" .. string_rep("n", #args)
end
end
--- Creates a TeX command that evaluates a Lua function
--- @param name string The name of the csname to define
--- @param func function
--- @param args table<string> The TeX types of the function arguments
--- @return nil
local function register_tex_cmd(name, func, args)
local scanning_func
name = mangle_name(name, args)
if not context then
local scanners = {}
for _, arg in ipairs(args) do
scanners[#scanners+1] = token['scan_' .. arg]
end
scanning_func = function()
local values = {}
for _, scanner in ipairs(scanners) do
values[#values+1] = scanner()
end
func(table.unpack(values))
end
end
if optex then
define_lua_command(name, scanning_func)
return
elseif plain or latex then
local index = luatexbase.new_luafunction(name)
lua.get_functions_table()[index] = scanning_func
token.set_lua(name, index)
elseif context then
interfaces.implement {
name = name,
public = true,
arguments = args,
actions = func
}
end
end
register_tex_cmd("if_enabled", lwc.if_lwc_enabled, {})
register_tex_cmd("enable", lwc.enable_callbacks, {})
register_tex_cmd("disable", lwc.disable_callbacks, {})
register_tex_cmd(
"nobreak",
function(str)
lwc.nobreak_behaviour = str
end,
{ "string" }
)
register_tex_cmd(
"debug",
function(str)
lwc.debug = str ~= "0" and str ~= "false" and str ~= "stop"
end,
{ "string" }
)
--- Silence the luatexbase "Enabling/Removing <callback>" info messages
---
--- Every time that a paragraph is typeset, \lwc/ hooks in
--- and typesets the paragraph 1 line longer. Some of these longer paragraphs
--- will have pretty bad badness values, so TeX will issue an over/underfull
--- hbox warning. To block these warnings, we hook into the `hpack_quality`
--- callback and disable it so that no warning is generated.
---
--- However, each time that we enable/disable the null `hpack_quality` callback,
--- luatexbase puts an info message in the log. This completely fills the log file
--- with useless error messages, so we disable it here.
---
--- This uses the Lua `debug` library to internally modify the log upvalue in the
--- `add_to_callback` function. This is almost certainly a terrible idea, but I don't
--- know of a better way.
local function silence_luatexbase()
local nups = debug.getinfo(luatexbase.add_to_callback).nups
for i = 1, nups do
local name, func = debug.getupvalue(luatexbase.add_to_callback, i)
if name == "luatexbase_log" then
debug.setupvalue(
luatexbase.add_to_callback,
i,
function(text)
if text:match("^Inserting") or text:match("^Removing") then
return
else
func(text)
end
end
)
return
end
end
end
-- Activate \lwc/
if plain or latex then
silence_luatexbase()
end
lwc.callbacks.remove_widows.enable()
return lwc
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