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local log = logging.new("mathmlfixes")
-- <mglyph> should be inside <mi>, so we don't process it
-- even though it is a token element
local token = {"mi", "mn", "mo", "mtext", "mspace", "ms"}
local token_elements = {}
for _, tok in ipairs(token) do token_elements[tok] = true end
local function is_token_element(el)
return token_elements[el:get_element_name()]
end
local function fix_token_elements(el)
-- find token elements that are children of other token elements
if is_token_element(el) then
local parent = el:get_parent()
if is_token_element(parent) then
-- change top element in nested token elements to mstyle
parent._name = "mstyle"
end
end
end
local function fix_nested_mstyle(el)
-- the <mstyle> element can be child of token elements
-- we must exterminate it
if el:get_element_name() == "mstyle" then
local parent = el:get_parent()
if is_token_element(parent) then
-- if parent doesn't have the mathvariant attribute copy it from <mstyle>
if not parent:get_attribute("mathvariant") then
local mathvariant = el:get_attribute("mathvariant")
parent._attr = parent._attr or {}
parent:set_attribute("mathvariant", mathvariant)
end
-- copy the contents of <mstyle> to the parent element
parent._children = el._children
end
end
end
local function fix_mathvariant(el)
-- set mathvariant of <mi> that is child of <mstyle> to have the same value
local function find_mstyle(x)
-- find if element has <mstyle> parent, and its value of mathvariant
if not x:is_element() then
return nil
elseif x:get_element_name() == "mstyle" then
return x:get_attribute("mathvariant")
else
return find_mstyle(x:get_parent())
end
end
if el:get_element_name() == "mi" then
-- process only <mi> that have mathvariant set
local oldmathvariant = el:get_attribute("mathvariant")
if oldmathvariant then
local mathvariant = find_mstyle(el:get_parent())
if mathvariant then
el:set_attribute("mathvariant", mathvariant)
end
end
end
end
-- put <mrow> as child of <math> if it already isn't here
local allowed_top_mrow = {
math=true
}
local function top_mrow(math)
local children = math:get_children()
local put_mrow = false
-- don't process elements with one or zero children
-- don't process elements that already are mrow
local parent = math:get_parent()
local parent_name
if parent then parent_name = parent:get_element_name() end
local current_name = math:get_element_name()
if #children < 2 or not allowed_top_mrow[current_name] or current_name == "mrow" or parent_name == "mrow" then return nil end
local mrow_count = 0
for _,v in ipairs(children) do
if v:is_element() and is_token_element(v) then
put_mrow = true
-- break
elseif v:is_element() and v:get_element_name() == "mrow" then
mrow_count = mrow_count + 1
end
end
if not put_mrow and math:get_element_name() == "math" and mrow_count == 0 then
-- put at least one <mrow> to each <math>
put_mrow = true
end
if put_mrow then
local mrow = math:create_element("mrow")
for _, el in ipairs(children) do
mrow:add_child_node(el)
end
math._children = {mrow}
end
end
local function get_fence(el, attr, form)
-- convert fence attribute to <mo> element
-- attr: open | close
-- form: prefix | postfix
local char = el:get_attribute(attr)
local mo
if char then
mo = el:create_element("mo", {fence="true", form = form})
mo:add_child_node(mo:create_text_node(char))
end
return mo
end
local function fix_mfenced(el)
-- TeX4ht uses in some cases <mfenced> element which is deprecated in MathML.
-- Firefox doesn't support it already.
if el:get_element_name() == "mfenced" then
-- we must replace it by <mrow><mo>start</mo><mfenced children...><mo>end</mo></mrow>
local open = get_fence(el, "open", "prefix")
local close = get_fence(el, "close", "postfix")
-- there can be also separator attribute, but it is not used in TeX4ht
-- change <mfenced> to <mrow> and remove all attributes
el._name = "mrow"
el._attr = {}
-- open must be first child, close needs to be last
if open then el:add_child_node(open, 1) end
if close then el:add_child_node(close) end
end
end
local function is_fence(el)
return el:get_element_name() == "mo" and el:get_attribute("fence") == "true"
end
local function fix_mo_to_mfenced(el)
-- LibreOffice NEEDS <mfenced> element. so we need to convert <mrow><mo fence="true">
-- to <mfenced>. ouch.
if is_fence(el) then
local parent = el:get_parent()
local open = el:get_text():gsub("%s*", "") -- convert mo content to text, so it can be used in
-- close needs to be the last element in the sibling list of the current element
local siblings = el:get_siblings()
el:remove_node() -- we don't need this element anymore
local close
for i = #siblings, 1, -1 do
last = siblings[i]
if last:is_element() then
if is_fence(last) then -- set close attribute only if the last element is fence
close = last:get_text():gsub("%s*", "")
last:remove_node() -- remove <mo>
end
break -- break looping over elements once we find last element
end
end
-- convert parent <mrow> to <mfenced>
parent._name = "mfenced"
parent._attr = {open = open, close = close}
end
end
local function fix_numbers(el)
-- convert <mn>1</mn><mo>.</mo><mn>3</mn> to <mn>1.3</mn>
if el:get_element_name() == "mn" then
local n = el:get_sibling_node(1)
-- test if next element is <mo class="MathClass-punc">.</mo>
if n and n:is_element()
and n:get_element_name() == "mo"
and n:get_attribute("class") == "MathClass-punc"
and n:get_text() == "."
then
-- get next element and test if it is <mn>
local x = el:get_sibling_node(2)
if x and x:is_element()
and x:get_element_name() == "mn"
then
-- join numbers and set it as text content of the current element
local newnumber = el:get_text() .. "." .. x:get_text()
log:debug("Joining numbers: " .. newnumber)
el._children = {}
local newchild = el:create_text_node(newnumber)
el:add_child_node(newchild)
-- remove elements that hold dot and decimal part
n:remove_node()
x:remove_node()
end
end
end
end
local function just_operators(list)
-- count <mo> and return true if list contains just them
local mo = 0
for _, x in ipairs(list) do
if x:get_element_name() == "mo" then mo = mo + 1 end
end
return mo
end
local function fix_operators(x)
-- change <mo> elements that are only children of any element to <mi>
-- this fixes issues in LibreOffice with a^{*}
-- I hope it doesn't introduce different issues
-- process only <mo>
if x:get_element_name() ~= "mo" then return nil end
local siblings = x:get_siblings()
-- test if current element list contains only <mo>
if just_operators(siblings) == #siblings then
if #siblings == 1 then
-- one <mo> translates to <mtext>
x._name = "mtext"
log:debug("changing one <mo> to <mtext>: " .. x:get_text())
-- I think we should use <mi>, but LO incorrectly renders it in <msubsup>,
-- even if we use the mathvariant="normal" attribute. <mtext> works, so
-- we use that instead.
-- x:set_attribute("mathvariant", "normal")
else
-- multiple <mo> translate to <mtext>
local text = {}
for _, el in ipairs(siblings) do
text[#text+1] = el:get_text()
end
-- replace first <mo> text with concetanated text content
-- of all <mo> elements
x._children = {}
local newtext = table.concat(text)
local text_el = x:create_text_node(newtext)
log:debug("changing <mo> to <mtext>: " .. newtext)
x:add_child_node(text_el)
-- change <mo> to <mtext>
x._name = "mtext"
-- remove subsequent <mo>
for i = 2, #siblings do
siblings[i]:remove_node()
end
end
end
end
return function(dom)
dom:traverse_elements(function(el)
if settings.output_format ~= "odt" then
-- LibreOffice needs <mfenced>, but Firefox doesn't
fix_mfenced(el)
else
fix_mo_to_mfenced(el)
end
fix_token_elements(el)
fix_nested_mstyle(el)
fix_numbers(el)
fix_operators(el)
fix_mathvariant(el)
top_mrow(el)
end)
return dom
end
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