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Messing around with This could be a better approach using
This seems to work quite well but some misalignments are still visible in certain cases. Just for fun but parallel typesetting is driving me nut, but it's a very interesting problem ;) Function for glue calculation on page transitions: -- Balance overflow content across the overflow frames.
local balanceOverflow = function(frame, contentHeight)
-- Get the opposite frame
local oppositeFrame = (frame == "left") and "right" or "left"
-- Calculate the height of the opposite frame
local oppositeHeight = calculateFrameHeight(oppositeFrame, typesetterPool[oppositeFrame])
-- Calculate the difference in height between the frames
local glueHeight = contentHeight - oppositeHeight
-- If the current frame is taller, add glue to the opposite frame
if glueHeight:tonumber() > 0 then
SU.debug(package._name, "Adding glue to overflow frame: ", oppositeFrame, " of height:", glueHeight)
table.insert(
typesetterPool[oppositeFrame].state.outputQueue,
SILE.types.node.vglue({ height = SILE.types.length(glueHeight) })
)
elseif glueHeight:tonumber() < 0 then
-- If the opposite frame is taller, add glue to the current frame
SU.debug(package._name, "Adding glue to overflow frame: ", oppositeFrame, " of height: ", -glueHeight)
table.insert(
typesetterPool[frame].state.outputQueue,
SILE.types.node.vglue({ height = SILE.types.length(-glueHeight) })
)
end
end
Modified -- Handles page-breaking logic for parallel frames.
local parallelPagebreak = function()
for _, thisPageFrames in ipairs(folioOrder) do
local hasOverflow = false
-- Collect overflow content for each frame.
-- We don't need to clear it after flushing the captured content,
-- because it will be cleared in the next page.
local overflowContent = {}
-- Initialize and process frames in one loop
for _, frame in ipairs(thisPageFrames) do
local typesetter = typesetterPool[frame]
typesetter:initFrame(typesetter.frame)
local thispage = {}
local linesToFit = typesetter.state.outputQueue
local targetLength = typesetter:getTargetLength():tonumber()
local currentHeight = 0
-- Fit content into the frame
while
#linesToFit > 0
and currentHeight + (linesToFit[1].height:tonumber() + linesToFit[1].depth:tonumber())
<= targetLength
do
local line = table.remove(linesToFit, 1)
currentHeight = currentHeight + (line.height:tonumber() + line.depth:tonumber())
table.insert(thispage, line)
end
if #linesToFit > 0 then
hasOverflow = true
overflowContent[frame] = linesToFit
-- Clear outputQueue for next page, because its content has been added to overflowContent.
typesetter.state.outputQueue = {}
else
-- Make sure that every frame in thisPageFrames has an entry in overflowContent.
-- Otherwise, balancing might fail when restoring overflow content.
overflowContent[frame] = {}
end
-- Output content on the current page
typesetter:outputLinesToPage(thispage)
end
-- End current page
SILE.documentState.documentClass:endPage()
if hasOverflow then
-- Start a new page
SILE.documentState.documentClass:newPage()
-- Restore overflow content to the frames
for _, frame in ipairs(thisPageFrames) do
local typesetter = typesetterPool[frame]
for _, line in ipairs(overflowContent[frame]) do
table.insert(typesetter.state.outputQueue, line)
end
end
-- Balance overflow content across frames after restoring the overflow content.
-- You can combine the balancing mechanism with the overflow content restoration,
-- because the balancing mechanism only needs to be called once the restoration is done.
for _, frame in ipairs(thisPageFrames) do
local typesetter = typesetterPool[frame]
local contentHeight = calculateFrameHeight(frame, typesetter)
balanceOverflow(frame, contentHeight)
end
-- Let \sync handle alignment and marking
SILE.call("sync")
end
end
end
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I believe I'm about 90% there with parallel frame alignment. I had some hard time dealing with "soft" glue (like While perfect line-by-line alignment might not be achieved with this way, the visual outcome is acceptable, I think.
And here is an Example and Another. I have acknowledged the Hope, someone will come up with a better solution. My modification of the original package: local base = require("packages.base")
local package = pl.class(base)
package._name = "parallel"
-- Typesetter pool for managing typesetters for different frames (e.g., left and right frames).
local typesetterPool = {}
-- Stores layout calculations for each frame, such as height, marking and overflow tracking.
local calculations = {}
-- Specifies the order of frames for synchronizing and page-breaking logic.
local folioOrder = {}
-- A null typesetter used as a placeholder. This typesetter doesn't output any content.
local nulTypesetter = pl.class(SILE.typesetters.base)
nulTypesetter.outputLinesToPage = function() end -- Override to suppress output
-- Utility function: Iterate through all typesetters and apply a callback function to each.
local allTypesetters = function(callback)
local oldtypesetter = SILE.typesetter -- Save the current typesetter
for frame, typesetter in pairs(typesetterPool) do
SILE.typesetter = typesetter -- Switch to the current frame's typesetter
callback(frame, typesetter) -- Execute the callback
end
SILE.typesetter = oldtypesetter -- Restore the original typesetter
end
-- Utility function: Calculate the height of new material for a given frame.
local calculateFrameHeight = function(frame, typesetter)
local height = calculations[frame].cumulativeHeight or SILE.types.length()
for i = calculations[frame].mark + 1, #typesetter.state.outputQueue do
local lineHeight = typesetter.state.outputQueue[i].height + typesetter.state.outputQueue[i].depth
height = height + lineHeight
end
return height
end
-- Create dummy content to fill up the overflowed frames.
local createDummyContent = function(height, frame, offset)
-- Retrieve document.baselineskip and document.lineskip
-- which are tables with the following fields: height, depth, is_vglue, adjustment, width
local baselineSkip = SILE.settings:get("document.baselineskip")
SU.debug(package._name, "Baseline skip is ", baselineSkip)
-- Safely retrieve lineskip or default to 0
local lineskip = SILE.settings:get("document.lineskip") or SILE.types.length.new({ length = 0 })
SU.debug(package._name, "Line skip is ", lineskip)
-- Extract the absolute lengths
local baselineHeight = baselineSkip.height and baselineSkip.height:tonumber() or 0
local lineSkipHeight = lineskip.height and lineskip.height:tonumber() or 0
-- Combine the lengths to get the total line height
local lineHeight = baselineHeight + lineSkipHeight
SU.debug(package._name, "textHeight = " .. lineHeight)
-- local typesetter = typesetterPool[frame]
-- local lineHeight = typesetter.state.outputQueue[1].height + typesetter.state.outputQueue[1].depth
-- Calculate the number of lines
local numLines = math.floor(height:tonumber() / lineHeight)
-- Validate offset
offset = offset or 0
if offset >= numLines then
SU.warn("Offset is larger than number of lines available; no dummy content will be generated.")
return
end
-- Get the typesetter for the frame
local typesetter = typesetterPool[frame]
SILE.call("color", { color = "white" }, function()
typesetter:typeset("sile")
for i = 1, numLines - offset do
-- Add dummy content and a line break
SILE.call("break")
typesetter:typeset("sile")
end
end)
end
local balanceFramesWithDummyContent = function(offset)
local frameHeights = {}
local maxHeight = SILE.types.length(0)
-- Step 1: Measure the height of all frames and track the maximum height
allTypesetters(function(frame, typesetter)
local height = calculateFrameHeight(frame, typesetter)
frameHeights[frame] = height
if height > maxHeight then
maxHeight = height -- Track the tallest frame
end
SU.debug(package._name, "Height of frame ", frame, ": ", height)
end)
-- Step 2: Add dummy content to shorter frames to match the maximum height
allTypesetters(function(frame, typesetter)
local heightDifference = maxHeight - frameHeights[frame]
if heightDifference:tonumber() > 0 then
-- Add dummy content to balance the frame height
SILE.typesetter = typesetter
createDummyContent(SILE.types.length(heightDifference), frame, offset or 0)
SU.debug(package._name, "Added dummy content to frame ", frame, " to balance height by: ", heightDifference)
end
end)
end
-- Balances the height of content across frames by adding glue to the shorter frame.
local addBalancingGlue = function(height)
allTypesetters(function(frame, typesetter)
calculations[frame].heightOfNewMaterial = calculateFrameHeight(frame, typesetter)
local glue = height - calculations[frame].heightOfNewMaterial
if glue:tonumber() > 0 then
table.insert(typesetter.state.outputQueue, SILE.types.node.vglue({ height = glue }))
SU.debug(package._name, "Already added balancing glue of", glue, " to bottom of frame", frame)
end
-- calculations[frame].mark = #typesetter.state.outputQueue
-- SU.debug(package._name, "Mark for frame", frame, "is", calculations[frame].mark)
end)
end
-- Adds a flexible glue (parskip) to the bottom of each frame
-- This is decoupled from addBalancingGlue calculations, serving a simple purpose.
local addParskipToFrames = function(parskipHeight)
allTypesetters(function(_, typesetter)
table.insert(typesetter.state.outputQueue, SILE.types.node.vglue({ height = parskipHeight }))
end)
end
-- Handles page-breaking logic for parallel frames.
-- Modify parallelPagebreak to use dummy content
local parallelPagebreak = function()
for _, thisPageFrames in ipairs(folioOrder) do
local hasOverflow = false
local overflowContent = {}
-- Initialize and process frames
for _, frame in ipairs(thisPageFrames) do
local typesetter = typesetterPool[frame]
typesetter:initFrame(typesetter.frame)
local thispage = {}
local linesToFit = typesetter.state.outputQueue
local targetLength = typesetter:getTargetLength():tonumber()
local currentHeight = 0
while
#linesToFit > 0
and currentHeight + (linesToFit[1].height:tonumber() + linesToFit[1].depth:tonumber())
<= targetLength
do
local line = table.remove(linesToFit, 1)
currentHeight = currentHeight + (line.height:tonumber() + line.depth:tonumber())
table.insert(thispage, line)
end
if #linesToFit > 0 then
hasOverflow = true
overflowContent[frame] = linesToFit
typesetter.state.outputQueue = {}
else
overflowContent[frame] = {}
end
typesetter:outputLinesToPage(thispage)
end
SILE.documentState.documentClass:endPage()
if hasOverflow then
-- Start a new page
SILE.documentState.documentClass:newPage()
-- Restore overflow content to the frames
for _, frame in ipairs(thisPageFrames) do
local typesetter = typesetterPool[frame]
for _, line in ipairs(overflowContent[frame]) do
table.insert(typesetter.state.outputQueue, line)
end
end
-- Balance the frames using dummy text
balanceFramesWithDummyContent()
-- Let \sync handle alignment and marking
SILE.call("sync")
end
end
end
-- Initialization function for the package.
function package:_init(options)
base._init(self, options)
-- Initialize the null typesetter.
SILE.typesetter = nulTypesetter(SILE.getFrame("page"))
-- Ensure the `frames` option is provided.
if type(options.frames) ~= "table" then
SU.error("Package parallel must be initialized with a set of appropriately named frames")
end
-- Set up typesetters for each frame.
for frame, typesetter in pairs(options.frames) do
typesetterPool[frame] = SILE.typesetters.base(SILE.getFrame(typesetter))
typesetterPool[frame].id = typesetter
typesetterPool[frame].buildPage = function() end -- Disable auto page-building
-- Register commands (e.g., \left, \right) for directing content to frames.
local fontcommand = frame .. ":font"
self:registerCommand(frame, function(_, _)
SILE.typesetter = typesetterPool[frame]
SILE.call(fontcommand)
end)
-- Define default font commands for frames if not already defined.
if not SILE.Commands[fontcommand] then
self:registerCommand(fontcommand, function(_, _) end)
end
end
-- Configure the order of frames for the folio (page layout).
if not options.folios then
folioOrder = { {} }
for frame, _ in pl.tablex.sort(options.frames) do
table.insert(folioOrder[1], frame)
end
else
folioOrder = options.folios
end
-- Customize the `newPage` method to synchronize frames.
-- Ensure that each new page starts clean but balanced
self.class.newPage = function(self_)
self.class._base.newPage(self_)
-- Reset calculations
allTypesetters(function(frame, _)
calculations[frame] = { mark = 0 }
end)
-- Align and balance frames
SILE.call("sync")
end
-- Initialize calculations for each frame.
allTypesetters(function(frame, _)
calculations[frame] = { mark = 0 }
end)
-- Override the `finish` method to handle parallel page-breaking.
local oldfinish = self.class.finish
self.class.finish = function(self_)
parallelPagebreak()
oldfinish(self_)
end
end
-- Registers commands for the package.
function package:registerCommands()
-- shortcut for \parskip
self:registerCommand("parskip", function(options, _)
local height = options.height or "12pt plus 3pt minus 1pt"
SILE.typesetter:leaveHmode()
SILE.typesetter:pushVglue(SILE.types.length(height))
end)
self:registerCommand("sync", function(_, _)
local anybreak = false
local maxheight = SILE.types.length()
-- Check for potential page breaks.
allTypesetters(function(_, typesetter)
typesetter:leaveHmode(true)
local lines = pl.tablex.copy(typesetter.state.outputQueue)
if SILE.pagebuilder:findBestBreak({ vboxlist = lines, target = typesetter:getTargetLength() }) then
anybreak = true
end
end)
-- Perform a page break if necessary.
if anybreak then
parallelPagebreak()
return
end
-- Calculate the height of new material for balancing.
allTypesetters(function(frame, typesetter)
calculations[frame].heightOfNewMaterial = calculateFrameHeight(frame, typesetter)
if calculations[frame].heightOfNewMaterial > maxheight then
maxheight = calculations[frame].heightOfNewMaterial
SU.debug(package._name, "Value of maxheight after balancing for frame ", frame, ": ", maxheight)
end
end)
-- Add balancing glue
addBalancingGlue(maxheight)
-- Check if parskip is effectively nil
local parskip = SILE.settings:get("document.parskip")
-- SU.debug("parallel", "parsing parskip", parskip.length, parskip.stretch, parskip.shrink)
if not parskip.length then
-- Insert flexible glue to manage space between two successive pairs of frames separated by the \sync command
-- Add parskip to the bottom of both frames
addParskipToFrames(SILE.types.length("12pt plus 3pt minus 1pt"))
else
-- Add the value of parskip set by user
addParskipToFrames(parskip)
end
end)
end
return package
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I have a modified
diglotclass like this:and a
parallelpackage:I've managed to add balancing glue to the bottom of shorter frames, but I'm still struggling with overflow handling when a frame spills over to the next page. I've been working on calculating the
overflowHeight(the height of all unprocessed line - the height of all processed ones) in theparallelPagebreakfunction for over a week, but I haven't been able to crack it. It's quite an interesting challenge.Another problem I have with
parallelpackage is displaying footnote text. I can see the frames for footnotes, but theirs contents are not typeset.Mininal example:
If you find it interesting, please play with it and share the outcome with me.
Thank you for you valuable time and interest.
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