Fixed Baseline Distance Paragraph Height

[SanjayTml]

I have been working on creating posters for different fonts using SILE and Lua. When I try to calculate the paragraph height after changing the linespacing method to fixed and providing a fixed baselinedistance value, I can not get the correct value.

I use the following lines of code to calculate the paragraph height:

`

SILE.call("font", {size = fontOptions.size * relratio}, function()

            SILE.process({name})                                                 -- name is the paragraph text
            SILE.typesetter:leaveHmode(1)
            subsidiary = SILE.pagebuilder:collateVboxes(SILE.typesetter.state.outputQueue)
            local queue = SILE.typesetter.state.outputQueue
            for i = 1, #queue do
                if queue[i].is_vbox then
                    linecounter = linecounter + 1
                    calcparheight = calcparheight + queue[i].height + queue[i].depth
                end
            end
            SILE.typesetter:pushState()
        end)

print("Paragraph height = ", subsidiary.height)
print("Calculated Paragraph height = ", calcparheight)

`

Here 'subsidiary.height' gives me the standard paragraph height that SILE calculates using vboxes, and 'calcparheight' gives me paragraph height with depth(ascenders & descenders) included after calculations(sum of each line height). Both of them work fine when the linespacing is off but gives incorrect paragraph height when linespacing is on.

I change the linespacing method inside Lua as below:

`

 SILE.call("linespacing-on")
 SILE.settings.set("linespacing.method",'fixed')
 SILE.settings.set("linespacing.fixed.baselinedistance", SILE.length('4.5em'))

`

I need help on fixing the above code or solving this using any other method or function in Lua or SILE to calculate the paragraph height.

[alerque]

I think your calculations using the default spacing might be wrong (but by happy accident coming in close). You do realize you cannot know the final height of a paragraph until during the page break routine when all aspects of the height are finalized, right? Anything you try to do in the flow of things like you are is going to be either a guess or you are going to fudge and force some things in the page builder to happen early and hence fix parts of the page before other parts, which can have weird side effects.

Do you have a more complete working example I can look at for where you are calculating this and what gets done with it afterwards?

[SanjayTml]

Thank you for the response. I have two files, one poster.lua and one text.sil

Poster.lua looks like:

local plain = SILE.require("classes/plain")
local poster = plain { id = "poster"}

function poster:init()
    SILE.settings.set("document.parindent", SILE.nodefactory.glue(0))
    return plain.init(self)
end

SILE.registerCommand("posterOutput", function(options, content)
    mystring = "This is Lorem Ipsum random paragraph. This paragraph should occupy the largest possible height of a single page without overflowing to another page. Thank you!"

    SILE.call("linespacing-on")
    SILE.settings.set("linespacing.method",'fixed')
    setmaxheight(mystring)
end)

-- Outputs the string in maximum height available for single page
function setmaxheight(str, setHeight)
    local fontOptions = SILE.font.loadDefaults({})
    local name = str
    if setHeight == nil then
        setHeight = SILE.measurement("95%fh"):absolute()
    end
    if name then
        local tokens = SILE.shaper:shapeToken(name,fontOptions)
        local w = 0
        local h = 0
        for j= 1,#tokens do
            w = w + tokens[j].width
            if h < tokens[j].height then
                h = tokens[j].height
            end
        end
        local fratio = 70/100 * SILE.scratch.pagewidth / 60/100 * SILE.scratch.pageheight
        local cratio = tokens[1].height / tokens[1].width
        local relratio = fratio/cratio
        local subsidiary = nil
        local parheight = nil
        local parwidth = nil
        local linecounter = 0
        local calcparheight = 0
        local largestlineheight = 0
        local smallestlineheight = 1000
        local currentlineheight = 0
        local l = SILE.length({ length = 20, stretch = 10, shrink = 10})
        table.remove(SILE.typesetter.state.nodes)
        local i = 0
        
        -- Initial parheight calculation with default values
        SILE.call("font", {size = fontOptions.size * relratio}, function()
                SILE.process({name})
                SILE.typesetter:leaveHmode(1)
                subsidiary = SILE.pagebuilder:collateVboxes(SILE.typesetter.state.outputQueue)
                local queue = SILE.typesetter.state.outputQueue
                for i = 1, #queue do
                    if queue[i].is_vbox then
                        linecounter = linecounter + 1
                        calcparheight = calcparheight + queue[i].height + queue[i].depth
                        currentlineheight = queue[i].height + queue[i].depth
                        if(currentlineheight > largestlineheight) then
                          largestlineheight = currentlineheight
                        end
                        if(currentlineheight ~= SILE.length('0pt'):absolute() and currentlineheight < smallestlineheight) then
                          smallestlineheight = currentlineheight
                        end
                    end
                end
                SILE.typesetter:pushState()
            end)
        local defaultlinespacing = SILE.settings.get("linespacing.fixed.baselinedistance"):absolute()
        local baselinedistancevalue = defaultlinespacing
        repeat
            local totalHeight = 0
            table.remove(SILE.typesetter.state.nodes)
            local newfontOptions = SILE.font.loadDefaults({size = fontOptions.size*relratio})
            local newtokens = SILE.shaper:shapeToken(str,newfontOptions)
            local wprime = 0
            local hprime = 0
            for k= 1, #newtokens do
                wprime = wprime + newtokens[k].width
                if newtokens[k].height > hprime then
                    hprime = newtokens[k].height
                end
            end
            baselinedistancevalue = SILE.length('4.5em'):absolute() + largestlineheight - hprime
            SILE.settings.set("linespacing.fixed.baselinedistance", baselinedistancevalue)
            parheight = calcparheight
            
            -- Adjust the font relratio(size)
                if(parheight < 50/100*setHeight) then
                    relratio = relratio * 1.75
                elseif(parheight < 80/100*setHeight) then
                    relratio = relratio * 1.25
                elseif(parheight < 90/100*setHeight) then
                    relratio = relratio * 1.05
                elseif(parheight > 1.25*setHeight) then
                    relratio = relratio * 0.7
                elseif(parheight > 95/100*setHeight) then
                    relratio = relratio * 0.9
                else
                    break
                end
                
            calcparheight = 0
            linecounter = 0
            smallestlineheight = largestlineheight + 1000
            currentlineheight = 0
            largestlineheight = 0
            subsidiary = nil
            table.remove(SILE.typesetter.state.nodes)

            -- Parheight Calculation with adjusted relratio(font size)
            SILE.call("font", {size = fontOptions.size * relratio}, function()
                    SILE.process({name})
                    SILE.typesetter:leaveHmode(1)
                    subsidiary = SILE.pagebuilder:collateVboxes(SILE.typesetter.state.outputQueue)
                    local queue = SILE.typesetter.state.outputQueue
                    for i = 1, #queue do
                        totalHeight = totalHeight + queue[i].height + queue[i].depth
                        if queue[i].is_vbox then
                            linecounter = linecounter + 1
                            calcparheight = calcparheight + queue[i].height + queue[i].depth
                            currentlineheight = queue[i].height + queue[i].depth
                            if(currentlineheight > largestlineheight) then
                              largestlineheight = currentlineheight
                            end
                            if(currentlineheight ~= SILE.length('0pt'):absolute() and currentlineheight < smallestlineheight) then
                              smallestlineheight = currentlineheight
                            end
                        end
                    end
                    SILE.typesetter:pushState()
                end)
            i = i+1
            if(i > 12 and parheight < 700) then
                    baselinedistancevalue = SILE.length('4.5em'):absolute() + largestlineheight - hprime
                    SILE.settings.set("linespacing.fixed.baselinedistance", baselinedistancevalue)
                    parheight = calcparheight
                    break
            end
        until(false)
        print(" Final parheight = ", parheight)
        SILE.call("hbox", {height = 0})

        -- Print on the pdf page
        SILE.call('font', {size = fontOptions.size * relratio}, function()
             SILE.typesetter:typeset(name)
        end)
end

text.sil looks like:

\begin[class=poster,papersize=1080pt x 720pt]{document}

% Loading Packages
\script[src=packages/linespacing]
\script[src=packages/background]
\script[src=packages/color]
\script[src=packages/frametricks]
\script[src=packages/specimen]
\script[src=packages/grid]
\script[src=packages/rebox]

% Settings
\nofolios   % Turn off page numbering
\background[color=#00ff00,allpages=true]    % change background color

% Body
\posterOutput[]

\end{document}

[Omikhleia]

Your code is hard to guess with uncomplete script, undeclared variables, etc.

Here is a working version:

\begin{document}
\script[src=packages/linespacing]
\script{
SILE.settings.set("linespacing.method",'fixed')
SILE.settings.set("linespacing.fixed.baselinedistance", SILE.length('4.5em'))

local calcparheight = SILE.length()
SILE.process({ "I have been working on creating posters for different fonts using SILE and Lua. When I try to calculate the paragraph height after changing the linespacing method to fixed and providing a fixed baselinedistance value, I can not get the correct value." })
SILE.typesetter:leaveHmode(1)
local subsidiary = SILE.pagebuilder:collateVboxes(SILE.typesetter.state.outputQueue)
local queue = SILE.typesetter.state.outputQueue
for i = 1, #queue do
   calcparheight = calcparheight + queue[i].height + queue[i].depth
end

print("Paragraph height = ", subsidiary.height + subsidiary.depth)
print("Calculated Paragraph height = ", calcparheight)
}
\end{document}

Outputs:

Paragraph height = 	55.009765625pt
Calculated Paragraph height = 	55.009765625pt

With both giving the same results, which is logical since the loop is (more or less) what the collateVboxes does (wrapping the vboxes in a single vbox, which will evaluate its height (see the implementation of the append method of nodefactory.vbox).

Note the results are the same with the beginning of the script being:

%\script[src=packages/linespacing]
\set[parameter=document.baselineskip,value=4.5em]
\set[parameter=document.lineskip,value=0]
\script{
--SILE.settings.set("linespacing.method",'fixed')
--SILE.settings.set("linespacing.fixed.baselinedistance", SILE.length('4.5em'))

(I.e. the default TeX linespacing but tried to make "fixed"... At least for this text only input in a single size)

Your initial code was testing on is_vbox so skipping the (linespacing etc.) glues -- No idea whether it is what you wanted or not...

[alerque]

If your goal is to center a paragraph vertically on a page you don't need to muck around with calculating its height. Just put one \vfill before the paragraph and one after and you're done. Note that the default page-end command includes a vfill already, so unless you manually eject the page all you need is \vfill + your content + \pagebreak.

The logic is that all the vfill's will automatically get their fair portion of the leftover vertical space when the page layout happens and if there are 2 on the page each will get half the space.

[Omikhleia]

I don't get it and probably missed the point. If you size the paragraph to the largest font possible for it to fill a full page, there's not much left to center vertically ??

EDIT. "Along with justification"... There we go.

(Obviously one would need to use a different page layout to get really centered without different top and bottom margins and also without folio space. But that's a wholly different topic.)

[SanjayTml]

@Omikhleia Can you show/share with me how you did the above?
I tried to edit my code but still no good results. Maybe I should start from the beginning again.

[Omikhleia]

@SanjayTml You are on a lucky day, I had kept it... Fully commented script poster.sil zipped and attached below. It was made for SILE 0.12.5, but it works too with SILE 0.13.2 -- except it shows some minor deprecation warnings.

poster.zip

(License: CC0 public domain)

Please note the solution might not be what you initially asked - it wasn't clear, and I certainly did not use a fixed baseline. That's IMHO not doable.
Please also note the algorithm to find the ratio is not very efficient. A dumb dichotomy between ratio 1 and the estimated maximum ratio (that one is quite cleverly guessed, though).

I hope my script deserves the "Answered" status ;)

[SanjayTml]

Thank you for the code. It worked as anticipated for normal paragraphs and not when we used a fixed baseline. I have marked it answered.