Reduce side bearings on single quote

[alerque]

Closes #323.

This currently a WIP, but when it does land it will be a significant change to metrics, so I will probably delay merging this until after a few small fixes hit and a minor dot release happens first.

test code

\begin[papersize=500pt x 1000pt]{document}
\script[src=packages/rules]
\nofolios
\neverindent
\font[family=Libertinus Sans,size=5pt]
\begin{raggedright}
\begin{script}

local _c = io.open(".fontship/last-commit", "r")
newver = _c:read("*a"):gsub("\n", "")
io.close(_c)

function extant(face, weight, style)
  face = face:gsub(" ", "")
  local fname = string.format("Libertinus%s-%s%s.otf", face, weight, style)
  local f = io.open(fname, "r")
  if f then
    io.close(f)
    return fname
  end
end

function tonum(weight)
  if weight == "Bold" then
    return 800
  elseif weight == "Semibold" then
    return 600
  end
  return 400
end

faces = { "Serif", "Serif Display", "Sans", --[[ "Mono", "Math", --[["SerifInitials", "Keyboard" ]]}
weights = { "", "Bold", "Semibold" }
styles = { "", "Regular", "Italic" }

SILE.registerCommand("sample", function (options, _)
  options.size = "25pt"
  SILE.call("font", options, function ()
    local str = "C'è po'. C'era D'est L'o A'e Saint' Ant's."
    SILE.typesetter:typeset(str)
    --SILE.call("font", { features = "+smcp" }, { "\\f\\ (f) [f] {f}" })
  end)
  SILE.call("skip", { height = "4pt" })
  SILE.call("par")
end)

SILE.registerCommand("label", function (options, content)
  SILE.process(content)
  SILE.call("hfill")
  SILE.call("break")
end)

for _, face in ipairs(faces) do
  for _, weight in ipairs(weights) do
    for _, style in ipairs(styles) do
      local fname = extant(face, weight, style)
      if fname then
        local disp = string.format("Libertinus %s – %s %s v", face, weight, style)
        SILE.call("label", {}, { disp .. "7.000" })
        SILE.call("sample", { family = "Libertinus "..face, weight = tonum(weight), style = style })
        SILE.call("label", {}, { disp .. newver })
        SILE.call("sample", { filename = fname })
        SILE.call("hrule", { width = "100%lw" })
        SILE.call("skip", { height = "4pt" })
      end
    end
  end
end

\end{script}
\end{raggedright}
\end{document}

@rriemann What do you think of this? (Besides the preview above you can download artifacts from the Actions tab of this PR to test for yourself.)

[rriemann]

Do the changes also apply to e.g. the Unicode Character 'RIGHT SINGLE QUOTATION MARK' (U+2019)?

[alerque]

Nope not yet. And that's egg on my face because that's what the original issue was about!

Here is a slightly more advanced test case that covers U+2019 as well:

SILE test code

\begin[papersize=500pt x 1060pt]{document}
\script[src=packages/rules]
\nofolios
\neverindent
\font[family=Libertinus Sans,size=5pt]
\begin{raggedright}
\begin{script}

local _c = io.open(".fontship/last-commit", "r")
newver = _c:read("*a"):gsub("\n", "")
io.close(_c)

function extant(face, weight, style)
  face = face:gsub(" ", "")
  local fname = string.format("Libertinus%s-%s%s.otf", face, weight, style)
  local f = io.open(fname, "r")
  if f then
    io.close(f)
    return fname
  end
end

function tonum(weight)
  if weight == "Bold" then
    return 800
  elseif weight == "Semibold" then
    return 600
  end
  return 400
end

faces = { "Serif", "Serif Display", "Sans", --[[ "Mono", "Math", --[["SerifInitials", "Keyboard" ]]}
weights = { "", "Bold", "Semibold" }
styles = { "", "Regular", "Italic" }

SILE.registerCommand("sample", function (options, _)
  options.size = "20pt"
  SILE.call("font", options, function ()
    local str = "C'è po'. C'era D'est L'o A'e Saint' Ant's."
    SILE.typesetter:typeset(str)
	SILE.call("break")
	local str2 = str:gsub("'", "’")
    SILE.typesetter:typeset(str2)
	SILE.call("break")
	SILE.call("font", { features = "+smcp" }, { str })
	SILE.call("break")
	SILE.call("font", { features = "+smcp" }, { str2 })
  end)
  SILE.call("skip", { height = "4pt" })
  SILE.call("par")
end)

SILE.registerCommand("label", function (options, content)
  SILE.process(content)
  SILE.call("hfill")
  SILE.call("break")
end)

for _, face in ipairs(faces) do
  for _, weight in ipairs(weights) do
    for _, style in ipairs(styles) do
      local fname = extant(face, weight, style)
      if fname then
        local disp = string.format("Libertinus %s – %s %s v", face, weight, style)
        SILE.call("label", {}, { disp .. "7.000" })
        SILE.call("sample", { family = "Libertinus "..face, weight = tonum(weight), style = style })
        SILE.call("label", {}, { disp .. newver })
        SILE.call("sample", { filename = fname })
        SILE.call("hrule", { width = "100%lw" })
        SILE.call("skip", { height = "4pt" })
      end
    end
  end
end

\end{script}
\end{raggedright}
\end{document}

Full test output: quote.pdf

Clearly not addressed yet...

[alerque]

Here it is with U+2019 adjusted similarly to U+0027.

[capnrefsmmat]

Should this change (or a similar one) also be applied to the italic font? The single quote can also have odd spacing there:

[alerque]

Yes. Actually all the other weights and styles need adjusting, but I was putting it off since I'm not ready to merge this (which will be a major breaking change). I'll do it eventually and probably keep it along with some other big changes in a devel branch for a while before enough comes together to do a breaking release.