14958605596

Committed 11 May 2025 06:34PM UTC coverage: 31.311% (-25.4%) from 56.689%

Build # 14958605596

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Merge 3e53926d5 into 443551a3e

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0.0

/packages/linespacing/init.lua

local base = require("packages.base")

local package = pl.class(base)
package._name = "linespacing"

local metrics = require("fontmetrics")

local metricscache = {}

local getLineMetrics = function (l)
   local linemetrics = { ascender = 0, descender = 0, lineheight = SILE.types.length() }
   if not l or not l.nodes then
      return linemetrics
   end
   for i = 1, #l.nodes do
      local node = l.nodes[i]
      if node.is_nnode then
         local m = metricscache[SILE.font._key(node.options)]
         if not m then
            local face = SILE.font.cache(node.options, SILE.shaper.getFace)
            m = metrics.get_typographic_extents(face)
            m.ascender = m.ascender * node.options.size
            m.descender = m.descender * node.options.size
            metricscache[SILE.font._key(node.options)] = m
         end
         SILE.settings:temporarily(function ()
            SILE.call("font", node.options, {})
            m.lineheight = SU.cast("length", SILE.settings:get("linespacing.css.line-height")):absolute()
         end)
         if m.ascender > linemetrics.ascender then
            linemetrics.ascender = m.ascender
         end
         if m.descender > linemetrics.descender then
            linemetrics.descender = m.descender
         end
         if m.lineheight > linemetrics.lineheight then
            linemetrics.lineheight = m.lineheight
         end
      end
   end
   return linemetrics
end

local linespacingLeading = function (_, vbox, previous)
   local method = SILE.settings:get("linespacing.method")

   local firstline = SILE.settings:get("linespacing.minimumfirstlineposition"):absolute()
   if not previous then
      if firstline.length:tonumber() > 0 then
         local toAdd = SILE.types.length(firstline.length - vbox.height)
         return SILE.types.node.vkern(toAdd)
      else
         return nil
      end
   end

   if method == "tex" then
      return SILE.typesetters.base:leadingFor(vbox, previous)
   end

   if method == "fit-glyph" then
      local extra = SILE.settings:get("linespacing.fit-glyph.extra-space"):absolute()
      local toAdd = SILE.types.length(extra)
      return SILE.types.node.vglue(toAdd)
   end

   if method == "fixed" then
      local btob = SILE.settings:get("linespacing.fixed.baselinedistance"):absolute()
      local toAdd = SILE.types.length(btob.length - (vbox.height + previous.depth), btob.stretch, btob.shrink)
      return SILE.types.node.vglue(toAdd)
   end

   -- For these methods, we need to read the font metrics
   if not metrics then
      SU.error("'" .. method .. "' line spacing method requires font metrics module, which is not available")
   end

   local thismetrics = getLineMetrics(vbox)
   local prevmetrics = getLineMetrics(previous)
   if method == "fit-font" then
      -- Distance to next baseline is max(descender) of fonts on previous +
      -- max(ascender) of fonts on next
      local extra = SILE.settings:get("linespacing.fit-font.extra-space"):absolute()
      local btob = prevmetrics.descender + thismetrics.ascender + extra
      local toAdd = btob - (vbox.height + (previous and previous.depth or 0))
      return SILE.types.node.vglue(toAdd)
   end

   if method == "css" then
      local lh = prevmetrics.lineheight
      local leading = (lh - (prevmetrics.ascender + prevmetrics.descender))
      if previous then
         previous.height = previous.height + leading / 2
         previous.depth = previous.depth + leading / 2
      end
      return SILE.types.node.vglue()
   end

   SU.error("Unknown line spacing method " .. method)
end

function package:_init ()
   base._init(self)
   self.class:registerPostinit(function (_)
      SILE.typesetter.leadingFor = linespacingLeading
   end)
end

function package:declareSettings ()
   SILE.settings:declare({
      parameter = "linespacing.method",
      default = "tex",
      type = "string",
      help = "How to set the line spacing (tex, fixed, fit-font, fit-glyph, css)",
   })

   SILE.settings:declare({
      parameter = "linespacing.fixed.baselinedistance",
      default = SILE.types.length("1.2em"),
      type = "length",
      help = "Distance from baseline to baseline in the case of fixed line spacing",
   })

   SILE.settings:declare({
      parameter = "linespacing.minimumfirstlineposition",
      default = SILE.types.length(0),
      type = "length",
   })

   SILE.settings:declare({
      parameter = "linespacing.fit-glyph.extra-space",
      default = SILE.types.length(0),
      type = "length",
   })

   SILE.settings:declare({
      parameter = "linespacing.fit-font.extra-space",
      default = SILE.types.length(0),
      type = "length",
   })

   SILE.settings:declare({
      parameter = "linespacing.css.line-height",
      default = SILE.types.length("1.2em"),
      type = "length",
   })
end

function package:registerCommands ()
   self:registerCommand("linespacing-on", function ()
      SILE.typesetter.leadingFor = linespacingLeading
   end)

   self:registerCommand("linespacing-off", function ()
      SILE.typesetter.leadingFor = SILE.typesetters.base.leadingFor
   end)
end

package.documentation = [[
\begin{document}
\linespacing-on
SILE’s default method of inserting leading between lines should be familiar to users of TeX, but it is not the most friendly system for book designers.
The \autodoc:package{linespacing} package provides a better choice of leading systems.

After loading the package, you are able to choose the linespacing mode by setting the \autodoc:setting{linespacing.method} parameter.
The following examples have funny sized words in them so that you can see how the different methods interact.

By default, this is set to \code{tex}. The other options available are:

\medskip
\set[parameter=linespacing.method,value=fixed]
\set[parameter=linespacing.fixed.baselinedistance,value=1.5em]
\begin{itemize}
\item{\code{fixed}. This set the lines at a fixed baseline-to-baseline distance, determined by the \autodoc:setting{linespacing.fixed.baselinedistance} parameter.
You can specify this parameter either relative to the type size (\code{1.2em}) or as a absolute distance (\code{15pt}).
This paragraph is set with a fixed 1.5em baseline-to-baseline distance.}
\end{itemize}

\medskip
\set[parameter=linespacing.method,value=fit-glyph]
\begin{itemize}
\item{\code{fit-glyph}. This sets the lines solid; that is, the lowest point on line 1 (either a descender like \font[size=20pt]{q} or, if there are no descenders, the baseline) will touch the \font[size=20pt]{highest} point of line 2, as in this paragraph.
You generally don’t want to use this as-is.}
\end{itemize}

\set[parameter=linespacing.fit-glyph.extra-space,value=5pt]

What you probably want to do is insert a constant (relative or absolute) s\font[size=20pt]{p}ace between the lines by setting the \autodoc:setting{linespacing.fit-glyph.extra-space} parameter.
\font[size=20pt]{T}his paragraph is set with 5 points of space between the descenders and the ascenders.

\medskip
\set[parameter=linespacing.method,value=fit-font]
\begin{itemize}
\item{\code{fit-font}. This inspects each \code{hbox} on the line, and asks the fonts it finds for their bounding boxes—the highest ascender and the lower descender.
It then sets the lines solid.
Essentially each character is treated as if it is the same height, rather like composing a slug of metal type.
If there are things other than text on your line, or the text is buried inside other boxes, this may not work well.}
\end{itemize}

\set[parameter=linespacing.fit-font.extra-space,value=5pt]

As with \code{fit-glyph}, you can insert extra space between the lines with the \autodoc:setting{linespacing.fit-font.extra-space} parameter.

\medskip
\set[parameter=linespacing.method,value=css]
\set[parameter=linespacing.css.line-height,value=2em]
\begin{itemize}
\item{\code{css}. This is similar to the method used in browsers; the baseline distance is set with the \autodoc:setting{linespacing.css.line-height} parameter, and the excess \font[size=20pt]{space} between this parameter and the actual height of the line is distributed between the top and bottom of the line.}
\end{itemize}
\medskip

\linespacing-off
\end{document}
]]

return package

1	local base = require("packages.base")	×
2
3	local package = pl.class(base)	×
4	package._name = "linespacing"	×
5
6	local metrics = require("fontmetrics")	×
7
8	local metricscache = {}	×
9
10	local getLineMetrics = function (l)
11	local linemetrics = { ascender = 0, descender = 0, lineheight = SILE.types.length() }	×
12	if not l or not l.nodes then	×
13	return linemetrics	×
14	end
15	for i = 1, #l.nodes do	×
16	local node = l.nodes[i]	×
17	if node.is_nnode then	×
18	local m = metricscache[SILE.font._key(node.options)]	×
19	if not m then	×
20	local face = SILE.font.cache(node.options, SILE.shaper.getFace)	×
21	m = metrics.get_typographic_extents(face)	×
22	m.ascender = m.ascender * node.options.size	×
23	m.descender = m.descender * node.options.size	×
24	metricscache[SILE.font._key(node.options)] = m	×
25	end
26	SILE.settings:temporarily(function ()	×
27	SILE.call("font", node.options, {})	×
28	m.lineheight = SU.cast("length", SILE.settings:get("linespacing.css.line-height")):absolute()	×
29	end)
30	if m.ascender > linemetrics.ascender then	×
31	linemetrics.ascender = m.ascender	×
32	end
33	if m.descender > linemetrics.descender then	×
34	linemetrics.descender = m.descender	×
35	end
36	if m.lineheight > linemetrics.lineheight then	×
37	linemetrics.lineheight = m.lineheight	×
38	end
39	end
40	end
41	return linemetrics	×
42	end
43
44	local linespacingLeading = function (_, vbox, previous)
45	local method = SILE.settings:get("linespacing.method")	×
46
47	local firstline = SILE.settings:get("linespacing.minimumfirstlineposition"):absolute()	×
48	if not previous then	×
49	if firstline.length:tonumber() > 0 then	×
50	local toAdd = SILE.types.length(firstline.length - vbox.height)	×
51	return SILE.types.node.vkern(toAdd)	×
52	else
53	return nil	×
54	end
55	end
56
57	if method == "tex" then	×
58	return SILE.typesetters.base:leadingFor(vbox, previous)	×
59	end
60
61	if method == "fit-glyph" then	×
62	local extra = SILE.settings:get("linespacing.fit-glyph.extra-space"):absolute()	×
63	local toAdd = SILE.types.length(extra)	×
64	return SILE.types.node.vglue(toAdd)	×
65	end
66
67	if method == "fixed" then	×
68	local btob = SILE.settings:get("linespacing.fixed.baselinedistance"):absolute()	×
69	local toAdd = SILE.types.length(btob.length - (vbox.height + previous.depth), btob.stretch, btob.shrink)	×
70	return SILE.types.node.vglue(toAdd)	×
71	end
72
73	-- For these methods, we need to read the font metrics
74	if not metrics then	×
75	SU.error("'" .. method .. "' line spacing method requires font metrics module, which is not available")	×
76	end
77
78	local thismetrics = getLineMetrics(vbox)	×
79	local prevmetrics = getLineMetrics(previous)	×
80	if method == "fit-font" then	×
81	-- Distance to next baseline is max(descender) of fonts on previous +
82	-- max(ascender) of fonts on next
83	local extra = SILE.settings:get("linespacing.fit-font.extra-space"):absolute()	×
84	local btob = prevmetrics.descender + thismetrics.ascender + extra	×
85	local toAdd = btob - (vbox.height + (previous and previous.depth or 0))	×
86	return SILE.types.node.vglue(toAdd)	×
87	end
88
89	if method == "css" then	×
90	local lh = prevmetrics.lineheight	×
91	local leading = (lh - (prevmetrics.ascender + prevmetrics.descender))	×
92	if previous then	×
93	previous.height = previous.height + leading / 2	×
94	previous.depth = previous.depth + leading / 2	×
95	end
96	return SILE.types.node.vglue()	×
97	end
98
99	SU.error("Unknown line spacing method " .. method)	×
100	end
101
102	function package:_init ()	×
103	base._init(self)	×
104	self.class:registerPostinit(function (_)	×
105	SILE.typesetter.leadingFor = linespacingLeading	×
106	end)
107	end
108
109	function package:declareSettings ()	×
110	SILE.settings:declare({	×
111	parameter = "linespacing.method",
112	default = "tex",
113	type = "string",
114	help = "How to set the line spacing (tex, fixed, fit-font, fit-glyph, css)",
115	})
116
117	SILE.settings:declare({	×
118	parameter = "linespacing.fixed.baselinedistance",
119	default = SILE.types.length("1.2em"),
120	type = "length",
121	help = "Distance from baseline to baseline in the case of fixed line spacing",
122	})
123
124	SILE.settings:declare({	×
125	parameter = "linespacing.minimumfirstlineposition",
126	default = SILE.types.length(0),
127	type = "length",
128	})
129
130	SILE.settings:declare({	×
131	parameter = "linespacing.fit-glyph.extra-space",
132	default = SILE.types.length(0),
133	type = "length",
134	})
135
136	SILE.settings:declare({	×
137	parameter = "linespacing.fit-font.extra-space",
138	default = SILE.types.length(0),
139	type = "length",
140	})
141
142	SILE.settings:declare({	×
143	parameter = "linespacing.css.line-height",
144	default = SILE.types.length("1.2em"),
145	type = "length",
146	})
147	end
148
149	function package:registerCommands ()	×
150	self:registerCommand("linespacing-on", function ()	×
151	SILE.typesetter.leadingFor = linespacingLeading	×
152	end)
153
154	self:registerCommand("linespacing-off", function ()	×
155	SILE.typesetter.leadingFor = SILE.typesetters.base.leadingFor	×
156	end)
157	end
158
159	package.documentation = [[
160	\begin{document}
161	\linespacing-on
162	SILE’s default method of inserting leading between lines should be familiar to users of TeX, but it is not the most friendly system for book designers.
163	The \autodoc:package{linespacing} package provides a better choice of leading systems.
164
165	After loading the package, you are able to choose the linespacing mode by setting the \autodoc:setting{linespacing.method} parameter.
166	The following examples have funny sized words in them so that you can see how the different methods interact.
167
168	By default, this is set to \code{tex}. The other options available are:
169
170	\medskip
171	\set[parameter=linespacing.method,value=fixed]
172	\set[parameter=linespacing.fixed.baselinedistance,value=1.5em]
173	\begin{itemize}
174	\item{\code{fixed}. This set the lines at a fixed baseline-to-baseline distance, determined by the \autodoc:setting{linespacing.fixed.baselinedistance} parameter.
175	You can specify this parameter either relative to the type size (\code{1.2em}) or as a absolute distance (\code{15pt}).
176	This paragraph is set with a fixed 1.5em baseline-to-baseline distance.}
177	\end{itemize}
178
179	\medskip
180	\set[parameter=linespacing.method,value=fit-glyph]
181	\begin{itemize}
182	\item{\code{fit-glyph}. This sets the lines solid; that is, the lowest point on line 1 (either a descender like \font[size=20pt]{q} or, if there are no descenders, the baseline) will touch the \font[size=20pt]{highest} point of line 2, as in this paragraph.
183	You generally don’t want to use this as-is.}
184	\end{itemize}
185
186	\set[parameter=linespacing.fit-glyph.extra-space,value=5pt]
187
188	What you probably want to do is insert a constant (relative or absolute) s\font[size=20pt]{p}ace between the lines by setting the \autodoc:setting{linespacing.fit-glyph.extra-space} parameter.
189	\font[size=20pt]{T}his paragraph is set with 5 points of space between the descenders and the ascenders.
190
191	\medskip
192	\set[parameter=linespacing.method,value=fit-font]
193	\begin{itemize}
194	\item{\code{fit-font}. This inspects each \code{hbox} on the line, and asks the fonts it finds for their bounding boxes—the highest ascender and the lower descender.
195	It then sets the lines solid.
196	Essentially each character is treated as if it is the same height, rather like composing a slug of metal type.
197	If there are things other than text on your line, or the text is buried inside other boxes, this may not work well.}
198	\end{itemize}
199
200	\set[parameter=linespacing.fit-font.extra-space,value=5pt]
201
202	As with \code{fit-glyph}, you can insert extra space between the lines with the \autodoc:setting{linespacing.fit-font.extra-space} parameter.
203
204	\medskip
205	\set[parameter=linespacing.method,value=css]
206	\set[parameter=linespacing.css.line-height,value=2em]
207	\begin{itemize}
208	\item{\code{css}. This is similar to the method used in browsers; the baseline distance is set with the \autodoc:setting{linespacing.css.line-height} parameter, and the excess \font[size=20pt]{space} between this parameter and the actual height of the line is distributed between the top and bottom of the line.}
209	\end{itemize}
210	\medskip
211
212	\linespacing-off
213	\end{document}
214	]]	×
215
216	return package	×

sile-typesetter / sile / 14958605596

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