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+if not modules then modules = { } end modules ['l-dimen'] = {
+ version = 1.001,
+ comment = "support for dimensions",
+ author = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+ copyright = "PRAGMA ADE / ConTeXt Development Team",
+ license = "see context related readme files"
+}
+
+--[[ldx--
+<p>Internally <l n='luatex'/> work with scaled point, which are
+represented by integers. However, in practice, at east at the
+<l n='tex'/> end we work with more generic units like points (pt). Going
+from scaled points (numbers) to one of those units can be
+done by using the conversion factors collected in the following
+table.</p>
+--ldx]]--
+
+local format, match, gsub, type, setmetatable = string.format, string.match, string.gsub, type, setmetatable
+local lpegmatch = lpeg.match
+
+number = number or { }
+
+number.tonumberf = function(n) return match(format("%.20f",n),"(.-0?)0*$") end -- one zero too much but alas
+number.tonumberg = function(n) return format("%.20g",n) end
+
+local dimenfactors = {
+ ["pt"] = 1/65536,
+ ["in"] = ( 100/ 7227)/65536,
+ ["cm"] = ( 254/ 7227)/65536,
+ ["mm"] = ( 2540/ 7227)/65536,
+ ["sp"] = 1, -- 65536 sp in 1pt
+ ["bp"] = ( 7200/ 7227)/65536,
+ ["pc"] = ( 1/ 12)/65536,
+ ["dd"] = ( 1157/ 1238)/65536,
+ ["cc"] = ( 1157/14856)/65536,
+ ["nd"] = (20320/21681)/65536,
+ ["nc"] = ( 5080/65043)/65536
+}
+
+--~ print(table.serialize(dimenfactors))
+--~
+--~ %.99g:
+--~
+--~ t={
+--~ ["bp"]=1.5201782378580324e-005,
+--~ ["cc"]=1.1883696112892098e-006,
+--~ ["cm"]=5.3628510057769479e-007,
+--~ ["dd"]=1.4260435335470516e-005,
+--~ ["em"]=0.000152587890625,
+--~ ["ex"]=6.103515625e-005,
+--~ ["in"]=2.1113586636917117e-007,
+--~ ["mm"]=5.3628510057769473e-008,
+--~ ["nc"]=1.1917446679504327e-006,
+--~ ["nd"]=1.4300936015405194e-005,
+--~ ["pc"]=1.2715657552083333e-006,
+--~ ["pt"]=1.52587890625e-005,
+--~ ["sp"]=1,
+--~ }
+--~
+--~ patched %s and tonumber
+--~
+--~ t={
+--~ ["bp"]=0.00001520178238,
+--~ ["cc"]=0.00000118836961,
+--~ ["cm"]=0.0000005362851,
+--~ ["dd"]=0.00001426043534,
+--~ ["em"]=0.00015258789063,
+--~ ["ex"]=0.00006103515625,
+--~ ["in"]=0.00000021113587,
+--~ ["mm"]=0.00000005362851,
+--~ ["nc"]=0.00000119174467,
+--~ ["nd"]=0.00001430093602,
+--~ ["pc"]=0.00000127156576,
+--~ ["pt"]=0.00001525878906,
+--~ ["sp"]=1,
+--~ }
+
+--[[ldx--
+<p>A conversion function that takes a number, unit (string) and optional
+format (string) is implemented using this table.</p>
+--ldx]]--
+
+-- was:
+
+local function todimen(n,unit,fmt)
+ if type(n) == 'string' then
+ return n
+ else
+ unit = unit or 'pt'
+ return format(fmt or "%s%s",n*dimenfactors[unit],unit)
+ -- if fmt then
+ -- return format(fmt,n*dimenfactors[unit],unit)
+ -- else
+ -- return match(format("%.20f",n*dimenfactors[unit]),"(.-0?)0*$") .. unit
+ -- end
+ end
+end
+
+--[[ldx--
+<p>We collect a bunch of converters in the <type>number</type> namespace.</p>
+--ldx]]--
+
+number.todimen = todimen
+number.dimenfactors = dimenfactors
+
+function number.topoints (n) return todimen(n,"pt") end
+function number.toinches (n) return todimen(n,"in") end
+function number.tocentimeters (n) return todimen(n,"cm") end
+function number.tomillimeters (n) return todimen(n,"mm") end
+function number.toscaledpoints(n) return todimen(n,"sp") end
+function number.toscaledpoints(n) return n .. "sp" end
+function number.tobasepoints (n) return todimen(n,"bp") end
+function number.topicas (n) return todimen(n "pc") end
+function number.todidots (n) return todimen(n,"dd") end
+function number.tociceros (n) return todimen(n,"cc") end
+function number.tonewdidots (n) return todimen(n,"nd") end
+function number.tonewciceros (n) return todimen(n,"nc") end
+
+--[[ldx--
+<p>More interesting it to implement a (sort of) dimen datatype, one
+that permits calculations too. First we define a function that
+converts a string to scaledpoints. We use <l n='lpeg'/>. We capture
+a number and optionally a unit. When no unit is given a constant
+capture takes place.</p>
+--ldx]]--
+
+local amount = (lpeg.S("+-")^0 * lpeg.R("09")^0 * lpeg.P(".")^0 * lpeg.R("09")^0) + lpeg.Cc("0")
+local unit = lpeg.R("az")^1
+
+local pattern = amount/tonumber * (unit^1/dimenfactors + lpeg.Cc(1)) -- tonumber is new
+
+--[[ldx--
+<p>We use a metatable to intercept errors. When no key is found in
+the table with factors, the metatable will be consulted for an
+alternative index function.</p>
+--ldx]]--
+
+local mt = { } setmetatable(dimenfactors,mt)
+
+mt.__index = function(t,s)
+ -- error("wrong dimension: " .. (s or "?")) -- better a message
+ return false
+end
+
+function string:todimen()
+ if type(self) == "number" then
+ return self
+ else
+ local value, unit = lpegmatch(pattern,self)
+ print(value,unit)
+ return value/unit
+ end
+end
+
+--[[ldx--
+<p>This converter accepts calls like:</p>
+
+<typing>
+string.todimen("10"))
+string.todimen(".10"))
+string.todimen("10.0"))
+string.todimen("10.0pt"))
+string.todimen("10pt"))
+string.todimen("10.0pt"))
+</typing>
+
+<p>And of course the often more efficient:</p>
+
+<typing>
+somestring:todimen("12.3cm")
+</typing>
+
+<p>With this in place, we can now implement a proper datatype for dimensions, one
+that permits us to do this:</p>
+
+<typing>
+s = dimen "10pt" + dimen "20pt" + dimen "200pt"
+ - dimen "100sp" / 10 + "20pt" + "0pt"
+</typing>
+
+<p>We create a local metatable for this new type:</p>
+--ldx]]--
+
+local dimensions = { }
+
+--[[ldx--
+<p>The main (and globally) visible representation of a dimen is defined next: it is
+a one-element table. The unit that is returned from the match is normally a number
+(one of the previously defined factors) but we also accept functions. Later we will
+see why.</p>
+--ldx]]--
+
+function dimen(a)
+ if a then
+ local ta= type(a)
+ if ta == "string" then
+ local value, unit = lpegmatch(pattern,a)
+ if type(unit) == "function" then
+ k = value/unit()
+ else
+ k = value/unit
+ end
+ a = k
+ elseif ta == "table" then
+ a = a[1]
+ end
+ return setmetatable({ a }, dimensions)
+ else
+ return setmetatable({ 0 }, dimensions)
+ end
+end
+
+--[[ldx--
+<p>This function return a small hash with a metatable attached. It is
+through this metatable that we can do the calculations. We could have
+shared some of the code but for reasons of speed we don't.</p>
+--ldx]]--
+
+function dimensions.__add(a, b)
+ local ta, tb = type(a), type(b)
+ if ta == "string" then a = a:todimen() elseif ta == "table" then a = a[1] end
+ if tb == "string" then b = b:todimen() elseif tb == "table" then b = b[1] end
+ return setmetatable({ a + b }, dimensions)
+end
+
+function dimensions.__sub(a, b)
+ local ta, tb = type(a), type(b)
+ if ta == "string" then a = a:todimen() elseif ta == "table" then a = a[1] end
+ if tb == "string" then b = b:todimen() elseif tb == "table" then b = b[1] end
+ return setmetatable({ a - b }, dimensions)
+end
+
+function dimensions.__mul(a, b)
+ local ta, tb = type(a), type(b)
+ if ta == "string" then a = a:todimen() elseif ta == "table" then a = a[1] end
+ if tb == "string" then b = b:todimen() elseif tb == "table" then b = b[1] end
+ return setmetatable({ a * b }, dimensions)
+end
+
+function dimensions.__div(a, b)
+ local ta, tb = type(a), type(b)
+ if ta == "string" then a = a:todimen() elseif ta == "table" then a = a[1] end
+ if tb == "string" then b = b:todimen() elseif tb == "table" then b = b[1] end
+ return setmetatable({ a / b }, dimensions)
+end
+
+function dimensions.__unm(a)
+ local ta = type(a)
+ if ta == "string" then a = a:todimen() elseif ta == "table" then a = a[1] end
+ return setmetatable({ - a }, dimensions)
+end
+
+--[[ldx--
+<p>It makes no sense to implement the power and modulo function but
+the next two do make sense because they permits is code like:</p>
+
+<typing>
+local a, b = dimen "10pt", dimen "11pt"
+...
+if a > b then
+ ...
+end
+</typing>
+--ldx]]--
+
+-- makes no sense: dimensions.__pow and dimensions.__mod
+
+function dimensions.__lt(a, b)
+ return a[1] < b[1]
+end
+
+function dimensions.__eq(a, b)
+ return a[1] == b[1]
+end
+
+--[[ldx--
+<p>We also need to provide a function for conversion to string (so that
+we can print dimensions). We print them as points, just like <l n='tex'/>.</p>
+--ldx]]--
+
+function dimensions.__tostring(a)
+ return a[1]/65536 .. "pt" -- instead of todimen(a[1])
+end
+
+--[[ldx--
+<p>Since it does not take much code, we also provide a way to access
+a few accessors</p>
+
+<typing>
+print(dimen().pt)
+print(dimen().sp)
+</typing>
+--ldx]]--
+
+function dimensions.__index(tab,key)
+ local d = dimenfactors[key]
+ if not d then
+ error("illegal property of dimen: " .. key)
+ d = 1
+ end
+ return 1/d
+end
+
+--[[ldx--
+<p>In the converter from string to dimension we support functions as
+factors. This is because in <l n='tex'/> we have a few more units:
+<type>ex</type> and <type>em</type>. These are not constant factors but
+depend on the current font. They are not defined by default, but need
+an explicit function call. This is because at the moment that this code
+is loaded, the relevant tables that hold the functions needed may not
+yet be available.</p>
+--ldx]]--
+
+function dimensions.texify() -- todo: %
+ local fti, fc = fonts and fonts.ids and fonts.ids, font and font.current
+ if fti and fc then
+ dimenfactors["ex"] = function() return fti[fc()].ex_height end
+ dimenfactors["em"] = function() return fti[fc()].quad end
+ else
+ dimenfactors["ex"] = 1/65536* 4 -- 4pt
+ dimenfactors["em"] = 1/65536*10 -- 10pt
+ end
+end
+
+--[[ldx--
+<p>In order to set the defaults we call this function now. At some point
+the macro package needs to make sure the function is called again.</p>
+--ldx]]--
+
+dimensions.texify()
+
+--[[ldx--
+<p>The previous code is rather efficient (also thanks to <l n='lpeg'/>) but we
+can speed it up by caching converted dimensions. On my machine (2008) the following
+loop takes about 25.5 seconds.</p>
+
+<typing>
+for i=1,1000000 do
+ local s = dimen "10pt" + dimen "20pt" + dimen "200pt"
+ - dimen "100sp" / 10 + "20pt" + "0pt"
+end
+</typing>
+
+<p>When we cache converted strings this becomes 16.3 seconds. In order not
+to waste too much memory on it, we tag the values of the cache as being
+week which mean that the garbage collector will collect them in a next
+sweep. This means that in most cases the speed up is mostly affecting the
+current couple of calculations and as such the speed penalty is small.</p>
+
+<p>We redefine two previous defined functions that can benefit from
+this:</p>
+--ldx]]--
+
+local known = { } setmetatable(known, { __mode = "v" })
+
+function dimen(a)
+ if a then
+ local ta= type(a)
+ if ta == "string" then
+ local k = known[a]
+ if k then
+ a = k
+ else
+ local value, unit = lpegmatch(pattern,a)
+ if type(unit) == "function" then
+ k = value/unit()
+ else
+ k = value/unit
+ end
+ known[a] = k
+ a = k
+ end
+ elseif ta == "table" then
+ a = a[1]
+ end
+ return setmetatable({ a }, dimensions)
+ else
+ return setmetatable({ 0 }, dimensions)
+ end
+end
+
+function string:todimen()
+ if type(self) == "number" then
+ return self
+ else
+ local k = known[self]
+ if not k then
+ local value, unit = lpegmatch(pattern,self)
+ if value and unit then
+ k = value/unit
+ else
+ k = 0
+ end
+ -- print(self,value,unit)
+ known[self] = k
+ end
+ return k
+ end
+end
+
+--[[ldx--
+<p>In a similar fashion we can define a glue datatype. In that case we
+probably use a hash instead of a one-element table.</p>
+--ldx]]--
+
+--[[ldx--
+<p>Goodie:s</p>
+--ldx]]--
+
+function number.percent(n) -- will be cleaned up once luatex 0.30 is out
+ local hsize = tex.hsize
+ if type(hsize) == "string" then
+ hsize = hsize:todimen()
+ end
+ return (n/100) * hsize
+end
+
+number["%"] = number.percent