2018-01-08 23:11:00

5 files changed, 392 insertions, 2 deletions

diff --git a/doc/context/sources/general/fonts/fonts/fonts-environment.tex b/doc/context/sources/general/fonts/fonts/fonts-environment.tex
index a8de89a42..c884d97e5 100644
--- a/doc/context/sources/general/fonts/fonts/fonts-environment.tex
+++ b/doc/context/sources/general/fonts/fonts/fonts-environment.tex
@@ -1,6 +1,46 @@
 \startenvironment fonts-environment
 
-    \blockligatures[fi,fl,ff] % we need to do this beforehand
+    % we need to do this beforehand
+
+    \blockligatures[fi,fl,ff]
+
+    \startbuffer[extraminus]
+    \startluacode
+        fonts.helpers.addextraprivate("smallminus", function(tfmdata)
+            local hchar = tfmdata.characters[0x002D]
+            local mchar = tfmdata.characters[0x2212]
+            if hchar and mchar then
+                return {
+                    width    = hchar.width,
+                    height   = mchar.height,
+                    commands = {
+                        { "down", hchar.height - mchar.height },
+                        { "char", 0x002D },
+                    }
+                }
+            end
+        end)
+        fonts.helpers.addextraprivate("highminus", function(tfmdata)
+            local hchar = tfmdata.characters[0x002D]
+            local mchar = tfmdata.characters[0x2212]
+            local xchar = tfmdata.characters[0x0058]
+            if hchar and mchar and xchar then
+                return {
+                    width    = hchar.width,
+                    height   = mchar.height,
+                    commands = {
+                        { "down", - xchar.height + mchar.height },
+                        { "char", 0x002D },
+                    }
+                }
+            end
+        end)
+    \stopluacode
+    \stopbuffer
+
+    \getbuffer[extraminus]
+
+    % so far for preloading
 
     \environment manuals-explaining-environment
     \environment manuals-explaining-cover
diff --git a/doc/context/sources/general/fonts/fonts/fonts-extensions.tex b/doc/context/sources/general/fonts/fonts/fonts-extensions.tex
index 1d84bfdc6..26b3d5f2d 100644
--- a/doc/context/sources/general/fonts/fonts/fonts-extensions.tex
+++ b/doc/context/sources/general/fonts/fonts/fonts-extensions.tex
@@ -2612,6 +2612,92 @@ gets defined and because we share resources it even has to happen before the
 first font gets loaded. So, the \type {\blockligatures} commands go before
 setting up the body font. This is no real problem because it's a hack anyway.
 
+The next example combines several tricks:
+
+\startbuffer[definitions]
+\startluacode
+    fonts.handlers.otf.addfeature {
+        name = "kernligatures",
+        type = "kern",
+        data = {
+            f = { i = 50, l = 50 },
+        }
+    }
+\stopluacode
+
+\blockligatures[u:fl:a]
+
+\definefontfeature[default:b][default][blockligatures=yes]
+\definefontfeature[default:k][default][blockligatures=yes,kernligatures=yes]
+
+\showfontkerns
+\stopbuffer
+
+\startbuffer[demo]
+{\definedfont[Brill*default   @ 11pt]auflage}\par
+{\definedfont[Brill*default:b @ 11pt]auflage}\par
+{\definedfont[Brill*default:k @ 11pt]auflage}\par
+\stopbuffer
+
+\typebuffer[definitions,demo] \getbuffer[definitions]
+
+\startlinecorrection
+    \externalfigure[demo.buffer][width=4cm]
+\stoplinecorrection
+
+Processing fonts is complicated by the fact that a text can be hyphenated. This
+complicates for instance ligature building which can cross the pre, post and|/|or
+replace bounds. The current implementation does a decent job although there will
+always be border cases. And, figuring out what goes wrong is a pain. There are
+several ways to trace what happens and here's one. As mentioned, blocking only
+works when we haven't not yet defined a font instance, so we use a funny size
+here.
+
+\startbuffer
+\blockligatures[u:fl:a]
+
+\definefontfeature
+  [blockligatures]
+  [default]
+  [blockligatures=yes]
+
+\startotfcompositionlist{texgyrepagella-regular*blockligatures @ 14.5pt}{l2r}
+    \HL
+    \showotfcompositionsample{auflage}
+    \showotfcompositionsample{a\discretionary{-}{}{}uflage}
+    \showotfcompositionsample{au\discretionary{-}{}{}flage}
+    \showotfcompositionsample{auf\discretionary{-}{}{}lage}
+    \showotfcompositionsample{aufl\discretionary{-}{}{}age}
+    \showotfcompositionsample{aufla\discretionary{-}{}{}ge}
+    \showotfcompositionsample{auflag\discretionary{-}{}{}e}
+    \HL
+    \showotfcompositionsample{auflegt}
+    \showotfcompositionsample{a\discretionary{-}{}{}uflegt}
+    \showotfcompositionsample{au\discretionary{-}{}{}flegt}
+    \showotfcompositionsample{auf\discretionary{-}{}{}legt}
+    \showotfcompositionsample{aufl\discretionary{-}{}{}egt}
+    \showotfcompositionsample{aufle\discretionary{-}{}{}gt}
+    \showotfcompositionsample{aufleg\discretionary{-}{}{}t}
+    \HL
+\stopotfcompositionlist
+\stopbuffer
+
+\typebuffer \getbuffer
+
+Here is another example. This one demonstrates that ligatures can force
+collapsing of discretionaries.
+
+\startbuffer
+\startotfcompositionlist{Serif*default @ 11pt}{l2r}
+    \HL
+    \showotfcompositionsample{effe}
+    \showotfcompositionsample{efficient}
+    \HL
+\stopotfcompositionlist
+\stopbuffer
+
+\typebuffer \getbuffer
+
 \stopsection
 
 \startsection[title=Collections]
diff --git a/doc/context/sources/general/fonts/fonts/fonts-features.tex b/doc/context/sources/general/fonts/fonts/fonts-features.tex
index f6a12c30d..d6d116856 100644
--- a/doc/context/sources/general/fonts/fonts/fonts-features.tex
+++ b/doc/context/sources/general/fonts/fonts/fonts-features.tex
@@ -1,4 +1,4 @@
-language=uk
+% language=uk
 
 \startcomponent fonts-features
 
@@ -2626,6 +2626,86 @@ changes in a lifetime than foreseen when \TEX\ showed up.
 
 \stopsection
 
+\startsection[title=Different spaces]
+
+The width of the space and its stretch and shrink are taken from the font. The so
+called emspace is the reference for much spacing related parameters. It is the
+width of character \type {0x2014}. The regular space width is taken from \type
+{0x0020}, the space character. When there is no space character, in the case of a
+monospaced font we take the emwidth, otherwise we take half the emwidth. As a
+last resort we can take the average width of characters. And of even that fails
+we take half of the font units. When there is no emwidth that one is set to the
+font units.
+
+In the \CONTEXT\ font loader we use a stretch that is 1/2 of the width of a space
+and the shrink is 1/3 the width of a space, so we use values that are quite
+similar to what \TEX\ always used.
+
+You can overload these values when a font is loaded and the overload is
+implemented as a feature. The next example demonstrates how this is done:
+
+\startbuffer
+\definefontfeature[morespace][spacing=0.50 plus 0.50 minus 0.250]
+\definefontfeature[lessspace][spacing=0.25 plus 0.25 minus 0.125]
+
+\definedfont[Serif*default]          \samplefile{klein}\blank
+\definedfont[Serif*default,morespace]\samplefile{klein}\blank
+\definedfont[Serif*default,lessspace]\samplefile{klein}\blank
+\definedfont[Serif*default]          \samplefile{klein}\blank
+\stopbuffer
+
+\typebuffer \blank \getbuffer \blank
+
+\stopsection
+
+\startsection[title=Dynamic features]
+
+We can enable and disable features any time in the input by using the
+\type {\feature} command. he following example was posted on the list:
+
+\startbuffer
+\definefont
+  [WeirdShapes]
+  [file:linlibertiner*default]
+
+\definefontfeature
+  [hist]
+  [hlig=yes]
+
+\definefontfeature
+  [rare]
+  [dlig=yes]
+
+\setupquotation
+  [style={\feature[+][hist,rare]}]
+
+\startlines
+\WeirdShapes
+strict {\feature[+][hist]strict}
+wurtzite {\feature[+][rare]wurtzite}
+\quotation{strict wurtzite}
+\stoplines
+\stopbuffer
+
+\typebuffer
+
+Or typeset:
+
+\getbuffer
+
+The \type {\feature} command takes as first argument a directive of what
+do do:
+
+\starttabulate[|T||]
+\NC + more        \NC add set to previous set and combine with font set \NC \NR
+\NC - less        \NC subtract set to previous set and combine with font set \NC \NR
+\NC = new         \NC replace font set \NC \NR
+\NC ! < reset     \NC forget sets and revert to font set \NC \NR
+\NC > old default \NC make sure the current set is used on top of the font set \NC \NR
+\stoptabulate
+
+\stopsection
+
 \stopchapter
 
 \stopcomponent
diff --git a/doc/context/sources/general/fonts/fonts/fonts-mkiv.tex b/doc/context/sources/general/fonts/fonts/fonts-mkiv.tex
index c5283ad41..6b05bb0c2 100644
--- a/doc/context/sources/general/fonts/fonts/fonts-mkiv.tex
+++ b/doc/context/sources/general/fonts/fonts/fonts-mkiv.tex
@@ -66,6 +66,7 @@
         \component fonts-math
         \component fonts-extensions
         \component fonts-hooks
+        \component fonts-tricks
     \stopbodymatter
 
     \startappendices
diff --git a/doc/context/sources/general/fonts/fonts/fonts-tricks.tex b/doc/context/sources/general/fonts/fonts/fonts-tricks.tex
new file mode 100644
index 000000000..6596a43fb
--- /dev/null
+++ b/doc/context/sources/general/fonts/fonts/fonts-tricks.tex
@@ -0,0 +1,183 @@
+% language=uk
+
+\startcomponent fonts-tricks
+
+\environment fonts-environment
+
+\startchapter[title=Tricks][color=middleorange]
+
+\startsection[title=Introduction]
+
+In this chapter topics that don't fit in the previous chapters are
+collected.
+
+\stopsection
+
+\startsection[title=Extra characters]
+
+In one of our projects we need a small (high) minus and here we discuss
+one way of achieving this. An option is to define a new character
+and use a font feature to add it, as in:
+
+\starttyping
+\startluacode
+  local function addextraminus(tfmdata)
+    fonts.helpers.addprivate(tfmdata, "smallminus", ... ) -- see below
+    fonts.helpers.addprivate(tfmdata, "highminus",  ... ) -- see below
+  end
+  fonts.constructors.newfeatures.otf.register {
+    name        = "extraminus",
+    description = "extra minus symbols",
+    default     = true,
+    manipulators = {
+      base = addextraminus,
+      node = addextraminus,
+    }
+  }
+\stopluacode
+\stoptyping
+
+However, why make it an option when we can just add it to any font. So,
+we can end up with just:
+
+\typebuffer[extraminus] % already defined before loading fonts
+
+It is important to do this before fonts get loaded. Next we need to decide how to
+access these characters. A straightforward way is:
+
+\startbuffer
+\def\smallminus{\privatechar{smallminus}}
+\def\highminus {\privatechar{highminus}}
+\stopbuffer
+
+\typebuffer \getbuffer
+
+An alternative is:
+
+\starttyping
+\definemathcommand [smallminus] [ord] {\privatechar{smallminus}}
+\definemathcommand [highminus]  [ord] {\privatechar{highminus}}
+\stoptyping
+
+but that fails in text mode. So, we can consider:
+
+\starttyping
+\def\smallminus{\mathortext{\mathord{\privatechar{smallminus}}}{\privatechar{smallminus}}}
+\def\highminus {\mathortext{\mathord{\privatechar {highminus}}}{\privatechar {highminus}}}
+\stoptyping
+
+or more compact
+
+\starttyping
+\def\smallminus{\mathortext\mathord\firstofoneargument{\privatechar{smallminus}}}
+\def\highminus {\mathortext\mathord\firstofoneargument{\privatechar {highminus}}}
+\stoptyping
+
+What method you choose depends on usage. With the first, simple definitions we
+get this:
+
+\startbuffer
+[\getprivateslot{smallminus}] [\getprivatechar{smallminus}] [\smallminus] $[\smallminus]$\par
+[\getprivateslot {highminus}] [\getprivatechar {highminus}] [\highminus ] $[\highminus ]$\par
+\stopbuffer
+
+\typebuffer \getbuffer
+
+Because we are fully expandable we can even use this in:
+
+\startbuffer
+\bTABLE[aligncharacter=yes,alignmentcharacter={text->\smallminus}]
+  \bTR \bTD \mathminus100\smallminus00+ \eTD \eTR
+  \bTR \bTD           100\smallminus00  \eTD \eTR
+  \bTR \bTD \mathminus 99\smallminus00+ \eTD \eTR
+  \bTR \bTD \mathminus 99\smallminus00  \eTD \eTR
+  \bTR \bTD           100\highminus     \eTD \eTR
+\eTABLE
+\stopbuffer
+
+\typebuffer
+
+\startlinecorrection
+\getbuffer
+\stoplinecorrection
+
+With the other definitions the alignment would not work. If you need both then
+you can define different commands for text and math.
+
+\stopsection
+
+\startsection[title=Tabular numbers]
+
+Some font features are meant to be used in controlled situations. An example is
+the \type {tnum} feature that triggers so called \quote {tabular figures} meaning
+numbers that have equal widths. Its opposite feature is \type {lnum} or lining
+figures. We have two predefined \CONTEXT\ font features for this:
+
+\starttyping
+\definefontfeature [inlinenumbers]  [lnum=yes,tnum=no]
+\definefontfeature [tabularnumbers] [tnum=yes,lnum=no]
+\stoptyping
+
+Some mechanisms in \CONTEXT\ had better be aware of this and one of them is the
+alignment mechanism in tables.
+
+\startbuffer[demo]
+\startcombination[before=,after=]
+    \startcontent
+        \switchtobodyfont[pagella]\showglyphs%
+        \disabledirectives[typesetters.characteralign.autofont]%
+        \bTABLE[alignmentcharacter=.,aligncharacter=yes]
+            \bTR \bTD  11.111 \eTD \eTR
+            \bTR \bTD   2.2   \eTD \eTR
+            \bTR \bTD 444.444 \eTD \eTR
+        \eTABLE
+        \enabledirectives[typesetters.characteralign.autofont]%
+    \stopcontent
+    \startcaption
+        \small manual \type {tnum}
+    \stopcaption
+    \startcontent
+        \switchtobodyfont[pagella]\showglyphs%
+        \bTABLE[alignmentcharacter=.,aligncharacter=yes]
+            \bTR \bTD  11.111 \eTD \eTR
+            \bTR \bTD   2.2   \eTD \eTR
+            \bTR \bTD 444.444 \eTD \eTR
+        \eTABLE
+    \stopcontent
+    \startcaption
+        \small auto \type {tnum}
+    \stopcaption
+\stopcombination
+\stopbuffer
+
+In the following examples we demonstrate how the automatic font adaption makes
+sure that tabular figures are used. The table is defined as:
+
+\typebuffer[demo]
+
+\startbuffer
+\dontleavehmode\hbox to .3\textwidth \bgroup
+    \hss\getbuffer[demo]\hss
+\egroup
+\stopbuffer
+
+In \in {figure}[fig:tabularnumbers] we see what the features do. We use the \type
+{\feature} or \type {\addfeature} macro for this. For the moment this trickery is
+controlled by a directive (beware: enabling them is global).
+
+\startplacefigure[reference=fig:tabularnumbers,title={Tabular numbers}]
+    \startcombination[nx=3,ny=2]
+        {\getbuffer}                             {\tt\nohyphens default}
+        {\addfeature  [inlinenumbers]\getbuffer} {\tt\nohyphens inlinenumbers}
+        {\addfeature [tabularnumbers]\getbuffer} {\tt\nohyphens tabularnumbers}
+        {\addfeature[oldstylenumbers]\getbuffer} {\tt\nohyphens oldstylenumbers}
+        {\addfeature[oldstylenumbers]%
+         \addfeature  [inlinenumbers]\getbuffer} {\tt\nohyphens oldstylenumbers\par inlinenumbers}
+        {\addfeature[oldstylenumbers]%
+         \addfeature [tabularnumbers]\getbuffer} {\tt\nohyphens oldstylenumbers\par tabularnumbers}
+    \stopcombination
+\stopplacefigure
+
+\stopsection
+
+\stopchapter