2018-01-08 23:11:00

1 files changed, 81 insertions, 1 deletions

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