feat(typesetters): Support U+00AD soft hyphen as discretionary break

typesetters/base.lua

@@ -132,6 +132,19 @@ function typesetter.declareSettings(_)
     help = "Width to break lines at"
   })
 
+  SILE.settings:declare({
+    parameter = "typesetter.softHyphen",
+    type = "boolean",
+    default = true,
+    help = "When true, soft hyphens are rendered as discretionary breaks, otherwise they are ignored"
+  })
+
+  SILE.settings:declare({
+    parameter = "typesetter.softHyphenWarning",
+    type = "boolean",
+    default = false,
+    help = "When true, a warning is issued when a soft hyphen is encountered"
+  })
 end
 
 function typesetter:initState ()
@@ -276,7 +289,29 @@ function typesetter:typeset (text)
     if token.separator then
       self:endline()
     else
-      self:setpar(token.string)
+      if SILE.settings:get("typesetter.softHyphen") then
+        local warnedshy = false
+        for token2 in SU.gtoke(token.string, luautf8.char(0x00AD)) do
+          if token2.separator then -- soft hyphen support
+            local discretionary = SILE.nodefactory.discretionary({})
+            local hbox = SILE.typesetter:makeHbox({ SILE.settings:get("font.hyphenchar") })
+            discretionary.prebreak = { hbox }
+            table.insert(SILE.typesetter.state.nodes, discretionary)
+            if not warnedshy and SILE.settings:get("typesetter.softHyphenWarning") then
+              SU.warn("Soft hyphen encountered and replaced with discretionary")
+            end
+            warnedshy = true
+          else
+            self:setpar(token2.string)
+          end
+        end
+      else
+        if SILE.settings:get("typesetter.softHyphenWarning") and luautf8.match(token.string, luautf8.char(0x00AD)) then
+          SU.warn("Soft hyphen encountered and ignored")
+        end
+        text = luautf8.gsub(token.string, luautf8.char(0x00AD), "")
+        self:setpar(text)
+      end
     end
   end
   SILE.traceStack:pop(pId)