feat(shapers): Add dummy shaper for use with alternative backends tha…

…t don't need shaping

core/sile.lua

@@ -222,10 +222,10 @@ function SILE.init ()
       SILE.shaper = SILE.shapers.harfbuzz()
       SILE.outputter = SILE.outputters.debug()
    elseif SILE.backend == "text" then
-      SILE.shaper = SILE.shapers.harfbuzz()
+      SILE.shaper = SILE.shapers.dummy()
       SILE.outputter = SILE.outputters.text()
    elseif SILE.backend == "dummy" then
-      SILE.shaper = SILE.shapers.harfbuzz()
+      SILE.shaper = SILE.shapers.dummy()
       SILE.outputter = SILE.outputters.dummy()
    end
    SILE.pagebuilder = SILE.pagebuilders.base()

shapers/dummy.lua

@@ -0,0 +1,28 @@
+local base = require("shapers.base")
+
+local shaper = pl.class(base)
+shaper._name = "dummy"
+
+function shaper.addShapedGlyphToNnodeValue (_, _, _) end
+
+function shaper.checkHBProblems (_, _, _) end
+
+function shaper.debugVersions (_) end
+
+function shaper.getFace () end
+
+function shaper.makeSpaceNode (_, _, _) end
+
+function shaper.preAddNodes (_, _, _) end
+
+function shaper:createNnodes (_, _) end
+
+function shaper:formNnode (_, _, _) end
+
+function shaper:measureChar (_) end
+
+function shaper:measureSpace (_) end
+
+function shaper:shapeToken (_, _) end
+
+return shaper