Add offset function to get the width of a Doc

Author: tarleb

README.md

@@ -332,6 +332,12 @@ If `a` and `b` are `Doc` elements, then `a // b` puts `a` above
 
 Returns `true` iff `doc` is the empty document, `false` otherwise.
 
+#### offset
+
+`offset (doc)`
+
+Returns the width of a `Doc` (as number of characters).
+
 
 License
 -------

src/Foreign/Lua/Module/DocLayout.hs

@@ -53,6 +53,7 @@ module Foreign.Lua.Module.DocLayout (
 
   -- * Document Querying
   , is_empty
+  , offset
 
   -- * Marshaling
   , peekDoc
@@ -114,6 +115,7 @@ pushModule = do
   Lua.addfunction "vfill"      vfill
   -- querying
   Lua.addfunction "is_empty"   is_empty
+  Lua.addfunction "offset"     offset
   -- rendering
   Lua.addfunction "render" render
   return 1
@@ -137,6 +139,9 @@ render doc optLength = return $ Doc.render (Lua.fromOptional optLength) doc
 is_empty :: Doc Text -> Lua Bool
 is_empty = return . Doc.isEmpty
 
+-- | Returns the width of a @'Doc'@.
+offset :: Doc Text -> Lua Int
+offset = return . Doc.offset
 
 --
 -- Constructors

test/test-doclayout.lua

@@ -58,6 +58,11 @@ return {
       assert.is_truthy(doclayout.is_empty(doclayout.empty))
       assert.is_truthy(doclayout.is_empty(''))
       assert.is_falsy(doclayout.is_empty('non-empty'))
+    end),
+
+    test('offset', function ()
+      assert.are_equal(doclayout.offset 'four', 4)
+      assert.are_equal(doclayout.offset(doclayout.literal 'four' / 'radio'), 5)
     end)
   },