1 files changed, 22 insertions(+), 1 deletions(-)

M src/Data/Text/ParagraphLayout/Internal/ParagraphLine.hs

@@ 3,6 3,7 @@ module Data.Text.ParagraphLayout.Internal.ParagraphLine
     ( GenericLayout
     , cutLines
     , mergeLines
+    , forceLeftAlign
     )
 where
 


@@ 22,9 23,14 @@ class GenericLayout pl where
     -- | Rectangle surrounding the layout, to be used for appending.
     rect :: pl -> Rect Int32
 
-    -- | Actual distance between the paragraph origin and the nearest fragment.
+    -- | Actual distance between the paragraph origin and the nearest fragment
+    -- on the Y axis.
     topDistance :: pl -> Int32
 
+    -- | Actual distance between the paragraph origin and the nearest fragment
+    -- on the X axis.
+    leftDistance :: pl -> Int32
+
     -- | Keep only fragments with the given line number.
     limitFragments :: Int -> pl -> pl
 


@@ 40,6 46,7 @@ instance GenericLayout (P.ParagraphLayout d) where
     empty = P.emptyParagraphLayout
     rect = P.paragraphRect
     topDistance pl = topFragmentOrigin $ P.paragraphFragments pl
+    leftDistance pl = leftmostFragmentOrigin $ P.paragraphFragments pl
     limitFragments n = P.filterFragments (fragmentIsOnLine n)
     shiftFragments dx dy = P.mapFragments (shiftFragment dx dy)
     appendFragments = P.appendFragments


@@ 48,6 55,7 @@ instance GenericLayout (R.ParagraphLayout d) where
     empty = R.emptyParagraphLayout
     rect = R.paragraphRect
     topDistance pl = topFragmentOrigin $ R.paragraphFragments pl
+    leftDistance pl = leftmostFragmentOrigin $ R.paragraphFragments pl
     limitFragments n = R.filterFragments (fragmentIsOnLine n)
     shiftFragments dx dy = R.mapFragments (shiftFragment dx dy)
     appendFragments = R.appendFragments


@@ 64,9 72,16 @@ cutLine n pl = trimTop $ limitFragments n pl
 trimTop :: GenericLayout pl => pl -> pl
 trimTop pl = shiftFragments 0 (-topDistance pl) pl
 
+-- | Add a constant to each fragment's `x_origin` so that their minimum is zero.
+trimLeft :: GenericLayout pl => pl -> pl
+trimLeft pl = shiftFragments (-leftDistance pl) 0 pl
+
 topFragmentOrigin :: [Fragment d] -> Int32
 topFragmentOrigin frags = maximum $ map (y_origin . fragmentRect) frags
 
+leftmostFragmentOrigin :: [Fragment d] -> Int32
+leftmostFragmentOrigin frags = minimum $ map (x_origin . fragmentRect) frags
+
 -- | Put the given paragraph layouts together as a vertically contiguous
 -- sequence.
 mergeLines :: GenericLayout pl => [pl] -> pl


@@ 81,3 96,9 @@ mergeLine pl nextLine = pl'
 
 fragmentIsOnLine :: Int -> Fragment d -> Bool
 fragmentIsOnLine n frag = n == fragmentLine frag
+
+-- | Rearrange fragments on each line so that they are stacked from the left.
+--
+-- Intended for comparing paragraph layouts of different maximum widths.
+forceLeftAlign :: (GenericLayout pl, LineNumbers pl) => pl -> pl
+forceLeftAlign pl = mergeLines $ map trimLeft $ cutLines pl