From 7f62b6d8ac2377b83ed8ac6cba392709fd8b5e67 Mon Sep 17 00:00:00 2001
From: Jaro <jaro@argonaut-constellation.org>
Date: Fri, 10 Mar 2023 02:54:09 +0100
Subject: [PATCH] Add dropWhileEnd to SeparableTextContainer.

---
 src/Data/Text/ParagraphLayout/Internal/ResolvedSpan.hs  | 1 +
 src/Data/Text/ParagraphLayout/Internal/Run.hs           | 3 ++-
 src/Data/Text/ParagraphLayout/Internal/TextContainer.hs | 7 +++++++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/Data/Text/ParagraphLayout/Internal/ResolvedSpan.hs b/src/Data/Text/ParagraphLayout/Internal/ResolvedSpan.hs
index 99ce7de..26e3f1d 100644
--- a/src/Data/Text/ParagraphLayout/Internal/ResolvedSpan.hs
+++ b/src/Data/Text/ParagraphLayout/Internal/ResolvedSpan.hs
@@ -43,6 +43,7 @@ instance TextContainer a => TextContainer (WithSpan a) where
 instance SeparableTextContainer a => SeparableTextContainer (WithSpan a) where
     splitTextAt8 n (WithSpan rs c) = (WithSpan rs c1, WithSpan rs c2)
         where (c1, c2) = splitTextAt8 n c
+    dropWhileEnd p (WithSpan rs c) = WithSpan rs (dropWhileEnd p c)
 
 splitBySpanIndex :: [WithSpan a] -> [[a]]
 splitBySpanIndex xs = [getBySpanIndex i xs | i <- [0..]]
diff --git a/src/Data/Text/ParagraphLayout/Internal/Run.hs b/src/Data/Text/ParagraphLayout/Internal/Run.hs
index 0f764b9..4448cf1 100644
--- a/src/Data/Text/ParagraphLayout/Internal/Run.hs
+++ b/src/Data/Text/ParagraphLayout/Internal/Run.hs
@@ -4,6 +4,7 @@ where
 import Data.List (mapAccumL)
 import Data.List.NonEmpty (NonEmpty((:|)))
 import Data.Text (Text)
+import qualified Data.Text as Text
 import Data.Text.Foreign (dropWord8, lengthWord8, takeWord8)
 import Data.Text.Glyphize (Direction(..))
 import qualified Data.Text.ICU.Char as ICUChar
@@ -15,7 +16,6 @@ import Data.Text.ParagraphLayout.Internal.Zipper
 
 type ScriptCode = String
 
-
 -- | Each span can be broken into one or more runs by Balkón.
 --
 -- Each run could have a different script, language, or direction.
@@ -40,6 +40,7 @@ instance SeparableTextContainer Run where
             t1 = takeWord8 (fromIntegral n) t
             t2 = dropWord8 (fromIntegral n) t
             t = getText r
+    dropWhileEnd p r = r { runText = Text.dropWhileEnd p (runText r) }
 
 type ProtoRun = (Zipper, Maybe Direction, ScriptCode)
 
diff --git a/src/Data/Text/ParagraphLayout/Internal/TextContainer.hs b/src/Data/Text/ParagraphLayout/Internal/TextContainer.hs
index 4fe13d3..0217674 100644
--- a/src/Data/Text/ParagraphLayout/Internal/TextContainer.hs
+++ b/src/Data/Text/ParagraphLayout/Internal/TextContainer.hs
@@ -2,6 +2,7 @@ module Data.Text.ParagraphLayout.Internal.TextContainer
     (SeparableTextContainer
     ,TextContainer
     ,collapse
+    ,dropWhileEnd
     ,getText
     ,splitTextAt8
     ,splitTextsAt8
@@ -25,17 +26,23 @@ instance TextContainer Text where
 -- | Class of data types containing `Text` that can be split at a given number
 -- of `Data.Word.Word8` units from the start of the text.
 class TextContainer a => SeparableTextContainer a where
+
     -- | Split the given `SeparableTextContainer` at the given number of
     -- `Data.Word.Word8` units from the start of the text, preserving whatever
     -- constraints the instance requires.
     splitTextAt8 :: Int -> a -> (a, a)
 
+    -- | Return the prefix remaining after dropping characters that satisfy
+    -- the given predicate from the end of the given `SeparableTextContainer`.
+    dropWhileEnd :: (Char -> Bool) -> a -> a
+
 -- | As a trivial instance, each `Text` can be split directly.
 instance SeparableTextContainer Text where
     splitTextAt8 n t = (t1, t2)
         where
             t1 = takeWord8 (fromIntegral n) t
             t2 = dropWord8 (fromIntegral n) t
+    dropWhileEnd = Text.dropWhileEnd
 
 -- | Treat a list of text containers as a contiguous sequence,
 -- and make a split at the given number of `Data.Word.Word8` from the beginning
-- 
2.30.2