Fix regression in grid tables for wide characters.

In the translation from String to Text, a char-width-sensitive
splitAt' was dropped.  This commit reinstates it.
Closes #7214.

src/Text/Pandoc/Shared.hs

@@ -153,12 +153,20 @@ splitTextBy isSep t
                 in  first : splitTextBy isSep (T.dropWhile isSep rest)
 
 splitTextByIndices :: [Int] -> T.Text -> [T.Text]
-splitTextByIndices ns = splitTextByRelIndices (zipWith (-) ns (0:ns))
+splitTextByIndices ns = splitTextByRelIndices (zipWith (-) ns (0:ns)) . T.unpack
  where
-  splitTextByRelIndices [] t = [t]
-  splitTextByRelIndices (x:xs) t =
-    let (first, rest) = T.splitAt x t
-     in first : splitTextByRelIndices xs rest
+  splitTextByRelIndices [] cs = [T.pack cs]
+  splitTextByRelIndices (x:xs) cs =
+    let (first, rest) = splitAt' x cs
+     in T.pack first : splitTextByRelIndices xs rest
+
+-- Note: don't replace this with T.splitAt, which is not sensitive
+-- to character widths!
+splitAt' :: Int -> [Char] -> ([Char],[Char])
+splitAt' _ []          = ([],[])
+splitAt' n xs | n <= 0 = ([],xs)
+splitAt' n (x:xs)      = (x:ys,zs)
+  where (ys,zs) = splitAt' (n - charWidth x) xs
 
 ordNub :: (Ord a) => [a] -> [a]
 ordNub l = go Set.empty l

test/command/7214.md

@@ -0,0 +1,28 @@
+```
+% pandoc
++------------+----------+------------------+
+|日本語      | の文字列 | words in english |
++------------+----------+------------------+
+|abc defghij | def      | xyz              |
++------------+----------+------------------+
+^D
+<table style="width:60%;">
+<colgroup>
+<col style="width: 18%" />
+<col style="width: 15%" />
+<col style="width: 26%" />
+</colgroup>
+<tbody>
+<tr class="odd">
+<td>日本語</td>
+<td>の文字列</td>
+<td>words in english</td>
+</tr>
+<tr class="even">
+<td>abc defghij</td>
+<td>def</td>
+<td>xyz</td>
+</tr>
+</tbody>
+</table>
+```