Fix take_range with padding to have colored background padding

Author: tompng

lib/reline/unicode.rb

@@ -223,6 +223,10 @@ def self.take_range(str, start_col, width, encoding: str.encoding, cover_begin:
           total_width += mbchar_width
           break if !cover_end && total_width > start_col + width
           if cover_begin ? start_col < total_width : start_col <= prev_width
+            if padding && chunk_start_col.nil? && start_col < prev_width
+              chunk << ' ' * (prev_width - start_col)
+              chunk_start_col = start_col
+            end
             chunk << gc
             chunk_start_col ||= prev_width
             chunk_end_col = total_width
@@ -233,15 +237,9 @@ def self.take_range(str, start_col, width, encoding: str.encoding, cover_begin:
     end
     chunk_start_col ||= start_col
     chunk_end_col ||= start_col
-    if padding
-      if start_col < chunk_start_col
-        chunk = ' ' * (chunk_start_col - start_col) + chunk
-        chunk_start_col = start_col
-      end
-      if chunk_end_col < start_col + width
-        chunk << ' ' * (start_col + width - chunk_end_col)
-        chunk_end_col = start_col + width
-      end
+    if padding && chunk_end_col < start_col + width
+      chunk << ' ' * (start_col + width - chunk_end_col)
+      chunk_end_col = start_col + width
     end
     [chunk, chunk_start_col, chunk_end_col - chunk_start_col]
   end

test/reline/test_unicode.rb

@@ -35,5 +35,6 @@ def test_take_range
     assert_equal [' うえ', 3, 5], Reline::Unicode.take_range('あいうえお', 3, 4, cover_end: true, padding: true)
     assert_equal [' うえお   ', 3, 10], Reline::Unicode.take_range('あいうえお', 3, 10, padding: true)
     assert_equal ["\e[31mc\1ABC\2d\e[0mef", 2, 4], Reline::Unicode.take_range("\e[31mabc\1ABC\2d\e[0mefghi", 2, 4)
+    assert_equal ["\e[47m い ", 1, 4], Reline::Unicode.take_range("\e[47mあいうえお\e[0m", 1, 4, padding: true)
   end
 end