Support grapheme cluster that has width >= 3 (#834)

Author: tompng

lib/reline/unicode.rb

@@ -220,7 +220,7 @@ def self.take_mbchar_range(str, start_col, width, cover_begin: false, cover_end:
  next
  elsif padding && !cover_begin && prev_width < start_col && start_col < total_width
  # Add preceding padding. This padding might have background color.
- chunk << ' '
+ chunk << ' ' * (total_width - start_col)
  chunk_start_col ||= start_col
  chunk_end_col = total_width
  next
@@ -234,7 +234,7 @@ def self.take_mbchar_range(str, start_col, width, cover_begin: false, cover_end:
  # Current character exceeds end_col
  if padding && end_col < total_width
  # Add succeeding padding. This padding might have background color.
- chunk << ' '
+ chunk << ' ' * (end_col - prev_width)
  chunk_start_col ||= prev_width
  chunk_end_col = end_col
  end

test/reline/test_unicode.rb

@@ -107,6 +107,21 @@ def test_take_mbchar_range
  assert_equal ["\e[41m \e[42mい\e[43m ", 1, 4], Reline::Unicode.take_mbchar_range("\e[41mあ\e[42mい\e[43mう", 1, 4, padding: true)
  end
 
+ def test_three_width_characters_take_mbchar_range
+ halfwidth_dakuten = 0xFF9E.chr('utf-8')
+ a = 'あ' + halfwidth_dakuten
+ b = 'い' + halfwidth_dakuten
+ c = 'う' + halfwidth_dakuten
+ line = 'x' + a + b + c + 'x'
+ assert_equal [' ' + b + ' ', 2, 6], Reline::Unicode.take_mbchar_range(line, 2, 6, padding: true)
+ assert_equal [' ' + b + ' ', 3, 6], Reline::Unicode.take_mbchar_range(line, 3, 6, padding: true)
+ assert_equal [b + c, 4, 6], Reline::Unicode.take_mbchar_range(line, 4, 6, padding: true)
+ assert_equal [a + b, 1, 6], Reline::Unicode.take_mbchar_range(line, 2, 6, cover_begin: true)
+ assert_equal [a + b, 1, 6], Reline::Unicode.take_mbchar_range(line, 3, 6, cover_begin: true)
+ assert_equal [b + c, 4, 6], Reline::Unicode.take_mbchar_range(line, 2, 6, cover_end: true)
+ assert_equal [b + c, 4, 6], Reline::Unicode.take_mbchar_range(line, 3, 6, cover_end: true)
+ end
+
  def test_common_prefix
  assert_equal('', Reline::Unicode.common_prefix([]))
  assert_equal('abc', Reline::Unicode.common_prefix(['abc']))