From 16d68a57e5da61e0cddfc30379881f2e8ac41e3c Mon Sep 17 00:00:00 2001
From: tompng <tomoyapenguin@gmail.com>
Date: Fri, 3 Nov 2023 17:44:46 +0900
Subject: [PATCH] Consider fullwidth take_range in differential rendering

---
 lib/reline/line_editor.rb       | 17 ++++++-----------
 test/reline/test_line_editor.rb | 30 ++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/lib/reline/line_editor.rb b/lib/reline/line_editor.rb
index 6877a0409c..79ff744130 100644
--- a/lib/reline/line_editor.rb
+++ b/lib/reline/line_editor.rb
@@ -373,9 +373,11 @@ def render_line_differential(old_items, new_items)
         Reline::IOGate.move_cursor_column base_x
         @output.write "\e[0m#{' ' * width}"
       else
-        x, w, content = new_items[level]
-        content = Reline::Unicode.take_range(content, base_x - x, width) unless x == base_x && w == width
-        Reline::IOGate.move_cursor_column base_x
+        x, _w, content = new_items[level]
+        cover_begin = base_x != 0 && new_levels[base_x - 1] == level
+        cover_end = new_levels[base_x + width] == level
+        content, pos = Reline::Unicode.take_mbchar_range(content, base_x - x, width, cover_begin: cover_begin, cover_end: cover_end, padding: true)
+        Reline::IOGate.move_cursor_column x + pos
         @output.write "\e[0m#{content}\e[0m"
       end
       base_x += width
@@ -654,13 +656,6 @@ def add_dialog_proc(name, p, context = nil)
 
   DIALOG_DEFAULT_HEIGHT = 20
 
-  private def padding_space_with_escape_sequences(str, width)
-    padding_width = width - calculate_width(str, true)
-    # padding_width should be only positive value. But macOS and Alacritty returns negative value.
-    padding_width = 0 if padding_width < 0
-    str + (' ' * padding_width)
-  end
-
   private def dialog_range(dialog, dialog_y)
     x_range = dialog.column...dialog.column + dialog.width
     y_range = dialog_y + dialog.vertical_offset...dialog_y + dialog.vertical_offset + dialog.contents.size
@@ -734,7 +729,7 @@ def add_dialog_proc(name, p, context = nil)
     dialog.contents = contents.map.with_index do |item, i|
       line_sgr = i == pointer ? enhanced_sgr : default_sgr
       str_width = dialog.width - (scrollbar_pos.nil? ? 0 : @block_elem_width)
-      str = padding_space_with_escape_sequences(Reline::Unicode.take_range(item, 0, str_width), str_width)
+      str, = Reline::Unicode.take_mbchar_range(item, 0, str_width, padding: true)
       colored_content = "#{line_sgr}#{str}"
       if scrollbar_pos
         if scrollbar_pos <= (i * 2) and (i * 2 + 1) < (scrollbar_pos + bar_height)
diff --git a/test/reline/test_line_editor.rb b/test/reline/test_line_editor.rb
index a5fcc3e2a1..016fbc8c3f 100644
--- a/test/reline/test_line_editor.rb
+++ b/test/reline/test_line_editor.rb
@@ -106,6 +106,36 @@ def test_dialog_move
       end
     end
 
+    def test_multibyte
+      base = [0, 12, '一二三一二三']
+      left = [0, 3, 'LLL']
+      right = [9, 3, 'RRR']
+      front = [3, 6, 'FFFFFF']
+      # 一 FFFFF 三
+      # 一二三一二三
+      assert_output '[COL_2]二三一二' do
+        @line_editor.render_line_differential([base, front], [base, nil])
+      end
+
+      # LLLFFFFF 三
+      # LLL 三一二三
+      assert_output '[COL_3] 三一二' do
+        @line_editor.render_line_differential([base, left, front], [base, left, nil])
+      end
+
+      # 一 FFFFFRRR
+      # 一二三一 RRR
+      assert_output '[COL_2]二三一 ' do
+        @line_editor.render_line_differential([base, right, front], [base, right, nil])
+      end
+
+      # LLLFFFFFRRR
+      # LLL 三一 RRR
+      assert_output '[COL_3] 三一 ' do
+        @line_editor.render_line_differential([base, left, right, front], [base, left, right, nil])
+      end
+    end
+
     def test_complex
       state_a = [nil, [19, 7, 'bbbbbbb'], [15, 8, 'cccccccc'], [10, 5, 'ddddd'], [18, 4, 'eeee'], [1, 3, 'fff'], [17, 2, 'gg'], [7, 1, 'h']]
       state_b = [[5, 9, 'aaaaaaaaa'], nil, [15, 8, 'cccccccc'], nil, [18, 4, 'EEEE'], [25, 4, 'ffff'], [17, 2, 'gg'], [2, 2, 'hh']]