bpython · sebastinas · Sep 6, 2020 · Aug 14, 2020
diff --git a/bpython/curtsiesfrontend/repl.py b/bpython/curtsiesfrontend/repl.py
@@ -402,7 +402,7 @@ def __init__(
         # so we're just using the same object
         self.interact = self.status_bar
 
-        # line currently being edited, without ps1 (usually '>>> ')
+        # logical line currently being edited, without ps1 (usually '>>> ')
         self._current_line = ""
 
         # current line of output - stdout and stdin go here
@@ -744,8 +744,9 @@ def process_key_event(self, e):
             )
             and self.config.curtsies_right_arrow_completion
             and self.cursor_offset == len(self.current_line)
+            # if at end of current line and user presses RIGHT (to autocomplete)
         ):
-
+            # then autocomplete
             self.current_line += self.current_suggestion
             self.cursor_offset = len(self.current_line)
         elif e in ("<UP>",) + key_dispatch[self.config.up_one_line_key]:
@@ -1435,6 +1436,23 @@ def current_output_line(self, value):
         self.current_stdouterr_line = ""
         self.stdin.current_line = "\n"
 
+    def number_of_padding_chars_on_current_cursor_line(self):
+        """ To avoid cutting off two-column characters at the end of lines where
+        there's only one column left, curtsies adds a padding char (u' ').
+        It's important to know about these for cursor positioning.
+
+        Should return zero unless there are fullwidth characters. """
+        full_line = self.current_cursor_line_without_suggestion
+        line_with_padding = "".join(
+            line.s
+            for line in paint.display_linize(
+                self.current_cursor_line_without_suggestion.s, self.width
+            )
+        )
+
+        # the difference in length here is how much padding there is
+        return len(line_with_padding) - len(full_line)
+
     def paint(
         self,
         about_to_exit=False,
@@ -1620,7 +1638,8 @@ def move_screen_up(current_line_start_row):
                     wcswidth(self.current_cursor_line_without_suggestion.s)
                     - wcswidth(self.current_line)
                     + wcswidth(self.current_line[: self.cursor_offset])
-                ),
+                )
+                + self.number_of_padding_chars_on_current_cursor_line(),
                 width,
             )
             assert cursor_column >= 0, (

diff --git a/bpython/curtsiesfrontend/replpainter.py b/bpython/curtsiesfrontend/replpainter.py
@@ -26,20 +26,24 @@ def display_linize(msg, columns, blank_line=False):
     """Returns lines obtained by splitting msg over multiple lines.
 
     Warning: if msg is empty, returns an empty list of lines"""
-    display_lines = (
-        [
-            msg[start:end]
-            for start, end in zip(
-                range(0, len(msg), columns),
-                range(columns, len(msg) + columns, columns),
-            )
-        ]
-        if msg
-        else ([""] if blank_line else [])
-    )
+    if not msg:
+        return [''] if blank_line else []
+    msg = fmtstr(msg)
+    try:
+        display_lines = list(msg.width_aware_splitlines(columns))
+    # use old method if wcwidth can't determine width of msg
+    except ValueError:
+        display_lines = (	    
+                [	        
+                    msg[start:end]	    
+                    for start, end in zip(	    
+                        range(0, len(msg), columns),	
+                        range(columns, len(msg) + columns, columns),	
+                    )	
+                ]	
+            )	
     return display_lines
 
-
 def paint_history(rows, columns, display_lines):
     lines = []
     for r, line in zip(range(rows), display_lines[-rows:]):

diff --git a/bpython/test/test_curtsies_painting.py b/bpython/test/test_curtsies_painting.py
@@ -271,6 +271,32 @@ def send_key(self, key):
         self.repl.process_event("<SPACE>" if key == " " else key)
         self.repl.paint()  # has some side effects we need to be wary of
 
+class TestWidthAwareness(HigherLevelCurtsiesPaintingTest):
+
+    def test_cursor_position_with_fullwidth_char(self):
+        self.repl.add_normal_character("間")
+
+        cursor_pos = self.repl.paint()[1]
+        self.assertEqual(cursor_pos, (0,6))
+
+    def test_cursor_position_with_padding_char(self):
+        # odd numbered so fullwidth chars don't wrap evenly
+        self.repl.width = 11 
+        [self.repl.add_normal_character(c) for c in "ｗｉｄｔｈ"]
+
+        cursor_pos = self.repl.paint()[1]
+        self.assertEqual(cursor_pos, (1,4))
+
+    def test_display_of_padding_chars(self):
+        self.repl.width = 11 
+        [self.repl.add_normal_character(c) for c in "ｗｉｄｔｈ"]
+
+        self.enter()
+        expected = [
+            '>>> ｗｉｄ ', # <--- note the added trailing space
+            'ｔｈ']
+        result = [d.s for d in self.repl.display_lines[0:2]]
+        self.assertEqual(result, expected) 
 
 class TestCurtsiesRewindRedraw(HigherLevelCurtsiesPaintingTest):
     def test_rewind(self):