gh-132267: fix desynchronized cursor position and buffer mismatch after resize

Author: ImFeH2

Lib/_pyrepl/console.py

@@ -71,7 +71,7 @@ def __init__(
             self.output_fd = f_out.fileno()
 
     @abstractmethod
-    def refresh(self, screen: list[str], xy: tuple[int, int]) -> None: ...
+    def refresh(self, screen: list[str], xy: tuple[int, int], clear_to_end: bool = False) -> None: ...
 
     @abstractmethod
     def prepare(self) -> None: ...
@@ -82,6 +82,9 @@ def restore(self) -> None: ...
     @abstractmethod
     def move_cursor(self, x: int, y: int) -> None: ...
 
+    @abstractmethod
+    def reset_cursor(self) -> None: ...
+
     @abstractmethod
     def set_cursor_vis(self, visible: bool) -> None: ...
 

Lib/_pyrepl/reader.py

@@ -344,7 +344,9 @@ def calc_screen(self) -> list[str]:
             pos -= line_len + 1
             prompt, prompt_len = self.process_prompt(prompt)
             chars, char_widths = disp_str(line, colors, offset)
-            wrapcount = (sum(char_widths) + prompt_len) // self.console.width
+            wrapcount = (sum(char_widths) + prompt_len) // (self.console.width - 1) # 1 for line continuations
+            if (sum(char_widths) + prompt_len) % (self.console.width - 1) == 0:
+                wrapcount -= 1
             if wrapcount == 0 or not char_widths:
                 offset += line_len + 1  # Takes all of the line plus the newline
                 last_refresh_line_end_offsets.append(offset)
@@ -639,6 +641,17 @@ def refresh(self) -> None:
         self.console.refresh(self.screen, self.cxy)
         self.dirty = False
 
+    def handle_resize(self) -> None:
+        """Handle a resize event."""
+        self.console.height, self.console.width = self.console.getheightwidth()
+        self.console.reset_cursor()
+        ns = len(self.console.screen) * ["\000" * self.console.width]
+        self.console.screen = ns
+
+        self.screen = self.calc_screen()
+        self.console.refresh(self.screen, self.cxy, clear_to_end=True)
+        self.dirty = True
+
     def do_cmd(self, cmd: tuple[str, list[str]]) -> None:
         """`cmd` is a tuple of "event_name" and "event", which in the current
         implementation is always just the "buffer" which happens to be a list
@@ -714,7 +727,7 @@ def handle1(self, block: bool = True) -> bool:
             elif event.evt == "scroll":
                 self.refresh()
             elif event.evt == "resize":
-                self.refresh()
+                self.handle_resize()
             else:
                 translate = False
 

Lib/_pyrepl/unix_console.py

@@ -223,7 +223,7 @@ def change_encoding(self, encoding: str) -> None:
         """
         self.encoding = encoding
 
-    def refresh(self, screen, c_xy):
+    def refresh(self, screen, c_xy, clear_to_end = False):
         """
         Refresh the console screen.
 
@@ -271,8 +271,9 @@ def refresh(self, screen, c_xy):
             self.posxy = 0, old_offset
             for i in range(old_offset - offset):
                 self.__write_code(self._ri)
-                oldscr.pop(-1)
                 oldscr.insert(0, "")
+                if len(oldscr) > height:
+                    oldscr.pop(-1)
         elif old_offset < offset and self._ind:
             self.__hide_cursor()
             self.__write_code(self._cup, self.height - 1, 0)
@@ -300,6 +301,12 @@ def refresh(self, screen, c_xy):
             self.__write_code(self._el)
             y += 1
 
+        if clear_to_end:
+            self.__move(wlen(newscr[-1]), len(newscr) - 1 + self.__offset)
+            self.posxy = wlen(newscr[-1]), len(newscr) - 1 + self.__offset
+            self.__write_code(b"\x1b[J") # clear to end of line
+            self.flushoutput()
+
         self.__show_cursor()
 
         self.screen = screen.copy()
@@ -321,6 +328,10 @@ def move_cursor(self, x, y):
             self.posxy = x, y
             self.flushoutput()
 
+    def reset_cursor(self) -> None:
+        self.posxy = 0, self.__offset
+        self.__write_code(self._cup, 0, 0)
+
     def prepare(self):
         """
         Prepare the console for input/output operations.
@@ -683,13 +694,18 @@ def __write_changed_line(self, y, oldline, newline, px_coord):
             self.__write(newline[x_pos])
             self.posxy = character_width + 1, y
 
+            if newline[-1] != oldline[-1]:
+                self.__move(self.width, y)
+                self.__write(newline[-1])
+                self.posxy = self.width - 1, y
+
         else:
             self.__hide_cursor()
             self.__move(x_coord, y)
             if wlen(oldline) > wlen(newline):
                 self.__write_code(self._el)
             self.__write(newline[x_pos:])
-            self.posxy = wlen(newline), y
+            self.posxy = min(wlen(newline), self.width - 1), y
 
         if "\x1b" in newline:
             # ANSI escape characters are present, so we can't assume
@@ -752,7 +768,6 @@ def __move_tall(self, x, y):
         self.__write_code(self._cup, y - self.__offset, x)
 
     def __sigwinch(self, signum, frame):
-        self.height, self.width = self.getheightwidth()
         self.event_queue.insert(Event("resize", None))
 
     def __hide_cursor(self):

Lib/_pyrepl/windows_console.py

@@ -111,6 +111,7 @@ def __init__(self, err: int | None, descr: str | None = None) -> None:
 MOVE_UP = "\x1b[{}A"
 MOVE_DOWN = "\x1b[{}B"
 CLEAR = "\x1b[H\x1b[J"
+HOME = "\x1b[H"
 
 # State of control keys: https://learn.microsoft.com/en-us/windows/console/key-event-record-str
 ALT_ACTIVE = 0x01 | 0x02
@@ -171,7 +172,7 @@ def __init__(
             # Console I/O is redirected, fallback...
             self.out = None
 
-    def refresh(self, screen: list[str], c_xy: tuple[int, int]) -> None:
+    def refresh(self, screen: list[str], c_xy: tuple[int, int], clear_to_end: bool = False) -> None:
         """
         Refresh the console screen.
 
@@ -234,6 +235,12 @@ def refresh(self, screen: list[str], c_xy: tuple[int, int]) -> None:
             self._erase_to_end()
             y += 1
 
+        if clear_to_end:
+            self._move_relative(wlen(newscr[-1]), self.__offset + len(newscr) - 1)
+            self.posxy = wlen(newscr[-1]), self.__offset + len(newscr) - 1
+            self.__write("\x1b[J")
+            self.flushoutput()
+
         self._show_cursor()
 
         self.screen = screen
@@ -287,7 +294,7 @@ def __write_changed_line(
             self._move_relative(0, y + 1)
             self.posxy = 0, y + 1
         else:
-            self.posxy = wlen(newline), y
+            self.posxy = min(wlen(newline), self.width - 1), y
 
             if "\x1b" in newline or y != self.posxy[1] or '\x1a' in newline:
                 # ANSI escape characters are present, so we can't assume
@@ -395,6 +402,10 @@ def move_cursor(self, x: int, y: int) -> None:
             self._move_relative(x, y)
             self.posxy = x, y
 
+    def reset_cursor(self) -> None:
+        self.posxy = 0, self.__offset
+        self.__write(HOME)
+
     def set_cursor_vis(self, visible: bool) -> None:
         if visible:
             self._show_cursor()

Lib/test/test_pyrepl/support.py

@@ -131,7 +131,7 @@ def getpending(self) -> Event:
     def getheightwidth(self) -> tuple[int, int]:
         return self.height, self.width
 
-    def refresh(self, screen: list[str], xy: tuple[int, int]) -> None:
+    def refresh(self, screen: list[str], xy: tuple[int, int], clear_to_end: bool = False) -> None:
         pass
 
     def prepare(self) -> None:
@@ -143,6 +143,9 @@ def restore(self) -> None:
     def move_cursor(self, x: int, y: int) -> None:
         pass
 
+    def reset_cursor(self) -> None:
+        pass
+
     def set_cursor_vis(self, visible: bool) -> None:
         pass
 

Lib/test/test_pyrepl/test_unix_console.py

@@ -258,7 +258,7 @@ def test_resize_bigger_on_multiline_function(self, _os_write):
         reader, console = handle_events_short_unix_console(events)
 
         console.height = 2
-        console.getheightwidth = MagicMock(lambda _: (2, 80))
+        console.getheightwidth = MagicMock(return_value=(2, 80))
 
         def same_reader(_):
             return reader
@@ -294,7 +294,7 @@ def test_resize_smaller_on_multiline_function(self, _os_write):
         reader, console = handle_events_unix_console_height_3(events)
 
         console.height = 1
-        console.getheightwidth = MagicMock(lambda _: (1, 80))
+        console.getheightwidth = MagicMock(return_value=(1, 80))
 
         def same_reader(_):
             return reader

Lib/test/test_pyrepl/test_windows_console.py

@@ -24,6 +24,7 @@
         MOVE_UP,
         MOVE_DOWN,
         ERASE_IN_LINE,
+        HOME,
     )
     import _pyrepl.windows_console as wc
 except ImportError:
@@ -102,7 +103,7 @@ def test_resize_wider(self):
 
         console.height = 20
         console.width = 80
-        console.getheightwidth = MagicMock(lambda _: (20, 80))
+        console.getheightwidth = MagicMock(return_value=(20, 80))
 
         def same_reader(_):
             return reader
@@ -117,9 +118,8 @@ def same_console(events):
             prepare_console=same_console,
         )
 
-        con.out.write.assert_any_call(self.move_right(2))
-        con.out.write.assert_any_call(self.move_up(2))
-        con.out.write.assert_any_call(b"567890")
+        con.out.write.assert_any_call(self.home())
+        con.out.write.assert_any_call(b"1234567890")
 
         con.restore()
 
@@ -130,7 +130,7 @@ def test_resize_narrower(self):
 
         console.height = 20
         console.width = 4
-        console.getheightwidth = MagicMock(lambda _: (20, 4))
+        console.getheightwidth = MagicMock(return_value=(20, 4))
 
         def same_reader(_):
             return reader
@@ -264,7 +264,7 @@ def test_resize_bigger_on_multiline_function(self):
         reader, console = self.handle_events_short(events)
 
         console.height = 2
-        console.getheightwidth = MagicMock(lambda _: (2, 80))
+        console.getheightwidth = MagicMock(return_value=(2, 80))
 
         def same_reader(_):
             return reader
@@ -280,8 +280,9 @@ def same_console(events):
         )
         con.out.write.assert_has_calls(
             [
-                call(self.move_left(5)),
+                call(self.home()),
                 call(self.move_up()),
+                call(self.erase_in_line()),
                 call(b"def f():"),
                 call(self.move_left(3)),
                 call(self.move_down()),
@@ -302,7 +303,7 @@ def test_resize_smaller_on_multiline_function(self):
         reader, console = self.handle_events_height_3(events)
 
         console.height = 1
-        console.getheightwidth = MagicMock(lambda _: (1, 80))
+        console.getheightwidth = MagicMock(return_value=(1, 80))
 
         def same_reader(_):
             return reader
@@ -318,8 +319,7 @@ def same_console(events):
         )
         con.out.write.assert_has_calls(
             [
-                call(self.move_left(5)),
-                call(self.move_up()),
+                call(self.home()),
                 call(self.erase_in_line()),
                 call(b"  foo"),
             ]
@@ -342,6 +342,9 @@ def move_right(self, cols=1):
     def erase_in_line(self):
         return ERASE_IN_LINE.encode("utf8")
 
+    def home(self):
+        return HOME.encode("utf8")
+
     def test_multiline_ctrl_z(self):
         # see gh-126332
         code = "abcdefghi"

Misc/NEWS.d/next/Library/2025-05-25-14-28-22.gh-issue-132267.lJOMvh.rst

@@ -0,0 +1,2 @@
+In the New REPL, resize triggers redraw now. Also fixed cross-line width
+calculation and content rendering during scrolling.