Add an option to use a modern wcwidth() instead of the system one

kitty/config.py

@@ -109,6 +109,7 @@ type_map = {
     'cursor_blink_interval': float,
     'cursor_stop_blinking_after': float,
     'enabled_layouts': to_layout_names,
+    'use_system_wcwidth': to_bool,
 }
 
 for name in 'foreground background cursor active_border_color inactive_border_color selection_foreground selection_background'.split():

kitty/data-types.c

@@ -20,6 +20,17 @@ drain_read(PyObject UNUSED *self, PyObject *fd) {
     Py_RETURN_NONE;
 }
 
+static PyObject*
+wcwidth_wrap(PyObject UNUSED *self, PyObject *chr) {
+    return PyLong_FromUnsignedLong(safe_wcwidth(PyLong_AsLong(chr)));
+}
+
+static PyObject*
+change_wcwidth_wrap(PyObject UNUSED *self, PyObject *use9) {
+    change_wcwidth(PyObject_IsTrue(use9));
+    Py_RETURN_NONE;
+}
+
 static PyMethodDef module_methods[] = {
     GL_METHODS
     {"drain_read", (PyCFunction)drain_read, METH_O, ""},
@@ -27,6 +38,8 @@ static PyMethodDef module_methods[] = {
     {"parse_bytes_dump", (PyCFunction)parse_bytes_dump, METH_VARARGS, ""},
     {"read_bytes", (PyCFunction)read_bytes, METH_VARARGS, ""},
     {"read_bytes_dump", (PyCFunction)read_bytes_dump, METH_VARARGS, ""},
+    {"wcwidth", (PyCFunction)wcwidth_wrap, METH_O, ""},
+    {"change_wcwidth", (PyCFunction)change_wcwidth_wrap, METH_O, ""},
     GLFW_FUNC_WRAPPERS
     {NULL, NULL, 0, NULL}        /* Sentinel */
 };

kitty/data-types.h

@@ -355,6 +355,8 @@ void historybuf_add_line(HistoryBuf *self, const Line *line);
 void historybuf_rewrap(HistoryBuf *self, HistoryBuf *other);
 void historybuf_init_line(HistoryBuf *self, index_type num, Line *l);
 
+unsigned int safe_wcwidth(uint32_t ch);
+void change_wcwidth(bool use9);
 void screen_align(Screen*);
 void screen_restore_cursor(Screen *);
 void screen_save_cursor(Screen *);

kitty/kitty.conf

@@ -73,6 +73,15 @@ open_url_modifiers ctrl+shift
 # use the operating system's default URL handler.
 open_url_with default
 
+# Choose whether to use the system implementation of wcwidth() (used to
+# control how many cells a character is rendered in).  If you use the system
+# implementation, then kitty and any programs running in it will agree. The
+# problem is that system implementations often are based on outdated unicode
+# standards and get the width of many characters, such as emoji, wrong. So if
+# you are using kitty with programs that have their own up-to-date wcwidth()
+# implementation, set this option to no.
+use_system_wcwidth yes
+
 # The value of the TERM environment variable to set
 term xterm-kitty
 

kitty/main.py

@@ -21,7 +21,7 @@ from .fast_data_types import (
     GLFW_CONTEXT_VERSION_MINOR, GLFW_OPENGL_PROFILE,
     GLFW_OPENGL_FORWARD_COMPAT, GLFW_OPENGL_CORE_PROFILE, GLFW_SAMPLES,
     glfw_set_error_callback, glfw_init, glfw_terminate, glfw_window_hint,
-    glfw_swap_interval, glfw_wait_events, Window
+    glfw_swap_interval, glfw_wait_events, Window, change_wcwidth
 )
 from .utils import safe_print
 
@@ -137,6 +137,7 @@ def main():
         main(args.replay_commands)
         return
     opts = load_config(args.config)
+    change_wcwidth(not opts.use_system_wcwidth)
     glfw_set_error_callback(on_glfw_error)
     enable_automatic_opengl_error_checking(False)
     if not glfw_init():

kitty/screen.c

@@ -10,6 +10,7 @@
 #include "unicode-data.h"
 #include "tracker.h"
 #include "modes.h"
+#include "wcwidth9.h"
 
 static const ScreenModes empty_modes = {0, .mDECAWM=true, .mDECTCEM=true, .mDECARM=true};
 
@@ -195,13 +196,21 @@ screen_designate_charset(Screen *self, uint32_t which, uint32_t as) {
     }
 }
 
-static inline unsigned int 
+static int (*wcwidth_impl)(wchar_t) = wcwidth;
+
+unsigned int 
 safe_wcwidth(uint32_t ch) {
-    int ans = wcwidth(ch);
+    int ans = wcwidth_impl(ch);
     if (ans < 0) ans = 1;
     return MIN(2, ans);
 }
 
+void
+change_wcwidth(bool use9) {
+    wcwidth_impl = (use9) ? wcwidth9 : wcwidth;
+}
+
+
 void
 screen_draw(Screen *self, uint32_t och) {
     if (is_ignored_char(och)) return;

kitty/utils.py

@@ -7,7 +7,6 @@ import os
 import signal
 import shlex
 import subprocess
-import ctypes
 import math
 from collections import namedtuple
 from contextlib import contextmanager
@@ -15,13 +14,7 @@ from functools import lru_cache
 from time import monotonic
 
 from .constants import isosx
-from .fast_data_types import glfw_get_physical_dpi
-
-libc = ctypes.CDLL(None)
-wcwidth_native = libc.wcwidth
-del libc
-wcwidth_native.argtypes = [ctypes.c_wchar]
-wcwidth_native.restype = ctypes.c_int
+from .fast_data_types import glfw_get_physical_dpi, wcwidth as wcwidth_impl
 
 
 def safe_print(*a, **k):
@@ -37,10 +30,10 @@ def ceil_int(x):
 
 @lru_cache(maxsize=2**13)
 def wcwidth(c: str) -> int:
-    ans = min(2, wcwidth_native(c))
-    if ans == -1:
-        ans = 1
-    return ans
+    try:
+        return wcwidth_impl(ord(c))
+    except TypeError:
+        return wcwidth_impl(ord(c[0]))
 
 
 @contextmanager