macOS: Add an setting to have the option key not behave as alt

CHANGELOG.rst

@@ -12,8 +12,8 @@ version 0.5.0 [future]
 
 - Add an option to have window focus follow mouse
 
-- Fix handling of option key on macOS. It now behaves just like the alt key on
+- macOS: Fix handling of option key. It now behaves just like the alt key on
-  Linux.
+  Linux. There is an option to make it type unicode characters instead.
 
 - Linux: Add support for startup notification on X11 desktops. kitty will
   now inform the window manager when its startup is complete.

kitty/config.py

@@ -261,6 +261,7 @@ type_map = {
     'initial_window_height': positive_int,
     'use_system_wcwidth': to_bool,
     'macos_hide_titlebar': to_bool,
+    'macos_option_as_alt': to_bool,
 }
 
 for name in (

kitty/keys.c

@@ -21,6 +21,7 @@ key_to_bytes(int glfw_key, bool smkx, bool extended, int mods, int action) {
 }
 
 #define SPECIAL_INDEX(key) ((key & 0x7f) | ( (mods & 0xF) << 7))
+#define IS_ALT_MODS(mods) (mods == GLFW_MOD_ALT || mods == (GLFW_MOD_ALT | GLFW_MOD_SHIFT))
 
 void
 set_special_key_combo(int glfw_key, int mods) {
@@ -42,12 +43,15 @@ active_window() {
 void
 on_text_input(unsigned int codepoint, int mods) {
     Window *w = active_window();
-    static char buf[10];
+    static char buf[16];
     unsigned int sz = 0;
 
     if (w != NULL) {
         bool is_text = mods <= GLFW_MOD_SHIFT;
         if (is_text) sz = encode_utf8(codepoint, buf);
+#ifdef __APPLE__
+        if (!OPT(macos_option_as_alt) && IS_ALT_MODS(mods)) sz = encode_utf8(codepoint, buf);
+#endif
         if (sz) schedule_write_to_child(w->id, buf, sz);
     }
 }
@@ -156,6 +160,9 @@ on_key_input(int key, int scancode, int action, int mods) {
     if (screen->scrolled_by && action == GLFW_PRESS && !is_modifier_key(key)) {
         screen_history_scroll(screen, SCROLL_FULL, false);  // scroll back to bottom
     }
+#ifdef __APPLE__
+    if (!OPT(macos_option_as_alt) && IS_ALT_MODS(mods)) return;
+#endif
     if (
             action == GLFW_PRESS ||
             (action == GLFW_REPEAT && screen->modes.mDECARM) ||

kitty/kitty.conf

@@ -319,3 +319,9 @@ map ctrl+shift+backspace restore_font_size
 
 # Hide the kitty window's title bar on macOS.
 macos_hide_titlebar no
+
+# Use the option key as an alt key. With this set to no, kitty will use 
+# the macOS native Option+Key = unicode character behavior. This will
+# break any Alt+key keyboard shortcuts in your terminal programs, but you
+# can use the macOS unicode input technique.
+macos_option_as_alt yes

kitty/state.c

@@ -162,6 +162,7 @@ PYWRAP1(set_options) {
     S(url_color, color_as_int);
     S(repaint_delay, repaint_delay);
     S(input_delay, repaint_delay);
+    S(macos_option_as_alt, PyObject_IsTrue);
 
     PyObject *chars = PyObject_GetAttrString(args, "select_by_word_characters");
     if (chars == NULL) return NULL;

kitty/state.h

@@ -19,6 +19,7 @@ typedef struct {
     color_type url_color;
     double repaint_delay, input_delay;
     bool focus_follows_mouse;
+    bool macos_option_as_alt;
 } Options;
 
 typedef struct {