Use a pipe rather than a signal to wait for terminal ready

Simpler code, more robust since there is no longer a race between the
installation of the signal handler and the dispatch of the signal

kitty/child.c

@@ -47,35 +47,22 @@ write_to_stderr(const char *text) {
 
 #define exit_on_err(m) { write_to_stderr(m); write_to_stderr(": "); write_to_stderr(strerror(errno)); exit(EXIT_FAILURE); }
 
-static sig_atomic_t sigwinch_arrived;
-
-void handle_sigwinch(int signal) {
-    if (signal == SIGWINCH) sigwinch_arrived = 1;
-}
-
 static inline void
-wait_for_sigwinch() {
-    sigwinch_arrived = 0;
-    sigset_t mask, oldmask;
-    struct sigaction sa;
-    sa.sa_handler = handle_sigwinch;
-    sa.sa_flags = SA_RESTART;
-    if (sigaction(SIGWINCH, &sa, NULL) == -1) {
-        exit_on_err("Failed to set the SIGWINCH signal handler");
+wait_for_terminal_ready(int fd) {
+    char data;
+    while(1) {
+        int ret = read(fd, &data, 1);
+        if (ret == -1 && (errno == EINTR || errno == EAGAIN)) continue;
+        break;
     }
-    sigemptyset(&mask);
-    sigaddset(&mask, SIGWINCH);
-    sigprocmask(SIG_BLOCK, &mask, &oldmask);
-    while(!sigwinch_arrived) sigsuspend(&oldmask);
-    sigprocmask(SIG_UNBLOCK, &mask, NULL);
 }
 
 static PyObject*
 spawn(PyObject *self UNUSED, PyObject *args) {
     PyObject *argv_p, *env_p;
-    int master, slave, stdin_read_fd, stdin_write_fd;
+    int master, slave, stdin_read_fd, stdin_write_fd, ready_read_fd, ready_write_fd;
     char *cwd, *exe;
-    if (!PyArg_ParseTuple(args, "ssO!O!iiii", &exe, &cwd, &PyTuple_Type, &argv_p, &PyTuple_Type, &env_p, &master, &slave, &stdin_read_fd, &stdin_write_fd)) return NULL;
+    if (!PyArg_ParseTuple(args, "ssO!O!iiiiii", &exe, &cwd, &PyTuple_Type, &argv_p, &PyTuple_Type, &env_p, &master, &slave, &stdin_read_fd, &stdin_write_fd, &ready_read_fd, &ready_write_fd)) return NULL;
     char name[2048] = {0};
     if (ttyname_r(slave, name, sizeof(name) - 1) != 0) { PyErr_SetFromErrno(PyExc_OSError); return NULL; }
     char **argv = serialize_string_tuple(argv_p);
@@ -98,8 +85,10 @@ spawn(PyObject *self UNUSED, PyObject *args) {
 #endif
             close(tfd);
 
-            // Wait for SIGWINCH which indicates kitty has setup the screen object
-            wait_for_sigwinch();
+            // Wait for READY_SIGNAL which indicates kitty has setup the screen object
+            close(ready_write_fd);
+            wait_for_terminal_ready(ready_read_fd);
+            close(ready_read_fd);
 
             // Redirect stdin/stdout/stderr to the pty
             if (dup2(slave, 1) == -1) exit_on_err("dup2() failed for fd number 1");

kitty/child.py

@@ -101,6 +101,8 @@ def fork(self):
         remove_cloexec(slave)
         fast_data_types.set_iutf8(master, True)
         stdin, self.stdin = self.stdin, None
+        ready_read_fd, ready_write_fd = os.pipe()
+        remove_cloexec(ready_read_fd)
         if stdin is not None:
             stdin_read_fd, stdin_write_fd = os.pipe()
             remove_cloexec(stdin_read_fd)
@@ -119,16 +121,22 @@ def fork(self):
             # Some macOS machines need the shell to have argv[0] prefixed by
             # hyphen, see https://github.com/kovidgoyal/kitty/issues/247
             argv[0] = ('-' + exe.split('/')[-1])
-        pid = fast_data_types.spawn(exe, self.cwd, tuple(argv), env, master, slave, stdin_read_fd, stdin_write_fd)
+        pid = fast_data_types.spawn(exe, self.cwd, tuple(argv), env, master, slave, stdin_read_fd, stdin_write_fd, ready_read_fd, ready_write_fd)
         os.close(slave)
         self.pid = pid
         self.child_fd = master
         if stdin is not None:
             os.close(stdin_read_fd)
             fast_data_types.thread_write(stdin_write_fd, stdin)
+        os.close(ready_read_fd)
+        self.terminal_ready_fd = ready_write_fd
         fcntl.fcntl(self.child_fd, fcntl.F_SETFL, fcntl.fcntl(self.child_fd, fcntl.F_GETFL) | os.O_NONBLOCK)
         return pid
 
+    def mark_terminal_ready(self):
+        os.close(self.terminal_ready_fd)
+        self.terminal_ready_fd = -1
+
     @property
     def cmdline(self):
         try:

kitty/window.py

@@ -16,13 +16,12 @@
 )
 from .fast_data_types import (
     BLIT_PROGRAM, CELL_BG_PROGRAM, CELL_FG_PROGRAM, CELL_PROGRAM,
-    CELL_SPECIAL_PROGRAM, CSI, DCS, DECORATION, DIM,
-    GRAPHICS_PREMULT_PROGRAM, GRAPHICS_PROGRAM, OSC, REVERSE, SCROLL_FULL,
-    SCROLL_LINE, SCROLL_PAGE, STRIKETHROUGH, Screen, add_window,
-    cell_size_for_window, compile_program, get_clipboard_string,
-    glfw_post_empty_event, init_cell_program, set_clipboard_string,
-    set_titlebar_color, set_window_render_data, update_window_title,
-    update_window_visibility, viewport_for_window
+    CELL_SPECIAL_PROGRAM, CSI, DCS, DECORATION, DIM, GRAPHICS_PREMULT_PROGRAM,
+    GRAPHICS_PROGRAM, OSC, REVERSE, SCROLL_FULL, SCROLL_LINE, SCROLL_PAGE,
+    STRIKETHROUGH, Screen, add_window, cell_size_for_window, compile_program,
+    get_clipboard_string, glfw_post_empty_event, init_cell_program,
+    set_clipboard_string, set_titlebar_color, set_window_render_data,
+    update_window_title, update_window_visibility, viewport_for_window
 )
 from .keys import keyboard_mode_name
 from .rgb import to_color
@@ -104,6 +103,7 @@ class Window:
     def __init__(self, tab, child, opts, args, override_title=None):
         self.action_on_close = None
         self.layout_data = None
+        self.pty_resized_once = False
         self.needs_attention = False
         self.override_title = override_title
         self.overlay_window_id = None
@@ -200,6 +200,9 @@ def set_geometry(self, window_idx, new_geometry):
             sg = self.update_position(new_geometry)
             self.needs_layout = False
             boss.child_monitor.resize_pty(self.id, *current_pty_size)
+            if not self.pty_resized_once:
+                self.pty_resized_once = True
+                self.child.mark_terminal_ready()
         else:
             sg = self.update_position(new_geometry)
         self.geometry = g = new_geometry