add wait-for-mapped option

config.c

@@ -916,6 +916,9 @@ parse_section_main(struct context *ctx)
     else if (streq(key, "login-shell"))
         return value_to_bool(ctx, &conf->login_shell);
 
+    else if (streq(key, "wait-for-mapped"))
+        return value_to_bool(ctx, &conf->wait_for_mapped);
+
     else if (streq(key, "title"))
         return value_to_str(ctx, &conf->title);
 
@@ -3592,6 +3595,7 @@ config_load(struct config *conf, const char *conf_path,
         .presentation_timings = false,
         .selection_target = SELECTION_TARGET_PRIMARY,
         .hold_at_exit = false,
+        .wait_for_mapped = false,
         .desktop_notifications = {
             .command = {
                 .argv = {.args = NULL},

config.h

@@ -237,6 +237,7 @@ struct config {
     char32_t *word_delimiters;
     bool login_shell;
     bool locked_title;
+    bool wait_for_mapped;
 
     struct {
         enum conf_size_type type;

doc/foot.1.scd

@@ -86,6 +86,10 @@ the foot command line
 *-L*,*--login-shell*
 	Start a login shell, by prepending a '-' to argv[0].
 
+*--wait-for-mapped*
+	Defer spawning the client application until the window has been
+	mapped. See *wait-for-mapped* in *foot.ini*(5).
+
 *--pty*
 	Display an existing pty instead of creating one. This is useful
 	for interacting with VM consoles.

doc/foot.ini.5.scd

@@ -43,6 +43,14 @@ empty string to be set, but it must be quoted: *KEY=""*
 	Boolean. If enabled, the shell will be launched as a login shell,
 	by prepending a '-' to argv[0]. Default: _no_.
 
+*wait-for-mapped*
+	Boolean. If enabled, defer spawning the client application until
+	the window has been mapped and the first frame has been
+	displayed. The client's first *TIOCGWINSZ* will then return the
+	final window size, working around startup issues in TUI
+	applications that mishandle early *SIGWINCH* signals.
+	Default: _no_.
+
 *term*
 	Value to set the environment variable *TERM* to. Default:
 	_@default_terminfo@_

main.c

@@ -88,6 +88,7 @@ print_usage(const char *prog_name)
         "  -m,--maximized                           start in maximized mode\n"
         "  -F,--fullscreen                          start in fullscreen mode\n"
         "  -L,--login-shell                         start shell as a login shell\n"
+        "     --wait-for-mapped                     defer client spawn until window is mapped\n"
         "  --pty=PATH                               display an existing PTY instead of creating one\n"
         "  -D,--working-directory=DIR               directory to start in (CWD)\n"
         "  -w,--window-size-pixels=WIDTHxHEIGHT     initial width and height, in pixels\n"
@@ -187,6 +188,7 @@ sanitize_signals(void)
 enum {
     PTY_OPTION = CHAR_MAX + 1,
     TOPLEVEL_TAG_OPTION = CHAR_MAX + 2,
+    WAIT_FOR_MAPPED_OPTION = CHAR_MAX + 3,
 };
 
 int
@@ -218,6 +220,7 @@ main(int argc, char *const *argv)
         {"app-id",                 required_argument, NULL, 'a'},
         {"toplevel-tag",           required_argument, NULL, TOPLEVEL_TAG_OPTION},
         {"login-shell",            no_argument,       NULL, 'L'},
+        {"wait-for-mapped",        no_argument,       NULL, WAIT_FOR_MAPPED_OPTION},
         {"working-directory",      required_argument, NULL, 'D'},
         {"font",                   required_argument, NULL, 'f'},
         {"window-size-pixels",     required_argument, NULL, 'w'},
@@ -280,6 +283,10 @@ main(int argc, char *const *argv)
             tll_push_back(overrides, xstrdup("login-shell=yes"));
             break;
 
+        case WAIT_FOR_MAPPED_OPTION:
+            tll_push_back(overrides, xstrdup("wait-for-mapped=yes"));
+            break;
+
         case 'T':
             tll_push_back(overrides, xstrjoin("title=", optarg));
             break;

render.c

@@ -4317,6 +4317,9 @@ frame_callback(void *data, struct wl_callback *wl_callback, uint32_t callback_da
     wl_callback_destroy(wl_callback);
     term->window->frame_callback = NULL;
 
+    /* --wait-for-mapped: first frame done, on-screen size is final */
+    term_spawn_pending(term);
+
     bool grid = term->render.pending.grid;
     bool csd = term->render.pending.csd;
     bool search = term->is_searching && term->render.pending.search;

terminal.c

@@ -294,6 +294,7 @@ fdm_ptmx(struct fdm *fdm, int fd, int events, void *data)
         }
 
         xassert(term->interactive_resizing.grid == NULL);
+
         vt_from_slave(term, buf, count);
     }
 
@@ -1435,16 +1436,38 @@ term_init(const struct config *conf, struct fdm *fdm, struct reaper *reaper,
     add_utmp_record(conf, reaper, ptmx);
 
     if (!pty_path) {
-        /* Start the slave/client */
-        if ((term->slave = slave_spawn(
-                 term->ptmx, argc, term->cwd, argv, envp, &conf->env_vars,
-                 conf->term, conf->shell, conf->login_shell,
-                 &conf->notifications)) == -1)
-        {
-            goto err;
-        }
+        if (conf->wait_for_mapped) {
+            /* Deep-copy: server.c frees argv/envp after term_init() returns */
+            char **argv_copy = xcalloc(argc + 1, sizeof(char *));
+            for (int i = 0; i < argc; i++)
+                argv_copy[i] = xstrdup(argv[i]);
 
-        reaper_add(term->reaper, term->slave, &fdm_client_terminated, term);
+            char **envp_copy = NULL;
+            if (envp != NULL) {
+                size_t n = 0;
+                while (envp[n] != NULL) n++;
+                envp_copy = xcalloc(n + 1, sizeof(char *));
+                for (size_t i = 0; i < n; i++)
+                    envp_copy[i] = xstrdup(envp[i]);
+            }
+
+            term->pending_spawn.armed = true;
+            term->pending_spawn.argc  = argc;
+            term->pending_spawn.argv  = argv_copy;
+            term->pending_spawn.envp  = envp_copy;
+            term->pending_spawn.cwd   = cwd != NULL ? xstrdup(cwd) : NULL;
+        } else {
+            /* Start the slave/client */
+            if ((term->slave = slave_spawn(
+                     term->ptmx, argc, term->cwd, argv, envp, &conf->env_vars,
+                     conf->term, conf->shell, conf->login_shell,
+                     &conf->notifications)) == -1)
+            {
+                goto err;
+            }
+
+            reaper_add(term->reaper, term->slave, &fdm_client_terminated, term);
+        }
     }
 
     /* Guess scale; we're not mapped yet, so we don't know on which
@@ -1517,6 +1540,54 @@ term_window_configured(struct terminal *term)
     }
 }
 
+/* free deferred spawn args in --wait-for-mapped */
+static void
+pending_spawn_free(struct terminal *term)
+{
+    for (int i = 0; i < term->pending_spawn.argc; i++)
+        free(term->pending_spawn.argv[i]);
+    free(term->pending_spawn.argv);
+    if (term->pending_spawn.envp != NULL) {
+        for (char **e = term->pending_spawn.envp; *e != NULL; e++)
+            free(*e);
+        free(term->pending_spawn.envp);
+    }
+    free(term->pending_spawn.cwd);
+
+    term->pending_spawn.argc = 0;
+    term->pending_spawn.argv = NULL;
+    term->pending_spawn.envp = NULL;
+    term->pending_spawn.cwd = NULL;
+}
+
+/* --wait-for-mapped: spawn the deferred client. Idempotent. */
+void
+term_spawn_pending(struct terminal *term)
+{
+    if (!term->pending_spawn.armed || term->shutdown.in_progress)
+        return;
+
+    term->pending_spawn.armed = false;
+
+    term->slave = slave_spawn(
+        term->ptmx, term->pending_spawn.argc, term->pending_spawn.cwd,
+        term->pending_spawn.argv,
+        (const char *const *)term->pending_spawn.envp,
+        &term->conf->env_vars, term->conf->term, term->conf->shell,
+        term->conf->login_shell, &term->conf->notifications);
+
+    pending_spawn_free(term);
+
+    if (term->slave == -1) {
+        LOG_ERR("deferred slave_spawn() failed");
+        if (!term->conf->hold_at_exit)
+            term_shutdown(term);
+        return;
+    }
+
+    reaper_add(term->reaper, term->slave, &fdm_client_terminated, term);
+}
+
 /*
  * Shutdown logic
  *
@@ -1825,6 +1896,9 @@ term_destroy(struct terminal *term)
 
     del_utmp_record(term->conf, term->reaper, term->ptmx);
 
+    /* Frees deferred spawn args if --wait-for-mapped never spawned; else no-op */
+    pending_spawn_free(term);
+
     fdm_del(term->fdm, term->selection.auto_scroll.fd);
     fdm_del(term->fdm, term->render.app_sync_updates.timer_fd);
     fdm_del(term->fdm, term->render.app_id.timer_fd);

terminal.h

@@ -419,6 +419,15 @@ struct terminal {
     pid_t slave;
     int ptmx;
 
+    /* --wait-for-mapped: deferred slave_spawn() args (#453) */
+    struct {
+        bool armed;
+        int argc;
+        char **argv;
+        char **envp;
+        char *cwd;
+    } pending_spawn;
+
     struct vt vt;
     struct grid *grid;
     struct grid normal;
@@ -868,6 +877,7 @@ int term_pt_or_px_as_pixels(
 
 
 void term_window_configured(struct terminal *term);
+void term_spawn_pending(struct terminal *term);
 
 void term_damage_rows(struct terminal *term, int start, int end);
 void term_damage_rows_in_view(struct terminal *term, int start, int end);

tests/test-config.c

@@ -488,6 +488,7 @@ test_section_main(void)
     test_c32string(&ctx, &parse_section_main, "word-delimiters", &conf.word_delimiters);
 
     test_boolean(&ctx, &parse_section_main, "login-shell", &conf.login_shell);
+    test_boolean(&ctx, &parse_section_main, "wait-for-mapped", &conf.wait_for_mapped);
     test_boolean(&ctx, &parse_section_main, "box-drawings-uses-font-glyphs", &conf.box_drawings_uses_font_glyphs);
     test_boolean(&ctx, &parse_section_main, "locked-title", &conf.locked_title);
     test_boolean(&ctx, &parse_section_main, "dpi-aware", &conf.dpi_aware);