tui: defer termcodes using a timer

With this implementation there is no "jank" during startup.

Using the main_loop in any fashion is janky. Using only the TUI loop
emits the termcodes too soon, or requires bad hacks like counting
tui_flush invocations (9 seems to work).

ref #7664
ref #7649
ref #7664
ref 27f9b1c

src/nvim/main.c

@@ -563,9 +563,6 @@ int main(int argc, char **argv)
     (void)eval_has_provider("clipboard");
   }
 
-  if (!headless_mode) {
-    ui_builtin_after_startup();
-  }
   TIME_MSG("before starting main loop");
   ILOG("starting main loop");
 

src/nvim/tui/tui.c

@@ -70,6 +70,7 @@ typedef struct {
   UIBridgeData *bridge;
   Loop *loop;
   bool stop;
+  uv_timer_t after_startup_timer;
   unibi_var_t params[9];
   char buf[OUTBUF_SIZE];
   size_t bufpos;
@@ -126,7 +127,6 @@ UI *tui_start(void)
 {
   UI *ui = xcalloc(1, sizeof(UI));
   ui->stop = tui_stop;
-  ui->after_startup = tui_after_startup;
   ui->rgb = p_tgc;
   ui->resize = tui_resize;
   ui->clear = tui_clear;
@@ -170,18 +170,6 @@ static size_t unibi_pre_fmt_str(TUIData *data, unsigned int unibi_index,
   return unibi_run(str, data->params, buf, len);
 }
 
-/// Emits some termcodes after Nvim startup, which were observed to slowdown
-/// rendering during startup in tmux 2.3 (+focus-events). #7649
-static void terminfo_after_startup_event(void **argv)
-{
-  UI *ui = argv[0];
-  TUIData *data = ui->data;
-  // Enable bracketed paste
-  unibi_out_ext(ui, data->unibi_ext.enable_bracketed_paste);
-  // Enable focus reporting
-  unibi_out_ext(ui, data->unibi_ext.enable_focus_reporting);
-}
-
 static void termname_set_event(void **argv)
 {
   char *termname = argv[0];
@@ -261,6 +249,9 @@ static void terminfo_start(UI *ui)
   unibi_out(ui, unibi_enter_ca_mode);
   unibi_out(ui, unibi_keypad_xmit);
   unibi_out(ui, unibi_clear_screen);
+  // Enable bracketed paste
+  unibi_out_ext(ui, data->unibi_ext.enable_bracketed_paste);
+
   uv_loop_init(&data->write_loop);
   if (data->out_isatty) {
     uv_tty_init(&data->write_loop, &data->output_handle.tty, data->out_fd, 0);
@@ -275,13 +266,6 @@ static void terminfo_start(UI *ui)
   }
 }
 
-static void tui_after_startup(UI *ui)
-{
-  TUIData *data = ui->data;
-  loop_schedule(data->loop,
-                event_create(terminfo_after_startup_event, 1, ui));
-}
-
 static void terminfo_stop(UI *ui)
 {
   TUIData *data = ui->data;
@@ -307,6 +291,18 @@ static void terminfo_stop(UI *ui)
   unibi_destroy(data->ut);
 }
 
+static void after_startup_timer_cb(uv_timer_t *handle)
+  FUNC_ATTR_NONNULL_ALL
+{
+  UI *ui = handle->data;
+  TUIData *data = ui->data;
+  uv_timer_stop(&data->after_startup_timer);
+
+  // Emit this after Nvim startup, not during.  This works around a tmux
+  // 2.3 bug(?) which caused slow drawing during startup.  #7649
+  unibi_out_ext(ui, data->unibi_ext.enable_focus_reporting);
+}
+
 static void tui_terminal_start(UI *ui)
 {
   TUIData *data = ui->data;
@@ -316,6 +312,8 @@ static void tui_terminal_start(UI *ui)
   update_size(ui);
   signal_watcher_start(&data->winch_handle, sigwinch_cb, SIGWINCH);
   term_input_start(&data->input);
+
+  uv_timer_start(&data->after_startup_timer, after_startup_timer_cb, 500, 0);
 }
 
 static void tui_terminal_stop(UI *ui)
@@ -349,6 +347,8 @@ static void tui_main(UIBridgeData *bridge, UI *ui)
 #ifdef UNIX
   signal_watcher_start(&data->cont_handle, sigcont_cb, SIGCONT);
 #endif
+  uv_timer_init(&data->loop->uv, &data->after_startup_timer);
+  data->after_startup_timer.data = ui;
 
 #if TERMKEY_VERSION_MAJOR > 0 || TERMKEY_VERSION_MINOR > 18
   data->input.tk_ti_hook_fn = tui_tk_ti_getstr;
@@ -367,6 +367,7 @@ static void tui_main(UIBridgeData *bridge, UI *ui)
     loop_poll_events(&tui_loop, -1);  // tui_loop.events is never processed
   }
 
+  uv_close((uv_handle_t *)&data->after_startup_timer, NULL);
   ui_bridge_stopped(bridge);
   term_input_destroy(&data->input);
   signal_watcher_stop(&data->cont_handle);

src/nvim/ui.c

@@ -138,14 +138,6 @@ void ui_builtin_start(void)
 #endif
 }
 
-/// Immediately after VimEnter event.
-void ui_builtin_after_startup(void)
-{
-#ifdef FEAT_TUI
-  UI_CALL(after_startup);
-#endif
-}
-
 void ui_builtin_stop(void)
 {
   UI_CALL(stop);

src/nvim/ui.h

@@ -36,7 +36,6 @@ struct ui_t {
 #endif
   void (*event)(UI *ui, char *name, Array args, bool *args_consumed);
   void (*stop)(UI *ui);
-  void (*after_startup)(UI *ui);
 };
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS

src/nvim/ui_bridge.c

@@ -42,7 +42,6 @@ UI *ui_bridge_attach(UI *ui, ui_main_fn ui_main, event_scheduler scheduler)
   rv->ui = ui;
   rv->bridge.rgb = ui->rgb;
   rv->bridge.stop = ui_bridge_stop;
-  rv->bridge.after_startup = ui_bridge_after_startup;
   rv->bridge.resize = ui_bridge_resize;
   rv->bridge.clear = ui_bridge_clear;
   rv->bridge.eol_clear = ui_bridge_eol_clear;
@@ -107,16 +106,6 @@ static void ui_thread_run(void *data)
   bridge->ui_main(bridge, bridge->ui);
 }
 
-static void ui_bridge_after_startup(UI *b)
-{
-  UI_BRIDGE_CALL(b, after_startup, 1, b);
-}
-static void ui_bridge_after_startup_event(void **argv)
-{
-  UI *ui = UI(argv[0]);
-  ui->after_startup(ui);
-}
-
 static void ui_bridge_stop(UI *b)
 {
   UIBridgeData *bridge = (UIBridgeData *)b;