Merge pull request #18375 from bfredl/tui_rework

feat(ui): refactor TUI from thread to separate process
2025-09-06 03:18:16 +00:00 · 2022-12-31 14:23:24 +01:00
parent 99cf111289 9fdcbbb406
commit cce736218f
39 changed files with 868 additions and 806 deletions
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -143,9 +143,9 @@ set(NVIM_VERSION_PATCH 0)
 set(NVIM_VERSION_PRERELEASE "-dev") # for package maintainers

 # API level
-set(NVIM_API_LEVEL 10)         # Bump this after any API change.
+set(NVIM_API_LEVEL 11)         # Bump this after any API change.
 set(NVIM_API_LEVEL_COMPAT 0)  # Adjust this after a _breaking_ API change.
-set(NVIM_API_PRERELEASE false)
+set(NVIM_API_PRERELEASE true)

 set(NVIM_VERSION_BUILD_TYPE "${CMAKE_BUILD_TYPE}")
 # NVIM_VERSION_CFLAGS set further below.
@@ -498,34 +498,30 @@ if(MSGPACK_HAS_FLOAT32)
  add_definitions(-DNVIM_MSGPACK_HAS_FLOAT32)
 endif()

-option(FEAT_TUI "Enable the Terminal UI" ON)
+find_package(UNIBILIUM 2.0 REQUIRED)
+include_directories(SYSTEM ${UNIBILIUM_INCLUDE_DIRS})

-if(FEAT_TUI)
-  find_package(UNIBILIUM 2.0 REQUIRED)
-  include_directories(SYSTEM ${UNIBILIUM_INCLUDE_DIRS})
+list(APPEND CMAKE_REQUIRED_INCLUDES "${UNIBILIUM_INCLUDE_DIRS}")
+list(APPEND CMAKE_REQUIRED_LIBRARIES "${UNIBILIUM_LIBRARIES}")
+check_c_source_compiles("
+#include <unibilium.h>

-  list(APPEND CMAKE_REQUIRED_INCLUDES "${UNIBILIUM_INCLUDE_DIRS}")
-  list(APPEND CMAKE_REQUIRED_LIBRARIES "${UNIBILIUM_LIBRARIES}")
-  check_c_source_compiles("
-  #include <unibilium.h>
-
-  int
-  main(void)
-  {
-    unibi_str_from_var(unibi_var_from_str(\"\"));
-    return unibi_num_from_var(unibi_var_from_num(0));
-  }
-  " UNIBI_HAS_VAR_FROM)
-  list(REMOVE_ITEM CMAKE_REQUIRED_INCLUDES "${UNIBILIUM_INCLUDE_DIRS}")
-  list(REMOVE_ITEM CMAKE_REQUIRED_LIBRARIES "${UNIBILIUM_LIBRARIES}")
-  if(UNIBI_HAS_VAR_FROM)
-    add_definitions(-DNVIM_UNIBI_HAS_VAR_FROM)
-  endif()
-
-  find_package(LibTermkey 0.22 REQUIRED)
-  include_directories(SYSTEM ${LIBTERMKEY_INCLUDE_DIRS})
+int
+main(void)
+{
+  unibi_str_from_var(unibi_var_from_str(\"\"));
+  return unibi_num_from_var(unibi_var_from_num(0));
+}
+" UNIBI_HAS_VAR_FROM)
+list(REMOVE_ITEM CMAKE_REQUIRED_INCLUDES "${UNIBILIUM_INCLUDE_DIRS}")
+list(REMOVE_ITEM CMAKE_REQUIRED_LIBRARIES "${UNIBILIUM_LIBRARIES}")
+if(UNIBI_HAS_VAR_FROM)
+  add_definitions(-DNVIM_UNIBI_HAS_VAR_FROM)
 endif()

+find_package(LibTermkey 0.22 REQUIRED)
+include_directories(SYSTEM ${LIBTERMKEY_INCLUDE_DIRS})
+
 find_package(LIBVTERM 0.3 REQUIRED)
 include_directories(SYSTEM ${LIBVTERM_INCLUDE_DIRS})

--- a/cmake.config/config.h.in
+++ b/cmake.config/config.h.in
@@ -56,8 +56,6 @@
 #endif
 #cmakedefine HAVE_FORKPTY

-#cmakedefine FEAT_TUI
-
 #ifndef UNIT_TESTING
 #cmakedefine LOG_LIST_ACTIONS
 #endif
--- a/runtime/doc/api.txt
+++ b/runtime/doc/api.txt
@@ -3471,6 +3471,12 @@ nvim_ui_pum_set_height({height})                    *nvim_ui_pum_set_height()*
    Parameters: ~
      • {height}  Popupmenu height, must be greater than zero.

+nvim_ui_set_focus({gained})                              *nvim_ui_set_focus()*
+    Tells the nvim server if focus was gained or lost by the GUI.
+
+    Attributes: ~
+        |RPC| only
+
 nvim_ui_set_option({name}, {value})                     *nvim_ui_set_option()*
    TODO: Documentation

--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -101,6 +101,11 @@ The following new APIs or features were added.

  See https://github.com/neovim/neovim/pull/14537.

+• |--remote-ui| option was added to connect to a remote instance and display
+  in it in a |TUI| in the local terminal. This can be used run a headless nvim
+  instance in the background and display its UI on demand, which previously
+  only was possible usiing a external UI implementation.
+
 ==============================================================================
 CHANGED FEATURES                                                 *news-changes*

@@ -109,6 +114,14 @@ The following changes to existing APIs or features add new behavior.
 • 'exrc' now supports `.nvim.lua` file.
 • 'exrc' is no longer marked deprecated.

+• The |TUI| is changed to run in a separate process (previously, a separate
+  thread was used). This is not supposed to be a visible change to the user,
+  but might be the cause of subtle changes of behavior and bugs.
+
+  Previously, the TUI could be disabled as a build time feature (+tui/-tui),
+  resulting in a nvim binary which only could be run headless or embedded
+  in an external process. As of this version, TUI is always avalibale.
+
 ==============================================================================
 REMOVED FEATURES                                                 *news-removed*

--- a/runtime/doc/remote.txt
+++ b/runtime/doc/remote.txt
@@ -52,6 +52,10 @@ The following command line arguments are available:
 								*--remote-expr*
   --remote-expr {expr}		Evaluate {expr} in server and print the result
 				on stdout.
+								*--remote-ui*
+   --remote-ui			Display the UI of the server in the terminal.
+				Fully interactive: keyboard and mouse input
+				are forwarded to the server.
 								*--server*
   --server {addr}		Connect to the named pipe or socket at the
 				given address for executing remote commands.
--- a/runtime/doc/ui.txt
+++ b/runtime/doc/ui.txt
@@ -56,6 +56,8 @@ with these (optional) keys:
 - `stdin_fd`		Read buffer from `fd` as if it was a stdin pipe
 			This option can only used by |--embed| ui,
 			see |ui-startup-stdin|.
+	`stdin_tty`		Tells if `stdin` is a `tty` or not.
+	`stdout_tty`		Tells if `stdout` is a `tty` or not.

 Specifying an unknown option is an error; UIs can check the |api-metadata|
 `ui_options` key for supported options.
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -39,7 +39,6 @@ set(GENERATED_FUNCS_METADATA ${GENERATED_DIR}/api/private/funcs_metadata.generat
 set(GENERATED_UI_EVENTS ${GENERATED_DIR}/ui_events.generated.h)
 set(GENERATED_UI_EVENTS_CALL ${GENERATED_DIR}/ui_events_call.generated.h)
 set(GENERATED_UI_EVENTS_REMOTE ${GENERATED_DIR}/ui_events_remote.generated.h)
-set(GENERATED_UI_EVENTS_BRIDGE ${GENERATED_DIR}/ui_events_bridge.generated.h)
 set(GENERATED_UI_EVENTS_CLIENT ${GENERATED_DIR}/ui_events_client.generated.h)
 set(GENERATED_UI_EVENTS_METADATA ${GENERATED_DIR}/api/private/ui_events_metadata.generated.h)
 set(GENERATED_EX_CMDS_ENUM ${GENERATED_INCLUDES_DIR}/ex_cmds_enum.generated.h)
@@ -111,9 +110,6 @@ foreach(subdir
        viml
        viml/parser
       )
-  if(${subdir} MATCHES "tui" AND NOT FEAT_TUI)
-    continue()
-  endif()

  file(MAKE_DIRECTORY ${GENERATED_DIR}/${subdir})
  file(MAKE_DIRECTORY ${GENERATED_INCLUDES_DIR}/${subdir})
@@ -220,7 +216,6 @@ foreach(sfile ${NVIM_SOURCES}
              ${GENERATED_API_DISPATCH}
              "${GENERATED_UI_EVENTS_CALL}"
              "${GENERATED_UI_EVENTS_REMOTE}"
-              "${GENERATED_UI_EVENTS_BRIDGE}"
              "${GENERATED_KEYSETS}"
              "${GENERATED_UI_EVENTS_CLIENT}"
              )
@@ -318,7 +313,6 @@ add_custom_command(
  OUTPUT ${GENERATED_UI_EVENTS}
         ${GENERATED_UI_EVENTS_CALL}
         ${GENERATED_UI_EVENTS_REMOTE}
-         ${GENERATED_UI_EVENTS_BRIDGE}
         ${GENERATED_UI_EVENTS_METADATA}
         ${GENERATED_UI_EVENTS_CLIENT}
  COMMAND ${LUA_PRG} ${API_UI_EVENTS_GENERATOR} ${CMAKE_CURRENT_LIST_DIR}
@@ -326,7 +320,6 @@ add_custom_command(
                     ${GENERATED_UI_EVENTS}
                     ${GENERATED_UI_EVENTS_CALL}
                     ${GENERATED_UI_EVENTS_REMOTE}
-                     ${GENERATED_UI_EVENTS_BRIDGE}
                     ${GENERATED_UI_EVENTS_METADATA}
                     ${GENERATED_UI_EVENTS_CLIENT}
  DEPENDS
--- a/src/nvim/api/keysets.lua
+++ b/src/nvim/api/keysets.lua
@@ -126,6 +126,8 @@ return {
    "global_link";
    "fallback";
    "blend";
+    "fg_indexed";
+    "bg_indexed";
  };
  highlight_cterm = {
    "bold";
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -14,9 +14,6 @@
 #include "nvim/api/private/helpers.h"
 #include "nvim/api/ui.h"
 #include "nvim/channel.h"
-#include "nvim/event/loop.h"
-#include "nvim/event/wstream.h"
-#include "nvim/globals.h"
 #include "nvim/grid.h"
 #include "nvim/highlight.h"
 #include "nvim/main.h"
@@ -30,6 +27,7 @@
 #include "nvim/types.h"
 #include "nvim/ui.h"
 #include "nvim/vim.h"
+#include "nvim/window.h"

 typedef struct {
  uint64_t channel_id;
@@ -285,6 +283,19 @@ void ui_attach(uint64_t channel_id, Integer width, Integer height, Boolean enabl
  api_free_dictionary(opts);
 }

+/// Tells the nvim server if focus was gained or lost by the GUI
+void nvim_ui_set_focus(uint64_t channel_id, Boolean gained, Error *error)
+  FUNC_API_SINCE(11) FUNC_API_REMOTE_ONLY
+{
+  if (!pmap_has(uint64_t)(&connected_uis, channel_id)) {
+    api_set_error(error, kErrorTypeException,
+                  "UI not attached to channel: %" PRId64, channel_id);
+    return;
+  }
+
+  do_autocmd_focusgained((bool)gained);
+}
+
 /// Deactivates UI events on the channel.
 ///
 /// Removes the client from the list of UIs. |nvim_list_uis()|
@@ -404,6 +415,24 @@ static void ui_set_option(UI *ui, bool init, String name, Object value, Error *e
    return;
  }

+  if (strequal(name.data, "stdin_tty")) {
+    if (value.type != kObjectTypeBoolean) {
+      api_set_error(error, kErrorTypeValidation, "stdin_tty must be a Boolean");
+      return;
+    }
+    stdin_isatty = value.data.boolean;
+    return;
+  }
+
+  if (strequal(name.data, "stdout_tty")) {
+    if (value.type != kObjectTypeBoolean) {
+      api_set_error(error, kErrorTypeValidation, "stdout_tty must be a Boolean");
+      return;
+    }
+    stdout_isatty = value.data.boolean;
+    return;
+  }
+
  // LEGACY: Deprecated option, use `ext_cmdline` instead.
  bool is_popupmenu = strequal(name.data, "popupmenu_external");

--- a/src/nvim/api/ui_events.in.h
+++ b/src/nvim/api/ui_events.in.h
@@ -31,7 +31,7 @@ void visual_bell(void)
 void flush(void)
  FUNC_API_SINCE(3) FUNC_API_REMOTE_IMPL;
 void suspend(void)
-  FUNC_API_SINCE(3) FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(3);
 void set_title(String title)
  FUNC_API_SINCE(3);
 void set_icon(String icon)
@@ -39,7 +39,7 @@ void set_icon(String icon)
 void screenshot(String path)
  FUNC_API_SINCE(7) FUNC_API_REMOTE_IMPL;
 void option_set(String name, Object value)
-  FUNC_API_SINCE(4) FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(4);
 // Stop event is not exported as such, represented by EOF in the msgpack stream.
 void stop(void)
  FUNC_API_NOEXPORT;
@@ -73,9 +73,9 @@ void default_colors_set(Integer rgb_fg, Integer rgb_bg, Integer rgb_sp, Integer
                        Integer cterm_bg)
  FUNC_API_SINCE(4) FUNC_API_REMOTE_IMPL;
 void hl_attr_define(Integer id, HlAttrs rgb_attrs, HlAttrs cterm_attrs, Array info)
-  FUNC_API_SINCE(5) FUNC_API_REMOTE_IMPL FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(5) FUNC_API_REMOTE_IMPL;
 void hl_group_set(String name, Integer id)
-  FUNC_API_SINCE(6) FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(6);
 void grid_resize(Integer grid, Integer width, Integer height)
  FUNC_API_SINCE(5) FUNC_API_REMOTE_IMPL FUNC_API_COMPOSITOR_IMPL FUNC_API_CLIENT_IMPL;
 void grid_clear(Integer grid)
@@ -112,8 +112,9 @@ void win_hide(Integer grid)
  FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;
 void win_close(Integer grid)
  FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;
+
 void msg_set_pos(Integer grid, Integer row, Boolean scrolled, String sep_char)
-  FUNC_API_SINCE(6) FUNC_API_BRIDGE_IMPL FUNC_API_COMPOSITOR_IMPL;
+  FUNC_API_SINCE(6) FUNC_API_COMPOSITOR_IMPL;

 void win_viewport(Integer grid, Window win, Integer topline, Integer botline, Integer curline,
                  Integer curcol, Integer line_count)
@@ -149,11 +150,11 @@ void cmdline_block_hide(void)
  FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;

 void wildmenu_show(Array items)
-  FUNC_API_SINCE(3) FUNC_API_REMOTE_IMPL FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(3) FUNC_API_REMOTE_IMPL;
 void wildmenu_select(Integer selected)
-  FUNC_API_SINCE(3) FUNC_API_REMOTE_IMPL FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(3) FUNC_API_REMOTE_IMPL;
 void wildmenu_hide(void)
-  FUNC_API_SINCE(3) FUNC_API_REMOTE_IMPL FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(3) FUNC_API_REMOTE_IMPL;

 void msg_show(String kind, Array content, Boolean replace_last)
  FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;
--- a/src/nvim/autocmd.c
+++ b/src/nvim/autocmd.c
@@ -2732,22 +2732,7 @@ void do_autocmd_uienter(uint64_t chanid, bool attached)

 // FocusGained

-static void focusgained_event(void **argv)
-{
-  bool *gainedp = argv[0];
-  do_autocmd_focusgained(*gainedp);
-  xfree(gainedp);
-}
-
-void autocmd_schedule_focusgained(bool gained)
-{
-  bool *gainedp = xmalloc(sizeof(*gainedp));
-  *gainedp = gained;
-  loop_schedule_deferred(&main_loop,
-                         event_create(focusgained_event, 1, gainedp));
-}
-
-static void do_autocmd_focusgained(bool gained)
+void do_autocmd_focusgained(bool gained)
 {
  static bool recursive = false;
  static Timestamp last_time = (time_t)0;
--- a/src/nvim/event/libuv_process.c
+++ b/src/nvim/event/libuv_process.c
@@ -40,11 +40,19 @@ int libuv_process_spawn(LibuvProcess *uvproc)
 #endif
  uvproc->uvopts.exit_cb = exit_cb;
  uvproc->uvopts.cwd = proc->cwd;
+
  uvproc->uvopts.stdio = uvproc->uvstdio;
  uvproc->uvopts.stdio_count = 3;
  uvproc->uvstdio[0].flags = UV_IGNORE;
  uvproc->uvstdio[1].flags = UV_IGNORE;
  uvproc->uvstdio[2].flags = UV_IGNORE;
+
+  if (ui_client_forward_stdin) {
+    assert(UI_CLIENT_STDIN_FD == 3);
+    uvproc->uvopts.stdio_count = 4;
+    uvproc->uvstdio[3].data.fd = 0;
+    uvproc->uvstdio[3].flags = UV_INHERIT_FD;
+  }
  uvproc->uv.data = proc;

  if (proc->env) {
--- a/src/nvim/event/libuv_process.h
+++ b/src/nvim/event/libuv_process.h
@@ -10,7 +10,7 @@ typedef struct libuv_process {
  Process process;
  uv_process_t uv;
  uv_process_options_t uvopts;
-  uv_stdio_container_t uvstdio[3];
+  uv_stdio_container_t uvstdio[4];
 } LibuvProcess;

 static inline LibuvProcess libuv_process_init(Loop *loop, void *data)
--- a/src/nvim/event/process.c
+++ b/src/nvim/event/process.c
@@ -14,6 +14,7 @@
 #include "nvim/globals.h"
 #include "nvim/log.h"
 #include "nvim/macros.h"
+#include "nvim/main.h"
 #include "nvim/os/process.h"
 #include "nvim/os/pty_process.h"
 #include "nvim/os/shell.h"
@@ -35,6 +36,9 @@ void __gcov_flush(void);

 static bool process_is_tearing_down = false;

+// Delay exit until handles are closed, to avoid deadlocks
+static int exit_need_delay = 0;
+
 /// @returns zero on success, or negative error code
 int process_spawn(Process *proc, bool in, bool out, bool err)
  FUNC_ATTR_NONNULL_ALL
@@ -398,12 +402,41 @@ static void process_close_handles(void **argv)
  exit_need_delay--;
 }

+static void exit_delay_cb(uv_timer_t *handle)
+{
+  uv_timer_stop(&main_loop.exit_delay_timer);
+  multiqueue_put(main_loop.fast_events, exit_event, 1, main_loop.exit_delay_timer.data);
+}
+
+static void exit_event(void **argv)
+{
+  int status = (int)(intptr_t)argv[0];
+  if (exit_need_delay) {
+    main_loop.exit_delay_timer.data = argv[0];
+    uv_timer_start(&main_loop.exit_delay_timer, exit_delay_cb, 0, 0);
+    return;
+  }
+
+  if (!exiting) {
+    os_exit(status);
+  }
+}
+
+void exit_from_channel(int status)
+{
+  multiqueue_put(main_loop.fast_events, exit_event, 1, status);
+}
+
 static void on_process_exit(Process *proc)
 {
  Loop *loop = proc->loop;
  ILOG("exited: pid=%d status=%d stoptime=%" PRIu64, proc->pid, proc->status,
       proc->stopped_time);

+  if (ui_client_channel_id) {
+    exit_from_channel(proc->status);
+  }
+
  // Process has terminated, but there could still be data to be read from the
  // OS. We are still in the libuv loop, so we cannot call code that polls for
  // more data directly. Instead delay the reading after the libuv loop by
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -1931,9 +1931,11 @@ static char *do_one_cmd(char **cmdlinep, int flags, cstack_T *cstack, LineGetter

  profile_cmd(&ea, cstack, fgetline, cookie);

-  // May go to debug mode.  If this happens and the ">quit" debug command is
-  // used, throw an interrupt exception and skip the next command.
-  dbg_check_breakpoint(&ea);
+  if (!exiting) {
+    // May go to debug mode.  If this happens and the ">quit" debug command is
+    // used, throw an interrupt exception and skip the next command.
+    dbg_check_breakpoint(&ea);
+  }
  if (!ea.skip && got_int) {
    ea.skip = true;
    (void)do_intthrow(cstack);
--- a/src/nvim/generators/gen_api_dispatch.lua
+++ b/src/nvim/generators/gen_api_dispatch.lua
@@ -60,6 +60,12 @@ for i = 6, #arg do
    if public and not fn.noexport then
      functions[#functions + 1] = tmp[j]
      function_names[fn.name] = true
+      if #fn.parameters >= 2 and fn.parameters[2][1] == 'Array' and fn.parameters[2][2] == 'uidata' then
+        -- function recieves the "args" as a parameter
+        fn.receives_array_args = true
+        -- remove the args parameter
+        table.remove(fn.parameters, 2)
+      end
      if #fn.parameters ~= 0 and fn.parameters[1][2] == 'channel_id' then
        -- this function should receive the channel id
        fn.receives_channel_id = true
@@ -159,7 +165,7 @@ local exported_attributes = {'name', 'return_type', 'method',
                             'since', 'deprecated_since'}
 local exported_functions = {}
 for _,f in ipairs(functions) do
-  if not (startswith(f.name, "nvim__") or f.name == "nvim_error_event") then
+  if not (startswith(f.name, "nvim__") or f.name == "nvim_error_event" or f.name == "redraw") then
    local f_exported = {}
    for _,attr in ipairs(exported_attributes) do
      f_exported[attr] = f[attr]
@@ -264,11 +270,13 @@ for i = 1, #functions do
      output:write('\n  '..rt..' '..converted..';')
    end
    output:write('\n')
-    output:write('\n  if (args.size != '..#fn.parameters..') {')
-    output:write('\n    api_set_error(error, kErrorTypeException, \
-      "Wrong number of arguments: expecting '..#fn.parameters..' but got %zu", args.size);')
-    output:write('\n    goto cleanup;')
-    output:write('\n  }\n')
+    if not fn.receives_array_args then
+      output:write('\n  if (args.size != '..#fn.parameters..') {')
+      output:write('\n    api_set_error(error, kErrorTypeException, \
+        "Wrong number of arguments: expecting '..#fn.parameters..' but got %zu", args.size);')
+      output:write('\n    goto cleanup;')
+      output:write('\n  }\n')
+    end

    -- Validation/conversion for each argument
    for j = 1, #fn.parameters do
@@ -350,12 +358,28 @@ for i = 1, #functions do
    if fn.receives_channel_id then
      -- if the function receives the channel id, pass it as first argument
      if #args > 0 or fn.can_fail then
-        output:write('channel_id, '..call_args)
+        output:write('channel_id, ')
+        if fn.receives_array_args then
+          -- if the function recieves the array args, pass it the second argument
+          output:write('args, ')
+        end
+        output:write(call_args)
      else
        output:write('channel_id')
+        if fn.receives_array_args then
+          output:write(', args')
+        end
      end
    else
-      output:write(call_args)
+      if fn.receives_array_args then
+        if #args > 0 or fn.call_fail then
+          output:write('args, '..call_args)
+        else
+          output:write('args')
+        end
+      else
+        output:write(call_args)
+      end
    end

    if fn.arena_return then
--- a/src/nvim/generators/gen_api_ui_events.lua
+++ b/src/nvim/generators/gen_api_ui_events.lua
@@ -3,14 +3,13 @@ local mpack = require('mpack')
 local nvimdir = arg[1]
 package.path = nvimdir .. '/?.lua;' .. package.path

-assert(#arg == 8)
+assert(#arg == 7)
 local input = io.open(arg[2], 'rb')
 local proto_output = io.open(arg[3], 'wb')
 local call_output = io.open(arg[4], 'wb')
 local remote_output = io.open(arg[5], 'wb')
-local bridge_output = io.open(arg[6], 'wb')
-local metadata_output = io.open(arg[7], 'wb')
-local client_output = io.open(arg[8], 'wb')
+local metadata_output = io.open(arg[6], 'wb')
+local client_output = io.open(arg[7], 'wb')

 local c_grammar = require('generators.c_grammar')
 local events = c_grammar.grammar:match(input:read('*all'))
@@ -119,62 +118,6 @@ for i = 1, #events do
      remote_output:write('  push_call(ui, "'..ev.name..'", args);\n')
      remote_output:write('}\n\n')
    end
-
-    if not ev.bridge_impl and not ev.noexport then
-      local send, argv, recv, recv_argv, recv_cleanup = '', '', '', '', ''
-      local argc = 1
-      for j = 1, #ev.parameters do
-        local param = ev.parameters[j]
-        local copy = 'copy_'..param[2]
-        if param[1] == 'String' then
-          send = send..'  String copy_'..param[2]..' = copy_string('..param[2]..', NULL);\n'
-          argv = argv..', '..copy..'.data, INT2PTR('..copy..'.size)'
-          recv = (recv..'  String '..param[2]..
-                          ' = (String){.data = argv['..argc..'],'..
-                          '.size = (size_t)argv['..(argc+1)..']};\n')
-          recv_argv = recv_argv..', '..param[2]
-          recv_cleanup = recv_cleanup..'  api_free_string('..param[2]..');\n'
-          argc = argc+2
-        elseif param[1] == 'Array' then
-          send = send..'  Array '..copy..' = copy_array('..param[2]..', NULL);\n'
-          argv = argv..', '..copy..'.items, INT2PTR('..copy..'.size)'
-          recv = (recv..'  Array '..param[2]..
-                          ' = (Array){.items = argv['..argc..'],'..
-                          '.size = (size_t)argv['..(argc+1)..']};\n')
-          recv_argv = recv_argv..', '..param[2]
-          recv_cleanup = recv_cleanup..'  api_free_array('..param[2]..');\n'
-          argc = argc+2
-        elseif param[1] == 'Object' then
-          send = send..'  Object *'..copy..' = xmalloc(sizeof(Object));\n'
-          send = send..'  *'..copy..' = copy_object('..param[2]..', NULL);\n'
-          argv = argv..', '..copy
-          recv = recv..'  Object '..param[2]..' = *(Object *)argv['..argc..'];\n'
-          recv_argv = recv_argv..', '..param[2]
-          recv_cleanup = (recv_cleanup..'  api_free_object('..param[2]..');\n'..
-                          '  xfree(argv['..argc..']);\n')
-          argc = argc+1
-        elseif param[1] == 'Integer' or param[1] == 'Boolean' then
-          argv = argv..', INT2PTR('..param[2]..')'
-          recv_argv = recv_argv..', PTR2INT(argv['..argc..'])'
-          argc = argc+1
-        else
-          assert(false)
-        end
-      end
-      bridge_output:write('static void ui_bridge_'..ev.name..
-                          '_event(void **argv)\n{\n')
-      bridge_output:write('  UI *ui = UI(argv[0]);\n')
-      bridge_output:write(recv)
-      bridge_output:write('  ui->'..ev.name..'(ui'..recv_argv..');\n')
-      bridge_output:write(recv_cleanup)
-      bridge_output:write('}\n\n')
-
-      bridge_output:write('static void ui_bridge_'..ev.name)
-      write_signature(bridge_output, ev, 'UI *ui')
-      bridge_output:write('\n{\n')
-      bridge_output:write(send)
-      bridge_output:write('  UI_BRIDGE_CALL(ui, '..ev.name..', '..argc..', ui'..argv..');\n}\n\n')
-    end
  end

  if not (ev.remote_only and ev.remote_impl) then
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -328,9 +328,6 @@ EXTERN sctx_T current_sctx INIT(= { 0, 0, 0 });
 // ID of the current channel making a client API call
 EXTERN uint64_t current_channel_id INIT(= 0);

-// ID of the client channel. Used by ui client
-EXTERN uint64_t ui_client_channel_id INIT(= 0);
-
 EXTERN bool did_source_packages INIT(= false);

 // Scope information for the code that indirectly triggered the current
@@ -494,9 +491,9 @@ EXTERN bool exiting INIT(= false);
 // internal value of v:dying
 EXTERN int v_dying INIT(= 0);
 // is stdin a terminal?
-EXTERN int stdin_isatty INIT(= true);
+EXTERN bool stdin_isatty INIT(= true);
 // is stdout a terminal?
-EXTERN int stdout_isatty INIT(= true);
+EXTERN bool stdout_isatty INIT(= true);
 /// filedesc set by embedder for reading first buffer like `cmd | nvim -`
 EXTERN int stdin_fd INIT(= -1);

@@ -1088,8 +1085,6 @@ typedef enum {
 // Only filled for Win32.
 EXTERN char windowsVersion[20] INIT(= { 0 });

-EXTERN int exit_need_delay INIT(= 0);
-
 /// While executing a regexp and set to OPTION_MAGIC_ON or OPTION_MAGIC_OFF this
 /// overrules p_magic.  Otherwise set to OPTION_MAGIC_NOT_SET.
 EXTERN optmagic_T magic_overruled INIT(= OPTION_MAGIC_NOT_SET);
--- a/src/nvim/highlight.c
+++ b/src/nvim/highlight.c
@@ -933,22 +933,26 @@ HlAttrs dict2hlattrs(Dict(highlight) *dict, bool use_rgb, int *link_id, Error *e
  CHECK_FLAG(dict, mask, italic, , HL_ITALIC);
  CHECK_FLAG(dict, mask, reverse, , HL_INVERSE);
  CHECK_FLAG(dict, mask, strikethrough, , HL_STRIKETHROUGH);
+  if (use_rgb) {
+    CHECK_FLAG(dict, mask, fg_indexed, , HL_FG_INDEXED);
+    CHECK_FLAG(dict, mask, bg_indexed, , HL_BG_INDEXED);
+  }
  CHECK_FLAG(dict, mask, nocombine, , HL_NOCOMBINE);
  CHECK_FLAG(dict, mask, default, _, HL_DEFAULT);

  if (HAS_KEY(dict->fg)) {
-    fg = object_to_color(dict->fg, "fg", true, err);
+    fg = object_to_color(dict->fg, "fg", use_rgb, err);
  } else if (HAS_KEY(dict->foreground)) {
-    fg = object_to_color(dict->foreground, "foreground", true, err);
+    fg = object_to_color(dict->foreground, "foreground", use_rgb, err);
  }
  if (ERROR_SET(err)) {
    return hlattrs;
  }

  if (HAS_KEY(dict->bg)) {
-    bg = object_to_color(dict->bg, "bg", true, err);
+    bg = object_to_color(dict->bg, "bg", use_rgb, err);
  } else if (HAS_KEY(dict->background)) {
-    bg = object_to_color(dict->background, "background", true, err);
+    bg = object_to_color(dict->background, "background", use_rgb, err);
  }
  if (ERROR_SET(err)) {
    return hlattrs;
@@ -1035,11 +1039,11 @@ HlAttrs dict2hlattrs(Dict(highlight) *dict, bool use_rgb, int *link_id, Error *e
    }
  }

-  // apply gui mask as default for cterm mask
-  if (!cterm_mask_provided) {
-    cterm_mask = mask;
-  }
  if (use_rgb) {
+    // apply gui mask as default for cterm mask
+    if (!cterm_mask_provided) {
+      cterm_mask = mask;
+    }
    hlattrs.rgb_ae_attr = mask;
    hlattrs.rgb_bg_color = bg;
    hlattrs.rgb_fg_color = fg;
@@ -1049,9 +1053,9 @@ HlAttrs dict2hlattrs(Dict(highlight) *dict, bool use_rgb, int *link_id, Error *e
    hlattrs.cterm_fg_color = ctermfg == -1 ? 0 : ctermfg + 1;
    hlattrs.cterm_ae_attr = cterm_mask;
  } else {
-    hlattrs.cterm_bg_color = ctermbg == -1 ? 0 : ctermbg + 1;
-    hlattrs.cterm_fg_color = ctermfg == -1 ? 0 : ctermfg + 1;
-    hlattrs.cterm_ae_attr = cterm_mask;
+    hlattrs.cterm_bg_color = bg == -1 ? 0 : bg + 1;
+    hlattrs.cterm_fg_color = fg == -1 ? 0 : fg + 1;
+    hlattrs.cterm_ae_attr = mask;
  }

  return hlattrs;
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -97,6 +97,7 @@
 #include "nvim/msgpack_rpc/helpers.h"
 #include "nvim/msgpack_rpc/server.h"
 #include "nvim/os/signal.h"
+#include "nvim/tui/tui.h"

 // values for "window_layout"
 enum {
@@ -278,8 +279,6 @@ int main(int argc, char **argv)
  // argument list "global_alist".
  command_line_scan(&params);

-  open_script_files(&params);
-
  nlua_init();

  TIME_MSG("init lua interpreter");
@@ -291,9 +290,29 @@ int main(int argc, char **argv)
    }
  }

-  server_init(params.listen_addr);
+  bool use_builtin_ui = (!headless_mode && !embedded_mode && !silent_mode);
+
+  // don't bind the server yet, if we are using builtin ui.
+  // This will be done when nvim server has been forked from the ui process
+  if (!use_builtin_ui) {
+    server_init(params.listen_addr);
+  }
+
  if (params.remote) {
-    remote_request(&params, params.remote, params.server_addr, argc, argv);
+    remote_request(&params, params.remote, params.server_addr, argc, argv,
+                   use_builtin_ui);
+  }
+
+  bool remote_ui = (ui_client_channel_id != 0);
+
+  if (use_builtin_ui && !remote_ui) {
+    ui_client_forward_stdin = !params.input_isatty;
+    uint64_t rv = ui_client_start_server(params.argc, params.argv);
+    if (!rv) {
+      os_errmsg("Failed to start Nvim server!\n");
+      getout(1);
+    }
+    ui_client_channel_id = rv;
  }

  if (GARGCOUNT > 0) {
@@ -349,17 +368,16 @@ int main(int argc, char **argv)
    input_start(STDIN_FILENO);
  }

+  if (ui_client_channel_id) {
+    ui_client_run(remote_ui);  // NORETURN
+  }
+
  // Wait for UIs to set up Nvim or show early messages
  // and prompts (--cmd, swapfile dialog, …).
  bool use_remote_ui = (embedded_mode && !headless_mode);
-  bool use_builtin_ui = (!headless_mode && !embedded_mode && !silent_mode);
-  if (use_remote_ui || use_builtin_ui) {
+  if (use_remote_ui) {
    TIME_MSG("waiting for UI");
-    if (use_remote_ui) {
-      remote_ui_wait_for_attach();
-    } else {
-      ui_builtin_start();
-    }
+    remote_ui_wait_for_attach();
    TIME_MSG("done waiting for UI");
    firstwin->w_prev_height = firstwin->w_height;  // may have changed
  }
@@ -370,12 +388,13 @@ int main(int argc, char **argv)
  win_new_screensize();
  TIME_MSG("clear screen");

-  if (ui_client_channel_id) {
-    ui_client_init(ui_client_channel_id);
-    ui_client_execute(ui_client_channel_id);
-    abort();  // unreachable
+  // Handle "foo | nvim". EDIT_FILE may be overwritten now. #6299
+  if (edit_stdin(&params)) {
+    params.edit_type = EDIT_STDIN;
  }

+  open_script_files(&params);
+
  // Default mappings (incl. menus)
  Error err = ERROR_INIT;
  Object o = NLUA_EXEC_STATIC("return vim._init_default_mappings()",
@@ -384,6 +403,7 @@ int main(int argc, char **argv)
  api_clear_error(&err);
  assert(o.type == kObjectTypeNil);
  api_free_object(o);
+
  TIME_MSG("init default mappings");

  init_default_autocmds();
@@ -483,7 +503,7 @@ int main(int argc, char **argv)
  // writing end of the pipe doesn't like, e.g., in case stdin and stderr
  // are the same terminal: "cat | vim -".
  // Using autocommands here may cause trouble...
-  if ((params.edit_type == EDIT_STDIN || stdin_fd >= 0) && !recoverymode) {
+  if (params.edit_type == EDIT_STDIN && !recoverymode) {
    read_stdin();
  }

@@ -837,15 +857,24 @@ static uint64_t server_connect(char *server_addr, const char **errmsg)

 /// Handle remote subcommands
 static void remote_request(mparm_T *params, int remote_args, char *server_addr, int argc,
-                           char **argv)
+                           char **argv, bool ui_only)
 {
+  bool is_ui = strequal(argv[remote_args], "--remote-ui");
+  if (ui_only && !is_ui) {
+    // TODO(bfredl): this implies always starting the TUI.
+    // if we be smart we could delay this past should_exit
+    return;
+  }
+
  const char *connect_error = NULL;
  uint64_t chan = server_connect(server_addr, &connect_error);
  Object rvobj = OBJECT_INIT;

-  if (strequal(argv[remote_args], "--remote-ui-test")) {
+  if (is_ui) {
    if (!chan) {
-      emsg(connect_error);
+      os_errmsg("Remote ui failed to start: ");
+      os_errmsg(connect_error);
+      os_errmsg("\n");
      exit(1);
    }

@@ -925,14 +954,14 @@ static void remote_request(mparm_T *params, int remote_args, char *server_addr,

 /// Decides whether text (as opposed to commands) will be read from stdin.
 /// @see EDIT_STDIN
-static bool edit_stdin(bool explicit, mparm_T *parmp)
+static bool edit_stdin(mparm_T *parmp)
 {
  bool implicit = !headless_mode
-                  && !embedded_mode
+                  && !(embedded_mode && stdin_fd <= 0)
                  && (!exmode_active || parmp->input_neverscript)
                  && !parmp->input_isatty
                  && parmp->scriptin == NULL;  // `-s -` was not given.
-  return explicit || implicit;
+  return parmp->had_stdin_file || implicit;
 }

 /// Scan the command line arguments.
@@ -941,7 +970,6 @@ static void command_line_scan(mparm_T *parmp)
  int argc = parmp->argc;
  char **argv = parmp->argv;
  int argv_idx;                         // index in argv[n][]
-  bool had_stdin_file = false;          // found explicit "-" argument
  bool had_minmin = false;              // found "--" argument
  int want_argument;                    // option argument with argument
  long n;
@@ -978,7 +1006,7 @@ static void command_line_scan(mparm_T *parmp)
              && parmp->edit_type != EDIT_STDIN) {
            mainerr(err_too_many_args, argv[0]);
          }
-          had_stdin_file = true;
+          parmp->had_stdin_file = true;
          parmp->edit_type = EDIT_STDIN;
        }
        argv_idx = -1;  // skip to next argument
@@ -1345,7 +1373,7 @@ scripterror:
      path_fix_case(p);
 #endif

-      int alist_fnum_flag = edit_stdin(had_stdin_file, parmp)
+      int alist_fnum_flag = edit_stdin(parmp)
                            ? 1   // add buffer nr after exp.
                            : 2;  // add buffer number now and use curbuf
      alist_add(&global_alist, p, alist_fnum_flag);
@@ -1373,11 +1401,6 @@ scripterror:
    xfree(swcmd);
  }

-  // Handle "foo | nvim". EDIT_FILE may be overwritten now. #6299
-  if (edit_stdin(had_stdin_file, parmp)) {
-    parmp->edit_type = EDIT_STDIN;
-  }
-
  TIME_MSG("parsing arguments");
 }

@@ -1527,11 +1550,16 @@ static void open_script_files(mparm_T *parmp)
  if (parmp->scriptin) {
    int error;
    if (strequal(parmp->scriptin, "-")) {
-      const int stdin_dup_fd = os_dup(STDIN_FILENO);
+      int stdin_dup_fd;
+      if (stdin_fd > 0) {
+        stdin_dup_fd = stdin_fd;
+      } else {
+        stdin_dup_fd = os_dup(STDIN_FILENO);
 #ifdef MSWIN
-      // Replace the original stdin with the console input handle.
-      os_replace_stdin_to_conin();
+        // Replace the original stdin with the console input handle.
+        os_replace_stdin_to_conin();
 #endif
+      }
      FileDescriptor *const stdin_dup = file_open_fd_new(&error, stdin_dup_fd,
                                                         kFileReadOnly|kFileNonBlocking);
      assert(stdin_dup != NULL);
--- a/src/nvim/main.h
+++ b/src/nvim/main.h
@@ -45,6 +45,7 @@ typedef struct {
  char *scriptin;                       // -s {filename}
  char *scriptout;                      // -w/-W {filename}
  bool scriptout_append;                // append (-w) instead of overwrite (-W)
+  bool had_stdin_file;                  // explicit - as a file to edit
 } mparm_T;

 #ifdef INCLUDE_GENERATED_DECLARATIONS
--- a/src/nvim/msgpack_rpc/channel.c
+++ b/src/nvim/msgpack_rpc/channel.c
@@ -250,8 +250,8 @@ static void parse_msgpack(Channel *channel)
        ui_client_event_raw_line(p->grid_line_event);
      } else if (p->ui_handler.fn != NULL && p->result.type == kObjectTypeArray) {
        p->ui_handler.fn(p->result.data.array);
-        arena_mem_free(arena_finish(&p->arena));
      }
+      arena_mem_free(arena_finish(&p->arena));
    } else if (p->type == kMessageTypeResponse) {
      ChannelCallFrame *frame = kv_last(channel->rpc.call_stack);
      if (p->request_id != frame->request_id) {
@@ -299,7 +299,7 @@ static void handle_request(Channel *channel, Unpacker *p, Array args)
  assert(p->type == kMessageTypeRequest || p->type == kMessageTypeNotification);

  if (!p->handler.fn) {
-    send_error(channel, p->type, p->request_id, p->unpack_error.msg);
+    send_error(channel, p->handler, p->type, p->request_id, p->unpack_error.msg);
    api_clear_error(&p->unpack_error);
    arena_mem_free(arena_finish(&p->arena));
    return;
@@ -358,6 +358,7 @@ static void request_event(void **argv)
    msgpack_packer response;
    msgpack_packer_init(&response, &out_buffer, msgpack_sbuffer_write);
    channel_write(channel, serialize_response(channel->id,
+                                              e->handler,
                                              e->type,
                                              e->request_id,
                                              &error,
@@ -440,11 +441,13 @@ static void internal_read_event(void **argv)
  wstream_release_wbuffer(buffer);
 }

-static void send_error(Channel *chan, MessageType type, uint32_t id, char *err)
+static void send_error(Channel *chan, MsgpackRpcRequestHandler handler, MessageType type,
+                       uint32_t id, char *err)
 {
  Error e = ERROR_INIT;
  api_set_error(&e, kErrorTypeException, "%s", err);
  channel_write(chan, serialize_response(chan->id,
+                                         handler,
                                         type,
                                         id,
                                         &e,
@@ -543,26 +546,8 @@ void rpc_close(Channel *channel)
  channel_decref(channel);

  if (channel->streamtype == kChannelStreamStdio
-      || channel->id == ui_client_channel_id) {
-    multiqueue_put(main_loop.fast_events, exit_event, 0);
-  }
-}
-
-static void exit_delay_cb(uv_timer_t *handle)
-{
-  uv_timer_stop(&main_loop.exit_delay_timer);
-  multiqueue_put(main_loop.fast_events, exit_event, 0);
-}
-
-static void exit_event(void **argv)
-{
-  if (exit_need_delay) {
-    uv_timer_start(&main_loop.exit_delay_timer, exit_delay_cb, 0, 0);
-    return;
-  }
-
-  if (!exiting) {
-    os_exit(0);
+      || (channel->id == ui_client_channel_id && channel->streamtype != kChannelStreamProc)) {
+    exit_from_channel(0);
  }
 }

@@ -612,18 +597,27 @@ static WBuffer *serialize_request(uint64_t channel_id, uint32_t request_id, cons
  return rv;
 }

-static WBuffer *serialize_response(uint64_t channel_id, MessageType type, uint32_t response_id,
-                                   Error *err, Object arg, msgpack_sbuffer *sbuffer)
+static WBuffer *serialize_response(uint64_t channel_id, MsgpackRpcRequestHandler handler,
+                                   MessageType type, uint32_t response_id, Error *err, Object arg,
+                                   msgpack_sbuffer *sbuffer)
 {
  msgpack_packer pac;
  msgpack_packer_init(&pac, sbuffer, msgpack_sbuffer_write);
  if (ERROR_SET(err) && type == kMessageTypeNotification) {
-    Array args = ARRAY_DICT_INIT;
-    ADD(args, INTEGER_OBJ(err->type));
-    ADD(args, STRING_OBJ(cstr_to_string(err->msg)));
-    msgpack_rpc_serialize_request(0, cstr_as_string("nvim_error_event"),
-                                  args, &pac);
-    api_free_array(args);
+    if (handler.fn == handle_nvim_paste) {
+      // TODO(bfredl): this is pretty much ad-hoc. maybe TUI and UI:s should be
+      // allowed to ask nvim to just scream directly in the users face
+      // instead of sending nvim_error_event, in general.
+      semsg("paste: %s", err->msg);
+      api_clear_error(err);
+    } else {
+      Array args = ARRAY_DICT_INIT;
+      ADD(args, INTEGER_OBJ(err->type));
+      ADD(args, STRING_OBJ(cstr_to_string(err->msg)));
+      msgpack_rpc_serialize_request(0, cstr_as_string("nvim_error_event"),
+                                    args, &pac);
+      api_free_array(args);
+    }
  } else {
    msgpack_rpc_serialize_response(response_id, err, arg, &pac);
  }
--- a/src/nvim/msgpack_rpc/unpacker.c
+++ b/src/nvim/msgpack_rpc/unpacker.c
@@ -298,7 +298,7 @@ error:
 //
 // When method is "grid_line", we furthermore decode a cell at a time like:
 //
-// <0>[2, "redraw", <10>[{11}["grid_line", <13>[g, r, c, [<14>[cell], <14>[cell], ...]], ...], <11>[...], ...]]
+// <0>[2, "redraw", <10>[{11}["grid_line", <14>[g, r, c, [<15>[cell], <15>[cell], ...]], ...], <11>[...], ...]]
 //
 // where [cell] is [char, repeat, attr], where 'repeat' and 'attr' is optional

@@ -318,17 +318,19 @@ bool unpacker_advance(Unpacker *p)
    }
  }

-  if (p->state >= 10 && p->state != 12) {
+  if (p->state >= 10 && p->state != 13) {
    if (!unpacker_parse_redraw(p)) {
      return false;
    }

-    if (p->state == 14) {
+    if (p->state == 15) {
      // grid_line event already unpacked
      goto done;
    } else {
+      assert(p->state == 12);
      // unpack other ui events using mpack_parse()
      p->arena = (Arena)ARENA_EMPTY;
+      p->state = 13;
    }
  }

@@ -355,11 +357,11 @@ done:
  case 2:
    p->state = 0;
    return true;
-  case 12:
-  case 14:
+  case 13:
+  case 15:
    p->ncalls--;
    if (p->ncalls > 0) {
-      p->state = (p->state == 14) ? 13 : 12;
+      p->state = (p->state == 15) ? 14 : 12;
    } else if (p->nevents > 0) {
      p->state = 11;
    } else {
@@ -428,14 +430,14 @@ redo:
      }
      return true;
    } else {
-      p->state = 13;
+      p->state = 14;
      p->arena = (Arena)ARENA_EMPTY;
      p->grid_line_event = arena_alloc(&p->arena, sizeof *p->grid_line_event, true);
      g = p->grid_line_event;
    }
    FALLTHROUGH;

-  case 13:
+  case 14:
    NEXT_TYPE(tok, MPACK_TOKEN_ARRAY);
    int eventarrsize = (int)tok.length;
    if (eventarrsize != 4) {
@@ -456,10 +458,10 @@ redo:

    p->read_ptr = data;
    p->read_size = size;
-    p->state = 14;
+    p->state = 15;
    FALLTHROUGH;

-  case 14:
+  case 15:
    assert(g->icell < g->ncells);

    NEXT_TYPE(tok, MPACK_TOKEN_ARRAY);
@@ -513,6 +515,9 @@ redo:
    }
    goto redo;

+  case 12:
+    return true;
+
  default:
    abort();
  }
--- a/src/nvim/tui/input.c
+++ b/src/nvim/tui/input.c
@@ -32,6 +32,7 @@
 #endif
 #include "nvim/event/rstream.h"
 #include "nvim/msgpack_rpc/channel.h"
+#include "nvim/ui.h"

 #define KEY_BUFFER_SIZE 0xfff

@@ -219,16 +220,11 @@ static void tinput_wait_enqueue(void **argv)
    const size_t len = rbuffer_size(input->key_buffer);
    String keys = { .data = xmallocz(len), .size = len };
    rbuffer_read(input->key_buffer, keys.data, len);
-    if (ui_client_channel_id) {
-      Array args = ARRAY_DICT_INIT;
-      ADD(args, STRING_OBJ(keys));  // 'data'
-      ADD(args, BOOLEAN_OBJ(true));  // 'crlf'
-      ADD(args, INTEGER_OBJ(input->paste));  // 'phase'
-      rpc_send_event(ui_client_channel_id, "nvim_paste", args);
-    } else {
-      multiqueue_put(main_loop.events, tinput_paste_event, 3,
-                     keys.data, keys.size, (intptr_t)input->paste);
-    }
+    Array args = ARRAY_DICT_INIT;
+    ADD(args, STRING_OBJ(keys));  // 'data'
+    ADD(args, BOOLEAN_OBJ(true));  // 'crlf'
+    ADD(args, INTEGER_OBJ(input->paste));  // 'phase'
+    rpc_send_event(ui_client_channel_id, "nvim_paste", args);
    if (input->paste == 1) {
      // Paste phase: "continue"
      input->paste = 2;
@@ -237,60 +233,22 @@ static void tinput_wait_enqueue(void **argv)
  } else {  // enqueue input for the main thread or Nvim server
    RBUFFER_UNTIL_EMPTY(input->key_buffer, buf, len) {
      const String keys = { .data = buf, .size = len };
-      size_t consumed;
-      if (ui_client_channel_id) {
-        Array args = ARRAY_DICT_INIT;
-        Error err = ERROR_INIT;
-        ADD(args, STRING_OBJ(copy_string(keys, NULL)));
-        // TODO(bfredl): could be non-blocking now with paste?
-        ArenaMem res_mem = NULL;
-        Object result = rpc_send_call(ui_client_channel_id, "nvim_input", args, &res_mem, &err);
-        consumed = result.type == kObjectTypeInteger ? (size_t)result.data.integer : 0;
-        arena_mem_free(res_mem);
-      } else {
-        consumed = input_enqueue(keys);
-      }
-      if (consumed) {
-        rbuffer_consumed(input->key_buffer, consumed);
-      }
+      Array args = ARRAY_DICT_INIT;
+      ADD(args, STRING_OBJ(copy_string(keys, NULL)));
+      // NOTE: This is non-blocking and won't check partially processed input,
+      // but should be fine as all big sends are handled with nvim_paste, not nvim_input
+      rpc_send_event(ui_client_channel_id, "nvim_input", args);
+      rbuffer_consumed(input->key_buffer, len);
      rbuffer_reset(input->key_buffer);
-      if (consumed < len) {
-        break;
-      }
    }
  }
-  uv_mutex_lock(&input->key_buffer_mutex);
-  input->waiting = false;
-  uv_cond_signal(&input->key_buffer_cond);
-  uv_mutex_unlock(&input->key_buffer_mutex);
-}
-
-static void tinput_paste_event(void **argv)
-{
-  String keys = { .data = argv[0], .size = (size_t)argv[1] };
-  intptr_t phase = (intptr_t)argv[2];
-
-  Error err = ERROR_INIT;
-  nvim_paste(keys, true, phase, &err);
-  if (ERROR_SET(&err)) {
-    semsg("paste: %s", err.msg);
-    api_clear_error(&err);
-  }
-
-  api_free_string(keys);
 }

 static void tinput_flush(TermInput *input, bool wait_until_empty)
 {
  size_t drain_boundary = wait_until_empty ? 0 : 0xff;
  do {
-    uv_mutex_lock(&input->key_buffer_mutex);
-    loop_schedule_fast(&main_loop, event_create(tinput_wait_enqueue, 1, input));
-    input->waiting = true;
-    while (input->waiting) {
-      uv_cond_wait(&input->key_buffer_cond, &input->key_buffer_mutex);
-    }
-    uv_mutex_unlock(&input->key_buffer_mutex);
+    tinput_wait_enqueue((void **)&input);
  } while (rbuffer_size(input->key_buffer) > drain_boundary);
 }

@@ -570,7 +528,10 @@ static bool handle_focus_event(TermInput *input)
    bool focus_gained = *rbuffer_get(input->read_stream.buffer, 2) == 'I';
    // Advance past the sequence
    rbuffer_consumed(input->read_stream.buffer, 3);
-    autocmd_schedule_focusgained(focus_gained);
+
+    Array args = ARRAY_DICT_INIT;
+    ADD(args, BOOLEAN_OBJ(focus_gained));
+    rpc_send_event(ui_client_channel_id, "nvim_ui_set_focus", args);
    return true;
  }
  return false;
@@ -617,10 +578,15 @@ static HandleState handle_bracketed_paste(TermInput *input)
  return kNotApplicable;
 }

-static void set_bg_deferred(void **argv)
+static void set_bg(char *bgvalue)
 {
-  char *bgvalue = argv[0];
-  set_tty_background(bgvalue);
+  if (ui_client_attached) {
+    Array args = ARRAY_DICT_INIT;
+    ADD(args, STRING_OBJ(cstr_to_string("term_background")));
+    ADD(args, STRING_OBJ(cstr_as_string(xstrdup(bgvalue))));
+
+    rpc_send_event(ui_client_channel_id, "nvim_ui_set_option", args);
+  }
 }

 // During startup, tui.c requests the background color (see `ext.get_bg`).
@@ -702,10 +668,11 @@ static HandleState handle_background_color(TermInput *input)
    double g = (double)rgb[1] / (double)rgb_max[1];
    double b = (double)rgb[2] / (double)rgb_max[2];
    double luminance = (0.299 * r) + (0.587 * g) + (0.114 * b);  // CCIR 601
-    char *bgvalue = luminance < 0.5 ? "dark" : "light";
+    bool is_dark = luminance < 0.5;
+    char *bgvalue = is_dark ? "dark" : "light";
    DLOG("bg response: %s", bgvalue);
-    loop_schedule_deferred(&main_loop,
-                           event_create(set_bg_deferred, 1, bgvalue));
+    ui_client_bg_respose = is_dark ? kTrue : kFalse;
+    set_bg(bgvalue);
    input->waiting_for_bg_response = 0;
  } else if (!done && !bad) {
    // An incomplete sequence was found, waiting for the next input.
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -1,7 +1,7 @@
 // This is an open source non-commercial project. Dear PVS-Studio, please check
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com

-// Terminal UI functions. Invoked (by ui_bridge.c) on the TUI thread.
+// Terminal UI functions. Invoked (by UI_CALL) on the UI process.

 #include <assert.h>
 #include <signal.h>
@@ -18,6 +18,7 @@
 #include "nvim/api/private/helpers.h"
 #include "nvim/api/vim.h"
 #include "nvim/ascii.h"
+#include "nvim/cursor_shape.h"
 #include "nvim/event/defs.h"
 #include "nvim/event/loop.h"
 #include "nvim/event/multiqueue.h"
@@ -37,18 +38,15 @@
 #include "nvim/os/input.h"
 #include "nvim/os/os.h"
 #include "nvim/os/signal.h"
-#include "nvim/ui.h"
-#include "nvim/vim.h"
 #ifdef MSWIN
 # include "nvim/os/os_win_console.h"
 #endif
-#include "nvim/cursor_shape.h"
-#include "nvim/macros.h"
 #include "nvim/tui/input.h"
 #include "nvim/tui/terminfo.h"
 #include "nvim/tui/tui.h"
 #include "nvim/ugrid.h"
-#include "nvim/ui_bridge.h"
+#include "nvim/ui.h"
+#include "nvim/vim.h"

 // Space reserved in two output buffers to make the cursor normal or invisible
 // when flushing. No existing terminal will require 32 bytes to do that.
@@ -91,7 +89,7 @@ typedef struct {
 } Rect;

 struct TUIData {
-  UIBridgeData *bridge;
+  UI *ui;
  Loop *loop;
  unibi_var_t params[9];
  char buf[OUTBUF_SIZE];
@@ -108,8 +106,8 @@ struct TUIData {
    uv_pipe_t pipe;
  } output_handle;
  bool out_isatty;
-  SignalWatcher winch_handle, cont_handle;
-  bool cont_received;
+  SignalWatcher winch_handle;
+  uv_timer_t startup_delay_timer;
  UGrid grid;
  kvec_t(Rect) invalid_regions;
  int row, col;
@@ -159,18 +157,18 @@ struct TUIData {
    int get_extkeys;
  } unibi_ext;
  char *space_buf;
+  bool stopped;
 };

 static int got_winch = 0;
 static bool cursor_style_enabled = false;
-
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "tui/tui.c.generated.h"
 #endif

 UI *tui_start(void)
 {
-  UI *ui = xcalloc(1, sizeof(UI));  // Freed by ui_bridge_stop().
+  UI *ui = xcalloc(1, sizeof(UI));  // Freed by tui_data_destroy().
  ui->stop = tui_stop;
  ui->grid_resize = tui_grid_resize;
  ui->grid_clear = tui_grid_clear;
@@ -199,14 +197,39 @@ UI *tui_start(void)
  ui->ui_ext[kUILinegrid] = true;
  ui->ui_ext[kUITermColors] = true;

-  return ui_bridge_attach(ui, tui_main, tui_scheduler);
+  TUIData *data = xcalloc(1, sizeof(TUIData));
+  ui->data = data;
+  data->ui = ui;
+  data->is_starting = true;
+  data->screenshot = NULL;
+  data->stopped = false;
+  data->loop = &main_loop;
+  kv_init(data->invalid_regions);
+  signal_watcher_init(data->loop, &data->winch_handle, ui);
+
+  // TODO(bfredl): zero hl is empty, send this explicitly?
+  kv_push(data->attrs, HLATTRS_INIT);
+
+  data->input.tk_ti_hook_fn = tui_tk_ti_getstr;
+  tinput_init(&data->input, &main_loop);
+  ugrid_init(&data->grid);
+  tui_terminal_start(ui);
+
+  uv_timer_init(&data->loop->uv, &data->startup_delay_timer);
+  data->startup_delay_timer.data = ui;
+  uv_timer_start(&data->startup_delay_timer, after_startup_cb,
+                 100, 0);
+
+  ui_attach_impl(ui, 0);
+
+  return ui;
 }

 void tui_enable_extkeys(TUIData *data)
 {
  TermInput input = data->input;
  unibi_term *ut = data->ut;
-  UI *ui = data->bridge->ui;
+  UI *ui = data->ui;

  switch (input.extkeys_type) {
  case kExtkeysCSIu:
@@ -237,13 +260,6 @@ static size_t unibi_pre_fmt_str(TUIData *data, unsigned int unibi_index, char *b
  return unibi_run(str, data->params, buf, len);
 }

-static void termname_set_event(void **argv)
-{
-  char *termname = argv[0];
-  set_tty_option("term", termname);
-  // Do not free termname, it is freed by set_tty_option.
-}
-
 static void terminfo_start(UI *ui)
 {
  TUIData *data = ui->data;
@@ -294,22 +310,19 @@ static void terminfo_start(UI *ui)
 #endif

  // Set up unibilium/terminfo.
-  char *termname = NULL;
+  ui_client_termname = NULL;
  if (term) {
-    os_env_var_lock();
    data->ut = unibi_from_term(term);
-    os_env_var_unlock();
    if (data->ut) {
-      termname = xstrdup(term);
-      data->term = xstrdup(term);
+      ui_client_termname = xstrdup(term);
+      if (!data->term) {
+        data->term = xstrdup(term);
+      }
    }
  }
  if (!data->ut) {
-    data->ut = terminfo_from_builtin(term, &termname);
+    data->ut = terminfo_from_builtin(term, &ui_client_termname);
  }
-  // Update 'term' option.
-  loop_schedule_deferred(&main_loop,
-                         event_create(termname_set_event, 1, termname));

  // None of the following work over SSH; see :help TERM .
  const char *colorterm = os_getenv("COLORTERM");
@@ -443,13 +456,18 @@ static void tui_terminal_start(UI *ui)
 {
  TUIData *data = ui->data;
  data->print_attr_id = -1;
-  ugrid_init(&data->grid);
  terminfo_start(ui);
  tui_guess_size(ui);
  signal_watcher_start(&data->winch_handle, sigwinch_cb, SIGWINCH);
  tinput_start(&data->input);
 }

+static void after_startup_cb(uv_timer_t *handle)
+{
+  UI *ui = handle->data;
+  tui_terminal_after_startup(ui);
+}
+
 static void tui_terminal_after_startup(UI *ui)
  FUNC_ATTR_NONNULL_ALL
 {
@@ -461,98 +479,50 @@ static void tui_terminal_after_startup(UI *ui)
  flush_buf(ui);
 }

+/// stop the terminal but allow it to restart later (like after suspend)
 static void tui_terminal_stop(UI *ui)
 {
  TUIData *data = ui->data;
  if (uv_is_closing(STRUCT_CAST(uv_handle_t, &data->output_handle))) {
    // Race between SIGCONT (tui.c) and SIGHUP (os/signal.c)? #8075
    ELOG("TUI already stopped (race?)");
-    ui->data = NULL;  // Flag UI as "stopped".
+    data->stopped = true;
    return;
  }
  tinput_stop(&data->input);
  signal_watcher_stop(&data->winch_handle);
  terminfo_stop(ui);
-  ugrid_free(&data->grid);
 }

 static void tui_stop(UI *ui)
 {
+  TUIData *data = ui->data;
  tui_terminal_stop(ui);
-  ui->data = NULL;  // Flag UI as "stopped".
+  tinput_destroy(&data->input);
+  data->stopped = true;
+  signal_watcher_close(&data->winch_handle, NULL);
+  uv_close((uv_handle_t *)&data->startup_delay_timer, NULL);
+  ui_detach_impl(ui, 0);
 }

 /// Returns true if UI `ui` is stopped.
 static bool tui_is_stopped(UI *ui)
 {
-  return ui->data == NULL;
+  TUIData *data = ui->data;
+  return data->stopped;
 }

-/// Main function of the TUI thread.
-static void tui_main(UIBridgeData *bridge, UI *ui)
+#ifdef EXITFREE
+void tui_free_all_mem(UI *ui)
 {
-  Loop tui_loop;
-  loop_init(&tui_loop, NULL);
-  TUIData *data = xcalloc(1, sizeof(TUIData));
-  ui->data = data;
-  data->bridge = bridge;
-  data->loop = &tui_loop;
-  data->is_starting = true;
-  data->screenshot = NULL;
-  kv_init(data->invalid_regions);
-  signal_watcher_init(data->loop, &data->winch_handle, ui);
-  signal_watcher_init(data->loop, &data->cont_handle, data);
-#ifdef UNIX
-  signal_watcher_start(&data->cont_handle, sigcont_cb, SIGCONT);
-#endif
-
-  // TODO(bfredl): zero hl is empty, send this explicitly?
-  kv_push(data->attrs, HLATTRS_INIT);
-
-  data->input.tk_ti_hook_fn = tui_tk_ti_getstr;
-  tinput_init(&data->input, &tui_loop);
-  tui_terminal_start(ui);
-
-  // Allow main thread to continue, we are ready to handle UI callbacks.
-  CONTINUE(bridge);
-
-  // "Active" loop: first ~100 ms of startup.
-  for (size_t ms = 0; ms < 100 && !tui_is_stopped(ui);) {
-    ms += (loop_poll_events(&tui_loop, 20) ? 20 : 1);
-  }
-  if (!tui_is_stopped(ui)) {
-    tui_terminal_after_startup(ui);
-  }
-  // "Passive" (I/O-driven) loop: TUI thread "main loop".
-  while (!tui_is_stopped(ui)) {
-    loop_poll_events(&tui_loop, -1);  // tui_loop.events is never processed
-  }
-
-  ui_bridge_stopped(bridge);
-  tinput_destroy(&data->input);
-  signal_watcher_stop(&data->cont_handle);
-  signal_watcher_close(&data->cont_handle, NULL);
-  signal_watcher_close(&data->winch_handle, NULL);
-  loop_close(&tui_loop, false);
+  TUIData *data = ui->data;
+  ugrid_free(&data->grid);
  kv_destroy(data->invalid_regions);
  kv_destroy(data->attrs);
  xfree(data->space_buf);
  xfree(data->term);
  xfree(data);
-}
-
-/// Handoff point between the main (ui_bridge) thread and the TUI thread.
-static void tui_scheduler(Event event, void *d)
-{
-  UI *ui = d;
-  TUIData *data = ui->data;
-  loop_schedule_fast(data->loop, event);  // `tui_loop` local to tui_main().
-}
-
-#ifdef UNIX
-static void sigcont_cb(SignalWatcher *watcher, int signum, void *data)
-{
-  ((TUIData *)data)->cont_received = true;
+  xfree(ui);
 }
 #endif

@@ -565,7 +535,6 @@ static void sigwinch_cb(SignalWatcher *watcher, int signum, void *data)
  }

  tui_guess_size(ui);
-  ui_schedule_refresh();
 }

 static bool attrs_differ(UI *ui, int id1, int id2, bool rgb)
@@ -1324,6 +1293,9 @@ static void tui_grid_scroll(UI *ui, Integer g, Integer startrow,  // -V751
 static void tui_hl_attr_define(UI *ui, Integer id, HlAttrs attrs, HlAttrs cterm_attrs, Array info)
 {
  TUIData *data = ui->data;
+  attrs.cterm_ae_attr = cterm_attrs.cterm_ae_attr;
+  attrs.cterm_fg_color = cterm_attrs.cterm_fg_color;
+  attrs.cterm_bg_color = cterm_attrs.cterm_bg_color;
  kv_a(data->attrs, (size_t)id) = attrs;
 }

@@ -1421,32 +1393,13 @@ static void show_verbose_terminfo(TUIData *data)
  ADD(end_fold, STRING_OBJ(cstr_to_string("Title")));
  ADD(chunks, ARRAY_OBJ(end_fold));

-  if (ui_client_channel_id) {
-    Array args = ARRAY_DICT_INIT;
-    ADD(args, ARRAY_OBJ(chunks));
-    ADD(args, BOOLEAN_OBJ(true));  // history
-    Dictionary opts = ARRAY_DICT_INIT;
-    PUT(opts, "verbose", BOOLEAN_OBJ(true));
-    ADD(args, DICTIONARY_OBJ(opts));
-    rpc_send_event(ui_client_channel_id, "nvim_echo", args);
-  } else {
-    loop_schedule_deferred(&main_loop, event_create(verbose_terminfo_event, 2,
-                                                    chunks.items, chunks.size));
-  }
-}
-
-static void verbose_terminfo_event(void **argv)
-{
-  Array chunks = { .items = argv[0], .size = (size_t)argv[1] };
-  Dict(echo_opts) opts = { .verbose = BOOLEAN_OBJ(true) };
-  Error err = ERROR_INIT;
-  nvim_echo(chunks, true, &opts, &err);
-  api_free_array(chunks);
-  if (ERROR_SET(&err)) {
-    fprintf(stderr, "TUI bought the farm: %s\n", err.msg);
-    exit(1);
-  }
-  api_clear_error(&err);
+  Array args = ARRAY_DICT_INIT;
+  ADD(args, ARRAY_OBJ(chunks));
+  ADD(args, BOOLEAN_OBJ(true));  // history
+  Dictionary opts = ARRAY_DICT_INIT;
+  PUT(opts, "verbose", BOOLEAN_OBJ(true));
+  ADD(args, DICTIONARY_OBJ(opts));
+  rpc_send_event(ui_client_channel_id, "nvim_echo", args);
 }

 #ifdef UNIX
@@ -1456,38 +1409,28 @@ static void suspend_event(void **argv)
  TUIData *data = ui->data;
  bool enable_mouse = data->mouse_enabled;
  tui_terminal_stop(ui);
-  data->cont_received = false;
  stream_set_blocking(input_global_fd(), true);   // normalize stream (#2598)
-  signal_stop();
+
  kill(0, SIGTSTP);
-  signal_start();
-  while (!data->cont_received) {
-    // poll the event loop until SIGCONT is received
-    loop_poll_events(data->loop, -1);
-  }
+
  tui_terminal_start(ui);
  tui_terminal_after_startup(ui);
  if (enable_mouse) {
    tui_mouse_on(ui);
  }
  stream_set_blocking(input_global_fd(), false);  // libuv expects this
-  // resume the main thread
-  CONTINUE(data->bridge);
 }
 #endif

 static void tui_suspend(UI *ui)
 {
-  TUIData *data = ui->data;
+// on a non-UNIX system, this is a no-op
 #ifdef UNIX
  // kill(0, SIGTSTP) won't stop the UI thread, so we must poll for SIGCONT
  // before continuing. This is done in another callback to avoid
  // loop_poll_events recursion
-  multiqueue_put_event(data->loop->fast_events,
+  multiqueue_put_event(resize_events,
                       event_create(suspend_event, 1, ui));
-#else
-  // Resume the main thread as suspending isn't implemented.
-  CONTINUE(data->bridge);
 #endif
 }

@@ -1547,6 +1490,13 @@ static void tui_option_set(UI *ui, String name, Object value)
    ui->rgb = value.data.boolean;
    data->print_attr_id = -1;
    invalidate(ui, 0, data->grid.height, 0, data->grid.width);
+
+    if (ui_client_channel_id) {
+      Array args = ARRAY_DICT_INIT;
+      ADD(args, STRING_OBJ(cstr_as_string(xstrdup("rgb"))));
+      ADD(args, BOOLEAN_OBJ(value.data.boolean));
+      rpc_send_event(ui_client_channel_id, "nvim_ui_set_option", args);
+    }
  } else if (strequal(name.data, "ttimeout")) {
    data->input.ttimeout = value.data.boolean;
  } else if (strequal(name.data, "ttimeoutlen")) {
@@ -1659,8 +1609,11 @@ static void tui_guess_size(UI *ui)
    height = DFLT_ROWS;
  }

-  data->bridge->bridge.width = ui->width = width;
-  data->bridge->bridge.height = ui->height = height;
+  ui->width = width;
+  ui->height = height;
+
+  // TODO(bfredl): only if different from last value
+  ui_schedule_refresh();
 }

 static void unibi_goto(UI *ui, int row, int col)
--- a/src/nvim/ui.c
+++ b/src/nvim/ui.c
@@ -10,6 +10,7 @@

 #include "auto/config.h"
 #include "klib/kvec.h"
+#include "nvim/api/private/helpers.h"
 #include "nvim/ascii.h"
 #include "nvim/autocmd.h"
 #include "nvim/buffer_defs.h"
@@ -31,16 +32,11 @@
 #include "nvim/option.h"
 #include "nvim/os/time.h"
 #include "nvim/strings.h"
+#include "nvim/tui/tui.h"
 #include "nvim/ui.h"
 #include "nvim/ui_compositor.h"
 #include "nvim/vim.h"
 #include "nvim/window.h"
-#ifdef FEAT_TUI
-# include "nvim/tui/tui.h"
-#else
-# include "nvim/msgpack_rpc/server.h"
-#endif
-#include "nvim/api/private/helpers.h"

 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "ui.c.generated.h"
@@ -126,28 +122,28 @@ void ui_init(void)
  kv_ensure_space(call_buf, 16);
 }

+static UI *builtin_ui = NULL;
+
+#ifdef EXITFREE
 void ui_free_all_mem(void)
 {
  kv_destroy(call_buf);
+  if (builtin_ui) {
+    tui_free_all_mem(builtin_ui);
+    builtin_ui = NULL;
+  }
 }
+#endif

 void ui_builtin_start(void)
 {
-#ifdef FEAT_TUI
-  tui_start();
-#else
-  fprintf(stderr, "Nvim headless-mode started.\n");
-  size_t len;
-  char **addrs = server_address_list(&len);
-  if (addrs != NULL) {
-    fprintf(stderr, "Listening on:\n");
-    for (size_t i = 0; i < len; i++) {
-      fprintf(stderr, "\t%s\n", addrs[i]);
-    }
-    xfree(addrs);
-  }
-  fprintf(stderr, "Press CTRL+C to exit.\n");
-#endif
+  builtin_ui = tui_start();
+}
+
+UI *ui_get_by_index(int idx)
+{
+  assert(idx < 16);
+  return uis[idx];
 }

 bool ui_rgb_attached(void)
@@ -186,7 +182,7 @@ void ui_refresh(void)
  }

  if (updating_screen) {
-    deferred_refresh_event(NULL);
+    ui_schedule_refresh();
    return;
  }

@@ -228,10 +224,20 @@ void ui_refresh(void)
    screen_resize(width, height);
    p_lz = save_p_lz;
  } else {
-    Array args = ARRAY_DICT_INIT;
-    ADD(args, INTEGER_OBJ((int)width));
-    ADD(args, INTEGER_OBJ((int)height));
-    rpc_send_event(ui_client_channel_id, "nvim_ui_try_resize", args);
+    if (ui_client_attached) {
+      // TODO(bfredl): ui_refresh() should only be used on the server
+      // we are in the client process. forward the resize
+      Array args = ARRAY_DICT_INIT;
+      ADD(args, INTEGER_OBJ((int)width));
+      ADD(args, INTEGER_OBJ((int)height));
+      rpc_send_event(ui_client_channel_id, "nvim_ui_try_resize", args);
+    } else {
+      /// TODO(bfredl): Messy! The screen does not yet exist, but we need to
+      /// communicate its size from the TUI to the client. Clean this up
+      /// in The UI Devirtualization Project.
+      Rows = height;
+      Columns = width;
+    }
  }

  if (ext_widgets[kUIMessages]) {
@@ -278,10 +284,6 @@ static void ui_refresh_event(void **argv)
 }

 void ui_schedule_refresh(void)
-{
-  loop_schedule_fast(&main_loop, event_create(deferred_refresh_event, 0));
-}
-static void deferred_refresh_event(void **argv)
 {
  multiqueue_put(resize_events, ui_refresh_event, 0);
 }
--- a/src/nvim/ui_bridge.c
+++ b/src/nvim/ui_bridge.c
@@ -1,223 +0,0 @@
-// This is an open source non-commercial project. Dear PVS-Studio, please check
-// it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
-
-// UI wrapper that sends requests to the UI thread.
-// Used by the built-in TUI and libnvim-based UIs.
-
-#include <stdbool.h>
-#include <stdint.h>
-#include <stdlib.h>
-
-#include "nvim/api/private/defs.h"
-#include "nvim/api/private/helpers.h"
-#include "nvim/event/loop.h"
-#include "nvim/grid_defs.h"
-#include "nvim/highlight_defs.h"
-#include "nvim/main.h"
-#include "nvim/memory.h"
-#include "nvim/ui.h"
-#include "nvim/ui_bridge.h"
-
-#ifdef INCLUDE_GENERATED_DECLARATIONS
-# include "ui_bridge.c.generated.h"
-#endif
-
-#define UI(b) (((UIBridgeData *)b)->ui)
-
-// Schedule a function call on the UI bridge thread.
-#define UI_BRIDGE_CALL(ui, name, argc, ...) \
-  ((UIBridgeData *)ui)->scheduler(event_create(ui_bridge_##name##_event, argc, __VA_ARGS__), UI(ui))
-
-#define INT2PTR(i) ((void *)(intptr_t)i)
-#define PTR2INT(p) ((Integer)(intptr_t)p)
-
-#ifdef INCLUDE_GENERATED_DECLARATIONS
-# include "ui_events_bridge.generated.h"
-#endif
-
-UI *ui_bridge_attach(UI *ui, ui_main_fn ui_main, event_scheduler scheduler)
-{
-  UIBridgeData *rv = xcalloc(1, sizeof(UIBridgeData));
-  rv->ui = ui;
-  rv->bridge.rgb = ui->rgb;
-  rv->bridge.width = ui->width;
-  rv->bridge.height = ui->height;
-  rv->bridge.stop = ui_bridge_stop;
-  rv->bridge.grid_resize = ui_bridge_grid_resize;
-  rv->bridge.grid_clear = ui_bridge_grid_clear;
-  rv->bridge.grid_cursor_goto = ui_bridge_grid_cursor_goto;
-  rv->bridge.mode_info_set = ui_bridge_mode_info_set;
-  rv->bridge.update_menu = ui_bridge_update_menu;
-  rv->bridge.busy_start = ui_bridge_busy_start;
-  rv->bridge.busy_stop = ui_bridge_busy_stop;
-  rv->bridge.mouse_on = ui_bridge_mouse_on;
-  rv->bridge.mouse_off = ui_bridge_mouse_off;
-  rv->bridge.mode_change = ui_bridge_mode_change;
-  rv->bridge.grid_scroll = ui_bridge_grid_scroll;
-  rv->bridge.hl_attr_define = ui_bridge_hl_attr_define;
-  rv->bridge.bell = ui_bridge_bell;
-  rv->bridge.visual_bell = ui_bridge_visual_bell;
-  rv->bridge.default_colors_set = ui_bridge_default_colors_set;
-  rv->bridge.flush = ui_bridge_flush;
-  rv->bridge.suspend = ui_bridge_suspend;
-  rv->bridge.set_title = ui_bridge_set_title;
-  rv->bridge.set_icon = ui_bridge_set_icon;
-  rv->bridge.screenshot = ui_bridge_screenshot;
-  rv->bridge.option_set = ui_bridge_option_set;
-  rv->bridge.raw_line = ui_bridge_raw_line;
-  rv->bridge.inspect = ui_bridge_inspect;
-  rv->scheduler = scheduler;
-
-  for (UIExtension i = 0; (int)i < kUIExtCount; i++) {
-    rv->bridge.ui_ext[i] = ui->ui_ext[i];
-  }
-
-  rv->ui_main = ui_main;
-  uv_mutex_init(&rv->mutex);
-  uv_cond_init(&rv->cond);
-  uv_mutex_lock(&rv->mutex);
-  rv->ready = false;
-
-  if (uv_thread_create(&rv->ui_thread, ui_thread_run, rv)) {
-    abort();
-  }
-
-  // Suspend the main thread until CONTINUE is called by the UI thread.
-  while (!rv->ready) {
-    uv_cond_wait(&rv->cond, &rv->mutex);
-  }
-  uv_mutex_unlock(&rv->mutex);
-
-  ui_attach_impl(&rv->bridge, 0);
-
-  return &rv->bridge;
-}
-
-void ui_bridge_stopped(UIBridgeData *bridge)
-{
-  uv_mutex_lock(&bridge->mutex);
-  bridge->stopped = true;
-  uv_mutex_unlock(&bridge->mutex);
-}
-
-static void ui_thread_run(void *data)
-{
-  UIBridgeData *bridge = data;
-  bridge->ui_main(bridge, bridge->ui);
-}
-
-static void ui_bridge_stop(UI *b)
-{
-  // Detach bridge first, so that "stop" is the last event the TUI loop
-  // receives from the main thread. #8041
-  ui_detach_impl(b, 0);
-
-  UIBridgeData *bridge = (UIBridgeData *)b;
-  bool stopped = bridge->stopped = false;
-  UI_BRIDGE_CALL(b, stop, 1, b);
-  for (;;) {
-    uv_mutex_lock(&bridge->mutex);
-    stopped = bridge->stopped;
-    uv_mutex_unlock(&bridge->mutex);
-    if (stopped) {  // -V547
-      break;
-    }
-    // TODO(justinmk): Remove this. Use a cond-wait above. #9274
-    loop_poll_events(&main_loop, 10);  // Process one event.
-  }
-  uv_thread_join(&bridge->ui_thread);
-  uv_mutex_destroy(&bridge->mutex);
-  uv_cond_destroy(&bridge->cond);
-  xfree(bridge->ui);  // Threads joined, now safe to free UI container. #7922
-  xfree(b);
-}
-static void ui_bridge_stop_event(void **argv)
-{
-  UI *ui = UI(argv[0]);
-  ui->stop(ui);
-}
-
-static void ui_bridge_hl_attr_define(UI *ui, Integer id, HlAttrs attrs, HlAttrs cterm_attrs,
-                                     Array info)
-{
-  HlAttrs *a = xmalloc(sizeof(HlAttrs));
-  *a = attrs;
-  UI_BRIDGE_CALL(ui, hl_attr_define, 3, ui, INT2PTR(id), a);
-}
-static void ui_bridge_hl_attr_define_event(void **argv)
-{
-  UI *ui = UI(argv[0]);
-  Array info = ARRAY_DICT_INIT;
-  ui->hl_attr_define(ui, PTR2INT(argv[1]), *((HlAttrs *)argv[2]),
-                     *((HlAttrs *)argv[2]), info);
-  xfree(argv[2]);
-}
-
-static void ui_bridge_raw_line_event(void **argv)
-{
-  UI *ui = UI(argv[0]);
-  ui->raw_line(ui, PTR2INT(argv[1]), PTR2INT(argv[2]), PTR2INT(argv[3]),
-               PTR2INT(argv[4]), PTR2INT(argv[5]), PTR2INT(argv[6]),
-               (LineFlags)PTR2INT(argv[7]), argv[8], argv[9]);
-  xfree(argv[8]);
-  xfree(argv[9]);
-}
-static void ui_bridge_raw_line(UI *ui, Integer grid, Integer row, Integer startcol, Integer endcol,
-                               Integer clearcol, Integer clearattr, LineFlags flags,
-                               const schar_T *chunk, const sattr_T *attrs)
-{
-  size_t ncol = (size_t)(endcol - startcol);
-  schar_T *c = xmemdup(chunk, ncol * sizeof(schar_T));
-  sattr_T *hl = xmemdup(attrs, ncol * sizeof(sattr_T));
-  UI_BRIDGE_CALL(ui, raw_line, 10, ui, INT2PTR(grid), INT2PTR(row),
-                 INT2PTR(startcol), INT2PTR(endcol), INT2PTR(clearcol),
-                 INT2PTR(clearattr), INT2PTR(flags), c, hl);
-}
-
-static void ui_bridge_suspend(UI *b)
-{
-  UIBridgeData *data = (UIBridgeData *)b;
-  uv_mutex_lock(&data->mutex);
-  UI_BRIDGE_CALL(b, suspend, 1, b);
-  data->ready = false;
-  // Suspend the main thread until CONTINUE is called by the UI thread.
-  while (!data->ready) {
-    uv_cond_wait(&data->cond, &data->mutex);
-  }
-  uv_mutex_unlock(&data->mutex);
-}
-static void ui_bridge_suspend_event(void **argv)
-{
-  UI *ui = UI(argv[0]);
-  ui->suspend(ui);
-}
-
-static void ui_bridge_option_set(UI *ui, String name, Object value)
-{
-  String copy_name = copy_string(name, NULL);
-  Object *copy_value = xmalloc(sizeof(Object));
-  *copy_value = copy_object(value, NULL);
-  UI_BRIDGE_CALL(ui, option_set, 4, ui, copy_name.data,
-                 INT2PTR(copy_name.size), copy_value);
-  // TODO(bfredl): when/if TUI/bridge teardown is refactored to use events, the
-  // commit that introduced this special case can be reverted.
-  // For now this is needed for nvim_list_uis().
-  if (strequal(name.data, "termguicolors")) {
-    ui->rgb = value.data.boolean;
-  }
-}
-static void ui_bridge_option_set_event(void **argv)
-{
-  UI *ui = UI(argv[0]);
-  String name = (String){ .data = argv[1], .size = (size_t)argv[2] };
-  Object value = *(Object *)argv[3];
-  ui->option_set(ui, name, value);
-  api_free_string(name);
-  api_free_object(value);
-  xfree(argv[3]);
-}
-
-static void ui_bridge_inspect(UI *ui, Dictionary *info)
-{
-  PUT(*info, "chan", INTEGER_OBJ(0));
-}
--- a/src/nvim/ui_bridge.h
+++ b/src/nvim/ui_bridge.h
@@ -1,47 +0,0 @@
-// Bridge for communication between a UI thread and nvim core.
-// Used by the built-in TUI and libnvim-based UIs.
-#ifndef NVIM_UI_BRIDGE_H
-#define NVIM_UI_BRIDGE_H
-
-#include <stdbool.h>
-#include <uv.h>
-
-#include "nvim/event/defs.h"
-#include "nvim/ui.h"
-
-struct ui_bridge_data;
-
-typedef struct ui_bridge_data UIBridgeData;
-typedef void (*ui_main_fn)(UIBridgeData *bridge, UI *ui);
-struct ui_bridge_data {
-  UI bridge;  // actual UI passed to ui_attach
-  UI *ui;     // UI pointer that will have its callback called in
-              // another thread
-  event_scheduler scheduler;
-  uv_thread_t ui_thread;
-  ui_main_fn ui_main;
-  uv_mutex_t mutex;
-  uv_cond_t cond;
-  // When the UI thread is called, the main thread will suspend until
-  // the call returns. This flag is used as a condition for the main
-  // thread to continue.
-  bool ready;
-  // When a stop request is sent from the main thread, it must wait until the UI
-  // thread finishes handling all events. This flag is set by the UI thread as a
-  // signal that it will no longer send messages to the main thread.
-  bool stopped;
-};
-
-#define CONTINUE(b) \
-  do { \
-    UIBridgeData *d = (UIBridgeData *)b; \
-    uv_mutex_lock(&d->mutex); \
-    d->ready = true; \
-    uv_cond_signal(&d->cond); \
-    uv_mutex_unlock(&d->mutex); \
-  } while (0)
-
-#ifdef INCLUDE_GENERATED_DECLARATIONS
-# include "ui_bridge.h.generated.h"
-#endif
-#endif  // NVIM_UI_BRIDGE_H
--- a/src/nvim/ui_client.c
+++ b/src/nvim/ui_client.c
@@ -6,6 +6,7 @@
 #include <stdlib.h>

 #include "nvim/api/private/helpers.h"
+#include "nvim/eval.h"
 #include "nvim/event/loop.h"
 #include "nvim/event/multiqueue.h"
 #include "nvim/globals.h"
@@ -24,23 +25,71 @@
 #endif
 // uncrustify:on

-void ui_client_init(uint64_t chan)
+uint64_t ui_client_start_server(int argc, char **argv)
 {
+  varnumber_T exit_status;
+  char **args = xmalloc(((size_t)(2 + argc)) * sizeof(char *));
+  int args_idx = 0;
+  args[args_idx++] = xstrdup((const char *)get_vim_var_str(VV_PROGPATH));
+  args[args_idx++] = xstrdup("--embed");
+  for (int i = 1; i < argc; i++) {
+    args[args_idx++] = xstrdup(argv[i]);
+  }
+  args[args_idx++] = NULL;
+
+  Channel *channel = channel_job_start(args, CALLBACK_READER_INIT,
+                                       CALLBACK_READER_INIT, CALLBACK_NONE,
+                                       false, true, true, false, kChannelStdinPipe,
+                                       NULL, 0, 0, NULL, &exit_status);
+  if (ui_client_forward_stdin) {
+    close(0);
+    dup(2);
+  }
+
+  return channel->id;
+}
+
+void ui_client_run(bool remote_ui)
+  FUNC_ATTR_NORETURN
+{
+  ui_builtin_start();
+
+  loop_poll_events(&main_loop, 1);
+
  Array args = ARRAY_DICT_INIT;
-  int width = Columns;
-  int height = Rows;
  Dictionary opts = ARRAY_DICT_INIT;

  PUT(opts, "rgb", BOOLEAN_OBJ(true));
  PUT(opts, "ext_linegrid", BOOLEAN_OBJ(true));
  PUT(opts, "ext_termcolors", BOOLEAN_OBJ(true));

-  ADD(args, INTEGER_OBJ((int)width));
-  ADD(args, INTEGER_OBJ((int)height));
+  if (ui_client_termname) {
+    PUT(opts, "term_name", STRING_OBJ(cstr_as_string(ui_client_termname)));
+  }
+  if (ui_client_bg_respose != kNone) {
+    bool is_dark = (ui_client_bg_respose == kTrue);
+    PUT(opts, "term_background", STRING_OBJ(cstr_as_string(is_dark ? "dark" : "light")));
+  }
+  PUT(opts, "term_colors", INTEGER_OBJ(t_colors));
+  if (!remote_ui) {
+    PUT(opts, "stdin_tty", BOOLEAN_OBJ(stdin_isatty));
+    PUT(opts, "stdout_tty", BOOLEAN_OBJ(stdout_isatty));
+    if (ui_client_forward_stdin) {
+      PUT(opts, "stdin_fd", INTEGER_OBJ(UI_CLIENT_STDIN_FD));
+    }
+  }
+
+  ADD(args, INTEGER_OBJ(Columns));
+  ADD(args, INTEGER_OBJ(Rows));
  ADD(args, DICTIONARY_OBJ(opts));

-  rpc_send_event(chan, "nvim_ui_attach", args);
-  ui_client_channel_id = chan;
+  rpc_send_event(ui_client_channel_id, "nvim_ui_attach", args);
+  ui_client_attached = true;
+
+  // os_exit() will be invoked when the client channel detaches
+  while (true) {
+    LOOP_PROCESS_EVENTS(&main_loop, resize_events, -1);
+  }
 }

 UIClientHandler ui_client_get_redraw_handler(const char *name, size_t name_len, Error *error)
@@ -63,20 +112,6 @@ Object handle_ui_client_redraw(uint64_t channel_id, Array args, Arena *arena, Er
  return NIL;
 }

-/// run the main thread in ui client mode
-///
-/// This is just a stub. the full version will handle input, resizing, etc
-void ui_client_execute(uint64_t chan)
-  FUNC_ATTR_NORETURN
-{
-  while (true) {
-    loop_poll_events(&main_loop, -1);
-    multiqueue_process_events(resize_events);
-  }
-
-  getout(0);
-}
-
 static HlAttrs ui_client_dict2hlattrs(Dictionary d, bool rgb)
 {
  Error err = ERROR_INIT;
@@ -85,7 +120,7 @@ static HlAttrs ui_client_dict2hlattrs(Dictionary d, bool rgb)
    // TODO(bfredl): log "err"
    return HLATTRS_INIT;
  }
-  return dict2hlattrs(&dict, true, NULL, &err);
+  return dict2hlattrs(&dict, rgb, NULL, &err);
 }

 void ui_client_event_grid_resize(Array args)
--- a/src/nvim/ui_client.h
+++ b/src/nvim/ui_client.h
@@ -17,6 +17,26 @@ EXTERN size_t grid_line_buf_size INIT(= 0);
 EXTERN schar_T *grid_line_buf_char INIT(= NULL);
 EXTERN sattr_T *grid_line_buf_attr INIT(= NULL);

+// ID of the ui client channel. If zero, the client is not running.
+EXTERN uint64_t ui_client_channel_id INIT(= 0);
+
+// TODO(bfredl): the current structure for how tui and ui_client.c communicate is a bit awkward.
+// This will be restructured as part of The UI Devirtualization Project.
+
+/// Whether ui client has sent nvim_ui_attach yet
+EXTERN bool ui_client_attached INIT(= false);
+
+/// Whether ui client has gotten a response about the bg color of the terminal,
+/// kTrue=dark, kFalse=light, kNone=no response yet
+EXTERN TriState ui_client_bg_respose INIT(= kNone);
+
+/// The ui client should forward its stdin to the nvim process
+/// by convention, this uses fd=3 (next free number after stdio)
+EXTERN bool ui_client_forward_stdin INIT(= false);
+
+EXTERN char *ui_client_termname INIT(= "null");
+
+#define UI_CLIENT_STDIN_FD 3
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "ui_client.h.generated.h"

--- a/src/nvim/version.c
+++ b/src/nvim/version.c
@@ -69,11 +69,7 @@ static char *features[] = {
  "-iconv",
 #endif

-#ifdef FEAT_TUI
  "+tui",
-#else
-  "-tui",
-#endif
  NULL
 };

--- a/test/functional/autocmd/focus_spec.lua
+++ b/test/functional/autocmd/focus_spec.lua
@@ -33,9 +33,17 @@ describe('autoread TUI FocusGained/FocusLost', function()

    helpers.write_file(path, '')
    lfs.touch(path, os.time() - 10)
-    feed_command('edit '..path)
-    feed_data('\027[O')

+    screen:expect{grid=[[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name]                                         }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]]}
+    feed_command('edit '..path)
    screen:expect{grid=[[
      {1: }                                                 |
      {4:~                                                 }|
@@ -45,6 +53,17 @@ describe('autoread TUI FocusGained/FocusLost', function()
      :edit xtest-foo                                   |
      {3:-- TERMINAL --}                                    |
    ]]}
+    feed_data('\027[O')
+    feed_data('\027[O')
+    screen:expect{grid=[[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:xtest-foo                                         }|
+      :edit xtest-foo                                   |
+      {3:-- TERMINAL --}                                    |
+    ]], unchanged=true}

    helpers.write_file(path, expected_addition)

--- a/test/functional/core/main_spec.lua
+++ b/test/functional/core/main_spec.lua
@@ -56,7 +56,7 @@ describe('Command-line option', function()
      screen:attach()
      local args = {
        nvim_prog_abs(), '-u', 'NONE', '-i', 'NONE',
-        '--cmd', 'set noswapfile shortmess+=IFW fileformats=unix',
+        '--cmd', '"set noswapfile shortmess+=IFW fileformats=unix"',
        '-s', '-'
      }

--- a/test/functional/core/startup_spec.lua
+++ b/test/functional/core/startup_spec.lua
@@ -544,7 +544,7 @@ describe('sysinit', function()
      nvim_exec()                                                 |
      cmd: aunmenu *                                              |
      >                                                           |
-      <" -u NONE -i NONE --cmd "set noruler" -D 1,1            All|
+      <" -u NONE -i NONE --cmd "set noruler" -D 1,0-1          All|
                                                                  |
    ]])
    command([[call chansend(g:id, "cont\n")]])
--- a/test/functional/helpers.lua
+++ b/test/functional/helpers.lua
@@ -243,7 +243,7 @@ function module.run_session(lsession, request_cb, notification_cb, setup_cb, tim
  end

  loop_running = true
-  session:run(on_request, on_notification, on_setup, timeout)
+  lsession:run(on_request, on_notification, on_setup, timeout)
  loop_running = false
  if last_error then
    local err = last_error
@@ -251,7 +251,7 @@ function module.run_session(lsession, request_cb, notification_cb, setup_cb, tim
    error(err)
  end

-  return session.eof_err
+  return lsession.eof_err
 end

 function module.run(request_cb, notification_cb, setup_cb, timeout)
@@ -465,8 +465,14 @@ end
 --    clear('-e')
 --    clear{args={'-e'}, args_rm={'-i'}, env={TERM=term}}
 function module.clear(...)
+  module.set_session(module.spawn_argv(false, ...))
+end
+
+-- same params as clear, but does returns the session instead
+-- of replacing the default session
+function module.spawn_argv(keep, ...)
  local argv, env, io_extra = module.new_argv(...)
-  module.set_session(module.spawn(argv, nil, env, nil, io_extra))
+  return module.spawn(argv, nil, env, keep, io_extra)
 end

 -- Builds an argument list for use in clear().
--- a/test/functional/terminal/api_spec.lua
+++ b/test/functional/terminal/api_spec.lua
@@ -19,6 +19,16 @@ describe('api', function()
  end)

  it("qa! RPC request during insert-mode", function()
+    screen:expect{grid=[[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]]}
+
    -- Start the socket from the child nvim.
    child_session.feed_data(":echo serverstart('"..socket_name.."')\n")

--- a/test/functional/terminal/tui_spec.lua
+++ b/test/functional/terminal/tui_spec.lua
@@ -24,6 +24,11 @@ local funcs = helpers.funcs
 local meths = helpers.meths
 local is_ci = helpers.is_ci
 local is_os = helpers.is_os
+local new_pipename = helpers.new_pipename
+local spawn_argv = helpers.spawn_argv
+local set_session = helpers.set_session
+local feed = helpers.feed
+local eval = helpers.eval

 if helpers.skip(helpers.is_os('win')) then return end

@@ -34,7 +39,7 @@ describe('TUI', function()

  before_each(function()
    clear()
-    local child_server = helpers.new_pipename()
+    local child_server = new_pipename()
    screen = thelpers.screen_setup(0,
      string.format([=[["%s", "--listen", "%s", "-u", "NONE", "-i", "NONE", "--cmd", "%s laststatus=2 background=dark"]]=],
        nvim_prog, child_server, nvim_set))
@@ -1191,6 +1196,15 @@ describe('TUI', function()

  it('paste: split "start paste" code', function()
    feed_data('i')
+    screen:expect{grid=[[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name]                                         }|
+      {3:-- INSERT --}                                      |
+      {3:-- TERMINAL --}                                    |
+    ]]}
    -- Send split "start paste" sequence.
    feed_data('\027[2')
    feed_data('00~pasted from terminal\027[201~')
@@ -1207,6 +1221,15 @@ describe('TUI', function()

  it('paste: split "stop paste" code', function()
    feed_data('i')
+    screen:expect{grid=[[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name]                                         }|
+      {3:-- INSERT --}                                      |
+      {3:-- TERMINAL --}                                    |
+    ]]}
    -- Send split "stop paste" sequence.
    feed_data('\027[200~pasted from terminal\027[20')
    feed_data('1~')
@@ -1232,6 +1255,15 @@ describe('TUI', function()
      end)(vim.paste)
    ]], {})
    feed_data('i')
+    screen:expect{grid=[[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name]                                         }|
+      {3:-- INSERT --}                                      |
+      {3:-- TERMINAL --}                                    |
+    ]]}
    feed_data('\027[200~pasted')  -- phase 1
    screen:expect([[
      pasted{1: }                                           |
@@ -1365,7 +1397,7 @@ describe('TUI', function()
                                                        |
      {4:~                                                 }|
      {5:                                                  }|
-      [[['chan', 0], ['height', 6], ['override', v:false|
+      [[['chan', 1], ['height', 6], ['override', v:false|
      ], ['rgb', v:false], ['width', 50]]]              |
      {10:Press ENTER or type command to continue}{1: }          |
      {3:-- TERMINAL --}                                    |
@@ -1467,6 +1499,15 @@ describe('TUI', function()
  it('<C-h> #10134', function()
    local screen = thelpers.screen_setup(0, '["'..nvim_prog
      ..[[", "-u", "NONE", "-i", "NONE", "--cmd", "set noruler", "--cmd", ':nnoremap <C-h> :echomsg "\<C-h\>"<CR>']]..']')
+    screen:expect{grid=[[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name]                                         }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]]}

    command([[call chansend(b:terminal_job_id, "\<C-h>")]])
    screen:expect([[
@@ -1493,6 +1534,15 @@ describe('TUI UIEnter/UILeave', function()
      ..[[, "--cmd", "autocmd VimEnter * :call add(g:evs, 'VimEnter')"]]
      ..']'
    )
+    screen:expect{grid=[[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name]                                         }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]]}
    feed_data(":echo g:evs\n")
    screen:expect{grid=[[
      {1: }                                                 |
@@ -1513,61 +1563,88 @@ describe('TUI FocusGained/FocusLost', function()
    clear()
    screen = thelpers.screen_setup(0, '["'..nvim_prog
      ..'", "-u", "NONE", "-i", "NONE", "--cmd", "set noswapfile noshowcmd noruler"]')
+    screen:expect{grid=[[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name]                                         }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]]}
    feed_data(":autocmd FocusGained * echo 'gained'\n")
    feed_data(":autocmd FocusLost * echo 'lost'\n")
    feed_data("\034\016")  -- CTRL-\ CTRL-N
  end)

  it('in normal-mode', function()
+    screen:expect{grid=[[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name]                                         }|
+      :autocmd FocusLost * echo 'lost'                  |
+      {3:-- TERMINAL --}                                    |
+    ]]}
    retry(2, 3 * screen.timeout, function()
-    feed_data('\027[I')
-    screen:expect([[
-      {1: }                                                 |
-      {4:~                                                 }|
-      {4:~                                                 }|
-      {4:~                                                 }|
-      {5:[No Name]                                         }|
-      gained                                            |
-      {3:-- TERMINAL --}                                    |
-    ]])
+      feed_data('\027[I')
+      screen:expect([[
+        {1: }                                                 |
+        {4:~                                                 }|
+        {4:~                                                 }|
+        {4:~                                                 }|
+        {5:[No Name]                                         }|
+        gained                                            |
+        {3:-- TERMINAL --}                                    |
+      ]])

-    feed_data('\027[O')
-    screen:expect([[
-      {1: }                                                 |
-      {4:~                                                 }|
-      {4:~                                                 }|
-      {4:~                                                 }|
-      {5:[No Name]                                         }|
-      lost                                              |
-      {3:-- TERMINAL --}                                    |
-    ]])
+      feed_data('\027[O')
+      screen:expect([[
+        {1: }                                                 |
+        {4:~                                                 }|
+        {4:~                                                 }|
+        {4:~                                                 }|
+        {5:[No Name]                                         }|
+        lost                                              |
+        {3:-- TERMINAL --}                                    |
+      ]])
    end)
  end)

  it('in insert-mode', function()
    feed_command('set noshowmode')
    feed_data('i')
+    screen:expect{grid=[[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name]                                         }|
+      :set noshowmode                                   |
+      {3:-- TERMINAL --}                                    |
+    ]]}
    retry(2, 3 * screen.timeout, function()
-    feed_data('\027[I')
-    screen:expect([[
-      {1: }                                                 |
-      {4:~                                                 }|
-      {4:~                                                 }|
-      {4:~                                                 }|
-      {5:[No Name]                                         }|
-      gained                                            |
-      {3:-- TERMINAL --}                                    |
-    ]])
-    feed_data('\027[O')
-    screen:expect([[
-      {1: }                                                 |
-      {4:~                                                 }|
-      {4:~                                                 }|
-      {4:~                                                 }|
-      {5:[No Name]                                         }|
-      lost                                              |
-      {3:-- TERMINAL --}                                    |
-    ]])
+      feed_data('\027[I')
+      screen:expect([[
+        {1: }                                                 |
+        {4:~                                                 }|
+        {4:~                                                 }|
+        {4:~                                                 }|
+        {5:[No Name]                                         }|
+        gained                                            |
+        {3:-- TERMINAL --}                                    |
+      ]])
+      feed_data('\027[O')
+      screen:expect([[
+        {1: }                                                 |
+        {4:~                                                 }|
+        {4:~                                                 }|
+        {4:~                                                 }|
+        {5:[No Name]                                         }|
+        lost                                              |
+        {3:-- TERMINAL --}                                    |
+      ]])
    end)
  end)

@@ -1604,6 +1681,15 @@ describe('TUI FocusGained/FocusLost', function()
    feed_data(":autocmd!\n")
    feed_data(":autocmd FocusLost * call append(line('$'), 'lost')\n")
    feed_data(":autocmd FocusGained * call append(line('$'), 'gained')\n")
+    screen:expect{grid=[[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name]                                         }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]]}
    retry(2, 3 * screen.timeout, function()
      -- Enter cmdline-mode.
      feed_data(':')
@@ -1662,9 +1748,7 @@ describe('TUI FocusGained/FocusLost', function()
    feed_data(":echom 'msg1'|echom 'msg2'|echom 'msg3'|echom 'msg4'|echom 'msg5'\n")
    -- Execute :messages to provoke the press-enter prompt.
    feed_data(":messages\n")
-    feed_data('\027[I')
-    feed_data('\027[I')
-    screen:expect([[
+    screen:expect{grid=[[
      msg1                                              |
      msg2                                              |
      msg3                                              |
@@ -1672,7 +1756,18 @@ describe('TUI FocusGained/FocusLost', function()
      msg5                                              |
      {10:Press ENTER or type command to continue}{1: }          |
      {3:-- TERMINAL --}                                    |
-    ]])
+    ]]}
+    feed_data('\027[I')
+    feed_data('\027[I')
+    screen:expect{grid=[[
+      msg1                                              |
+      msg2                                              |
+      msg3                                              |
+      msg4                                              |
+      msg5                                              |
+      {10:Press ENTER or type command to continue}{1: }          |
+      {3:-- TERMINAL --}                                    |
+    ]], unchanged=true}
  end)
 end)

@@ -2040,7 +2135,7 @@ describe("TUI", function()

    retry(nil, 3000, function()  -- Wait for log file to be flushed.
      local log = read_file('Xtest_tui_verbose_log') or ''
-      eq('--- Terminal info --- {{{\n', string.match(log, '%-%-%- Terminal.-\n'))
+      eq('--- Terminal info --- {{{\n', string.match(log, '%-%-%- Terminal.-\n')) -- }}}
      ok(#log > 50)
    end)
  end)
@@ -2164,3 +2259,165 @@ describe('TUI bg color', function()
    screen:expect{any='new_bg=dark'}
  end)
 end)
+
+-- These tests require `thelpers` because --headless/--embed
+-- does not initialize the TUI.
+describe("TUI as a client", function()
+
+  it("connects to remote instance (with its own TUI)", function()
+    local server_super = spawn_argv(false) -- equivalent to clear()
+    local client_super = spawn_argv(true)
+
+    set_session(server_super)
+    local server_pipe = new_pipename()
+    local screen_server = thelpers.screen_setup(0,
+      string.format([=[["%s", "--listen", "%s", "-u", "NONE", "-i", "NONE", "--cmd", "%s laststatus=2 background=dark"]]=],
+        nvim_prog, server_pipe, nvim_set))
+
+    feed_data("iHello, World")
+    screen_server:expect{grid=[[
+      Hello, World{1: }                                     |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name] [+]                                     }|
+      {3:-- INSERT --}                                      |
+      {3:-- TERMINAL --}                                    |
+    ]]}
+    feed_data("\027")
+    screen_server:expect{grid=[[
+      Hello, Worl{1:d}                                      |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name] [+]                                     }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]]}
+
+    set_session(client_super)
+    local screen_client = thelpers.screen_setup(0,
+      string.format([=[["%s", "-u", "NONE", "-i", "NONE", "--server", "%s", "--remote-ui"]]=],
+                    nvim_prog, server_pipe))
+
+      screen_client:expect{grid=[[
+        Hello, Worl{1:d}                                      |
+        {4:~                                                 }|
+        {4:~                                                 }|
+        {4:~                                                 }|
+        {5:[No Name] [+]                                     }|
+                                                          |
+        {3:-- TERMINAL --}                                    |
+      ]]}
+
+    feed_data(":q!\n")
+
+    server_super:close()
+    client_super:close()
+  end)
+
+  it("connects to remote instance (--headless)", function()
+    local server = helpers.spawn_argv(false) -- equivalent to clear()
+    local client_super = spawn_argv(true)
+
+    set_session(server)
+    local server_pipe = eval'v:servername'
+    feed'iHalloj!<esc>'
+
+    set_session(client_super)
+    local screen = thelpers.screen_setup(0,
+      string.format([=[["%s", "-u", "NONE", "-i", "NONE", "--server", "%s", "--remote-ui"]]=],
+                    nvim_prog, server_pipe))
+
+    screen:expect{grid=[[
+      Halloj{1:!}                                           |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]]}
+
+    client_super:close()
+    server:close()
+  end)
+
+
+  it("throws error when no server exists", function()
+    clear()
+    local screen = thelpers.screen_setup(0,
+      string.format([=[["%s", "-u", "NONE", "-i", "NONE", "--server", "127.0.0.1:2436546", "--remote-ui"]]=],
+                    nvim_prog))
+
+    screen:try_resize(60, 7)
+
+    screen:expect([[
+      Remote ui failed to start: {MATCH:.*}|
+                                                                  |
+      [Process exited 1]{1: }                                         |
+                                                                  |
+                                                                  |
+                                                                  |
+      {3:-- TERMINAL --}                                              |
+    ]])
+  end)
+
+  it("exits when server quits", function()
+    local server_super = spawn_argv(false) -- equivalent to clear()
+    local client_super = spawn_argv(true)
+
+    set_session(server_super)
+    local server_pipe = new_pipename()
+    local screen_server = thelpers.screen_setup(0,
+      string.format([=[["%s", "--listen", "%s", "-u", "NONE", "-i", "NONE", "--cmd", "%s laststatus=2 background=dark"]]=],
+        nvim_prog, server_pipe, nvim_set))
+
+    feed_data("iHello, World")
+    screen_server:expect{grid=[[
+      Hello, World{1: }                                     |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name] [+]                                     }|
+      {3:-- INSERT --}                                      |
+      {3:-- TERMINAL --}                                    |
+    ]]}
+    feed_data("\027")
+    screen_server:expect{grid=[[
+      Hello, Worl{1:d}                                      |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name] [+]                                     }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]]}
+
+    set_session(client_super)
+    local screen_client = thelpers.screen_setup(0,
+      string.format([=[["%s", "-u", "NONE", "-i", "NONE", "--server", "%s", "--remote-ui"]]=],
+                    nvim_prog, server_pipe))
+
+    screen_client:expect{grid=[[
+      Hello, Worl{1:d}                                      |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name] [+]                                     }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]]}
+
+    -- quitting the server
+    set_session(server_super)
+    feed_data(":q!\n")
+    screen_server:expect({any="Process exited 0"})
+
+    -- assert that client has exited
+    screen_client:expect({any="Process exited 0"})
+
+    server_super:close()
+    client_super:close()
+  end)
+end)
--- a/test/functional/ui/screen.lua
+++ b/test/functional/ui/screen.lua
@@ -1550,7 +1550,8 @@ function Screen:_get_attr_id(attr_state, attrs, hl_id)
      attr_state.modified = true
      return id
    end
-    return "UNEXPECTED "..self:_pprint_attrs(self._attr_table[hl_id][1])
+    local kind = self._options.rgb and 1 or 2
+    return "UNEXPECTED "..self:_pprint_attrs(self._attr_table[hl_id][kind])
  else
    if self:_equal_attrs(attrs, {}) then
      -- ignore this attrs
--- a/test/unit/tui_spec.lua
+++ b/test/unit/tui_spec.lua
@@ -33,7 +33,7 @@ itp('handle_background_color', function()
    term_input.waiting_for_bg_response = 1
    eq(kComplete, handle_background_color(term_input))
    eq(0, term_input.waiting_for_bg_response)
-    eq(1, multiqueue.multiqueue_size(events))
+    eq(0, multiqueue.multiqueue_size(events))

    local event = multiqueue.multiqueue_get(events)
    local bg_event = ffi.cast("Event*", event.argv[1])