Merge PR #3246 'Run builtin TUI in a another thread'

15 files changed, 975 insertions, 312 deletions

diff --git a/src/nvim/CMakeLists.txt b/src/nvim/CMakeLists.txt
index 5e547ed290..ba08ed1c82 100644
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -2,12 +2,15 @@ include(CheckLibraryExists)
 
 option(USE_GCOV "Enable gcov support" OFF)
 
+if(NOT CLANG_TSAN)
+# GCOV and TSAN results in false data race reports
 if(USE_GCOV)
   message(STATUS "Enabling gcov support")
   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} --coverage")
   set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} --coverage")
   set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} --coverage")
 endif()
+endif()
 
 set(GENERATED_DIR ${PROJECT_BINARY_DIR}/src/nvim/auto)
 set(DISPATCH_GENERATOR ${PROJECT_SOURCE_DIR}/scripts/msgpack-gen.lua)
diff --git a/src/nvim/event/defs.h b/src/nvim/event/defs.h
index 5126d52241..b802866a3d 100644
--- a/src/nvim/event/defs.h
+++ b/src/nvim/event/defs.h
@@ -4,7 +4,7 @@
 #include <assert.h>
 #include <stdarg.h>
 
-#define EVENT_HANDLER_MAX_ARGC 4
+#define EVENT_HANDLER_MAX_ARGC 6
 
 typedef void (*argv_callback)(void **argv);
 typedef struct message {
@@ -12,6 +12,7 @@ typedef struct message {
   argv_callback handler;
   void *argv[EVENT_HANDLER_MAX_ARGC];
 } Event;
+typedef void(*event_scheduler)(Event event, void *data);
 
 #define VA_EVENT_INIT(event, p, h, a)                   \
   do {                                                  \
diff --git a/src/nvim/event/loop.c b/src/nvim/event/loop.c
index 3d3288f858..088e059d19 100644
--- a/src/nvim/event/loop.c
+++ b/src/nvim/event/loop.c
@@ -10,20 +10,19 @@
 # include "event/loop.c.generated.h"
 #endif
 
-typedef struct idle_event {
-  uv_idle_t idle;
-  Event event;
-} IdleEvent;
-
 
 void loop_init(Loop *loop, void *data)
 {
   uv_loop_init(&loop->uv);
+  loop->recursive = 0;
   loop->uv.data = loop;
   loop->children = kl_init(WatcherPtr);
   loop->children_stop_requests = 0;
   loop->events = queue_new_parent(loop_on_put, loop);
   loop->fast_events = queue_new_child(loop->events);
+  loop->thread_events = queue_new_parent(NULL, NULL);
+  uv_mutex_init(&loop->mutex);
+  uv_async_init(&loop->uv, &loop->async, async_cb);
   uv_signal_init(&loop->uv, &loop->children_watcher);
   uv_timer_init(&loop->uv, &loop->children_kill_timer);
   uv_timer_init(&loop->uv, &loop->poll_timer);
@@ -31,9 +30,7 @@ void loop_init(Loop *loop, void *data)
 
 void loop_poll_events(Loop *loop, int ms)
 {
-  static int recursive = 0;
-
-  if (recursive++) {
+  if (loop->recursive++) {
     abort();  // Should not re-enter uv_run
   }
 
@@ -55,10 +52,19 @@ void loop_poll_events(Loop *loop, int ms)
     uv_timer_stop(&loop->poll_timer);
   }
 
-  recursive--;  // Can re-enter uv_run now
+  loop->recursive--;  // Can re-enter uv_run now
   queue_process_events(loop->fast_events);
 }
 
+// Schedule an event from another thread
+void loop_schedule(Loop *loop, Event event)
+{
+  uv_mutex_lock(&loop->mutex);
+  queue_put_event(loop->thread_events, event);
+  uv_async_send(&loop->async);
+  uv_mutex_unlock(&loop->mutex);
+}
+
 void loop_on_put(Queue *queue, void *data)
 {
   Loop *loop = data;
@@ -72,14 +78,32 @@ void loop_on_put(Queue *queue, void *data)
 
 void loop_close(Loop *loop)
 {
+  uv_mutex_destroy(&loop->mutex);
   uv_close((uv_handle_t *)&loop->children_watcher, NULL);
   uv_close((uv_handle_t *)&loop->children_kill_timer, NULL);
   uv_close((uv_handle_t *)&loop->poll_timer, NULL);
+  uv_close((uv_handle_t *)&loop->async, NULL);
   do {
     uv_run(&loop->uv, UV_RUN_DEFAULT);
   } while (uv_loop_close(&loop->uv));
+  queue_free(loop->events);
+  queue_free(loop->fast_events);
+  queue_free(loop->thread_events);
+  kl_destroy(WatcherPtr, loop->children);
+}
+
+static void async_cb(uv_async_t *handle)
+{
+  Loop *l = handle->loop->data;
+  uv_mutex_lock(&l->mutex);
+  while (!queue_empty(l->thread_events)) {
+    Event ev = queue_get(l->thread_events);
+    queue_put_event(l->fast_events, ev);
+  }
+  uv_mutex_unlock(&l->mutex);
 }
 
 static void timer_cb(uv_timer_t *handle)
 {
 }
+
diff --git a/src/nvim/event/loop.h b/src/nvim/event/loop.h
index 9212a45aa4..0c1fcb5ed9 100644
--- a/src/nvim/event/loop.h
+++ b/src/nvim/event/loop.h
@@ -16,11 +16,14 @@ KLIST_INIT(WatcherPtr, WatcherPtr, _noop)
 
 typedef struct loop {
   uv_loop_t uv;
-  Queue *events, *fast_events;
+  Queue *events, *fast_events, *thread_events;
   klist_t(WatcherPtr) *children;
   uv_signal_t children_watcher;
   uv_timer_t children_kill_timer, poll_timer;
   size_t children_stop_requests;
+  uv_async_t async;
+  uv_mutex_t mutex;
+  int recursive;
 } Loop;
 
 #define CREATE_EVENT(queue, handler, argc, ...)                  \
diff --git a/src/nvim/event/queue.c b/src/nvim/event/queue.c
index 19eca14144..c5ef22d426 100644
--- a/src/nvim/event/queue.c
+++ b/src/nvim/event/queue.c
@@ -105,16 +105,15 @@ static Queue *queue_new(Queue *parent, put_callback put_cb, void *data)
 void queue_free(Queue *queue)
 {
   assert(queue);
-  if (queue->parent) {
-    while (!QUEUE_EMPTY(&queue->headtail)) {
-      QUEUE *q = QUEUE_HEAD(&queue->headtail);
-      QueueItem *item = queue_node_data(q);
-      assert(!item->link);
+  while (!QUEUE_EMPTY(&queue->headtail)) {
+    QUEUE *q = QUEUE_HEAD(&queue->headtail);
+    QueueItem *item = queue_node_data(q);
+    if (queue->parent) {
       QUEUE_REMOVE(&item->data.item.parent->node);
       xfree(item->data.item.parent);
-      QUEUE_REMOVE(q);
-      xfree(item);
     }
+    QUEUE_REMOVE(q);
+    xfree(item);
   }
 
   xfree(queue);
@@ -128,9 +127,8 @@ Event queue_get(Queue *queue)
 void queue_put_event(Queue *queue, Event event)
 {
   assert(queue);
-  assert(queue->parent);  // don't push directly to the parent queue
   queue_push(queue, event);
-  if (queue->parent->put_cb) {
+  if (queue->parent && queue->parent->put_cb) {
     queue->parent->put_cb(queue->parent, queue->parent->data);
   }
 }
@@ -177,11 +175,11 @@ static Event queue_remove(Queue *queue)
     rv = child->data.item.event;
     xfree(child);
   } else {
-    assert(queue->parent);
-    assert(!queue_empty(queue->parent));
-    // remove the corresponding link node in the parent queue
-    QUEUE_REMOVE(&item->data.item.parent->node);
-    xfree(item->data.item.parent);
+    if (queue->parent) {
+      // remove the corresponding link node in the parent queue
+      QUEUE_REMOVE(&item->data.item.parent->node);
+      xfree(item->data.item.parent);
+    }
     rv = item->data.item.event;
   }
 
@@ -195,11 +193,13 @@ static void queue_push(Queue *queue, Event event)
   item->link = false;
   item->data.item.event = event;
   QUEUE_INSERT_TAIL(&queue->headtail, &item->node);
-  // push link node to the parent queue
-  item->data.item.parent = xmalloc(sizeof(QueueItem));
-  item->data.item.parent->link = true;
-  item->data.item.parent->data.queue = queue;
-  QUEUE_INSERT_TAIL(&queue->parent->headtail, &item->data.item.parent->node);
+  if (queue->parent) {
+    // push link node to the parent queue
+    item->data.item.parent = xmalloc(sizeof(QueueItem));
+    item->data.item.parent->link = true;
+    item->data.item.parent->data.queue = queue;
+    QUEUE_INSERT_TAIL(&queue->parent->headtail, &item->data.item.parent->node);
+  }
 }
 
 static QueueItem *queue_node_data(QUEUE *q)
diff --git a/src/nvim/log.c b/src/nvim/log.c
index 3575f49e78..08b6d0483e 100644
--- a/src/nvim/log.c
+++ b/src/nvim/log.c
@@ -16,29 +16,49 @@
 
 #define USR_LOG_FILE "$HOME/.nvimlog"
 
+static uv_mutex_t mutex;
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "log.c.generated.h"
 #endif
 
+void log_init(void)
+{
+  uv_mutex_init(&mutex);
+}
+
+void log_lock(void)
+{
+  uv_mutex_lock(&mutex);
+}
+
+void log_unlock(void)
+{
+  uv_mutex_unlock(&mutex);
+}
+
 bool do_log(int log_level, const char *func_name, int line_num, bool eol,
             const char* fmt, ...) FUNC_ATTR_UNUSED
 {
+  log_lock();
+  bool ret = false;
   FILE *log_file = open_log_file();
 
   if (log_file == NULL) {
-    return false;
+    goto end;
   }
 
   va_list args;
   va_start(args, fmt);
-  bool ret = v_do_log_to_file(log_file, log_level, func_name, line_num, eol,
+  ret = v_do_log_to_file(log_file, log_level, func_name, line_num, eol,
                               fmt, args);
   va_end(args);
 
   if (log_file != stderr && log_file != stdout) {
     fclose(log_file);
   }
+end:
+  log_unlock();
   return ret;
 }
 
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 3e096ee190..dd2b813b1c 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -177,6 +177,7 @@ void event_teardown(void)
 /// Needed for unit tests. Must be called after `time_init()`.
 void early_init(void)
 {
+  log_init();
   fs_init();
   handle_init();
 
diff --git a/src/nvim/msgpack_rpc/channel.c b/src/nvim/msgpack_rpc/channel.c
index 45e78d6e79..34ff7c6374 100644
--- a/src/nvim/msgpack_rpc/channel.c
+++ b/src/nvim/msgpack_rpc/channel.c
@@ -825,6 +825,7 @@ static void log_server_msg(uint64_t channel_id,
   msgpack_unpack_next(&unpacked, packed->data, packed->size, NULL);
   uint64_t type = unpacked.data.via.array.ptr[0].via.u64;
   DLOGN("[msgpack-rpc] nvim -> client(%" PRIu64 ") ", channel_id);
+  log_lock();
   FILE *f = open_log_file();
   fprintf(f, type ? (type == 1 ? RES : NOT) : REQ);
   log_msg_close(f, unpacked.data);
@@ -836,6 +837,7 @@ static void log_client_msg(uint64_t channel_id,
                            msgpack_object msg)
 {
   DLOGN("[msgpack-rpc] client(%" PRIu64 ") -> nvim ", channel_id);
+  log_lock();
   FILE *f = open_log_file();
   fprintf(f, is_request ? REQ : RES);
   log_msg_close(f, msg);
@@ -847,6 +849,7 @@ static void log_msg_close(FILE *f, msgpack_object msg)
   fputc('\n', f);
   fflush(f);
   fclose(f);
+  log_unlock();
 }
 #endif
 
diff --git a/src/nvim/tui/term_input.inl b/src/nvim/tui/input.c
index c396557160..b680e885df 100644
--- a/src/nvim/tui/term_input.inl
+++ b/src/nvim/tui/input.c
@@ -1,21 +1,86 @@
-#include <termkey.h>
 
+#include "nvim/tui/input.h"
+#include "nvim/vim.h"
+#include "nvim/api/vim.h"
+#include "nvim/api/private/helpers.h"
 #include "nvim/ascii.h"
 #include "nvim/misc2.h"
 #include "nvim/os/os.h"
 #include "nvim/os/input.h"
 #include "nvim/event/rstream.h"
-#include "nvim/event/time.h"
 
 #define PASTETOGGLE_KEY "<f37>"
 
-struct term_input {
-  int in_fd;
-  bool paste_enabled;
-  TermKey *tk;
-  TimeWatcher timer_handle;
-  Stream read_stream;
-};
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "tui/input.c.generated.h"
+#endif
+
+void term_input_init(TermInput *input, Loop *loop)
+{
+  input->loop = loop;
+  input->paste_enabled = false;
+  input->in_fd = 0;
+
+  const char *term = os_getenv("TERM");
+  if (!term) {
+    term = "";  // termkey_new_abstract assumes non-null (#2745)
+  }
+  input->tk = termkey_new_abstract(term, 0);
+  int curflags = termkey_get_canonflags(input->tk);
+  termkey_set_canonflags(input->tk, curflags | TERMKEY_CANON_DELBS);
+  // setup input handle
+  rstream_init_fd(loop, &input->read_stream, input->in_fd, 0xfff, input);
+  // initialize a timer handle for handling ESC with libtermkey
+  time_watcher_init(loop, &input->timer_handle, input);
+  // Set the pastetoggle option to a special key that will be sent when
+  // \e[20{0,1}~/ are received
+  Error err = ERROR_INIT;
+  vim_set_option(cstr_as_string("pastetoggle"),
+      STRING_OBJ(cstr_as_string(PASTETOGGLE_KEY)), &err);
+}
+
+void term_input_destroy(TermInput *input)
+{
+  time_watcher_close(&input->timer_handle, NULL);
+  stream_close(&input->read_stream, NULL);
+  termkey_destroy(input->tk);
+}
+
+void term_input_start(TermInput *input)
+{
+  rstream_start(&input->read_stream, read_cb);
+}
+
+void term_input_stop(TermInput *input)
+{
+  rstream_stop(&input->read_stream);
+  time_watcher_stop(&input->timer_handle);
+}
+
+void term_input_set_encoding(TermInput *input, char* enc)
+{
+  int enc_flag = strcmp(enc, "utf-8") == 0 ? TERMKEY_FLAG_UTF8
+                                           : TERMKEY_FLAG_RAW;
+  termkey_set_flags(input->tk, enc_flag);
+}
+
+static void input_enqueue_event(void **argv)
+{
+  char *buf = argv[0];
+  input_enqueue(cstr_as_string(buf));
+  xfree(buf);
+}
+
+static void input_done_event(void **argv)
+{
+  input_done();
+}
+
+static void enqueue_input(char *buf, size_t size)
+{
+  loop_schedule(&loop, event_create(1, input_enqueue_event, 1,
+        xstrndup(buf, size)));
+}
 
 static void forward_simple_utf8(TermKeyKey *key)
 {
@@ -33,7 +98,7 @@ static void forward_simple_utf8(TermKeyKey *key)
   }
 
   buf[len] = 0;
-  input_enqueue((String){.data = buf, .size = len});
+  enqueue_input(buf, len);
 }
 
 static void forward_modified_utf8(TermKey *tk, TermKeyKey *key)
@@ -48,7 +113,7 @@ static void forward_modified_utf8(TermKey *tk, TermKeyKey *key)
     len = termkey_strfkey(tk, buf, sizeof(buf), key, TERMKEY_FORMAT_VIM);
   }
 
-  input_enqueue((String){.data = buf, .size = len});
+  enqueue_input(buf, len);
 }
 
 static void forward_mouse_event(TermKey *tk, TermKeyKey *key)
@@ -99,7 +164,7 @@ static void forward_mouse_event(TermKey *tk, TermKeyKey *key)
   }
 
   len += (size_t)snprintf(buf + len, sizeof(buf) - len, "><%d,%d>", col, row);
-  input_enqueue((String){.data = buf, .size = len});
+  enqueue_input(buf, len);
 }
 
 static TermKeyResult tk_getkey(TermKey *tk, TermKeyKey *key, bool force)
@@ -175,16 +240,16 @@ static bool handle_bracketed_paste(TermInput *input)
       int state = get_real_state();
       if (state & NORMAL) {
         // Enter insert mode
-        input_enqueue(cstr_as_string("i"));
+        enqueue_input("i", 1);
       } else if (state & VISUAL) {
         // Remove the selected text and enter insert mode
-        input_enqueue(cstr_as_string("c"));
+        enqueue_input("c", 1);
       } else if (!(state & INSERT)) {
         // Don't mess with the paste option
         return true;
       }
     }
-    input_enqueue(cstr_as_string(PASTETOGGLE_KEY));
+    enqueue_input(PASTETOGGLE_KEY, sizeof(PASTETOGGLE_KEY) - 1);
     input->paste_enabled = enable;
     return true;
   }
@@ -227,9 +292,9 @@ static void read_cb(Stream *stream, RBuffer *buf, size_t c, void *data,
       // ls *.md | xargs nvim
       input->in_fd = 2;
       stream_close(&input->read_stream, NULL);
-      queue_put(loop.fast_events, restart_reading, 1, input);
+      queue_put(input->loop->fast_events, restart_reading, 1, input);
     } else {
-      input_done();
+      loop_schedule(&loop, event_create(1, input_done_event, 0));
     }
     return;
   }
@@ -275,51 +340,6 @@ static void read_cb(Stream *stream, RBuffer *buf, size_t c, void *data,
 static void restart_reading(void **argv)
 {
   TermInput *input = argv[0];
-  rstream_init_fd(&loop, &input->read_stream, input->in_fd, 0xfff, input);
+  rstream_init_fd(input->loop, &input->read_stream, input->in_fd, 0xfff, input);
   rstream_start(&input->read_stream, read_cb);
 }
-
-static TermInput *term_input_new(void)
-{
-  TermInput *rv = xmalloc(sizeof(TermInput));
-  rv->paste_enabled = false;
-  rv->in_fd = 0;
-
-  const char *term = os_getenv("TERM");
-  if (!term) {
-    term = "";  // termkey_new_abstract assumes non-null (#2745)
-  }
-  rv->tk = termkey_new_abstract(term, 0);
-  int curflags = termkey_get_canonflags(rv->tk);
-  termkey_set_canonflags(rv->tk, curflags | TERMKEY_CANON_DELBS);
-  // setup input handle
-  rstream_init_fd(&loop, &rv->read_stream, rv->in_fd, 0xfff, rv);
-  rstream_start(&rv->read_stream, read_cb);
-  // initialize a timer handle for handling ESC with libtermkey
-  time_watcher_init(&loop, &rv->timer_handle, rv);
-  // Set the pastetoggle option to a special key that will be sent when
-  // \e[20{0,1}~/ are received
-  Error err = ERROR_INIT;
-  vim_set_option(cstr_as_string("pastetoggle"),
-      STRING_OBJ(cstr_as_string(PASTETOGGLE_KEY)), &err);
-  return rv;
-}
-
-static void term_input_destroy(TermInput *input)
-{
-  time_watcher_stop(&input->timer_handle);
-  time_watcher_close(&input->timer_handle, NULL);
-  rstream_stop(&input->read_stream);
-  stream_close(&input->read_stream, NULL);
-  termkey_destroy(input->tk);
-  // Run once to remove references to input/timer handles
-  loop_poll_events(&loop, 0);
-  xfree(input);
-}
-
-static void term_input_set_encoding(TermInput *input, char* enc)
-{
-  int enc_flag = strcmp(enc, "utf-8") == 0 ? TERMKEY_FLAG_UTF8
-                                           : TERMKEY_FLAG_RAW;
-  termkey_set_flags(input->tk, enc_flag);
-}
diff --git a/src/nvim/tui/input.h b/src/nvim/tui/input.h
new file mode 100644
index 0000000000..033f53b4e2
--- /dev/null
+++ b/src/nvim/tui/input.h
@@ -0,0 +1,23 @@
+#ifndef NVIM_TUI_INPUT_H
+#define NVIM_TUI_INPUT_H
+
+#include <stdbool.h>
+
+#include <termkey.h>
+#include "nvim/event/stream.h"
+#include "nvim/event/time.h"
+
+typedef struct term_input {
+  int in_fd;
+  bool paste_enabled;
+  TermKey *tk;
+  TimeWatcher timer_handle;
+  Loop *loop;
+  Stream read_stream;
+} TermInput;
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "tui/input.h.generated.h"
+#endif
+
+#endif  // NVIM_TUI_INPUT_H
diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index acc2ccc682..b2bb80a092 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -17,46 +17,45 @@
 #include "nvim/event/loop.h"
 #include "nvim/event/signal.h"
 #include "nvim/tui/tui.h"
+#include "nvim/tui/input.h"
+#include "nvim/os/input.h"
+#include "nvim/os/os.h"
 #include "nvim/strings.h"
+#include "nvim/ugrid.h"
+#include "nvim/ui_bridge.h"
 
 // Space reserved in the output buffer to restore the cursor to normal when
 // flushing. No existing terminal will require 32 bytes to do that.
 #define CNORM_COMMAND_MAX_SIZE 32
 #define OUTBUF_SIZE 0xffff
 
-typedef struct term_input TermInput;
-
-#include "term_input.inl"
-
 typedef struct {
   int top, bot, left, right;
 } Rect;
 
 typedef struct {
-  char data[7];
-  HlAttrs attrs;
-} Cell;
-
-typedef struct {
+  UIBridgeData *bridge;
+  Loop *loop;
+  bool stop;
   unibi_var_t params[9];
   char buf[OUTBUF_SIZE];
   size_t bufpos, bufsize;
-  TermInput *input;
-  uv_loop_t *write_loop;
+  TermInput input;
+  uv_loop_t write_loop;
   unibi_term *ut;
   uv_tty_t output_handle;
-  SignalWatcher winch_handle;
-  Rect scroll_region;
+  SignalWatcher winch_handle, cont_handle;
+  bool cont_received;
+  // Event scheduled by the ui bridge. Since the main thread suspends until
+  // the event is handled, it is fine to use a single field instead of a queue
+  Event scheduled_event;
+  UGrid grid;
   kvec_t(Rect) invalid_regions;
-  int row, col;
-  int bg, fg;
   int out_fd;
-  int old_height;
   bool can_use_terminal_scroll;
   bool mouse_enabled;
   bool busy;
-  HlAttrs attrs, print_attrs;
-  Cell **screen;
+  HlAttrs print_attrs;
   int showing_mode;
   struct {
     int enable_mouse, disable_mouse;
@@ -72,32 +71,41 @@ static bool volatile got_winch = false;
 # include "tui/tui.c.generated.h"
 #endif
 
-#define EMPTY_ATTRS ((HlAttrs){false, false, false, false, false, -1, -1})
-
-#define FOREACH_CELL(ui, top, bot, left, right, go, code)               \
-  do {                                                                  \
-    TUIData *data = ui->data;                                           \
-    for (int row = top; row <= bot; ++row) {                            \
-      Cell *cells = data->screen[row];                                  \
-      if (go) {                                                         \
-        unibi_goto(ui, row, left);                                      \
-      }                                                                 \
-      for (int col = left; col <= right; ++col) {                       \
-        Cell *cell = cells + col;                                       \
-        (void)(cell);                                                   \
-        code;                                                           \
-      }                                                                 \
-    }                                                                   \
-  } while (0)
-
 
 UI *tui_start(void)
 {
-  TUIData *data = xcalloc(1, sizeof(TUIData));
   UI *ui = xcalloc(1, sizeof(UI));
-  ui->data = data;
-  data->attrs = data->print_attrs = EMPTY_ATTRS;
-  data->fg = data->bg = -1;
+  ui->stop = tui_stop;
+  ui->rgb = os_getenv("NVIM_TUI_ENABLE_TRUE_COLOR") != NULL;
+  ui->resize = tui_resize;
+  ui->clear = tui_clear;
+  ui->eol_clear = tui_eol_clear;
+  ui->cursor_goto = tui_cursor_goto;
+  ui->update_menu = tui_update_menu;
+  ui->busy_start = tui_busy_start;
+  ui->busy_stop = tui_busy_stop;
+  ui->mouse_on = tui_mouse_on;
+  ui->mouse_off = tui_mouse_off;
+  ui->mode_change = tui_mode_change;
+  ui->set_scroll_region = tui_set_scroll_region;
+  ui->scroll = tui_scroll;
+  ui->highlight_set = tui_highlight_set;
+  ui->put = tui_put;
+  ui->bell = tui_bell;
+  ui->visual_bell = tui_visual_bell;
+  ui->update_fg = tui_update_fg;
+  ui->update_bg = tui_update_bg;
+  ui->flush = tui_flush;
+  ui->suspend = tui_suspend;
+  ui->set_title = tui_set_title;
+  ui->set_icon = tui_set_icon;
+  ui->set_encoding = tui_set_encoding;
+  return ui_bridge_attach(ui, tui_main, tui_scheduler);
+}
+
+static void terminfo_start(UI *ui)
+{
+  TUIData *data = ui->data;
   data->can_use_terminal_scroll = true;
   data->bufpos = 0;
   data->bufsize = sizeof(data->buf) - CNORM_COMMAND_MAX_SIZE;
@@ -109,12 +117,8 @@ UI *tui_start(void)
   data->unibi_ext.enter_insert_mode = -1;
   data->unibi_ext.enter_replace_mode = -1;
   data->unibi_ext.exit_insert_mode = -1;
-
   // write output to stderr if stdout is not a tty
   data->out_fd = os_isatty(1) ? 1 : (os_isatty(2) ? 2 : 1);
-  kv_init(data->invalid_regions);
-  // setup term input
-  data->input = term_input_new();
   // setup unibilium
   data->ut = unibi_from_env();
   if (!data->ut) {
@@ -128,62 +132,14 @@ UI *tui_start(void)
   unibi_out(ui, unibi_clear_screen);
   // Enable bracketed paste
   unibi_out(ui, data->unibi_ext.enable_bracketed_paste);
-  // setup output handle in a separate event loop(we wanna do synchronous
-  // write to the tty)
-  data->write_loop = xmalloc(sizeof(uv_loop_t));
-  uv_loop_init(data->write_loop);
-  uv_tty_init(data->write_loop, &data->output_handle, data->out_fd, 0);
+  uv_loop_init(&data->write_loop);
+  uv_tty_init(&data->write_loop, &data->output_handle, data->out_fd, 0);
   uv_tty_set_mode(&data->output_handle, UV_TTY_MODE_RAW);
-
-  // Obtain screen dimensions
-  update_size(ui);
-
-  // listen for SIGWINCH
-  signal_watcher_init(&loop, &data->winch_handle, ui);
-  data->winch_handle.events = queue_new_child(loop.events);
-  signal_watcher_start(&data->winch_handle, sigwinch_cb, SIGWINCH);
-
-  ui->stop = tui_stop;
-  ui->rgb = os_getenv("NVIM_TUI_ENABLE_TRUE_COLOR") != NULL;
-  ui->data = data;
-  ui->resize = tui_resize;
-  ui->clear = tui_clear;
-  ui->eol_clear = tui_eol_clear;
-  ui->cursor_goto = tui_cursor_goto;
-  ui->update_menu = tui_update_menu;
-  ui->busy_start = tui_busy_start;
-  ui->busy_stop = tui_busy_stop;
-  ui->mouse_on = tui_mouse_on;
-  ui->mouse_off = tui_mouse_off;
-  ui->mode_change = tui_mode_change;
-  ui->set_scroll_region = tui_set_scroll_region;
-  ui->scroll = tui_scroll;
-  ui->highlight_set = tui_highlight_set;
-  ui->put = tui_put;
-  ui->bell = tui_bell;
-  ui->visual_bell = tui_visual_bell;
-  ui->update_fg = tui_update_fg;
-  ui->update_bg = tui_update_bg;
-  ui->flush = tui_flush;
-  ui->suspend = tui_suspend;
-  ui->set_title = tui_set_title;
-  ui->set_icon = tui_set_icon;
-  ui->set_encoding = tui_set_encoding;
-  // Attach
-  ui_attach(ui);
-  return ui;
 }
 
-static void tui_stop(UI *ui)
+static void terminfo_stop(UI *ui)
 {
   TUIData *data = ui->data;
-  // Destroy common stuff
-  kv_destroy(data->invalid_regions);
-  signal_watcher_stop(&data->winch_handle);
-  queue_free(data->winch_handle.events);
-  signal_watcher_close(&data->winch_handle, NULL);
-  // Destroy input stuff
-  term_input_destroy(data->input);
   // Destroy output stuff
   tui_mode_change(ui, NORMAL);
   tui_mouse_off(ui);
@@ -196,24 +152,99 @@ static void tui_stop(UI *ui)
   flush_buf(ui);
   uv_tty_reset_mode();
   uv_close((uv_handle_t *)&data->output_handle, NULL);
-  uv_run(data->write_loop, UV_RUN_DEFAULT);
-  if (uv_loop_close(data->write_loop)) {
+  uv_run(&data->write_loop, UV_RUN_DEFAULT);
+  if (uv_loop_close(&data->write_loop)) {
     abort();
   }
-  xfree(data->write_loop);
   unibi_destroy(data->ut);
-  destroy_screen(data);
+}
+
+static void tui_terminal_start(UI *ui)
+{
+  TUIData *data = ui->data;
+  data->print_attrs = EMPTY_ATTRS;
+  ugrid_init(&data->grid);
+  terminfo_start(ui);
+  update_size(ui);
+  signal_watcher_start(&data->winch_handle, sigwinch_cb, SIGWINCH);
+  term_input_start(&data->input);
+}
+
+static void tui_terminal_stop(UI *ui)
+{
+  TUIData *data = ui->data;
+  term_input_stop(&data->input);
+  signal_watcher_stop(&data->winch_handle);
+  terminfo_stop(ui);
+  ugrid_free(&data->grid);
+}
+
+static void tui_stop(UI *ui)
+{
+  tui_terminal_stop(ui);
+  TUIData *data = ui->data;
+  data->stop = true;
+}
+
+// Main function of the TUI thread
+static void tui_main(UIBridgeData *bridge, 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;
+  kv_init(data->invalid_regions);
+  signal_watcher_init(data->loop, &data->winch_handle, ui);
+  signal_watcher_init(data->loop, &data->cont_handle, data);
+  signal_watcher_start(&data->cont_handle, sigcont_cb, SIGCONT);
+  // initialize input reading structures
+  term_input_init(&data->input, &tui_loop);
+  tui_terminal_start(ui);
+  data->stop = false;
+  // allow the main thread to continue, we are ready to start handling UI
+  // callbacks
+  CONTINUE(bridge);
+
+  while (!data->stop) {
+    loop_poll_events(&tui_loop, -1);
+  }
+
+  term_input_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);
+  kv_destroy(data->invalid_regions);
   xfree(data);
-  ui_detach(ui);
   xfree(ui);
 }
 
+static void tui_scheduler(Event event, void *d)
+{
+  UI *ui = d;
+  TUIData *data = ui->data;
+  loop_schedule(data->loop, event);
+}
+
+static void refresh_event(void **argv)
+{
+  ui_refresh();
+}
+
+static void sigcont_cb(SignalWatcher *watcher, int signum, void *data)
+{
+  ((TUIData *)data)->cont_received = true;
+}
+
 static void sigwinch_cb(SignalWatcher *watcher, int signum, void *data)
 {
   got_winch = true;
   UI *ui = data;
   update_size(ui);
-  ui_refresh();
+  // run refresh_event in nvim main loop
+  loop_schedule(&loop, event_create(1, refresh_event, 0));
 }
 
 static bool attrs_differ(HlAttrs a1, HlAttrs a2)
@@ -234,9 +265,10 @@ static void update_attrs(UI *ui, HlAttrs attrs)
 
   data->print_attrs = attrs;
   unibi_out(ui, unibi_exit_attribute_mode);
+  UGrid *grid = &data->grid;
 
-  int fg = attrs.foreground != -1 ? attrs.foreground : data->fg;
-  int bg = attrs.background != -1 ? attrs.background : data->bg;
+  int fg = attrs.foreground != -1 ? attrs.foreground : grid->fg;
+  int bg = attrs.background != -1 ? attrs.background : grid->bg;
 
   if (ui->rgb) {
     if (fg != -1) {
@@ -278,25 +310,25 @@ static void update_attrs(UI *ui, HlAttrs attrs)
   }
 }
 
-static void print_cell(UI *ui, Cell *ptr)
+static void print_cell(UI *ui, UCell *ptr)
 {
   update_attrs(ui, ptr->attrs);
   out(ui, ptr->data, strlen(ptr->data));
 }
 
-static void clear_region(UI *ui, int top, int bot, int left, int right,
-    bool refresh)
+static void clear_region(UI *ui, int top, int bot, int left, int right)
 {
   TUIData *data = ui->data;
-  HlAttrs clear_attrs = EMPTY_ATTRS;
-  clear_attrs.foreground = data->fg;
-  clear_attrs.background = data->bg;
-  update_attrs(ui, clear_attrs);
+  UGrid *grid = &data->grid;
 
   bool cleared = false;
-  if (refresh && data->bg == -1 && right == ui->width -1) {
+  if (grid->bg == -1 && right == ui->width -1) {
     // Background is set to the default color and the right edge matches the
     // screen end, try to use terminal codes for clearing the requested area.
+    HlAttrs clear_attrs = EMPTY_ATTRS;
+    clear_attrs.foreground = grid->fg;
+    clear_attrs.background = grid->bg;
+    update_attrs(ui, clear_attrs);
     if (left == 0) {
       if (bot == ui->height - 1) {
         if (top == 0) {
@@ -319,36 +351,26 @@ static void clear_region(UI *ui, int top, int bot, int left, int right,
     }
   }
 
-  bool clear = refresh && !cleared;
-  FOREACH_CELL(ui, top, bot, left, right, clear, {
-    cell->data[0] = ' ';
-    cell->data[1] = 0;
-    cell->attrs = clear_attrs;
-    if (clear) {
+  if (!cleared) {
+    // could not clear using faster terminal codes, refresh the whole region
+    int currow = -1;
+    UGRID_FOREACH_CELL(grid, top, bot, left, right, {
+      if (currow != row) {
+        unibi_goto(ui, row, col);
+        currow = row;
+      }
       print_cell(ui, cell);
-    }
-  });
+    });
+  }
 
   // restore cursor
-  unibi_goto(ui, data->row, data->col);
+  unibi_goto(ui, grid->row, grid->col);
 }
 
 static void tui_resize(UI *ui, int width, int height)
 {
   TUIData *data = ui->data;
-  destroy_screen(data);
-
-  data->screen = xmalloc((size_t)height * sizeof(Cell *));
-  for (int i = 0; i < height; i++) {
-    data->screen[i] = xcalloc((size_t)width, sizeof(Cell));
-  }
-
-  data->old_height = height;
-  data->scroll_region.top = 0;
-  data->scroll_region.bot = height - 1;
-  data->scroll_region.left = 0;
-  data->scroll_region.right = width - 1;
-  data->row = data->col = 0;
+  ugrid_resize(&data->grid, width, height);
 
   if (!got_winch) {  // Try to resize the terminal window.
     char r[16];  // enough for 9999x9999
@@ -362,22 +384,23 @@ static void tui_resize(UI *ui, int width, int height)
 static void tui_clear(UI *ui)
 {
   TUIData *data = ui->data;
-  clear_region(ui, data->scroll_region.top, data->scroll_region.bot,
-      data->scroll_region.left, data->scroll_region.right, true);
+  UGrid *grid = &data->grid;
+  ugrid_clear(grid);
+  clear_region(ui, grid->top, grid->bot, grid->left, grid->right);
 }
 
 static void tui_eol_clear(UI *ui)
 {
   TUIData *data = ui->data;
-  clear_region(ui, data->row, data->row, data->col,
-      data->scroll_region.right, true);
+  UGrid *grid = &data->grid;
+  ugrid_eol_clear(grid);
+  clear_region(ui, grid->row, grid->row, grid->col, grid->right);
 }
 
 static void tui_cursor_goto(UI *ui, int row, int col)
 {
   TUIData *data = ui->data;
-  data->row = row;
-  data->col = col;
+  ugrid_goto(&data->grid, row, col);
   unibi_goto(ui, row, col);
 }
 
@@ -435,11 +458,7 @@ static void tui_set_scroll_region(UI *ui, int top, int bot, int left,
     int right)
 {
   TUIData *data = ui->data;
-  data->scroll_region.top = top;
-  data->scroll_region.bot = bot;
-  data->scroll_region.left = left;
-  data->scroll_region.right = right;
-
+  ugrid_set_scroll_region(&data->grid, top, bot, left, right);
   data->can_use_terminal_scroll =
     left == 0 && right == ui->width - 1
     && ((top == 0 && bot == ui->height - 1)
@@ -449,31 +468,24 @@ static void tui_set_scroll_region(UI *ui, int top, int bot, int left,
 static void tui_scroll(UI *ui, int count)
 {
   TUIData *data = ui->data;
-  int top = data->scroll_region.top;
-  int bot = data->scroll_region.bot;
-  int left = data->scroll_region.left;
-  int right = data->scroll_region.right;
+  UGrid *grid = &data->grid;
+  int clear_top, clear_bot;
+  ugrid_scroll(grid, count, &clear_top, &clear_bot);
 
   if (data->can_use_terminal_scroll) {
     // Change terminal scroll region and move cursor to the top
-    data->params[0].i = top;
-    data->params[1].i = bot;
+    data->params[0].i = grid->top;
+    data->params[1].i = grid->bot;
     unibi_out(ui, unibi_change_scroll_region);
-    unibi_goto(ui, top, left);
+    unibi_goto(ui, grid->top, grid->left);
     // also set default color attributes or some terminals can become funny
     HlAttrs clear_attrs = EMPTY_ATTRS;
-    clear_attrs.foreground = data->fg;
-    clear_attrs.background = data->bg;
+    clear_attrs.foreground = grid->fg;
+    clear_attrs.background = grid->bg;
     update_attrs(ui, clear_attrs);
   }
 
-  // Compute start/stop/step for the loop below, also use terminal scroll
-  // if possible
-  int start, stop, step;
   if (count > 0) {
-    start = top;
-    stop = bot - count + 1;
-    step = 1;
     if (data->can_use_terminal_scroll) {
       if (count == 1) {
         unibi_out(ui, unibi_delete_line);
@@ -484,9 +496,6 @@ static void tui_scroll(UI *ui, int count)
     }
 
   } else {
-    start = bot;
-    stop = top - count - 1;
-    step = -1;
     if (data->can_use_terminal_scroll) {
       if (count == -1) {
         unibi_out(ui, unibi_insert_line);
@@ -502,52 +511,30 @@ static void tui_scroll(UI *ui, int count)
     data->params[0].i = 0;
     data->params[1].i = ui->height - 1;
     unibi_out(ui, unibi_change_scroll_region);
-    unibi_goto(ui, data->row, data->col);
-  }
-
-  int i;
-  // Scroll internal screen
-  for (i = start; i != stop; i += step) {
-    Cell *target_row = data->screen[i] + left;
-    Cell *source_row = data->screen[i + count] + left;
-    memcpy(target_row, source_row, sizeof(Cell) * (size_t)(right - left + 1));
-  }
-
-  // clear emptied region, updating the terminal if its builtin scrolling
-  // facility was used. This is done when the background color is not the
-  // default, since scrolling may leave wrong background in the cleared area.
-  bool update_clear = data->bg != -1 && data->can_use_terminal_scroll;
-  if (count > 0) {
-    clear_region(ui, stop, stop + count - 1, left, right, update_clear);
+    unibi_goto(ui, grid->row, grid->col);
+
+    if (grid->bg != -1) {
+      // Update the cleared area of the terminal if its builtin scrolling
+      // facility was used and the background color is not the default. This is
+      // required because scrolling may leave wrong background in the cleared
+      // area.
+      clear_region(ui, clear_top, clear_bot, grid->left, grid->right);
+    }
   } else {
-    clear_region(ui, stop + count + 1, stop, left, right, update_clear);
-  }
-
-  if (!data->can_use_terminal_scroll) {
     // Mark the entire scroll region as invalid for redrawing later
-    invalidate(ui, data->scroll_region.top, data->scroll_region.bot,
-        data->scroll_region.left, data->scroll_region.right);
+    invalidate(ui, grid->top, grid->bot, grid->left, grid->right);
   }
 }
 
 static void tui_highlight_set(UI *ui, HlAttrs attrs)
 {
-  ((TUIData *)ui->data)->attrs = attrs;
+  ((TUIData *)ui->data)->grid.attrs = attrs;
 }
 
 static void tui_put(UI *ui, uint8_t *text, size_t size)
 {
   TUIData *data = ui->data;
-  Cell *cell = data->screen[data->row] + data->col;
-  cell->data[size] = 0;
-  cell->attrs = data->attrs;
-
-  if (text) {
-    memcpy(cell->data, text, size);
-  }
-
-  print_cell(ui, cell);
-  data->col += 1;
+  print_cell(ui, ugrid_put(&data->grid, text, size));
 }
 
 static void tui_bell(UI *ui)
@@ -562,40 +549,64 @@ static void tui_visual_bell(UI *ui)
 
 static void tui_update_fg(UI *ui, int fg)
 {
-  ((TUIData *)ui->data)->fg = fg;
+  ((TUIData *)ui->data)->grid.fg = fg;
 }
 
 static void tui_update_bg(UI *ui, int bg)
 {
-  ((TUIData *)ui->data)->bg = bg;
+  ((TUIData *)ui->data)->grid.bg = bg;
 }
 
 static void tui_flush(UI *ui)
 {
   TUIData *data = ui->data;
+  UGrid *grid = &data->grid;
 
   while (kv_size(data->invalid_regions)) {
     Rect r = kv_pop(data->invalid_regions);
-    FOREACH_CELL(ui, r.top, r.bot, r.left, r.right, true, {
+    int currow = -1;
+    UGRID_FOREACH_CELL(grid, r.top, r.bot, r.left, r.right, {
+      if (currow != row) {
+        unibi_goto(ui, row, col);
+        currow = row;
+      }
       print_cell(ui, cell);
     });
   }
 
-  unibi_goto(ui, data->row, data->col);
+  unibi_goto(ui, grid->row, grid->col);
 
   flush_buf(ui);
 }
 
-static void tui_suspend(UI *ui)
+static void suspend_event(void **argv)
 {
+  UI *ui = argv[0];
   TUIData *data = ui->data;
   bool enable_mouse = data->mouse_enabled;
-  tui_stop(ui);
+  tui_terminal_stop(ui);
+  data->cont_received = false;
   kill(0, SIGTSTP);
-  ui = tui_start();
+  while (!data->cont_received) {
+    // poll the event loop until SIGCONT is received
+    loop_poll_events(data->loop, -1);
+  }
+  tui_terminal_start(ui);
   if (enable_mouse) {
     tui_mouse_on(ui);
   }
+  // resume the main thread
+  CONTINUE(data->bridge);
+}
+
+static void tui_suspend(UI *ui)
+{
+  TUIData *data = ui->data;
+  // 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
+  queue_put_event(data->loop->fast_events,
+      event_create(1, suspend_event, 1, ui));
 }
 
 static void tui_set_title(UI *ui, char *title)
@@ -617,7 +628,7 @@ static void tui_set_icon(UI *ui, char *icon)
 static void tui_set_encoding(UI *ui, char* enc)
 {
   TUIData *data = ui->data;
-  term_input_set_encoding(data->input, enc);
+  term_input_set_encoding(&data->input, enc);
 }
 
 static void invalidate(UI *ui, int top, int bot, int left, int right)
@@ -698,8 +709,8 @@ end:
     height = DFLT_ROWS;
   }
 
-  ui->width = width;
-  ui->height = height;
+  data->bridge->bridge.width = ui->width = width;
+  data->bridge->bridge.height = ui->height = height;
 }
 
 static void unibi_goto(UI *ui, int row, int col)
@@ -882,7 +893,7 @@ static void flush_buf(UI *ui)
   buf.base = data->buf;
   buf.len = data->bufpos;
   uv_write(&req, (uv_stream_t *)&data->output_handle, &buf, 1, NULL);
-  uv_run(data->write_loop, UV_RUN_DEFAULT);
+  uv_run(&data->write_loop, UV_RUN_DEFAULT);
   data->bufpos = 0;
 
   if (!data->busy) {
@@ -891,13 +902,3 @@ static void flush_buf(UI *ui)
     unibi_out(ui, unibi_cursor_invisible);
   }
 }
-
-static void destroy_screen(TUIData *data)
-{
-  if (data->screen) {
-    for (int i = 0; i < data->old_height; i++) {
-      xfree(data->screen[i]);
-    }
-    xfree(data->screen);
-  }
-}
diff --git a/src/nvim/ugrid.c b/src/nvim/ugrid.c
new file mode 100644
index 0000000000..127b18feb6
--- /dev/null
+++ b/src/nvim/ugrid.c
@@ -0,0 +1,137 @@
+#include <assert.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <limits.h>
+
+#include "nvim/vim.h"
+#include "nvim/ui.h"
+#include "nvim/ugrid.h"
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "ugrid.c.generated.h"
+#endif
+
+void ugrid_init(UGrid *grid)
+{
+  grid->attrs = EMPTY_ATTRS;
+  grid->fg = grid->bg = -1;
+  grid->cells = NULL;
+}
+
+void ugrid_free(UGrid *grid)
+{
+  destroy_cells(grid);
+}
+
+void ugrid_resize(UGrid *grid, int width, int height)
+{
+  destroy_cells(grid);
+  grid->cells = xmalloc((size_t)height * sizeof(UCell *));
+  for (int i = 0; i < height; i++) {
+    grid->cells[i] = xcalloc((size_t)width, sizeof(UCell));
+  }
+
+  grid->top = 0;
+  grid->bot = height - 1;
+  grid->left = 0;
+  grid->right = width - 1;
+  grid->row = grid->col = 0;
+  grid->width = width;
+  grid->height = height;
+}
+
+void ugrid_clear(UGrid *grid)
+{
+  clear_region(grid, grid->top, grid->bot, grid->left, grid->right);
+}
+
+void ugrid_eol_clear(UGrid *grid)
+{
+  clear_region(grid, grid->row, grid->row, grid->col, grid->right);
+}
+
+void ugrid_goto(UGrid *grid, int row, int col)
+{
+  grid->row = row;
+  grid->col = col;
+}
+
+void ugrid_set_scroll_region(UGrid *grid, int top, int bot, int left, int right)
+{
+  grid->top = top;
+  grid->bot = bot;
+  grid->left = left;
+  grid->right = right;
+}
+
+void ugrid_scroll(UGrid *grid, int count, int *clear_top, int *clear_bot)
+{
+  // Compute start/stop/step for the loop below
+  int start, stop, step;
+  if (count > 0) {
+    start = grid->top;
+    stop = grid->bot - count + 1;
+    step = 1;
+  } else {
+    start = grid->bot;
+    stop = grid->top - count - 1;
+    step = -1;
+  }
+
+  int i;
+
+  // Copy cell data
+  for (i = start; i != stop; i += step) {
+    UCell *target_row = grid->cells[i] + grid->left;
+    UCell *source_row = grid->cells[i + count] + grid->left;
+    memcpy(target_row, source_row,
+        sizeof(UCell) * (size_t)(grid->right - grid->left + 1));
+  }
+
+  // clear cells in the emptied region,
+  if (count > 0) {
+    *clear_top = stop;
+    *clear_bot = stop + count - 1;
+  } else {
+    *clear_bot = stop;
+    *clear_top = stop + count + 1;
+  }
+  clear_region(grid, *clear_top, *clear_bot, grid->left, grid->right);
+}
+
+UCell *ugrid_put(UGrid *grid, uint8_t *text, size_t size)
+{
+  UCell *cell = grid->cells[grid->row] + grid->col;
+  cell->data[size] = 0;
+  cell->attrs = grid->attrs;
+
+  if (text) {
+    memcpy(cell->data, text, size);
+  }
+
+  grid->col += 1;
+  return cell;
+}
+
+static void clear_region(UGrid *grid, int top, int bot, int left, int right)
+{
+  HlAttrs clear_attrs = EMPTY_ATTRS;
+  clear_attrs.foreground = grid->fg;
+  clear_attrs.background = grid->bg;
+  UGRID_FOREACH_CELL(grid, top, bot, left, right, {
+    cell->data[0] = ' ';
+    cell->data[1] = 0;
+    cell->attrs = clear_attrs;
+  });
+}
+
+static void destroy_cells(UGrid *grid)
+{
+  if (grid->cells) {
+    for (int i = 0; i < grid->height; i++) {
+      xfree(grid->cells[i]);
+    }
+    xfree(grid->cells);
+  }
+}
+
diff --git a/src/nvim/ugrid.h b/src/nvim/ugrid.h
new file mode 100644
index 0000000000..e41461fa16
--- /dev/null
+++ b/src/nvim/ugrid.h
@@ -0,0 +1,40 @@
+#ifndef NVIM_UGRID_H
+#define NVIM_UGRID_H
+
+#include "nvim/ui.h"
+
+typedef struct ucell UCell;
+typedef struct ugrid UGrid;
+
+struct ucell {
+  char data[7];
+  HlAttrs attrs;
+};
+
+struct ugrid {
+  int top, bot, left, right;
+  int row, col;
+  int bg, fg;
+  int width, height;
+  HlAttrs attrs;
+  UCell **cells;
+};
+
+#define EMPTY_ATTRS ((HlAttrs){false, false, false, false, false, -1, -1})
+
+#define UGRID_FOREACH_CELL(grid, top, bot, left, right, code)           \
+  do {                                                                  \
+    for (int row = top; row <= bot; ++row) {                            \
+      UCell *row_cells = (grid)->cells[row];                            \
+      for (int col = left; col <= right; ++col) {                       \
+        UCell *cell = row_cells + col;                                  \
+        (void)(cell);                                                   \
+        code;                                                           \
+      }                                                                 \
+    }                                                                   \
+  } while (0)
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "ugrid.h.generated.h"
+#endif
+#endif  // NVIM_UGRID_H
diff --git a/src/nvim/ui_bridge.c b/src/nvim/ui_bridge.c
new file mode 100644
index 0000000000..6e1a27cc9c
--- /dev/null
+++ b/src/nvim/ui_bridge.c
@@ -0,0 +1,347 @@
+// FIXME(tarruda): This module is very repetitive. It might be a good idea to
+// automatically generate it with a lua script during build
+#include <assert.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <limits.h>
+
+#include "nvim/vim.h"
+#include "nvim/ui.h"
+#include "nvim/memory.h"
+#include "nvim/ui_bridge.h"
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "ui_bridge.c.generated.h"
+#endif
+
+#define UI(b) (((UIBridgeData *)b)->ui)
+
+// Call a function in the UI thread
+#define UI_CALL(ui, name, argc, ...)                                      \
+  ((UIBridgeData *)ui)->scheduler(                                        \
+    event_create(1, ui_bridge_##name##_event, argc, __VA_ARGS__), UI(ui))
+
+#define INT2PTR(i) ((void *)(uintptr_t)i)
+#define PTR2INT(p) ((int)(uintptr_t)p)
+
+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.stop = ui_bridge_stop;
+  rv->bridge.resize = ui_bridge_resize;
+  rv->bridge.clear = ui_bridge_clear;
+  rv->bridge.eol_clear = ui_bridge_eol_clear;
+  rv->bridge.cursor_goto = ui_bridge_cursor_goto;
+  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.set_scroll_region = ui_bridge_set_scroll_region;
+  rv->bridge.scroll = ui_bridge_scroll;
+  rv->bridge.highlight_set = ui_bridge_highlight_set;
+  rv->bridge.put = ui_bridge_put;
+  rv->bridge.bell = ui_bridge_bell;
+  rv->bridge.visual_bell = ui_bridge_visual_bell;
+  rv->bridge.update_fg = ui_bridge_update_fg;
+  rv->bridge.update_bg = ui_bridge_update_bg;
+  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.set_encoding = ui_bridge_set_encoding;
+  rv->scheduler = scheduler;
+
+  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();
+  }
+
+  while (!rv->ready) {
+    uv_cond_wait(&rv->cond, &rv->mutex);
+  }
+  uv_mutex_unlock(&rv->mutex);
+
+  ui_attach(&rv->bridge);
+  return &rv->bridge;
+}
+
+static void ui_thread_run(void *data)
+{
+  UIBridgeData *bridge = data;
+  bridge->ui_main(bridge, bridge->ui);
+}
+
+static void ui_bridge_stop(UI *b)
+{
+  UI_CALL(b, stop, 1, b);
+  UIBridgeData *bridge = (UIBridgeData *)b;
+  uv_thread_join(&bridge->ui_thread);
+  uv_mutex_destroy(&bridge->mutex);
+  uv_cond_destroy(&bridge->cond);
+  ui_detach(b);
+  xfree(b);
+}
+static void ui_bridge_stop_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->stop(ui);
+}
+
+static void ui_bridge_resize(UI *b, int width, int height)
+{
+  UI_CALL(b, resize, 3, b, INT2PTR(width), INT2PTR(height));
+}
+static void ui_bridge_resize_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->resize(ui, PTR2INT(argv[1]), PTR2INT(argv[2]));
+}
+
+static void ui_bridge_clear(UI *b)
+{
+  UI_CALL(b, clear, 1, b);
+}
+static void ui_bridge_clear_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->clear(ui);
+}
+
+static void ui_bridge_eol_clear(UI *b)
+{
+  UI_CALL(b, eol_clear, 1, b);
+}
+static void ui_bridge_eol_clear_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->eol_clear(ui);
+}
+
+static void ui_bridge_cursor_goto(UI *b, int row, int col)
+{
+  UI_CALL(b, cursor_goto, 3, b, INT2PTR(row), INT2PTR(col));
+}
+static void ui_bridge_cursor_goto_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->cursor_goto(ui, PTR2INT(argv[1]), PTR2INT(argv[2]));
+}
+
+static void ui_bridge_update_menu(UI *b)
+{
+  UI_CALL(b, update_menu, 1, b);
+}
+static void ui_bridge_update_menu_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->update_menu(ui);
+}
+
+static void ui_bridge_busy_start(UI *b)
+{
+  UI_CALL(b, busy_start, 1, b);
+}
+static void ui_bridge_busy_start_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->busy_start(ui);
+}
+
+static void ui_bridge_busy_stop(UI *b)
+{
+  UI_CALL(b, busy_stop, 1, b);
+}
+static void ui_bridge_busy_stop_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->busy_stop(ui);
+}
+
+static void ui_bridge_mouse_on(UI *b)
+{
+  UI_CALL(b, mouse_on, 1, b);
+}
+static void ui_bridge_mouse_on_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->mouse_on(ui);
+}
+
+static void ui_bridge_mouse_off(UI *b)
+{
+  UI_CALL(b, mouse_off, 1, b);
+}
+static void ui_bridge_mouse_off_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->mouse_off(ui);
+}
+
+static void ui_bridge_mode_change(UI *b, int mode)
+{
+  UI_CALL(b, mode_change, 2, b, INT2PTR(mode));
+}
+static void ui_bridge_mode_change_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->mode_change(ui, PTR2INT(argv[1]));
+}
+
+static void ui_bridge_set_scroll_region(UI *b, int top, int bot, int left,
+    int right)
+{
+  UI_CALL(b, set_scroll_region, 5, b, INT2PTR(top), INT2PTR(bot),
+      INT2PTR(left), INT2PTR(right));
+}
+static void ui_bridge_set_scroll_region_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->set_scroll_region(ui, PTR2INT(argv[1]), PTR2INT(argv[2]),
+      PTR2INT(argv[3]), PTR2INT(argv[4]));
+}
+
+static void ui_bridge_scroll(UI *b, int count)
+{
+  UI_CALL(b, scroll, 2, b, INT2PTR(count));
+}
+static void ui_bridge_scroll_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->scroll(ui, PTR2INT(argv[1]));
+}
+
+static void ui_bridge_highlight_set(UI *b, HlAttrs attrs)
+{
+  HlAttrs *a = xmalloc(sizeof(HlAttrs));
+  *a = attrs;
+  UI_CALL(b, highlight_set, 2, b, a);
+}
+static void ui_bridge_highlight_set_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->highlight_set(ui, *((HlAttrs *)argv[1]));
+  xfree(argv[1]);
+}
+
+static void ui_bridge_put(UI *b, uint8_t *text, size_t size)
+{
+  uint8_t *t = xmalloc(8);
+  memcpy(t, text, size);
+  UI_CALL(b, put, 3, b, t, INT2PTR(size));
+}
+static void ui_bridge_put_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->put(ui, (uint8_t *)argv[1], (size_t)(uintptr_t)argv[2]);
+  xfree(argv[1]);
+}
+
+static void ui_bridge_bell(UI *b)
+{
+  UI_CALL(b, bell, 1, b);
+}
+static void ui_bridge_bell_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->bell(ui);
+}
+
+static void ui_bridge_visual_bell(UI *b)
+{
+  UI_CALL(b, visual_bell, 1, b);
+}
+static void ui_bridge_visual_bell_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->visual_bell(ui);
+}
+
+static void ui_bridge_update_fg(UI *b, int fg)
+{
+  UI_CALL(b, update_fg, 2, b, INT2PTR(fg));
+}
+static void ui_bridge_update_fg_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->update_fg(ui, PTR2INT(argv[1]));
+}
+
+static void ui_bridge_update_bg(UI *b, int bg)
+{
+  UI_CALL(b, update_bg, 2, b, INT2PTR(bg));
+}
+static void ui_bridge_update_bg_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->update_bg(ui, PTR2INT(argv[1]));
+}
+
+static void ui_bridge_flush(UI *b)
+{
+  UI_CALL(b, flush, 1, b);
+}
+static void ui_bridge_flush_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->flush(ui);
+}
+
+static void ui_bridge_suspend(UI *b)
+{
+  UIBridgeData *data = (UIBridgeData *)b;
+  uv_mutex_lock(&data->mutex);
+  UI_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_set_title(UI *b, char *title)
+{
+  UI_CALL(b, set_title, 2, b, title ? xstrdup(title) : NULL);
+}
+static void ui_bridge_set_title_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->set_title(ui, argv[1]);
+  xfree(argv[1]);
+}
+
+static void ui_bridge_set_icon(UI *b, char *icon)
+{
+  UI_CALL(b, set_icon, 2, b, icon ? xstrdup(icon) : NULL);
+}
+static void ui_bridge_set_icon_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->set_icon(ui, argv[1]);
+  xfree(argv[1]);
+}
+
+static void ui_bridge_set_encoding(UI *b, char* enc)
+{
+  UI_CALL(b, set_encoding, 2, b, xstrdup(enc));
+}
+static void ui_bridge_set_encoding_event(void **argv)
+{
+  UI *ui = UI(argv[0]);
+  ui->set_encoding(ui, argv[1]);
+  xfree(argv[1]);
+}
diff --git a/src/nvim/ui_bridge.h b/src/nvim/ui_bridge.h
new file mode 100644
index 0000000000..76e9e27989
--- /dev/null
+++ b/src/nvim/ui_bridge.h
@@ -0,0 +1,40 @@
+// Bridge used for communication between a builtin UI thread and nvim core
+#ifndef NVIM_UI_BRIDGE_H
+#define NVIM_UI_BRIDGE_H
+
+#include <uv.h>
+
+#include "nvim/ui.h"
+#include "nvim/event/defs.h"
+
+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 it's 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;
+};
+
+#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