31 files changed, 441 insertions, 454 deletions

diff --git a/src/nvim/CMakeLists.txt b/src/nvim/CMakeLists.txt
index 3b05c7329c..184bcc0548 100644
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -77,7 +77,6 @@ set(CONV_SOURCES
   search.c
   sha256.c
   spell.c
-  strings.c
   syntax.c
   tag.c
   term.c
diff --git a/src/nvim/charset.c b/src/nvim/charset.c
index bbe80a519c..9e5194a5df 100644
--- a/src/nvim/charset.c
+++ b/src/nvim/charset.c
@@ -1855,7 +1855,7 @@ int hexhex2nr(char_u *p)
 #endif // if defined(FEAT_TERMRESPONSE) || defined(FEAT_GUI_GTK)
        // || defined(PROTO)
 
-/// Return TRUE if "str" starts with a backslash that should be removed.
+/// Return true if "str" starts with a backslash that should be removed.
 /// For WIN32 this is only done when the character after the
 /// backslash is not a normal file name character.
 /// '$' is a valid file name character, we don't remove the backslash before
@@ -1869,8 +1869,8 @@ int hexhex2nr(char_u *p)
 ///
 /// @param str
 ///
-/// @return TRUE if `str` starts with a backslash that should be removed.
-int rem_backslash(char_u *str)
+/// @return true if `str` starts with a backslash that should be removed.
+bool rem_backslash(const char_u *str)
 {
 #ifdef BACKSLASH_IN_FILENAME
   return str[0] == '\\'
diff --git a/src/nvim/digraph.c b/src/nvim/digraph.c
index 6587a43452..2b5fdea2fe 100644
--- a/src/nvim/digraph.c
+++ b/src/nvim/digraph.c
@@ -1813,10 +1813,10 @@ void ex_loadkeymap(exarg_T *eap)
     if ((*p != '"') && (*p != NUL)) {
       kmap_T *kp = GA_APPEND_VIA_PTR(kmap_T, &curbuf->b_kmap_ga);
       s = skiptowhite(p);
-      kp->from = vim_strnsave(p, (int)(s - p));
+      kp->from = vim_strnsave(p, (size_t)(s - p));
       p = skipwhite(s);
       s = skiptowhite(p);
-      kp->to = vim_strnsave(p, (int)(s - p));
+      kp->to = vim_strnsave(p, (size_t)(s - p));
 
       if ((STRLEN(kp->from) + STRLEN(kp->to) >= KMAP_LLEN)
           || (*kp->from == NUL)
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 8be25bc34e..be69bdbe61 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -6593,7 +6593,7 @@ static struct fst {
   {"synconcealed",    2, 2, f_synconcealed},
   {"synstack",        2, 2, f_synstack},
   {"system",          1, 2, f_system},
-  {"systemlist",      1, 2, f_systemlist},
+  {"systemlist",      1, 3, f_systemlist},
   {"tabpagebuflist",  0, 1, f_tabpagebuflist},
   {"tabpagenr",       0, 1, f_tabpagenr},
   {"tabpagewinnr",    1, 2, f_tabpagewinnr},
@@ -14523,7 +14523,7 @@ static void f_synstack(typval_T *argvars, typval_T *rettv)
   }
 }
 
-static list_T* string_to_list(char_u *str, size_t len)
+static list_T* string_to_list(char_u *str, size_t len, bool keepempty)
 {
   list_T *list = list_alloc();
 
@@ -14543,6 +14543,11 @@ static list_T* string_to_list(char_u *str, size_t len)
     list_append(list, li);
   }
 
+  // Optionally retain final newline, if present
+  if (keepempty && str[len-1] == NL) {
+      list_append_string(list, (char_u*)"", 0);
+  }
+
   return list;
 }
 
@@ -14585,7 +14590,11 @@ static void get_system_output_as_rettv(typval_T *argvars, typval_T *rettv,
   }
 
   if (retlist) {
-    rettv->vval.v_list = string_to_list((char_u *) res, nread);
+    int keepempty = 0;
+    if (argvars[1].v_type != VAR_UNKNOWN && argvars[2].v_type != VAR_UNKNOWN) {
+      keepempty = get_tv_number(&argvars[2]);
+    }
+    rettv->vval.v_list = string_to_list((char_u *) res, nread, keepempty != 0);
     rettv->vval.v_list->lv_refcount++;
     rettv->v_type = VAR_LIST;
 
@@ -19723,7 +19732,7 @@ static void apply_job_autocmds(int id, char *name, char *type,
     str_slot->li_tv.v_type = VAR_LIST;
     str_slot->li_tv.v_lock = 0;
     str_slot->li_tv.vval.v_list =
-      string_to_list((char_u *) received, received_len);
+      string_to_list((char_u *) received, received_len, false);
     str_slot->li_tv.vval.v_list->lv_refcount++;
     list_append(list, str_slot);
 
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 556e0c01e3..44caa67847 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -47,6 +47,7 @@
 #include "nvim/garray.h"
 #include "nvim/memory.h"
 #include "nvim/move.h"
+#include "nvim/mouse.h"
 #include "nvim/normal.h"
 #include "nvim/ops.h"
 #include "nvim/option.h"
@@ -3602,10 +3603,16 @@ void do_sub(exarg_T *eap)
       eap->flags = EXFLAG_PRINT;
     }
 
-    do_join(eap->line2 - eap->line1 + 1, FALSE, TRUE, FALSE, true);
-    sub_nlines = sub_nsubs = eap->line2 - eap->line1 + 1;
-    do_sub_msg(false);
-    ex_may_print(eap);
+    linenr_T joined_lines_count = eap->line2 < curbuf->b_ml.ml_line_count
+                                  ? eap->line2 - eap->line1 + 2
+                                  : eap->line2 - eap->line1 + 1;
+    if (joined_lines_count > 1) {
+      do_join(joined_lines_count, FALSE, TRUE, FALSE, true);
+      sub_nsubs = joined_lines_count - 1;
+      sub_nlines = 1;
+      do_sub_msg(false);
+      ex_may_print(eap);
+    }
 
     return;
   }
diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index 24a1ccf85d..794e9930b9 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -157,7 +157,6 @@ void do_debug(char_u *cmd)
 
   /* Make sure we are in raw mode and start termcap mode.  Might have side
    * effects... */
-  settmode(TMODE_RAW);
   starttermcap();
 
   ++RedrawingDisabled;          /* don't redisplay the window */
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 3967c916bb..e180be4421 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -5107,7 +5107,6 @@ static void ex_highlight(exarg_T *eap)
 void not_exiting(void)
 {
   exiting = FALSE;
-  settmode(TMODE_RAW);
 }
 
 /*
@@ -5994,7 +5993,6 @@ do_exedit (
 {
   int n;
   int need_hide;
-  int exmode_was = exmode_active;
 
   /*
    * ":vi" command ends Ex mode.
@@ -6014,8 +6012,6 @@ do_exedit (
           eap->nextcmd = NULL;
         }
 
-        if (exmode_was != EXMODE_VIM)
-          settmode(TMODE_RAW);
         RedrawingDisabled = 0;
         no_wait_return = 0;
         need_wait_return = FALSE;
@@ -6446,7 +6442,7 @@ static void ex_winsize(exarg_T *eap)
   p = arg;
   h = getdigits(&arg);
   if (*p != NUL && *arg == NUL)
-    set_shellsize(w, h, TRUE);
+    screen_resize(w, h, TRUE);
   else
     EMSG(_("E465: :winsize requires two number arguments"));
 }
@@ -7482,7 +7478,7 @@ static void ex_tag_cmd(exarg_T *eap, char_u *name)
  * If found return one of the SPEC_ values and set "*usedlen" to the length of
  * the variable.  Otherwise return -1 and "*usedlen" is unchanged.
  */
-int find_cmdline_var(char_u *src, int *usedlen)
+int find_cmdline_var(const char_u *src, int *usedlen) FUNC_ATTR_NONNULL_ALL
 {
   int len;
   int i;
diff --git a/src/nvim/ex_eval.c b/src/nvim/ex_eval.c
index ef3facb18b..196f8e6136 100644
--- a/src/nvim/ex_eval.c
+++ b/src/nvim/ex_eval.c
@@ -386,21 +386,19 @@ int do_intthrow(struct condstack *cstack)
 char_u *get_exception_string(void *value, int type, char_u *cmdname, int *should_free)
 {
   char_u      *ret, *mesg;
-  int cmdlen;
   char_u      *p, *val;
 
   if (type == ET_ERROR) {
     *should_free = FALSE;
     mesg = ((struct msglist *)value)->throw_msg;
     if (cmdname != NULL && *cmdname != NUL) {
-      cmdlen = (int)STRLEN(cmdname);
-      ret = vim_strnsave((char_u *)"Vim(",
-          4 + cmdlen + 2 + (int)STRLEN(mesg));
+      size_t cmdlen = STRLEN(cmdname);
+      ret = vim_strnsave((char_u *)"Vim(", 4 + cmdlen + 2 + STRLEN(mesg));
       STRCPY(&ret[4], cmdname);
       STRCPY(&ret[4 + cmdlen], "):");
       val = ret + 4 + cmdlen + 2;
     } else {
-      ret = vim_strnsave((char_u *)"Vim:", 4 + (int)STRLEN(mesg));
+      ret = vim_strnsave((char_u *)"Vim:", 4 + STRLEN(mesg));
       val = ret + 4;
     }
 
@@ -708,7 +706,7 @@ static void report_pending(int action, int pending, void *value)
     if (pending & CSTP_THROW) {
       vim_snprintf((char *)IObuff, IOSIZE,
           (char *)mesg, _("Exception"));
-      mesg = vim_strnsave(IObuff, (int)STRLEN(IObuff) + 4);
+      mesg = vim_strnsave(IObuff, STRLEN(IObuff) + 4);
       STRCAT(mesg, ": %s");
       s = (char *)((except_T *)value)->value;
     } else if ((pending & CSTP_ERROR) && (pending & CSTP_INTERRUPT))
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index 70db2dc479..e56592923d 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -48,6 +48,7 @@
 #include "nvim/keymap.h"
 #include "nvim/garray.h"
 #include "nvim/move.h"
+#include "nvim/mouse.h"
 #include "nvim/ops.h"
 #include "nvim/option.h"
 #include "nvim/os_unix.h"
@@ -270,10 +271,6 @@ getcmdline (
   setmouse();
   ui_cursor_shape();            /* may show different cursor shape */
 
-  /* When inside an autocommand for writing "exiting" may be set and
-  * terminal mode set to cooked.  Need to set raw mode here then. */
-  settmode(TMODE_RAW);
-
   init_history();
   hiscnt = hislen;              /* set hiscnt to impossible history value */
   histype = hist_char2type(firstc);
diff --git a/src/nvim/file_search.c b/src/nvim/file_search.c
index a51f088586..9267e7991c 100644
--- a/src/nvim/file_search.c
+++ b/src/nvim/file_search.c
@@ -308,7 +308,7 @@ vim_findfile_init (
       && (vim_ispathsep(path[1]) || path[1] == NUL)
       && (!tagfile || vim_strchr(p_cpo, CPO_DOTTAG) == NULL)
       && rel_fname != NULL) {
-    int len = (int)(path_tail(rel_fname) - rel_fname);
+    size_t len = (size_t)(path_tail(rel_fname) - rel_fname);
 
     if (!vim_isAbsName(rel_fname) && len + 1 < MAXPATHL) {
       /* Make the start dir an absolute path name. */
@@ -375,8 +375,9 @@ vim_findfile_init (
       search_ctx->ffsc_stopdirs_v = ptr;
       walker = vim_strchr(walker, ';');
       if (walker) {
+        assert(walker - helper >= 0);
         search_ctx->ffsc_stopdirs_v[dircount-1] =
-          vim_strnsave(helper, (int)(walker - helper));
+          vim_strnsave(helper, (size_t)(walker - helper));
         walker++;
       } else
         /* this might be "", which means ascent till top
@@ -404,7 +405,8 @@ vim_findfile_init (
     char    *errpt;
 
     /* save the fix part of the path */
-    search_ctx->ffsc_fix_path = vim_strnsave(path, (int)(wc_part - path));
+    assert(wc_part - path >= 0);
+    search_ctx->ffsc_fix_path = vim_strnsave(path, (size_t)(wc_part - path));
 
     /*
      * copy wc_path and add restricts to the '**' wildcard.
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index 3be9d89d87..021b12208e 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -1812,7 +1812,6 @@ failed:
      * Switch on raw mode now and clear the screen.
      */
     if (read_stdin) {
-      settmode(TMODE_RAW);              /* set to raw mode */
       starttermcap();
       screenclear();
     }
@@ -2387,9 +2386,6 @@ buf_write (
   else
     overwriting = FALSE;
 
-  if (exiting)
-    settmode(TMODE_COOK);           /* when exiting allow typeahead now */
-
   ++no_wait_return;                 /* don't wait for return yet */
 
   /*
diff --git a/src/nvim/macros.h b/src/nvim/macros.h
index f8fd6ac6a2..215ad3a1f7 100644
--- a/src/nvim/macros.h
+++ b/src/nvim/macros.h
@@ -143,8 +143,9 @@
 /* get length of multi-byte char, not including composing chars */
 # define mb_cptr2len(p)     (enc_utf8 ? utf_ptr2len(p) : (*mb_ptr2len)(p))
 
-# define MB_COPY_CHAR(f, \
-                      t) if (has_mbyte) mb_copy_char(&f, &t); else *t++ = *f++
+# define MB_COPY_CHAR(f, t) \
+  if (has_mbyte) mb_copy_char((const char_u **)(&f), &t); \
+  else *t++ = *f++
 # define MB_CHARLEN(p)      (has_mbyte ? mb_charlen(p) : (int)STRLEN(p))
 # define MB_CHAR2LEN(c)     (has_mbyte ? mb_char2len(c) : 1)
 # define PTR2CHAR(p)        (has_mbyte ? mb_ptr2char(p) : (int)*(p))
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 68ae000c35..8e19cf3686 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -43,6 +43,7 @@
 #include "nvim/log.h"
 #include "nvim/memory.h"
 #include "nvim/move.h"
+#include "nvim/mouse.h"
 #include "nvim/normal.h"
 #include "nvim/ops.h"
 #include "nvim/option.h"
@@ -60,10 +61,13 @@
 #include "nvim/os/time.h"
 #include "nvim/os/input.h"
 #include "nvim/os/os.h"
+#include "nvim/os/time.h"
+#include "nvim/os/event.h"
 #include "nvim/os/signal.h"
 #include "nvim/msgpack_rpc/helpers.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
+#include "nvim/api/private/handle.h"
 
 /* Maximum number of commands from + or -c arguments. */
 #define MAX_ARG_CMDS 10
@@ -142,13 +146,60 @@ static char *(main_errors[]) =
 #define ME_INVALID_ARG          5
 };
 
+/// Performs early initialization.
+///
+/// Needed for unit tests. Must be called after `time_init()`.
+void early_init(void)
+{
+  handle_init();
+
+  (void)mb_init();      // init mb_bytelen_tab[] to ones
+  eval_init();          // init global variables
+
+#ifdef __QNXNTO__
+  qnx_init();           // PhAttach() for clipboard, (and gui)
+#endif
+
+  // Init the table of Normal mode commands.
+  init_normal_cmds();
+
+#if defined(HAVE_LOCALE_H) || defined(X_LOCALE)
+  // Setup to use the current locale (for ctype() and many other things).
+  // NOTE: Translated messages with encodings other than latin1 will not
+  // work until set_init_1() has been called!
+  init_locale();
+#endif
+
+  // Allocate the first window and buffer.
+  // Can't do anything without it, exit when it fails.
+  if (!win_alloc_first()) {
+    mch_exit(0);
+  }
+
+  init_yank();                  // init yank buffers
+
+  alist_init(&global_alist);    // Init the argument list to empty.
+  global_alist.id = 0;
+
+  // Set the default values for the options.
+  // NOTE: Non-latin1 translated messages are working only after this,
+  // because this is where "has_mbyte" will be set, which is used by
+  // msg_outtrans_len_attr().
+  // First find out the home directory, needed to expand "~" in options.
+  init_homedir();               // find real value of $HOME
+  set_init_1();
+  TIME_MSG("inits 1");
+
+  set_lang_var();               // set v:lang and v:ctype
+}
+
 #ifndef NO_VIM_MAIN     /* skip this for unittests */
 int main(int argc, char **argv)
 {
   char_u      *fname = NULL;            /* file name from command line */
   mparm_T params;                       /* various parameters passed between
                                          * main() and other functions. */
-  mch_early_init();
+  time_init();
 
   /* Many variables are in "params" so that we can pass them to invoked
    * functions without a lot of arguments.  "argc" and "argv" are also
@@ -157,24 +208,7 @@ int main(int argc, char **argv)
 
   init_startuptime(&params);
 
-  (void)mb_init();      /* init mb_bytelen_tab[] to ones */
-  eval_init();          /* init global variables */
-
-#ifdef __QNXNTO__
-  qnx_init();           /* PhAttach() for clipboard, (and gui) */
-#endif
-
-  /* Init the table of Normal mode commands. */
-  init_normal_cmds();
-
-#if defined(HAVE_LOCALE_H) || defined(X_LOCALE)
-  /*
-   * Setup to use the current locale (for ctype() and many other things).
-   * NOTE: Translated messages with encodings other than latin1 will not
-   * work until set_init_1() has been called!
-   */
-  init_locale();
-#endif
+  early_init();
 
   /*
    * Check if we have an interactive window.
@@ -185,32 +219,6 @@ int main(int argc, char **argv)
   check_and_set_isatty(&params);
 
   /*
-   * Allocate the first window and buffer.
-   * Can't do anything without it, exit when it fails.
-   */
-  if (win_alloc_first() == FAIL)
-    mch_exit(0);
-
-  init_yank();                  /* init yank buffers */
-
-  alist_init(&global_alist);    /* Init the argument list to empty. */
-  global_alist.id = 0;
-
-  /*
-   * Set the default values for the options.
-   * NOTE: Non-latin1 translated messages are working only after this,
-   * because this is where "has_mbyte" will be set, which is used by
-   * msg_outtrans_len_attr().
-   * First find out the home directory, needed to expand "~" in options.
-   */
-  init_homedir();               /* find real value of $HOME */
-  set_init_1();
-  TIME_MSG("inits 1");
-
-  set_lang_var();               /* set v:lang and v:ctype */
-
-
-  /*
    * Figure out the way to work from the command name argv[0].
    * "vimdiff" starts diff mode, "rvim" sets "restricted", etc.
    */
@@ -252,14 +260,12 @@ int main(int argc, char **argv)
    */
 
 
-  /*
-   * mch_init() sets up the terminal (window) for use.  This must be
-   * done after resetting full_screen, otherwise it may move the cursor
-   * Note that we may use mch_exit() before mch_init()!
-   */
-  mch_init();
+  // term_init() sets up the terminal (window) for use.  This must be
+  // done after resetting full_screen, otherwise it may move the cursor
+  term_init();
   TIME_MSG("shell init");
 
+  event_init();
 
   if (!embedded_mode) {
     // Print a warning if stdout is not a terminal.
@@ -276,7 +282,7 @@ int main(int argc, char **argv)
       // In embedded mode don't do terminal-related initializations, assume an
       // initial screen size of 80x20
       full_screen = true;
-      set_shellsize(80, 20, false);
+      screen_resize(80, 20, false);
     } else {
       // set terminal name and get terminal capabilities (will set full_screen)
       // Do some initialization of the screen
diff --git a/src/nvim/mbyte.c b/src/nvim/mbyte.c
index d79a46ceaa..9b4513e979 100644
--- a/src/nvim/mbyte.c
+++ b/src/nvim/mbyte.c
@@ -3002,7 +3002,7 @@ int utf_head_off(const char_u *base, const char_u *p)
 /*
  * Copy a character from "*fp" to "*tp" and advance the pointers.
  */
-void mb_copy_char(char_u **fp, char_u **tp)
+void mb_copy_char(const char_u **fp, char_u **tp)
 {
   int l = (*mb_ptr2len)(*fp);
 
diff --git a/src/nvim/memory.c b/src/nvim/memory.c
index 4c5a45b8b6..f959ea55e4 100644
--- a/src/nvim/memory.c
+++ b/src/nvim/memory.c
@@ -305,6 +305,7 @@ char *xstpncpy(char *restrict dst, const char *restrict src, size_t maxlen)
 /// @param size Size of destination buffer
 /// @return Length of the source string (i.e.: strlen(src))
 size_t xstrlcpy(char *restrict dst, const char *restrict src, size_t size)
+  FUNC_ATTR_NONNULL_ALL
 {
     size_t ret = strlen(src);
 
@@ -348,7 +349,7 @@ char *xstrdup(const char *str)
 /// @param c   The byte to search for.
 /// @param len The length of the memory object.
 /// @returns a pointer to the found byte in src[len], or NULL.
-void *xmemrchr(void *src, uint8_t c, size_t len)
+void *xmemrchr(const void *src, uint8_t c, size_t len)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
 {
   while (len--) {
diff --git a/src/nvim/misc1.c b/src/nvim/misc1.c
index 230e198121..fc848466c6 100644
--- a/src/nvim/misc1.c
+++ b/src/nvim/misc1.c
@@ -42,6 +42,7 @@
 #include "nvim/misc2.h"
 #include "nvim/garray.h"
 #include "nvim/move.h"
+#include "nvim/mouse.h"
 #include "nvim/option.h"
 #include "nvim/os_unix.h"
 #include "nvim/path.h"
@@ -2286,8 +2287,6 @@ int ask_yesno(char_u *str, int direct)
   int r = ' ';
   int save_State = State;
 
-  if (exiting)                  /* put terminal in raw mode for this question */
-    settmode(TMODE_RAW);
   ++no_wait_return;
 #ifdef USE_ON_FLY_SCROLL
   dont_scroll = TRUE;           /* disallow scrolling here */
diff --git a/src/nvim/mouse.c b/src/nvim/mouse.c
index 7fc581a7c0..439cdbd5c8 100644
--- a/src/nvim/mouse.c
+++ b/src/nvim/mouse.c
@@ -2,8 +2,12 @@
 
 #include "nvim/mouse.h"
 #include "nvim/vim.h"
-#include "nvim/screen.h"
+#include "nvim/ascii.h"
 #include "nvim/window.h"
+#include "nvim/strings.h"
+#include "nvim/screen.h"
+#include "nvim/ui.h"
+#include "nvim/os_unix.h"
 #include "nvim/term.h"
 #include "nvim/fold.h"
 #include "nvim/diff.h"
@@ -165,11 +169,9 @@ retnomove:
     // (MOUSE_FOCUS was set above if we dragged first).
     if (dragwin == NULL || (flags & MOUSE_RELEASED))
       win_enter(wp, true);                      // can make wp invalid!
-# ifdef CHECK_DOUBLE_CLICK
     // set topline, to be able to check for double click ourselves
     if (curwin != old_curwin)
       set_mouse_topline(curwin);
-# endif
     if (on_status_line) {                       // In (or below) status line
       // Don't use start_arrow() if we're in the same window
       if (curwin == old_curwin)
@@ -436,3 +438,62 @@ win_T *mouse_find_win(int *rowp, int *colp)
   }
   return fp->fr_win;
 }
+
+/*
+ * setmouse() - switch mouse on/off depending on current mode and 'mouse'
+ */
+void setmouse(void)
+{
+  int checkfor;
+
+
+  /* be quick when mouse is off */
+  if (*p_mouse == NUL)
+    return;
+
+  /* don't switch mouse on when not in raw mode (Ex mode) */
+  if (cur_tmode != TMODE_RAW) {
+    mch_setmouse(false);
+    return;
+  }
+
+  if (VIsual_active)
+    checkfor = MOUSE_VISUAL;
+  else if (State == HITRETURN || State == ASKMORE || State == SETWSIZE)
+    checkfor = MOUSE_RETURN;
+  else if (State & INSERT)
+    checkfor = MOUSE_INSERT;
+  else if (State & CMDLINE)
+    checkfor = MOUSE_COMMAND;
+  else if (State == CONFIRM || State == EXTERNCMD)
+    checkfor = ' ';     /* don't use mouse for ":confirm" or ":!cmd" */
+  else
+    checkfor = MOUSE_NORMAL;        /* assume normal mode */
+
+  if (mouse_has(checkfor))
+    mch_setmouse(true);
+  else
+    mch_setmouse(false);
+}
+
+/*
+ * Return true if
+ * - "c" is in 'mouse', or
+ * - 'a' is in 'mouse' and "c" is in MOUSE_A, or
+ * - the current buffer is a help file and 'h' is in 'mouse' and we are in a
+ *   normal editing mode (not at hit-return message).
+ */
+int mouse_has(int c)
+{
+  for (char_u *p = p_mouse; *p; ++p)
+    switch (*p) {
+    case 'a': if (vim_strchr((char_u *)MOUSE_A, c) != NULL)
+        return true;
+      break;
+    case MOUSE_HELP: if (c != MOUSE_RETURN && curbuf->b_help)
+        return true;
+      break;
+    default: if (c == *p) return true; break;
+    }
+  return false;
+}
diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index 0a43d59607..1b21100933 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -46,6 +46,7 @@
 #include "nvim/misc2.h"
 #include "nvim/keymap.h"
 #include "nvim/move.h"
+#include "nvim/mouse.h"
 #include "nvim/ops.h"
 #include "nvim/option.h"
 #include "nvim/quickfix.h"
@@ -7374,3 +7375,11 @@ static void nv_cursorhold(cmdarg_T *cap)
   did_cursorhold = true;
   cap->retval |= CA_COMMAND_BUSY;       /* don't call edit() now */
 }
+
+/*
+ * Return TRUE when 'mousemodel' is set to "popup" or "popup_setpos".
+ */
+static int mouse_model_popup(void)
+{
+  return p_mousem[0] == 'p';
+}
diff --git a/src/nvim/option.c b/src/nvim/option.c
index ee70b5bf8a..2882d7a511 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -66,6 +66,7 @@
 #include "nvim/garray.h"
 #include "nvim/cursor_shape.h"
 #include "nvim/move.h"
+#include "nvim/mouse.h"
 #include "nvim/normal.h"
 #include "nvim/os_unix.h"
 #include "nvim/path.h"
@@ -5540,7 +5541,7 @@ set_num_option (
       *pp = old_value;
     else if (full_screen
              )
-      set_shellsize((int)Columns, (int)Rows, TRUE);
+      screen_resize((int)Columns, (int)Rows, TRUE);
     else {
       /* Postpone the resizing; check the size and cmdline position for
        * messages. */
diff --git a/src/nvim/os/env.c b/src/nvim/os/env.c
index 3aefbc39d1..b2e62453c5 100644
--- a/src/nvim/os/env.c
+++ b/src/nvim/os/env.c
@@ -43,7 +43,7 @@ char *os_getenvname_at_index(size_t index)
   if (str == NULL) {
     return NULL;
   }
-  int namesize = 0;
+  size_t namesize = 0;
   while (str[namesize] != '=' && str[namesize] != NUL) {
     namesize++;
   }
diff --git a/src/nvim/os/shell.c b/src/nvim/os/shell.c
index 1b279f18f5..cdd85e4e96 100644
--- a/src/nvim/os/shell.c
+++ b/src/nvim/os/shell.c
@@ -104,14 +104,10 @@ int os_call_shell(char_u *cmd, ShellOpts opts, char_u *extra_arg)
 {
   DynamicBuffer input = DYNAMIC_BUFFER_INIT;
   char *output = NULL, **output_ptr = NULL;
-  int current_state = State, old_mode = cur_tmode;
+  int current_state = State;
   bool forward_output = true;
   out_flush();
 
-  if (opts & kShellOptCooked) {
-    settmode(TMODE_COOK);
-  }
-
   // While the child is running, ignore terminating signals
   signal_reject_deadly();
 
@@ -155,10 +151,6 @@ int os_call_shell(char_u *cmd, ShellOpts opts, char_u *extra_arg)
     msg_putchar('\n');
   }
 
-  if (old_mode == TMODE_RAW) {
-    // restore mode
-    settmode(TMODE_RAW);
-  }
   State = current_state;
   signal_accept_deadly();
 
diff --git a/src/nvim/os/time.c b/src/nvim/os/time.c
index a4871ef499..3794e813d2 100644
--- a/src/nvim/os/time.c
+++ b/src/nvim/os/time.c
@@ -6,6 +6,7 @@
 #include <uv.h>
 
 #include "nvim/os/time.h"
+#include "nvim/os/event.h"
 #include "nvim/vim.h"
 #include "nvim/term.h"
 
@@ -38,31 +39,22 @@ uint64_t os_hrtime(void)
 /// @param ignoreinput If true, allow a SIGINT to interrupt us
 void os_delay(uint64_t milliseconds, bool ignoreinput)
 {
-  os_microdelay(milliseconds * 1000, ignoreinput);
+  if (ignoreinput) {
+    if (milliseconds > INT_MAX) {
+      milliseconds = INT_MAX;
+    }
+    event_poll_until((int)milliseconds, got_int);
+  } else {
+    os_microdelay(milliseconds * 1000);
+  }
 }
 
 /// Sleeps for a certain amount of microseconds
 ///
 /// @param microseconds Number of microseconds to sleep
-/// @param ignoreinput If true, allow a SIGINT to interrupt us
-void os_microdelay(uint64_t microseconds, bool ignoreinput)
+void os_microdelay(uint64_t microseconds)
 {
-  int old_tmode;
-
-  if (ignoreinput) {
-    // Go to cooked mode without echo, to allow SIGINT interrupting us
-    // here
-    old_tmode = curr_tmode;
-
-    if (curr_tmode == TMODE_RAW)
-      settmode(TMODE_SLEEP);
-
-    microdelay(microseconds);
-
-    settmode(old_tmode);
-  } else {
-    microdelay(microseconds);
-  }
+  microdelay(microseconds);
 }
 
 /// Portable version of POSIX localtime_r()
diff --git a/src/nvim/os_unix.c b/src/nvim/os_unix.c
index 3bf1198b46..677976e3e1 100644
--- a/src/nvim/os_unix.c
+++ b/src/nvim/os_unix.c
@@ -1,6 +1,5 @@
 /*
  * VIM - Vi IMproved	by Bram Moolenaar
- *	      OS/2 port by Paul Slootman
  *	      VMS merge by Zoltan Arpadffy
  *
  * Do ":help uganda"  in Vim to read copying and usage conditions.
@@ -10,7 +9,7 @@
 
 /*
  * os_unix.c -- code for all flavors of Unix (BSD, SYSV, SVR4, POSIX, ...)
- *	     Also for BeOS and Atari MiNT.
+ *	     Also for BeOS
  *
  * A lot of this file was originally written by Juergen Weigert and later
  * changed beyond recognition.
@@ -38,6 +37,7 @@
 #include "nvim/message.h"
 #include "nvim/misc1.h"
 #include "nvim/misc2.h"
+#include "nvim/mouse.h"
 #include "nvim/garray.h"
 #include "nvim/path.h"
 #include "nvim/screen.h"
@@ -82,47 +82,22 @@ static int did_set_title = FALSE;
 static char_u   *oldicon = NULL;
 static int did_set_icon = FALSE;
 
-
-
-/*
- * Write s[len] to the screen.
- */
-void mch_write(char_u *s, int len)
-{
-  if (embedded_mode) {
-    // TODO(tarruda): This is a temporary hack to stop Neovim from writing
-    // messages to stdout in embedded mode. In the future, embedded mode will
-    // be the only possibility(GUIs will always start neovim with a msgpack-rpc
-    // over stdio) and this function won't exist.
-    //
-    // The reason for this is because before Neovim fully migrates to a
-    // msgpack-rpc-driven architecture, we must have a fully functional
-    // UI working
-    return;
-  }
-
-  ignored = (int)write(1, (char *)s, len);
-  if (p_wd)             /* Unix is too fast, slow down a bit more */
-    os_microdelay(p_wd, false);
-}
-
 /*
  * If the machine has job control, use it to suspend the program,
  * otherwise fake it by starting a new shell.
  */
 void mch_suspend(void)
 {
-  /* BeOS does have SIGTSTP, but it doesn't work. */
-#if defined(SIGTSTP) && !defined(__BEOS__)
+#if defined(SIGTSTP)
   out_flush();              /* needed to make cursor visible on some systems */
   settmode(TMODE_COOK);
   out_flush();              /* needed to disable mouse on some systems */
 
-
+  // Note: compiler defines _REENTRANT when given -pthread flag.
 # if defined(_REENTRANT) && defined(SIGCONT)
   sigcont_received = FALSE;
 # endif
-  kill(0, SIGTSTP);         /* send ourselves a STOP signal */
+  uv_kill(0, SIGTSTP);         // send ourselves a STOP signal
 # if defined(_REENTRANT) && defined(SIGCONT)
   /*
    * Wait for the SIGCONT signal to be handled. It generally happens
@@ -154,20 +129,6 @@ void mch_suspend(void)
 #endif
 }
 
-void mch_init(void)
-{
-  Columns = 80;
-  Rows = 24;
-
-  out_flush();
-
-#ifdef MACOS_CONVERT
-  mac_conv_init();
-#endif
-
-  event_init();
-}
-
 static int get_x11_title(int test_only)
 {
   return FALSE;
@@ -478,12 +439,6 @@ int mch_nodetype(char_u *name)
   return NODE_WRITABLE;
 }
 
-void mch_early_init(void)
-{
-  handle_init();
-  time_init();
-}
-
 #if defined(EXITFREE) || defined(PROTO)
 void mch_free_mem(void)
 {
@@ -569,9 +524,8 @@ void mch_settmode(int tmode)
 {
   static int first = TRUE;
 
-  /* Why is NeXT excluded here (and not in os_unixx.h)? */
 #if defined(ECHOE) && defined(ICANON) && (defined(HAVE_TERMIO_H) || \
-  defined(HAVE_TERMIOS_H)) && !defined(__NeXT__)
+  defined(HAVE_TERMIOS_H))
   /*
    * for "new" tty systems
    */
@@ -599,9 +553,8 @@ void mch_settmode(int tmode)
      */
     tnew.c_iflag &= ~ICRNL;
     tnew.c_lflag &= ~(ICANON | ECHO | ISIG | ECHOE
-# if defined(IEXTEN) && !defined(__MINT__)
+# if defined(IEXTEN)
                       | IEXTEN      /* IEXTEN enables typing ^V on SOLARIS */
-                                    /* but it breaks function keys on MINT */
 # endif
                       );
 # ifdef ONLCR       /* don't map NL -> CR NL, we do it ourselves */
@@ -667,9 +620,8 @@ void get_stty(void)
   char_u buf[2];
   char_u  *p;
 
-  /* Why is NeXT excluded here (and not in os_unixx.h)? */
 #if defined(ECHOE) && defined(ICANON) && (defined(HAVE_TERMIO_H) || \
-  defined(HAVE_TERMIOS_H)) && !defined(__NeXT__)
+  defined(HAVE_TERMIOS_H))
   /* for "new" tty systems */
 # ifdef HAVE_TERMIOS_H
   struct termios keys;
diff --git a/src/nvim/os_unix_defs.h b/src/nvim/os_unix_defs.h
index 2a44ec3412..ebea86ebcf 100644
--- a/src/nvim/os_unix_defs.h
+++ b/src/nvim/os_unix_defs.h
@@ -8,17 +8,13 @@
  * Do ":help credits" in Vim to see a list of people who contributed.
  */
 
-/*
- * NextStep has a problem with configure, undefine a few things:
- */
-
 #include <stdio.h>
 #include <ctype.h>
 
-# include <sys/types.h>
-# include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/stat.h>
 
-# include <stdlib.h>
+#include <stdlib.h>
 
 #ifdef HAVE_UNISTD_H
 # include <unistd.h>
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index 2dbf3f8888..0225eb72c1 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -103,6 +103,7 @@
 #include "nvim/ex_cmds.h"
 #include "nvim/ex_cmds2.h"
 #include "nvim/ex_getln.h"
+#include "nvim/edit.h"
 #include "nvim/farsi.h"
 #include "nvim/fileio.h"
 #include "nvim/fold.h"
@@ -120,6 +121,7 @@
 #include "nvim/move.h"
 #include "nvim/normal.h"
 #include "nvim/option.h"
+#include "nvim/os_unix.h"
 #include "nvim/path.h"
 #include "nvim/popupmnu.h"
 #include "nvim/quickfix.h"
@@ -129,6 +131,7 @@
 #include "nvim/strings.h"
 #include "nvim/syntax.h"
 #include "nvim/term.h"
+#include "nvim/ui.h"
 #include "nvim/undo.h"
 #include "nvim/version.h"
 #include "nvim/window.h"
@@ -8117,3 +8120,98 @@ int screen_screenrow(void)
   return screen_cur_row;
 }
 
+/*
+ * Set size of the Vim shell.
+ * If 'mustset' is TRUE, we must set Rows and Columns, do not get the real
+ * window size (this is used for the :win command).
+ * If 'mustset' is FALSE, we may try to get the real window size and if
+ * it fails use 'width' and 'height'.
+ */
+void screen_resize(int width, int height, int mustset)
+{
+  static int busy = FALSE;
+
+  /*
+   * Avoid recursiveness, can happen when setting the window size causes
+   * another window-changed signal.
+   */
+  if (busy)
+    return;
+
+  if (width < 0 || height < 0)      /* just checking... */
+    return;
+
+  if (State == HITRETURN || State == SETWSIZE) {
+    /* postpone the resizing */
+    State = SETWSIZE;
+    return;
+  }
+
+  /* curwin->w_buffer can be NULL when we are closing a window and the
+   * buffer has already been closed and removing a scrollbar causes a resize
+   * event. Don't resize then, it will happen after entering another buffer.
+   */
+  if (curwin->w_buffer == NULL)
+    return;
+
+  ++busy;
+
+
+  if (mustset || (ui_get_shellsize() == FAIL && height != 0)) {
+    Rows = height;
+    Columns = width;
+    check_shellsize();
+    mch_set_shellsize();
+  } else
+    check_shellsize();
+
+  /* The window layout used to be adjusted here, but it now happens in
+   * screenalloc() (also invoked from screenclear()).  That is because the
+   * "busy" check above may skip this, but not screenalloc(). */
+
+  if (State != ASKMORE && State != EXTERNCMD && State != CONFIRM)
+    screenclear();
+  else
+    screen_start();         /* don't know where cursor is now */
+
+  if (starting != NO_SCREEN) {
+    maketitle();
+    changed_line_abv_curs();
+    invalidate_botline();
+
+    /*
+     * We only redraw when it's needed:
+     * - While at the more prompt or executing an external command, don't
+     *   redraw, but position the cursor.
+     * - While editing the command line, only redraw that.
+     * - in Ex mode, don't redraw anything.
+     * - Otherwise, redraw right now, and position the cursor.
+     * Always need to call update_screen() or screenalloc(), to make
+     * sure Rows/Columns and the size of ScreenLines[] is correct!
+     */
+    if (State == ASKMORE || State == EXTERNCMD || State == CONFIRM
+        || exmode_active) {
+      screenalloc(false);
+      repeat_message();
+    } else {
+      if (curwin->w_p_scb)
+        do_check_scrollbind(TRUE);
+      if (State & CMDLINE) {
+        update_screen(NOT_VALID);
+        redrawcmdline();
+      } else {
+        update_topline();
+        if (pum_visible()) {
+          redraw_later(NOT_VALID);
+          ins_compl_show_pum();           /* This includes the redraw. */
+        } else
+          update_screen(NOT_VALID);
+        if (redrawing())
+          setcursor();
+      }
+    }
+    cursor_on();            /* redrawing may have switched it off */
+  }
+  out_flush();
+  --busy;
+}
diff --git a/src/nvim/search.c b/src/nvim/search.c
index e9184d84cd..3055729bf8 100644
--- a/src/nvim/search.c
+++ b/src/nvim/search.c
@@ -39,6 +39,7 @@
 #include "nvim/misc1.h"
 #include "nvim/misc2.h"
 #include "nvim/move.h"
+#include "nvim/mouse.h"
 #include "nvim/normal.h"
 #include "nvim/option.h"
 #include "nvim/path.h"
diff --git a/src/nvim/strings.c b/src/nvim/strings.c
index 6c69b3b34a..20008bca16 100644
--- a/src/nvim/strings.c
+++ b/src/nvim/strings.c
@@ -49,7 +49,8 @@
 /*
  * Copy "string" into newly allocated memory.
  */
-char_u *vim_strsave(char_u *string) FUNC_ATTR_NONNULL_RET
+char_u *vim_strsave(const char_u *string)
+  FUNC_ATTR_NONNULL_RET FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
   return (char_u *)xstrdup((char *)string);
 }
@@ -60,7 +61,8 @@ char_u *vim_strsave(char_u *string) FUNC_ATTR_NONNULL_RET
  * The allocated memory always has size "len + 1", also when "string" is
  * shorter.
  */
-char_u *vim_strnsave(char_u *string, int len) FUNC_ATTR_NONNULL_RET
+char_u *vim_strnsave(const char_u *string, size_t len)
+  FUNC_ATTR_NONNULL_RET FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
   return (char_u *)strncpy(xmallocz(len), (char *)string, len);
 }
@@ -69,31 +71,30 @@ char_u *vim_strnsave(char_u *string, int len) FUNC_ATTR_NONNULL_RET
  * Same as vim_strsave(), but any characters found in esc_chars are preceded
  * by a backslash.
  */
-char_u *vim_strsave_escaped(char_u *string, char_u *esc_chars)
-  FUNC_ATTR_NONNULL_RET
+char_u *vim_strsave_escaped(const char_u *string, const char_u *esc_chars)
+  FUNC_ATTR_NONNULL_RET FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
-  return vim_strsave_escaped_ext(string, esc_chars, '\\', FALSE);
+  return vim_strsave_escaped_ext(string, esc_chars, '\\', false);
 }
 
 /*
- * Same as vim_strsave_escaped(), but when "bsl" is TRUE also escape
+ * Same as vim_strsave_escaped(), but when "bsl" is true also escape
  * characters where rem_backslash() would remove the backslash.
  * Escape the characters with "cc".
  */
-char_u *vim_strsave_escaped_ext(char_u *string, char_u *esc_chars, int cc, int bsl)
-  FUNC_ATTR_NONNULL_RET
+char_u *vim_strsave_escaped_ext(const char_u *string, const char_u *esc_chars,
+                                char_u cc, bool bsl)
+  FUNC_ATTR_NONNULL_RET FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
-  unsigned length;
-  int l;
-
   /*
    * First count the number of backslashes required.
    * Then allocate the memory and insert them.
    */
-  length = 1;                           /* count the trailing NUL */
-  for (char_u *p = string; *p; p++) {
-    if (has_mbyte && (l = (*mb_ptr2len)(p)) > 1) {
-      length += l;                      /* count a multibyte char */
+  size_t length = 1;                    // count the trailing NUL
+  for (const char_u *p = string; *p; p++) {
+    size_t l;
+    if (has_mbyte && (l = (size_t)(*mb_ptr2len)(p)) > 1) {
+      length += l;                      // count a multibyte char
       p += l - 1;
       continue;
     }
@@ -104,9 +105,10 @@ char_u *vim_strsave_escaped_ext(char_u *string, char_u *esc_chars, int cc, int b
 
   char_u *escaped_string = xmalloc(length);
   char_u *p2 = escaped_string;
-  for (char_u *p = string; *p; p++) {
-    if (has_mbyte && (l = (*mb_ptr2len)(p)) > 1) {
-      memmove(p2, p, (size_t)l);
+  for (const char_u *p = string; *p; p++) {
+    size_t l;
+    if (has_mbyte && (l = (size_t)(*mb_ptr2len)(p)) > 1) {
+      memcpy(p2, p, l);
       p2 += l;
       p += l - 1;                     /* skip multibyte char  */
       continue;
@@ -130,10 +132,10 @@ char_u *vim_strsave_escaped_ext(char_u *string, char_u *esc_chars, int cc, int b
  * When "do_newline" is false do not escape newline unless it is csh shell.
  * Returns the result in allocated memory.
  */
-char_u *vim_strsave_shellescape(char_u *string, bool do_special, bool do_newline)
+char_u *vim_strsave_shellescape(const char_u *string,
+                                bool do_special, bool do_newline)
+  FUNC_ATTR_NONNULL_RET FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
-  unsigned length;
-  char_u      *p;
   char_u      *d;
   char_u      *escaped_string;
   int l;
@@ -146,8 +148,8 @@ char_u *vim_strsave_shellescape(char_u *string, bool do_special, bool do_newline
   csh_like = csh_like_shell();
 
   /* First count the number of extra bytes required. */
-  length = (unsigned)STRLEN(string) + 3;    /* two quotes and a trailing NUL */
-  for (p = string; *p != NUL; mb_ptr_adv(p)) {
+  size_t length = STRLEN(string) + 3;       // two quotes and a trailing NUL
+  for (const char_u *p = string; *p != NUL; mb_ptr_adv(p)) {
     if (*p == '\'')
       length += 3;                      /* ' => '\'' */
     if ((*p == '\n' && (csh_like || do_newline))
@@ -169,7 +171,7 @@ char_u *vim_strsave_shellescape(char_u *string, bool do_special, bool do_newline
   /* add opening quote */
   *d++ = '\'';
 
-  for (p = string; *p != NUL; ) {
+  for (const char_u *p = string; *p != NUL; ) {
     if (*p == '\'') {
       *d++ = '\'';
       *d++ = '\\';
@@ -207,7 +209,8 @@ char_u *vim_strsave_shellescape(char_u *string, bool do_special, bool do_newline
  * Like vim_strsave(), but make all characters uppercase.
  * This uses ASCII lower-to-upper case translation, language independent.
  */
-char_u *vim_strsave_up(char_u *string)
+char_u *vim_strsave_up(const char_u *string)
+  FUNC_ATTR_NONNULL_RET FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
   char_u *p1;
 
@@ -220,7 +223,8 @@ char_u *vim_strsave_up(char_u *string)
  * Like vim_strnsave(), but make all characters uppercase.
  * This uses ASCII lower-to-upper case translation, language independent.
  */
-char_u *vim_strnsave_up(char_u *string, int len) FUNC_ATTR_NONNULL_RET
+char_u *vim_strnsave_up(const char_u *string, size_t len)
+  FUNC_ATTR_NONNULL_RET FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
   char_u *p1 = vim_strnsave(string, len);
   vim_strup(p1);
@@ -231,14 +235,15 @@ char_u *vim_strnsave_up(char_u *string, int len) FUNC_ATTR_NONNULL_RET
  * ASCII lower-to-upper case translation, language independent.
  */
 void vim_strup(char_u *p)
+  FUNC_ATTR_NONNULL_ALL
 {
   char_u  *p2;
-  int c;
+  char_u c;
 
   if (p != NULL) {
     p2 = p;
     while ((c = *p2) != NUL)
-      *p2++ = (c < 'a' || c > 'z') ? c : (c - 0x20);
+      *p2++ = (char_u)((c < 'a' || c > 'z') ? c : c - 0x20);
   }
 }
 
@@ -246,7 +251,8 @@ void vim_strup(char_u *p)
  * Make string "s" all upper-case and return it in allocated memory.
  * Handles multi-byte characters as well as possible.
  */
-char_u *strup_save(char_u *orig)
+char_u *strup_save(const char_u *orig)
+  FUNC_ATTR_NONNULL_RET FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
   char_u *res = vim_strsave(orig);
 
@@ -264,8 +270,8 @@ char_u *strup_save(char_u *orig)
       int newl = utf_char2len(uc);
       if (newl != l) {
         // TODO(philix): use xrealloc() in strup_save()
-        char_u *s = xmalloc(STRLEN(res) + 1 + newl - l);
-        memmove(s, res, p - res);
+        char_u *s = xmalloc(STRLEN(res) + (size_t)(1 + newl - l));
+        memcpy(s, res, (size_t)(p - res));
         STRCPY(s + (p - res) + newl, p + l);
         p = s + (p - res);
         free(res);
@@ -277,7 +283,7 @@ char_u *strup_save(char_u *orig)
     } else if (has_mbyte && (l = (*mb_ptr2len)(p)) > 1)
       p += l;                 /* skip multi-byte character */
     else {
-      *p = TOUPPER_LOC(*p);         /* note that toupper() can be a macro */
+      *p = (char_u) TOUPPER_LOC(*p);  // note that toupper() can be a macro
       p++;
     }
   }
@@ -289,6 +295,7 @@ char_u *strup_save(char_u *orig)
  * copy a space a number of times
  */
 void copy_spaces(char_u *ptr, size_t count)
+  FUNC_ATTR_NONNULL_ALL
 {
   size_t i = count;
   char_u      *p = ptr;
@@ -301,7 +308,8 @@ void copy_spaces(char_u *ptr, size_t count)
  * Copy a character a number of times.
  * Does not work for multi-byte characters!
  */
-void copy_chars(char_u *ptr, size_t count, int c)
+void copy_chars(char_u *ptr, size_t count, char_u c)
+  FUNC_ATTR_NONNULL_ALL
 {
   size_t i = count;
   char_u      *p = ptr;
@@ -314,6 +322,7 @@ void copy_chars(char_u *ptr, size_t count, int c)
  * delete spaces at the end of a string
  */
 void del_trailing_spaces(char_u *ptr)
+  FUNC_ATTR_NONNULL_ALL
 {
   char_u      *q;
 
@@ -326,7 +335,8 @@ void del_trailing_spaces(char_u *ptr)
  * Like strncpy(), but always terminate the result with one NUL.
  * "to" must be "len + 1" long!
  */
-void vim_strncpy(char_u *to, char_u *from, size_t len)
+void vim_strncpy(char_u *restrict to, const char_u *restrict from, size_t len)
+  FUNC_ATTR_NONNULL_ALL
 {
   STRNCPY(to, from, len);
   to[len] = NUL;
@@ -336,13 +346,15 @@ void vim_strncpy(char_u *to, char_u *from, size_t len)
  * Like strcat(), but make sure the result fits in "tosize" bytes and is
  * always NUL terminated.
  */
-void vim_strcat(char_u *to, char_u *from, size_t tosize)
+void vim_strcat(char_u *restrict to, const char_u *restrict from,
+                size_t tosize)
+  FUNC_ATTR_NONNULL_ALL
 {
   size_t tolen = STRLEN(to);
   size_t fromlen = STRLEN(from);
 
   if (tolen + fromlen + 1 > tosize) {
-    memmove(to + tolen, from, tosize - tolen - 1);
+    memcpy(to + tolen, from, tosize - tolen - 1);
     to[tosize - 1] = NUL;
   } else
     STRCPY(to + tolen, from);
@@ -354,7 +366,8 @@ void vim_strcat(char_u *to, char_u *from, size_t tosize)
  * Doesn't work for multi-byte characters.
  * return 0 for match, < 0 for smaller, > 0 for bigger
  */
-int vim_stricmp(char *s1, char *s2)
+int vim_stricmp(const char *s1, const char *s2)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
 {
   int i;
 
@@ -377,7 +390,8 @@ int vim_stricmp(char *s1, char *s2)
  * Doesn't work for multi-byte characters.
  * return 0 for match, < 0 for smaller, > 0 for bigger
  */
-int vim_strnicmp(char *s1, char *s2, size_t len)
+int vim_strnicmp(const char *s1, const char *s2, size_t len)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
 {
   int i;
 
@@ -400,16 +414,16 @@ int vim_strnicmp(char *s1, char *s2, size_t len)
  * with characters from 128 to 255 correctly.  It also doesn't return a
  * pointer to the NUL at the end of the string.
  */
-char_u *vim_strchr(char_u *string, int c)
+char_u *vim_strchr(const char_u *string, int c)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
 {
-  char_u      *p;
   int b;
 
-  p = string;
+  const char_u *p = string;
   if (enc_utf8 && c >= 0x80) {
     while (*p != NUL) {
       if (utf_ptr2char(p) == c)
-        return p;
+        return (char_u *) p;
       p += (*mb_ptr2len)(p);
     }
     return NULL;
@@ -420,7 +434,7 @@ char_u *vim_strchr(char_u *string, int c)
     c = ((unsigned)c >> 8) & 0xff;
     while ((b = *p) != NUL) {
       if (b == c && p[1] == n2)
-        return p;
+        return (char_u *) p;
       p += (*mb_ptr2len)(p);
     }
     return NULL;
@@ -428,14 +442,14 @@ char_u *vim_strchr(char_u *string, int c)
   if (has_mbyte) {
     while ((b = *p) != NUL) {
       if (b == c)
-        return p;
+        return (char_u *) p;
       p += (*mb_ptr2len)(p);
     }
     return NULL;
   }
   while ((b = *p) != NUL) {
     if (b == c)
-      return p;
+      return (char_u *) p;
     ++p;
   }
   return NULL;
@@ -446,13 +460,14 @@ char_u *vim_strchr(char_u *string, int c)
  * strings with characters above 128 correctly. It also doesn't return a
  * pointer to the NUL at the end of the string.
  */
-char_u *vim_strbyte(char_u *string, int c)
+char_u *vim_strbyte(const char_u *string, int c)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
 {
-  char_u      *p = string;
+  const char_u *p = string;
 
   while (*p != NUL) {
     if (*p == c)
-      return p;
+      return (char_u *) p;
     ++p;
   }
   return NULL;
@@ -463,24 +478,26 @@ char_u *vim_strbyte(char_u *string, int c)
  * Return NULL if not found.
  * Does not handle multi-byte char for "c"!
  */
-char_u *vim_strrchr(char_u *string, int c)
+char_u *vim_strrchr(const char_u *string, int c)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
 {
-  char_u      *retval = NULL;
-  char_u      *p = string;
+  const char_u *retval = NULL;
+  const char_u *p = string;
 
   while (*p) {
     if (*p == c)
       retval = p;
     mb_ptr_adv(p);
   }
-  return retval;
+  return (char_u *) retval;
 }
 
 /*
  * Vim has its own isspace() function, because on some machines isspace()
  * can't handle characters above 128.
  */
-int vim_isspace(int x)
+bool vim_isspace(int x)
+  FUNC_ATTR_CONST
 {
   return (x >= 9 && x <= 13) || x == ' ';
 }
@@ -493,6 +510,7 @@ int vim_isspace(int x)
 # include "strings.c.generated.h"
 #endif
 static int sort_compare(const void *s1, const void *s2)
+  FUNC_ATTR_NONNULL_ALL
 {
   return STRCMP(*(char **)s1, *(char **)s2);
 }
@@ -503,24 +521,26 @@ void sort_strings(char_u **files, int count)
 }
 
 /*
- * Return TRUE if string "s" contains a non-ASCII character (128 or higher).
- * When "s" is NULL FALSE is returned.
+ * Return true if string "s" contains a non-ASCII character (128 or higher).
+ * When "s" is NULL false is returned.
  */
-int has_non_ascii(char_u *s)
+bool has_non_ascii(const char_u *s)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
 {
-  char_u      *p;
+  const char_u *p;
 
   if (s != NULL)
     for (p = s; *p != NUL; ++p)
       if (*p >= 128)
-        return TRUE;
-  return FALSE;
+        return true;
+  return false;
 }
 
 /*
  * Concatenate two strings and return the result in allocated memory.
  */
-char_u *concat_str(char_u *str1, char_u *str2) FUNC_ATTR_NONNULL_RET
+char_u *concat_str(const char_u *restrict str1, const char_u *restrict str2)
+  FUNC_ATTR_NONNULL_RET FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
   size_t l = STRLEN(str1);
   char_u *dest = xmalloc(l + STRLEN(str2) + 1);
diff --git a/src/nvim/term.c b/src/nvim/term.c
index 3d1053bd2f..54508b1daa 100644
--- a/src/nvim/term.c
+++ b/src/nvim/term.c
@@ -43,6 +43,7 @@
 #include "nvim/keymap.h"
 #include "nvim/memory.h"
 #include "nvim/move.h"
+#include "nvim/mouse.h"
 #include "nvim/normal.h"
 #include "nvim/option.h"
 #include "nvim/os_unix.h"
@@ -639,7 +640,7 @@ static struct builtin_term builtin_termcaps[] =
   {K_BS,              "\x7f"},          /* for some reason 0177 doesn't work */
 # endif
 
-# if defined(ALL_BUILTIN_TCAPS) || defined(__MINT__)
+# if defined(ALL_BUILTIN_TCAPS)
   /*
    * Ordinary vt52
    */
@@ -998,7 +999,7 @@ static struct builtin_term builtin_termcaps[] =
 
 
 
-#if defined(UNIX) && !defined(__MINT__)
+#if defined(UNIX)
 # define DEFAULT_TERM   (char_u *)"ansi"
 #endif
 
@@ -1010,6 +1011,30 @@ static struct builtin_term builtin_termcaps[] =
 # define DEFAULT_TERM   (char_u *)"dumb"
 #endif
 
+/// Sets up the terminal window for use.
+///
+/// This must be done after resetting full_screen, otherwise it may move the
+/// cursor.
+///
+/// @remark We may call mch_exit() before calling this.
+void term_init(void)
+{
+  Columns = 80;
+  Rows = 24;
+
+  // Prevent buffering output.
+  // Output gets explicitly buffered and flushed by out_flush() at times like,
+  // for example, when the user presses a key. Without this line, vim will not
+  // render the screen correctly.
+  setbuf(stdout, NULL);
+
+  out_flush();
+
+#ifdef MACOS_CONVERT
+  mac_conv_init();
+#endif
+}
+
 /*
  * Term_strings contains currently used terminal output strings.
  * It is initialized with the default values by parse_builtin_tcap().
@@ -1448,7 +1473,7 @@ int set_termname(char_u *term)
     width = 80;
     height = 24;            /* most terminals are 24 lines */
   }
-  set_shellsize(width, height, FALSE);          /* may change Rows */
+  screen_resize(width, height, FALSE);          /* may change Rows */
   if (starting != NO_SCREEN) {
     if (scroll_region)
       scroll_region_reset();                    /* In case Rows changed */
@@ -1482,7 +1507,6 @@ int set_termname(char_u *term)
 #  define HMT_PTERM     8
 #  define HMT_URXVT     16
 #  define HMT_SGR       32
-static int has_mouse_termcode = 0;
 
 void 
 set_mouse_termcode (
@@ -1493,16 +1517,6 @@ set_mouse_termcode (
   char_u name[2] = { n, KE_FILLER };
 
   add_termcode(name, s, FALSE);
-  if (n == KS_NETTERM_MOUSE)
-    has_mouse_termcode |= HMT_NETTERM;
-  else if (n == KS_DEC_MOUSE)
-    has_mouse_termcode |= HMT_DEC;
-  else if (n == KS_URXVT_MOUSE)
-    has_mouse_termcode |= HMT_URXVT;
-  else if (n == KS_SGR_MOUSE)
-    has_mouse_termcode |= HMT_SGR;
-  else
-    has_mouse_termcode |= HMT_NORMAL;
 }
 
 # if (defined(UNIX) && defined(FEAT_MOUSE_TTY)) || defined(PROTO)
@@ -1514,16 +1528,6 @@ del_mouse_termcode (
   char_u name[2] = { n, KE_FILLER };
 
   del_termcode(name);
-  if (n == KS_NETTERM_MOUSE)
-    has_mouse_termcode &= ~HMT_NETTERM;
-  else if (n == KS_DEC_MOUSE)
-    has_mouse_termcode &= ~HMT_DEC;
-  else if (n == KS_URXVT_MOUSE)
-    has_mouse_termcode &= ~HMT_URXVT;
-  else if (n == KS_SGR_MOUSE)
-    has_mouse_termcode &= ~HMT_SGR;
-  else
-    has_mouse_termcode &= ~HMT_NORMAL;
 }
 # endif
 
@@ -1822,11 +1826,35 @@ void termcapinit(char_u *name)
   set_termname(T_NAME != NULL ? T_NAME : term);
 }
 
+/// Write s[len] to the screen.
+void term_write(char_u *s, size_t len)
+{
+  if (embedded_mode) {
+    // TODO(tarruda): This is a temporary hack to stop Neovim from writing
+    // messages to stdout in embedded mode. In the future, embedded mode will
+    // be the only possibility(GUIs will always start neovim with a msgpack-rpc
+    // over stdio) and this function won't exist.
+    //
+    // The reason for this is because before Neovim fully migrates to a
+    // msgpack-rpc-driven architecture, we must have a fully functional
+    // UI working
+    return;
+  }
+
+  (void) fwrite(s, len, 1, stdout);
+
+#ifdef UNIX
+  if (p_wd) {           // Unix is too fast, slow down a bit more
+    os_microdelay(p_wd);
+  }
+#endif
+}
+
 /*
  * the number of calls to ui_write is reduced by using the buffer "out_buf"
  */
 #  define OUT_SIZE      2047
-/* Add one to allow mch_write() in os_win32.c to append a NUL */
+// Add one to allow term_write() in os_win32.c to append a NUL
 static char_u out_buf[OUT_SIZE + 1];
 static int out_pos = 0;                 /* number of chars in out_buf */
 
@@ -2241,7 +2269,7 @@ void win_new_shellsize(void)
  */
 void shell_resized(void)
 {
-  set_shellsize(0, 0, FALSE);
+  screen_resize(0, 0, FALSE);
 }
 
 /*
@@ -2263,102 +2291,6 @@ void shell_resized_check(void)
 }
 
 /*
- * Set size of the Vim shell.
- * If 'mustset' is TRUE, we must set Rows and Columns, do not get the real
- * window size (this is used for the :win command).
- * If 'mustset' is FALSE, we may try to get the real window size and if
- * it fails use 'width' and 'height'.
- */
-void set_shellsize(int width, int height, int mustset)
-{
-  static int busy = FALSE;
-
-  /*
-   * Avoid recursiveness, can happen when setting the window size causes
-   * another window-changed signal.
-   */
-  if (busy)
-    return;
-
-  if (width < 0 || height < 0)      /* just checking... */
-    return;
-
-  if (State == HITRETURN || State == SETWSIZE) {
-    /* postpone the resizing */
-    State = SETWSIZE;
-    return;
-  }
-
-  /* curwin->w_buffer can be NULL when we are closing a window and the
-   * buffer has already been closed and removing a scrollbar causes a resize
-   * event. Don't resize then, it will happen after entering another buffer.
-   */
-  if (curwin->w_buffer == NULL)
-    return;
-
-  ++busy;
-
-
-  if (mustset || (ui_get_shellsize() == FAIL && height != 0)) {
-    Rows = height;
-    Columns = width;
-    check_shellsize();
-    mch_set_shellsize();
-  } else
-    check_shellsize();
-
-  /* The window layout used to be adjusted here, but it now happens in
-   * screenalloc() (also invoked from screenclear()).  That is because the
-   * "busy" check above may skip this, but not screenalloc(). */
-
-  if (State != ASKMORE && State != EXTERNCMD && State != CONFIRM)
-    screenclear();
-  else
-    screen_start();         /* don't know where cursor is now */
-
-  if (starting != NO_SCREEN) {
-    maketitle();
-    changed_line_abv_curs();
-    invalidate_botline();
-
-    /*
-     * We only redraw when it's needed:
-     * - While at the more prompt or executing an external command, don't
-     *   redraw, but position the cursor.
-     * - While editing the command line, only redraw that.
-     * - in Ex mode, don't redraw anything.
-     * - Otherwise, redraw right now, and position the cursor.
-     * Always need to call update_screen() or screenalloc(), to make
-     * sure Rows/Columns and the size of ScreenLines[] is correct!
-     */
-    if (State == ASKMORE || State == EXTERNCMD || State == CONFIRM
-        || exmode_active) {
-      screenalloc(false);
-      repeat_message();
-    } else {
-      if (curwin->w_p_scb)
-        do_check_scrollbind(TRUE);
-      if (State & CMDLINE) {
-        update_screen(NOT_VALID);
-        redrawcmdline();
-      } else {
-        update_topline();
-        if (pum_visible()) {
-          redraw_later(NOT_VALID);
-          ins_compl_show_pum();           /* This includes the redraw. */
-        } else
-          update_screen(NOT_VALID);
-        if (redrawing())
-          setcursor();
-      }
-    }
-    cursor_on();            /* redrawing may have switched it off */
-  }
-  out_flush();
-  --busy;
-}
-
-/*
  * Set the terminal to TMODE_RAW (for Normal mode) or TMODE_COOK (for external
  * commands and Ex mode).
  */
@@ -2593,73 +2525,6 @@ int swapping_screen(void)
 }
 
 /*
- * setmouse() - switch mouse on/off depending on current mode and 'mouse'
- */
-void setmouse(void)
-{
-  int checkfor;
-
-
-  /* be quick when mouse is off */
-  if (*p_mouse == NUL || has_mouse_termcode == 0)
-    return;
-
-  /* don't switch mouse on when not in raw mode (Ex mode) */
-  if (cur_tmode != TMODE_RAW) {
-    mch_setmouse(FALSE);
-    return;
-  }
-
-  if (VIsual_active)
-    checkfor = MOUSE_VISUAL;
-  else if (State == HITRETURN || State == ASKMORE || State == SETWSIZE)
-    checkfor = MOUSE_RETURN;
-  else if (State & INSERT)
-    checkfor = MOUSE_INSERT;
-  else if (State & CMDLINE)
-    checkfor = MOUSE_COMMAND;
-  else if (State == CONFIRM || State == EXTERNCMD)
-    checkfor = ' ';     /* don't use mouse for ":confirm" or ":!cmd" */
-  else
-    checkfor = MOUSE_NORMAL;        /* assume normal mode */
-
-  if (mouse_has(checkfor))
-    mch_setmouse(TRUE);
-  else
-    mch_setmouse(FALSE);
-}
-
-/*
- * Return TRUE if
- * - "c" is in 'mouse', or
- * - 'a' is in 'mouse' and "c" is in MOUSE_A, or
- * - the current buffer is a help file and 'h' is in 'mouse' and we are in a
- *   normal editing mode (not at hit-return message).
- */
-int mouse_has(int c)
-{
-  for (char_u *p = p_mouse; *p; ++p)
-    switch (*p) {
-    case 'a': if (vim_strchr((char_u *)MOUSE_A, c) != NULL)
-        return TRUE;
-      break;
-    case MOUSE_HELP: if (c != MOUSE_RETURN && curbuf->b_help)
-        return TRUE;
-      break;
-    default: if (c == *p) return TRUE; break;
-    }
-  return FALSE;
-}
-
-/*
- * Return TRUE when 'mousemodel' is set to "popup" or "popup_setpos".
- */
-int mouse_model_popup(void)
-{
-  return p_mousem[0] == 'p';
-}
-
-/*
  * By outputting the 'cursor very visible' termcap code, for some windowed
  * terminals this makes the screen scrolled to the correct position.
  * Used when starting Vim or returning from a shell.
@@ -2954,11 +2819,9 @@ static void switch_to_8bit(void)
   LOG_TR("Switching to 8 bit");
 }
 
-#ifdef CHECK_DOUBLE_CLICK
 static linenr_T orig_topline = 0;
 static int orig_topfill = 0;
-#endif
-#if defined(CHECK_DOUBLE_CLICK) || defined(PROTO)
+
 /*
  * Checking for double clicks ourselves.
  * "orig_topline" is used to avoid detecting a double-click when the window
@@ -2973,7 +2836,6 @@ void set_mouse_topline(win_T *wp)
   orig_topline = wp->w_topline;
   orig_topfill = wp->w_topfill;
 }
-#endif
 
 /*
  * Check if typebuf.tb_buf[] contains a terminal key code.
@@ -3664,7 +3526,6 @@ int check_termcode(int max_offset, char_u *buf, int bufsize, int *buflen)
           is_drag = TRUE;
         current_button = held_button;
       } else if (wheel_code == 0)   {
-# ifdef CHECK_DOUBLE_CLICK
         {
           static int orig_mouse_col = 0;
           static int orig_mouse_row = 0;
@@ -3698,9 +3559,6 @@ int check_termcode(int max_offset, char_u *buf, int bufsize, int *buflen)
           orig_topline = curwin->w_topline;
           orig_topfill = curwin->w_topfill;
         }
-# else
-        orig_num_clicks = NUM_MOUSE_CLICKS(mouse_code);
-# endif
         is_click = TRUE;
         orig_mouse_code = mouse_code;
       }
diff --git a/src/nvim/term.h b/src/nvim/term.h
index 17154b8c26..3f70f484a7 100644
--- a/src/nvim/term.h
+++ b/src/nvim/term.h
@@ -52,10 +52,6 @@
  * 128 = 16384 columns, now it's reduced to 10000. */
 #define MOUSE_COLOFF 10000
 
-#if defined(UNIX)
-# define CHECK_DOUBLE_CLICK 1  /* Checking for double clicks ourselves. */
-#endif
-
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "term.h.generated.h"
 #endif
diff --git a/src/nvim/ui.c b/src/nvim/ui.c
index 526cc3e47e..eab6251288 100644
--- a/src/nvim/ui.c
+++ b/src/nvim/ui.c
@@ -55,7 +55,7 @@ void ui_write(char_u *s, int len)
         s = tofree;
     }
 
-    mch_write(s, len);
+    term_write(s, len);
 
     if (output_conv.vc_type != CONV_NONE)
       free(tofree);
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 315d5f07de..bd461a873f 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -41,6 +41,7 @@
 #include "nvim/file_search.h"
 #include "nvim/garray.h"
 #include "nvim/move.h"
+#include "nvim/mouse.h"
 #include "nvim/normal.h"
 #include "nvim/option.h"
 #include "nvim/os_unix.h"