vim-patch:8.1.0035: not easy to switch between prompt buffer and other windows

Problem:    Not easy to switch between prompt buffer and other windows.
Solution:   Accept CTRL-W commands in Insert mode.  Start and stop Insert mode
            as one would expect.
6d41c78e35

Cherry-pick channel.txt change from:
d2f3a8b878

b_prompt_insert was already ported.

src/nvim/edit.c

@@ -655,10 +655,17 @@ static int insert_check(VimState *state)
 
 static int insert_execute(VimState *state, int key)
 {
+  InsertState *const s = (InsertState *)state;
+  if (stop_insert_mode) {
+    // Insert mode ended, possibly from a callback.
+    s->count = 0;
+    s->nomove = true;
+    return 0;
+  }
+
   if (key == K_IGNORE || key == K_NOP) {
     return -1;  // get another key
   }
-  InsertState *s = (InsertState *)state;
   s->c = key;
 
   // Don't want K_EVENT with cursorhold for the second key, e.g., after CTRL-V.
@@ -984,6 +991,15 @@ static int insert_handle_key(InsertState *s)
     break;
 
   case Ctrl_W:        // delete word before the cursor
+    if (bt_prompt(curbuf) && (mod_mask & MOD_MASK_SHIFT) == 0) {
+      // In a prompt window CTRL-W is used for window commands.
+      // Use Shift-CTRL-W to delete a word.
+      stuffcharReadbuff(Ctrl_W);
+      restart_edit = 'i';
+      s->nomove = true;
+      s->count = 0;
+      return 0;
+    }
     s->did_backspace = ins_bs(s->c, BACKSPACE_WORD, &s->inserted_space);
     auto_format(false, true);
     break;
@@ -1653,6 +1669,17 @@ static void init_prompt(int cmdchar_todo)
     coladvance(MAXCOL);
     changed_bytes(curbuf->b_ml.ml_line_count, 0);
   }
+
+  // Insert always starts after the prompt, allow editing text after it.
+  if (Insstart_orig.lnum != curwin->w_cursor.lnum || Insstart_orig.col != (colnr_T)STRLEN(prompt)) {
+    Insstart.lnum = curwin->w_cursor.lnum;
+    Insstart.col = STRLEN(prompt);
+    Insstart_orig = Insstart;
+    Insstart_textlen = Insstart.col;
+    Insstart_blank_vcol = MAXCOL;
+    arrow_used = false;
+  }
+
   if (cmdchar_todo == 'A') {
     coladvance(MAXCOL);
   }

src/nvim/testdir/test_prompt_buffer.vim

@@ -145,10 +145,9 @@ func Test_prompt_buffer_edit()
   call assert_beeps("normal! \<C-X>")
   " pressing CTRL-W in the prompt buffer should trigger the window commands
   call assert_equal(1, winnr())
-  " In Nvim, CTRL-W commands aren't usable from insert mode in a prompt buffer
-  " exe "normal A\<C-W>\<C-W>"
-  " call assert_equal(2, winnr())
-  " wincmd w
+  exe "normal A\<C-W>\<C-W>"
+  call assert_equal(2, winnr())
+  wincmd w
   close!
   call assert_equal(0, prompt_setprompt([], ''))
 endfunc

src/nvim/window.c

@@ -2229,6 +2229,28 @@ static void win_equal_rec(win_T *next_curwin, bool current, frame_T *topfr, int
   }
 }
 
+static void leaving_window(win_T *const win)
+  FUNC_ATTR_NONNULL_ALL
+{
+  // When leaving a prompt window stop Insert mode and perhaps restart
+  // it when entering that window again.
+  win->w_buffer->b_prompt_insert = restart_edit;
+  restart_edit = NUL;
+
+  // When leaving the window (or closing the window) was done from a
+  // callback we need to break out of the Insert mode loop.
+  if (State & INSERT) {
+    stop_insert_mode = true;
+  }
+}
+
+static void entering_window(win_T *const win)
+  FUNC_ATTR_NONNULL_ALL
+{
+  // When entering the prompt window may restart Insert mode.
+  restart_edit = win->w_buffer->b_prompt_insert;
+}
+
 /// Closes all windows for buffer `buf`.
 ///
 /// @param keep_curwin don't close `curwin`
@@ -2367,6 +2389,7 @@ static bool close_last_window_tabpage(win_T *win, bool free_buf, tabpage_T *prev
       shell_new_rows();
     }
   }
+  entering_window(curwin);
 
   // Since goto_tabpage_tp above did not trigger *Enter autocommands, do
   // that now.
@@ -2434,10 +2457,10 @@ int win_close(win_T *win, bool free_buf)
   }
 
   if (win == curwin) {
-    /*
-     * Guess which window is going to be the new current window.
-     * This may change because of the autocommands (sigh).
-     */
+    leaving_window(curwin);
+
+    // Guess which window is going to be the new current window.
+    // This may change because of the autocommands (sigh).
     if (!win->w_floating) {
       wp = frame2win(win_altframe(win, NULL));
     } else {
@@ -3801,6 +3824,8 @@ int win_new_tabpage(int after, char_u *filename)
 
     lastused_tabpage = old_curtab;
 
+    entering_window(curwin);
+
     apply_autocmds(EVENT_WINNEW, NULL, NULL, false, curbuf);
     apply_autocmds(EVENT_WINENTER, NULL, NULL, false, curbuf);
     apply_autocmds(EVENT_TABNEW, filename, filename, false, curbuf);
@@ -3956,6 +3981,7 @@ static int leave_tabpage(buf_T *new_curbuf, bool trigger_leave_autocmds)
 {
   tabpage_T *tp = curtab;
 
+  leaving_window(curwin);
   reset_VIsual_and_resel();     // stop Visual mode
   if (trigger_leave_autocmds) {
     if (new_curbuf != curbuf) {
@@ -4478,6 +4504,10 @@ static void win_enter_ext(win_T *const wp, const int flags)
     return;
   }
 
+  if (!curwin_invalid) {
+    leaving_window(curwin);
+  }
+
   if (!curwin_invalid && (flags & WEE_TRIGGER_LEAVE_AUTOCMDS)) {
     // Be careful: If autocommands delete the window, return now.
     if (wp->w_buffer != curbuf) {
@@ -4525,6 +4555,7 @@ static void win_enter_ext(win_T *const wp, const int flags)
 
   fix_current_dir();
 
+  entering_window(curwin);
   // Careful: autocommands may close the window and make "wp" invalid
   if (flags & WEE_TRIGGER_NEW_AUTOCMDS) {
     apply_autocmds(EVENT_WINNEW, NULL, NULL, false, curbuf);