patch 8.2.4052: not easy to resize a window from a plugin

Problem:    Not easy to resize a window from a plugin.
Solution:   Add win_move_separator() and win_move_statusline() functions.
            (Daniel Steinberg, closes #9486)

runtime/doc/builtin.txt

@@ -695,6 +695,8 @@ win_gettype([{nr}])		String	type of window {nr}
 win_gotoid({expr})		Number	go to window with ID {expr}
 win_id2tabwin({expr})		List	get tab and window nr from window ID
 win_id2win({expr})		Number	get window nr from window ID
+win_move_separator({nr})	Number	move window vertical separator
+win_move_statusline({nr})	Number	move window status line
 win_screenpos({nr})		List	get screen position of window {nr}
 win_splitmove({nr}, {target} [, {options}])
 				Number	move window {nr} to split of {target}
@@ -9567,6 +9569,35 @@ win_id2win({expr})					*win_id2win()*
 		Can also be used as a |method|: >
 			GetWinid()->win_id2win()
 
+win_move_separator({nr}, {offset})			*win_move_separator()*
+		Move window {nr}'s vertical separator (i.e., the right border)
+		by {offset} columns, as if being dragged by the mouse. {nr}
+		can be a window number or |window-ID|. A positive {offset}
+		moves right and a negative {offset} moves left. Moving a
+		window's vertical separator will change the width of the
+		window and the width of other windows adjacent to the vertical
+		separator. The magnitude of movement may be smaller than
+		specified (e.g., as a consequence of maintaining
+		'winminwidth'). Returns TRUE if the window can be found and
+		FALSE otherwise.
+
+		Can also be used as a |method|: >
+			GetWinnr()->win_move_separator(offset)
+
+win_move_statusline({nr}, {offset})			*win_move_statusline()*
+		Move window {nr}'s status line (i.e., the bottom border) by
+		{offset} rows, as if being dragged by the mouse. {nr} can be a
+		window number or |window-ID|. A positive {offset} moves down
+		and a negative {offset} moves up. Moving a window's status
+		line will change the height of the window and the height of
+		other windows adjacent to the status line. The magnitude of
+		movement may be smaller than specified (e.g., as a consequence
+		of maintaining 'winminheight'). Returns TRUE if the window can
+		be found and FALSE otherwise.
+
+		Can also be used as a |method|: >
+			GetWinnr()->win_move_statusline(offset)
+
 win_screenpos({nr})					*win_screenpos()*
 		Return the screen position of window {nr} as a list with two
 		numbers: [row, col].  The first window always has position

runtime/doc/usr_41.txt

@@ -963,6 +963,8 @@ Buffers, windows and the argument list:
 	win_gotoid()		go to window with ID
 	win_id2tabwin()		get tab and window nr from window ID
 	win_id2win()		get window nr from window ID
+	win_move_separator()	move window vertical separator
+	win_move_statusline()	move window status line
 	win_splitmove()		move window to a split of another window
 	getbufinfo()		get a list with buffer information
 	gettabinfo()		get a list with tab page information

src/evalfunc.c

@@ -2398,6 +2398,10 @@ static funcentry_T global_functions[] =
 			ret_list_number,    f_win_id2tabwin},
     {"win_id2win",	1, 1, FEARG_1,	    arg1_number,
 			ret_number,	    f_win_id2win},
+    {"win_move_separator", 2, 2, FEARG_1,   arg2_number,
+			ret_number_bool,    f_win_move_separator},
+    {"win_move_statusline", 2, 2, FEARG_1,  arg2_number,
+			ret_number_bool,    f_win_move_statusline},
     {"win_screenpos",	1, 1, FEARG_1,	    arg1_number,
 			ret_list_number,    f_win_screenpos},
     {"win_splitmove",   2, 3, FEARG_1,	    arg3_number_number_dict,

src/evalwindow.c

@@ -835,6 +835,56 @@ f_win_id2win(typval_T *argvars, typval_T *rettv)
     rettv->vval.v_number = win_id2win(argvars);
 }
 
+/*
+ * "win_move_separator()" function
+ */
+    void
+f_win_move_separator(typval_T *argvars, typval_T *rettv)
+{
+    win_T	*wp;
+    int		offset;
+
+    rettv->vval.v_number = FALSE;
+
+    if (in_vim9script()
+	    && (check_for_number_arg(argvars, 0) == FAIL
+		|| check_for_number_arg(argvars, 1) == FAIL))
+	return;
+
+    wp = find_win_by_nr_or_id(&argvars[0]);
+    if (wp == NULL || win_valid_popup(wp))
+	return;
+
+    offset = (int)tv_get_number(&argvars[1]);
+    win_drag_vsep_line(wp, offset);
+    rettv->vval.v_number = TRUE;
+}
+
+/*
+ * "win_move_statusline()" function
+ */
+    void
+f_win_move_statusline(typval_T *argvars, typval_T *rettv)
+{
+    win_T	*wp;
+    int		offset;
+
+    rettv->vval.v_number = FALSE;
+
+    if (in_vim9script()
+	    && (check_for_number_arg(argvars, 0) == FAIL
+		|| check_for_number_arg(argvars, 1) == FAIL))
+	return;
+
+    wp = find_win_by_nr_or_id(&argvars[0]);
+    if (wp == NULL || win_valid_popup(wp))
+	return;
+
+    offset = (int)tv_get_number(&argvars[1]);
+    win_drag_status_line(wp, offset);
+    rettv->vval.v_number = TRUE;
+}
+
 /*
  * "win_screenpos()" function
  */

src/proto/evalwindow.pro

@@ -18,6 +18,8 @@ void f_win_getid(typval_T *argvars, typval_T *rettv);
 void f_win_gotoid(typval_T *argvars, typval_T *rettv);
 void f_win_id2tabwin(typval_T *argvars, typval_T *rettv);
 void f_win_id2win(typval_T *argvars, typval_T *rettv);
+void f_win_move_separator(typval_T *argvars, typval_T *rettv);
+void f_win_move_statusline(typval_T *argvars, typval_T *rettv);
 void f_win_screenpos(typval_T *argvars, typval_T *rettv);
 void f_win_splitmove(typval_T *argvars, typval_T *rettv);
 void f_win_gettype(typval_T *argvars, typval_T *rettv);

src/testdir/test_window_cmd.vim

@@ -1395,5 +1395,103 @@ func Test_window_minimal_size()
   set winminwidth& winminheight&
 endfunc
 
+func Test_win_move_separator()
+  edit a
+  leftabove vsplit b
+  let w = winwidth(0)
+  " check win_move_separator from left window on left window
+  call assert_equal(1, winnr())
+  for offset in range(5)
+    call assert_true(win_move_separator(0, offset))
+    call assert_equal(w + offset, winwidth(0))
+    call assert_true(0->win_move_separator(-offset))
+    call assert_equal(w, winwidth(0))
+  endfor
+  " check win_move_separator from right window on left window number
+  wincmd l
+  call assert_notequal(1, winnr())
+  for offset in range(5)
+    call assert_true(1->win_move_separator(offset))
+    call assert_equal(w + offset, winwidth(1))
+    call assert_true(win_move_separator(1, -offset))
+    call assert_equal(w, winwidth(1))
+  endfor
+  " check win_move_separator from right window on left window ID
+  let id = win_getid(1)
+  for offset in range(5)
+    call assert_true(win_move_separator(id, offset))
+    call assert_equal(w + offset, winwidth(id))
+    call assert_true(id->win_move_separator(-offset))
+    call assert_equal(w, winwidth(id))
+  endfor
+  " check that win_move_separator doesn't error with offsets beyond moving
+  " possibility
+  call assert_true(win_move_separator(id, 5000))
+  call assert_true(winwidth(id) > w)
+  call assert_true(win_move_separator(id, -5000))
+  call assert_true(winwidth(id) < w)
+  " check that win_move_separator returns false for an invalid window
+  wincmd =
+  let w = winwidth(0)
+  call assert_false(win_move_separator(-1, 1))
+  call assert_equal(w, winwidth(0))
+  " check that win_move_separator returns false for a popup window
+  let id = popup_create(['hello', 'world'], {})
+  let w = winwidth(id)
+  call assert_false(win_move_separator(id, 1))
+  call assert_equal(w, winwidth(id))
+  call popup_close(id)
+  %bwipe!
+endfunc
+
+func Test_win_move_statusline()
+  edit a
+  leftabove split b
+  let h = winheight(0)
+  " check win_move_statusline from top window on top window
+  call assert_equal(1, winnr())
+  for offset in range(5)
+    call assert_true(win_move_statusline(0, offset))
+    call assert_equal(h + offset, winheight(0))
+    call assert_true(0->win_move_statusline(-offset))
+    call assert_equal(h, winheight(0))
+  endfor
+  " check win_move_statusline from bottom window on top window number
+  wincmd j
+  call assert_notequal(1, winnr())
+  for offset in range(5)
+    call assert_true(1->win_move_statusline(offset))
+    call assert_equal(h + offset, winheight(1))
+    call assert_true(win_move_statusline(1, -offset))
+    call assert_equal(h, winheight(1))
+  endfor
+  " check win_move_statusline from bottom window on top window ID
+  let id = win_getid(1)
+  for offset in range(5)
+    call assert_true(win_move_statusline(id, offset))
+    call assert_equal(h + offset, winheight(id))
+    call assert_true(id->win_move_statusline(-offset))
+    call assert_equal(h, winheight(id))
+  endfor
+  " check that win_move_statusline doesn't error with offsets beyond moving
+  " possibility
+  call assert_true(win_move_statusline(id, 5000))
+  call assert_true(winheight(id) > h)
+  call assert_true(win_move_statusline(id, -5000))
+  call assert_true(winheight(id) < h)
+  " check that win_move_statusline returns false for an invalid window
+  wincmd =
+  let h = winheight(0)
+  call assert_false(win_move_statusline(-1, 1))
+  call assert_equal(h, winheight(0))
+  " check that win_move_statusline returns false for a popup window
+  let id = popup_create(['hello', 'world'], {})
+  let h = winheight(id)
+  call assert_false(win_move_statusline(id, 1))
+  call assert_equal(h, winheight(id))
+  call popup_close(id)
+  %bwipe!
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4052,
 /**/
     4051,
 /**/