vim-patch:8.2.3627: difficult to know where the text starts in a window (#16377)

vim-patch:8.2.3627: difficult to know where the text starts in a window

Problem:    difficult to know where the text starts in a window. (Sergey
            Vlasov)
Solution:   Add the "textoff" entry in the result of getwininfo().
            (closes vim/vim#9163)
cdf5fdb294

Fix indent in Test_getbufwintabinfo().

runtime/doc/eval.txt

@@ -5562,6 +5562,9 @@ getwininfo([{winid}])					*getwininfo()*
 					otherwise
 			wincol		leftmost screen column of the window;
 					"col" from |win_screenpos()|
+			textoff		number of columns occupied by any
+					'foldcolumn', 'signcolumn' and line
+					number in front of the text
 			winid		|window-ID|
 			winnr		window number
 			winrow		topmost screen line of the window;

src/nvim/eval.c

@@ -6851,7 +6851,7 @@ dict_T *get_win_info(win_T *wp, int16_t tpnr, int16_t winnr)
   tv_dict_add_nr(dict, S_LEN("width"), wp->w_width);
   tv_dict_add_nr(dict, S_LEN("bufnr"), wp->w_buffer->b_fnum);
   tv_dict_add_nr(dict, S_LEN("wincol"), wp->w_wincol + 1);
-
+  tv_dict_add_nr(dict, S_LEN("textoff"), win_col_off(wp));
   tv_dict_add_nr(dict, S_LEN("terminal"), bt_terminal(wp->w_buffer));
   tv_dict_add_nr(dict, S_LEN("quickfix"), bt_quickfix(wp->w_buffer));
   tv_dict_add_nr(dict, S_LEN("loclist"),

src/nvim/testdir/test_bufwintabinfo.vim

@@ -42,6 +42,7 @@ function Test_getbufwintabinfo()
 
   only
   let w1_id = win_getid()
+  setl foldcolumn=3
   new
   let w2_id = win_getid()
   tabnew | let w3_id = win_getid()
@@ -60,6 +61,7 @@ function Test_getbufwintabinfo()
   call assert_equal(winbufnr(2), winlist[1].bufnr)
   call assert_equal(winheight(2), winlist[1].height)
   call assert_equal(1, winlist[1].wincol)
+  call assert_equal(3, winlist[1].textoff)  " foldcolumn
   call assert_equal(tablineheight + winheight(1) + 2, winlist[1].winrow)
 
   call assert_equal(1, winlist[2].winnr)