Make scrolloff and sidescrolloff global-local

It was noticed, that sidescrolloff and scrolloff options behave
differently in comparison to other global-local window options like
'listchars'

So make those two behave like other global-local options.

Add a few tests to make sure all global-local window options behave
similar

fixes vim#12956

runtime/doc/options.txt

@@ -374,6 +374,12 @@ used.  Thus it does the same as: >
 Note: In the future more global options can be made |global-local|.  Using
 ":setlocal" on a global option might work differently then.
 
+							*window-global-local*
+One special feature are |global-local| window options. Those options are not
+only local to the window, but in addition to the buffer inside the window.
+Each buffer remembers uses its own local version of that option value, so when
+you edit the same buffer in a different window, it carries along and re-uses
+the window-local options.
 
 						*option-value-function*
 Some options ('completefunc', 'imactivatefunc', 'imstatusfunc', 'omnifunc',

src/option.c

@@ -6652,6 +6652,8 @@ copy_winopt(winopt_T *from, winopt_T *to)
     to->wo_sms = from->wo_sms;
     to->wo_crb = from->wo_crb;
     to->wo_crb_save = from->wo_crb_save;
+    to->wo_siso = from->wo_siso;
+    to->wo_so = from->wo_so;
 #ifdef FEAT_SPELL
     to->wo_spell = from->wo_spell;
 #endif

src/structs.h

@@ -312,6 +312,10 @@ typedef struct
     char_u	*wo_scl;
 # define w_p_scl w_onebuf_opt.wo_scl	// 'signcolumn'
 #endif
+    long	wo_siso;
+# define w_p_siso w_onebuf_opt.wo_siso	// 'sidescrolloff' local value
+    long	wo_so;
+# define w_p_so w_onebuf_opt.wo_so	// 'scrolloff' local value
 #ifdef FEAT_TERMINAL
     char_u	*wo_twk;
 # define w_p_twk w_onebuf_opt.wo_twk	// 'termwinkey'
@@ -3977,8 +3981,6 @@ struct window_S
     int		*w_p_cc_cols;	    // array of columns to highlight or NULL
     char_u	w_p_culopt_flags;   // flags for cursorline highlighting
 #endif
-    long	w_p_siso;	    // 'sidescrolloff' local value
-    long	w_p_so;		    // 'scrolloff' local value
 
 #ifdef FEAT_LINEBREAK
     int		w_briopt_min;	    // minimum width for breakindent

src/testdir/test_options.vim

@@ -1689,4 +1689,89 @@ func Test_string_option_revert_on_failure()
   bw!
 endfunc
 
+func Test_set_option_window_global_local()
+  new Xbuffer1
+  let [ _gso, _lso ] = [ &g:scrolloff, &l:scrolloff ]
+  setlocal scrolloff=2
+  setglobal scrolloff=3
+  setl modified
+  " A new buffer has its own window-local options
+  hide enew
+  call assert_equal(-1, &l:scrolloff)
+  call assert_equal(3, &g:scrolloff)
+  " A new window opened with its own buffer-local options
+  new
+  call assert_equal(-1, &l:scrolloff)
+  call assert_equal(3, &g:scrolloff)
+  " Re-open Xbuffer1 and it should use
+  " the previous set window-local options
+  b Xbuffer1
+  call assert_equal(2, &l:scrolloff)
+  call assert_equal(3, &g:scrolloff)
+  bw!
+  bw!
+  let &g:scrolloff =  _gso
+endfunc
+
+func GetGlobalLocalWindowOptions()
+  new
+  sil! r $VIMRUNTIME/doc/options.txt
+  " Filter for global or local to window
+  v/^'.*'.*\n.*global or local to window |global-local/d
+  " get option value and type
+  sil %s/^'\([^']*\)'.*'\s\+\(\w\+\)\s\+(default \%(\(".*"\|\d\+\|empty\)\).*/\1 \2 \3/g
+  sil %s/empty/""/g
+  " split the result
+  let result=getline(1,'$')->map({_, val -> split(val, ' ')})
+  bw!
+  return result
+endfunc
+
+func Test_set_option_window_global_local_all()
+  new Xbuffer2
+
+  let optionlist = GetGlobalLocalWindowOptions()
+  for [opt, type, default] in optionlist
+    let _old = eval('&g:' .. opt)
+    if type == 'string'
+      if opt == 'fillchars'
+        exe 'setl ' .. opt .. '=vert:+'
+        exe 'setg ' .. opt .. '=vert:+,fold:+'
+      elseif opt == 'listchars'
+        exe 'setl ' .. opt .. '=tab:>>'
+        exe 'setg ' .. opt .. '=tab:++'
+      elseif opt == 'virtualedit'
+        exe 'setl ' .. opt .. '=all'
+        exe 'setg ' .. opt .. '=block'
+      else
+        exe 'setl ' .. opt .. '=Local'
+        exe 'setg ' .. opt .. '=Global'
+      endif
+    elseif type == 'number'
+      exe 'setl ' .. opt .. '=5'
+      exe 'setg ' .. opt .. '=10'
+    endif
+    setl modified
+    hide enew
+    if type == 'string'
+      call assert_equal('', eval('&l:' .. opt))
+      if opt == 'fillchars'
+        call assert_equal('vert:+,fold:+', eval('&g:' .. opt), 'option:' .. opt)
+      elseif opt == 'listchars'
+        call assert_equal('tab:++', eval('&g:' .. opt), 'option:' .. opt)
+      elseif opt == 'virtualedit'
+        call assert_equal('block', eval('&g:' .. opt), 'option:' .. opt)
+      else
+        call assert_equal('Global', eval('&g:' .. opt), 'option:' .. opt)
+      endif
+    elseif type == 'number'
+      call assert_equal(-1, eval('&l:' .. opt), 'option:' .. opt)
+      call assert_equal(10, eval('&g:' .. opt), 'option:' .. opt)
+    endif
+    bw!
+    exe 'let &g:' .. opt .. '=' .. default
+  endfor
+  bw!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/window.c

@@ -5546,8 +5546,8 @@ win_alloc(win_T *after, int hidden)
     new_wp->w_scbind_pos = 1;
 
     // use global option value for global-local options
-    new_wp->w_p_so = -1;
-    new_wp->w_p_siso = -1;
+    new_wp->w_allbuf_opt.wo_so = new_wp->w_p_so = -1;
+    new_wp->w_allbuf_opt.wo_siso = new_wp->w_p_siso = -1;
 
     // We won't calculate w_fraction until resizing the window
     new_wp->w_fraction = 0;