patch 8.2.2236: 'scroll' option can change when setting the statusline

Problem:    'scroll' option can change when setting the statusline or tabline
            but the option context is not updated.
Solution:   Update the script context when the scroll option is changed as a
            side effect. (Christian Brabandt, closes #7533)

runtime/doc/options.txt

@@ -6321,7 +6321,9 @@ A jump table for the options with a short description can be found at |Q_op|.
 			local to window
 	Number of lines to scroll with CTRL-U and CTRL-D commands.  Will be
 	set to half the number of lines in the window when the window size
-	changes.  If you give a count to the CTRL-U or CTRL-D command it will
+	changes.  This may happen when enabling the |status-line| or
+	'tabline' option after setting the 'scroll' option.
+	If you give a count to the CTRL-U or CTRL-D command it will
 	be used as the new value for 'scroll'.  Reset to half the window
 	height with ":set scroll=0".
 

src/scriptfile.c

@@ -1553,6 +1553,7 @@ scriptnames_slash_adjust(void)
 
 /*
  * Get a pointer to a script name.  Used for ":verbose set".
+ * Message appended to "Last set from "
  */
     char_u *
 get_scriptname(scid_T id)
@@ -1567,6 +1568,8 @@ get_scriptname(scid_T id)
 	return (char_u *)_("environment variable");
     if (id == SID_ERROR)
 	return (char_u *)_("error handler");
+    if (id == SID_WINLAYOUT)
+	return (char_u *)_("changed window size");
     return SCRIPT_ITEM(id)->sn_name;
 }
 

src/testdir/test_options.vim

@@ -1013,4 +1013,22 @@ func Test_isfname_with_options()
   setlocal keywordprg&
 endfunc
 
+" Test that resetting laststatus does change scroll option
+func Test_opt_reset_scroll()
+  CheckRunVimInTerminal
+  let vimrc =<< trim [CODE]
+    set scroll=2
+    set laststatus=2
+  [CODE]
+  call writefile(vimrc, 'Xscroll')
+  let buf = RunVimInTerminal('-S Xscroll', {'rows': 16, 'cols': 45})
+  call term_sendkeys(buf, ":verbose set scroll?\n")
+  call WaitForAssert({-> assert_match('Last set.*window size', term_getline(buf, 15))})
+  call assert_match('^\s*scroll=7$', term_getline(buf, 14))
+  call StopVimInTerminal(buf)
+
+  " clean up
+  call delete('Xscroll')
+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 */
+/**/
+    2236,
 /**/
     2235,
 /**/

src/vim.h

@@ -1232,6 +1232,7 @@ extern int (*dyn_libintl_wputenv)(const wchar_t *envstring);
 #define SID_ENV		-4	// for sourcing environment variable
 #define SID_ERROR	-5	// option was reset because of an error
 #define SID_NONE	-6	// don't set scriptID
+#define SID_WINLAYOUT	-7	// changing window size
 
 /*
  * Events for autocommands.

src/window.c

@@ -6325,9 +6325,21 @@ win_new_width(win_T *wp, int width)
     void
 win_comp_scroll(win_T *wp)
 {
+#if defined(FEAT_EVAL)
+    int old_w_p_scr = wp->w_p_scr;
+#endif
+
     wp->w_p_scr = ((unsigned)wp->w_height >> 1);
     if (wp->w_p_scr == 0)
 	wp->w_p_scr = 1;
+#if defined(FEAT_EVAL)
+    if (wp->w_p_scr != old_w_p_scr)
+    {
+	// Used by "verbose set scroll".
+	wp->w_p_script_ctx[WV_SCROLL].sc_sid = SID_WINLAYOUT;
+	wp->w_p_script_ctx[WV_SCROLL].sc_lnum = 0;
+    }
+#endif
 }
 
 /*