patch 8.0.1767: with 'incsearch' text may jump up and down

Problem:    With 'incsearch' text may jump up and down. ()
Solution:   Besides w_botline also save and restore w_empty_rows.
            (closes # 2530)

src/ex_getln.c

@@ -237,8 +237,9 @@ getcmdline(
     int		old_topfill;
     int		init_topfill = curwin->w_topfill;
 # endif
-    linenr_T	old_botline;
+    linenr_T	old_botline, old_empty_rows;
     linenr_T	init_botline = curwin->w_botline;
+    linenr_T	init_empty_rows = curwin->w_empty_rows;
     int		did_incsearch = FALSE;
     int		incsearch_postponed = FALSE;
 #endif
@@ -291,6 +292,7 @@ getcmdline(
     old_topfill = curwin->w_topfill;
 # endif
     old_botline = curwin->w_botline;
+    old_empty_rows = curwin->w_empty_rows;
 #endif
 
     /*
@@ -1075,6 +1077,7 @@ getcmdline(
 			old_topfill = init_topfill;
 # endif
 			old_botline = init_botline;
+			old_empty_rows = init_empty_rows;
 		    }
 #endif
 		    redrawcmd();
@@ -1804,6 +1807,7 @@ getcmdline(
 			old_topfill = curwin->w_topfill;
 # endif
 			old_botline = curwin->w_botline;
+			old_empty_rows = curwin->w_empty_rows;
 			update_screen(NOT_VALID);
 			redrawcmdline();
 		    }
@@ -2020,6 +2024,7 @@ cmdline_changed:
 	    curwin->w_topfill = old_topfill;
 # endif
 	    curwin->w_botline = old_botline;
+	    curwin->w_empty_rows = old_empty_rows;
 	    changed_cline_bef_curs();
 	    update_topline();
 
@@ -2114,6 +2119,7 @@ returncmd:
 	curwin->w_topfill = old_topfill;
 # endif
 	curwin->w_botline = old_botline;
+	curwin->w_empty_rows = old_empty_rows;
 	highlight_match = FALSE;
 	validate_cursor();	/* needed for TAB */
 	redraw_all_later(SOME_VALID);

src/testdir/dumps/Test_incsearch_scrolling_01.dump

@@ -0,0 +1,9 @@
+|.+0&#ffffff0@69
+@50| @19
+|.@69
+@50| @19
+@70
+|t+1&&|a|r|g|e+0&&|t| @63
+|@+0#4040ff13&@2| @66
+|/+0#0000000&|t|a|r|g> @64
+@70

src/testdir/test_search.vim

@@ -1,6 +1,7 @@
 " Test for the search command
 
 source shared.vim
+source screendump.vim
 
 func Test_search_cmdline()
   if !exists('+incsearch')
@@ -690,6 +691,36 @@ func Test_search_cmdline_incsearch_highlight_attr()
   bwipe!
 endfunc
 
+func Test_incsearch_scrolling()
+  if !CanRunVimInTerminal()
+    return
+  endif
+  call assert_equal(0, &scrolloff)
+  call writefile([
+	\ 'let dots = repeat(".", 120)',
+	\ 'set incsearch cmdheight=2 scrolloff=0',
+	\ 'call setline(1, [dots, dots, dots, "", "target", dots, dots])',
+	\ 'normal gg',
+	\ 'redraw',
+	\ ], 'Xscript')
+  let buf = RunVimInTerminal('-S Xscript', {'rows': 9, 'cols': 70})
+  " Need to send one key at a time to force a redraw
+  call term_sendkeys(buf, '/')
+  sleep 100m
+  call term_sendkeys(buf, 't')
+  sleep 100m
+  call term_sendkeys(buf, 'a')
+  sleep 100m
+  call term_sendkeys(buf, 'r')
+  sleep 100m
+  call term_sendkeys(buf, 'g')
+  call VerifyScreenDump(buf, 'Test_incsearch_scrolling_01', {})
+
+  call term_sendkeys(buf, "\<Esc>")
+  call StopVimInTerminal(buf)
+  call delete('Xscript')
+endfunc
+
 func Test_search_undefined_behaviour()
   if !has("terminal")
     return

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1767,
 /**/
     1766,
 /**/