vim-patch:8.2.1345: Redraw error when using visual block and scroll

Problem:    Redraw error when using visual block and scroll.
Solution:   Add check for w_topline. ( closes vim/vim#6597)
f8992d47cd

test/functional/legacy/visual_mode_spec.lua

@@ -0,0 +1,42 @@
+-- Test visual line mode selection redraw after scrolling
+
+local helpers = require('test.functional.helpers')(after_each)
+
+local Screen = require('test.functional.ui.screen')
+local call = helpers.call
+local clear = helpers.clear
+local feed = helpers.feed
+local feed_command = helpers.feed_command
+local funcs = helpers.funcs
+local meths = helpers.meths
+local eq = helpers.eq
+
+describe('visual line mode', function()
+  local screen
+
+  it('redraws properly after scrolling with matchparen loaded and scrolloff=1', function()
+    clear{args={'-u', 'NORC'}}
+    screen = Screen.new(30, 7)
+    screen:attach()
+    screen:set_default_attr_ids({
+      [1] = {bold = true},
+      [2] = {background = Screen.colors.LightGrey},
+    })
+
+    eq(1, meths.get_var('loaded_matchparen'))
+    feed_command('set scrolloff=1')
+    funcs.setline(1, {'a', 'b', 'c', 'd', 'e', '', '{', '}', '{', 'f', 'g', '}'})
+    call('cursor', 5, 1)
+
+    feed('V<c-d><c-d>')
+    screen:expect([[
+      {2:{}                             |
+      {2:}}                             |
+      {2:{}                             |
+      {2:f}                             |
+      ^g                             |
+      }                             |
+      {1:-- VISUAL LINE --}             |
+    ]])
+  end)
+end)