vim-patch:9.0.1759: Visual highlight not working with cursor at end of screen line

Problem:  Visual highlight not working with cursor at end of screen line
          and 'showbreak'.
Solution: Only update "vcol_prev" when drawing buffer text.

closes: vim/vim#12865

8fc6a1dae0

test/functional/legacy/visual_spec.lua

@@ -0,0 +1,69 @@
+local helpers = require('test.functional.helpers')(after_each)
+
+local Screen = require('test.functional.ui.screen')
+local clear = helpers.clear
+local feed = helpers.feed
+local exec = helpers.exec
+
+before_each(clear)
+
+describe('Visual highlight', function()
+  local screen
+
+  before_each(function()
+    screen = Screen.new(50, 6)
+    screen:set_default_attr_ids({
+      [0] = {foreground = Screen.colors.Blue, bold = true},  -- NonText
+      [1] = {bold = true},  -- ModeMsg
+      [2] = {background = Screen.colors.LightGrey},  -- Visual
+    })
+    screen:attach()
+  end)
+
+  -- oldtest: Test_visual_block_with_virtualedit()
+  it('shows selection correctly with virtualedit=block', function()
+    exec([[
+      call setline(1, ['aaaaaa', 'bbbb', 'cc'])
+      set virtualedit=block
+      normal G
+    ]])
+
+    feed('<C-V>gg$')
+    screen:expect([[
+      {2:aaaaaa}^                                            |
+      {2:bbbb   }                                           |
+      {2:cc     }                                           |
+      {0:~                                                 }|
+      {0:~                                                 }|
+      {1:-- VISUAL BLOCK --}                                |
+    ]])
+
+    feed('<Esc>gg<C-V>G$')
+    screen:expect([[
+      {2:aaaaaa }                                           |
+      {2:bbbb   }                                           |
+      {2:cc}^ {2:    }                                           |
+      {0:~                                                 }|
+      {0:~                                                 }|
+      {1:-- VISUAL BLOCK --}                                |
+    ]])
+  end)
+
+  -- oldtest: Test_visual_hl_with_showbreak()
+  it("with cursor at end of screen line and 'showbreak'", function()
+    exec([[
+      setlocal showbreak=+
+      call setline(1, repeat('a', &columns + 10))
+      normal g$v4lo
+    ]])
+
+    screen:expect([[
+      aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa^a|
+      {0:+}{2:aaaa}aaaaaa                                       |
+      {0:~                                                 }|
+      {0:~                                                 }|
+      {0:~                                                 }|
+      {1:-- VISUAL --}                                      |
+    ]])
+  end)
+end)