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
(cherry picked from commit 03e7d4fc85)

test/old/testdir/test_visual.vim

@@ -1556,5 +1556,23 @@ func Test_heap_buffer_overflow()
   set updatecount&
 endfunc
 
+" Test Visual highlight with cursor at end of screen line and 'showbreak'
+func Test_visual_hl_with_showbreak()
+  CheckScreendump
+
+  let lines =<< trim END
+    setlocal showbreak=+
+    call setline(1, repeat('a', &columns + 10))
+    normal g$v4lo
+  END
+  call writefile(lines, 'XTest_visual_sbr', 'D')
+
+  let buf = RunVimInTerminal('-S XTest_visual_sbr', {'rows': 6, 'cols': 50})
+  call VerifyScreenDump(buf, 'Test_visual_hl_with_showbreak', {})
+
+  " clean up
+  call term_sendkeys(buf, "\<Esc>")
+  call StopVimInTerminal(buf)
+endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab