vim-patch:8.1.2303: cursor in wrong position after horizontal scroll

Problem:    Cursor in wrong position after horizontal scroll.
Solution:   Set w_valid_leftcol.  (closes vim/vim#5214, closes vim/vim#5224)
08f23636ae

src/nvim/move.c

@@ -943,6 +943,9 @@ void curs_columns(
     redraw_later(SOME_VALID);
   }
 
+  // now w_leftcol is valid, avoid check_cursor_moved() thinking otherwise
+  curwin->w_valid_leftcol = curwin->w_leftcol;
+
   curwin->w_valid |= VALID_WCOL|VALID_WROW|VALID_VIRTCOL;
 }
 

src/nvim/testdir/test_matchadd_conceal.vim

@@ -312,3 +312,31 @@ func Test_cursor_column_in_concealed_line_after_window_scroll()
   call StopVimInTerminal(buf)
   call delete('Xcolesearch')
 endfunc
+
+func Test_cursor_column_in_concealed_line_after_leftcol_change()
+  CheckRunVimInTerminal
+
+  " Test for issue #5214 fix.
+  let lines =<< trim END
+    0put = 'ab' .. repeat('-', &columns) .. 'c'
+    call matchadd('Conceal', '-')
+    set nowrap ss=0 cole=3 cocu=n
+  END
+  call writefile(lines, 'Xcurs-columns')
+  let buf = RunVimInTerminal('-S Xcurs-columns', {})
+
+  " Go to the end of the line (3 columns beyond the end of the screen).
+  " Horizontal scroll would center the cursor in the screen line, but conceal
+  " makes it go to screen column 1.
+  call term_sendkeys(buf, "$")
+  call term_wait(buf)
+
+  " Are the concealed parts of the current line really hidden?
+  call assert_equal('c', term_getline(buf, '.'))
+
+  " BugFix check: Is the window's cursor column properly updated for conceal?
+  call assert_equal(1, term_getcursor(buf)[1])
+
+  call StopVimInTerminal(buf)
+  call delete('Xcurs-columns')
+endfunc