patch 9.0.1828: cursor wrong with virt text before double-width char

Problem:  Wrong cursor position with virtual text before double-width
          char at window edge.
Solution: Check for double-width char before adding virtual text size.

closes: #12977

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
diff --git a/src/testdir/test_textprop.vim b/src/testdir/test_textprop.vim
index 030955b..c006912 100644
--- a/src/testdir/test_textprop.vim
+++ b/src/testdir/test_textprop.vim
@@ -2810,6 +2810,22 @@
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_prop_inserts_text_before_double_width_wrap()
+  CheckRunVimInTerminal
+
+  let lines =<< trim END
+    call setline(1, repeat('a', 40) .. '口' .. '12345')
+    call prop_type_add('theprop', #{highlight: 'Special'})
+    call prop_add(1, 41, #{type: 'theprop', text: repeat('b', 9)})
+    normal! $
+  END
+  call writefile(lines, 'XscriptPropsBeforeDoubleWidthWrap', 'D')
+  let buf = RunVimInTerminal('-S XscriptPropsBeforeDoubleWidthWrap', #{rows: 3, cols: 50})
+  call VerifyScreenDump(buf, 'Test_prop_inserts_text_before_double_width_wrap_1', {})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 func Test_prop_inserts_text_lcs_extends()
   CheckRunVimInTerminal