patch 8.1.1559: popup window title property not implemented yet
Problem: Popup window title property not implemented yet.
Solution: Implement the title property.
diff --git a/src/structs.h b/src/structs.h
index 09158a0..5787d2b 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -2891,6 +2891,7 @@
pos_save_T w_save_cursor; /* backup of cursor pos and topline */
#ifdef FEAT_TEXT_PROP
int w_popup_flags; // POPF_ values
+ char_u *w_popup_title;
poppos_T w_popup_pos;
int w_popup_fixed; // do not shift popup to fit on screen
int w_zindex;