patch 8.1.1553: not easy to change the text in a popup window
Problem: Not easy to change the text in a popup window.
Solution: Add popup_settext(). (Ben Jackson, closes #4549)
Also display a space for an empty popup.
diff --git a/src/proto/popupwin.pro b/src/proto/popupwin.pro
index 6e93791..e026506 100644
--- a/src/proto/popupwin.pro
+++ b/src/proto/popupwin.pro
@@ -14,6 +14,7 @@
void f_popup_close(typval_T *argvars, typval_T *rettv);
void f_popup_hide(typval_T *argvars, typval_T *rettv);
void f_popup_show(typval_T *argvars, typval_T *rettv);
+void f_popup_settext(typval_T *argvars, typval_T *rettv);
void popup_close(int id);
void popup_close_tabpage(tabpage_T *tp, int id);
void close_all_popups(void);