patch 8.1.1445: popup window border highlight not implemented yet
Problem: Popup window border highlight not implemented yet.
Solution: Implement the "borderhighlight" option.
diff --git a/src/structs.h b/src/structs.h
index fb27745..f6db264 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -2890,6 +2890,8 @@
int w_wantcol; // "col" for popup window
int w_popup_padding[4]; // popup padding top/right/bot/left
int w_popup_border[4]; // popup border top/right/bot/left
+ char_u *w_border_highlight[4]; // popup border highlight
+ int w_border_char[8]; // popup border characters
varnumber_T w_popup_last_changedtick; // b:changedtick when position was
// computed
callback_T w_filter_cb; // popup filter callback