--- button.c	2021-02-04 09:00:26.000000000 +0800
+++ button.patched.c	2021-02-07 21:31:45.960978282 +0800
@@ -5258,6 +5258,10 @@
     if (screen->extend_coords == SET_PIXEL_POSITION_MOUSE) {
 	row = event->y - OriginY(screen);
 	col = event->x - OriginX(screen);
+	if (row < 0)
+	    row = 0;
+	if (col < 0)
+	    col = 0;
     } else {
 	/* Compute character position of mouse pointer */
 	row = (event->y - screen->border) / FontHeight(screen);