top: ensure those potential focused tasks stay focused

When that 'F' focus command has been applied to a task
in forest view it should remain as the topmost process
in a particular window. But without this patch that is
not guaranteed. Newly forked/cloned tasks 'above' such
a process result in task(s) appearing which shouldn't.

The effect was as if that up arrow key scrolled beyond
the topmost parent task, which would never be allowed.

[ since scrolling is permitted within a focus range, ]
[ when any task 'above' our focus/topmost task ends, ]
[ we respond as if scrolled with the down arrow key. ]

[ that result is completely appropriate. if the user ]
[ wishes to return to a focused parent, the up arrow ]
[ or home key can be used to accomplish such a goal. ]

Signed-off-by: Jim Warner <james.warner@comcast.net>

top/top.c

@@ -4598,6 +4598,11 @@ static void forest_config (WIN_t *q) {
       while (i+1 < PIDSmaxt && rSv(i+1) > level)
          ++i;
       q->focus_end = i + 1;  // make 'focus_end' a proper fencpost
+      // watch out for newly forked/cloned tasks 'above' us ...
+      if (q->begtask < q->focus_beg) {
+         q->begtask = q->focus_beg;
+         q->begnext = 0;     // as 'mkVIZoff' but in any window
+      }
    }
  #undef rSv
 } // end: forest_config
@@ -6213,7 +6218,7 @@ static void window_hlp (void) {
 
    reversed = 0;
    // potentially scroll forward ...
-   if (w->begnext > beg) {
+   if (w->begnext > 0) {
 fwd_redux:
       for (i = w->begtask; i < end; i++) {
          if (wins_usrselect(w, i)