[PATCHv2 2/2] perf hists browser: Fix UI bug after zoom into thread/dso/symbol

[He Kuang <hekuang@huawei.com>]

When zoom into thread/dso/symbol, the fold/unfold stat is cleared in
hists__filter_by_thread/dso/symbol(), but h->nr_rows is not cleared. So
if we toggle fold stat on the unfold entires, nr_entries got a wrong
value.

This bug can be reproduced as follows:

$ perf record -g -e syscalls:sys_enter_open ls
$ perf report

    Children      Self  Command  Shared Object            Symbol
  ================================================================
  +   50.00%     0.00%  ls       ld64.so  [.]  _dl_get_ready_to_run
  -   50.00%     0.00%  ls       ld64.so  [.]  _dl_load_shared_library
      _dl_load_shared_library <= [Zoom into thread/dso]
      _dl_get_ready_to_run
      _start
  ...

In the new thread hists, all entries reset to fold, if we unfold the
same entry as we previously unfolded, nr_entries got wrong value, and we
can't move down cursor to bottom row.

                                                         Thread: ls
    Children      Self  Command  Shared Object            Symbol
  ================================================================
  +   50.00%     0.00%  ls       ld64.so  [.]  _dl_get_ready_to_run
  -   50.00%     0.00%  ls       ld64.so  [.]  _dl_load_shared_library
      _dl_load_shared_library
      _dl_get_ready_to_run <= [cursor may stop here, can't move down]
      _start
  ...

This patch clear h->nr_rows to fix this bug.

Signed-off-by: He Kuang <hekuang@huawei.com>
---
 tools/perf/util/hist.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 70b48a6..24aff7d 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -1169,6 +1169,7 @@ static void hists__remove_entry_filter(struct hists *hists, struct hist_entry *h
 	/* force fold unfiltered entry for simplicity */
 	h->ms.unfolded = false;
 	h->row_offset = 0;
+	h->nr_rows = 0;
 
 	hists->stats.nr_non_filtered_samples += h->stat.nr_events;
 
-- 
2.2.0.33.gc18b867