[PATCH] perf hists browser: Fix UI bug after fold/unfold

[He Kuang <hekuang@huawei.com>]

In perf hists browser, the fold/unfold stat of each hist entry is
recorded but hb->nr_callchain_rows loses its value after zoom out and
zoom in back. This causes a wrong row cursor range that restrict user to
move down anymore.

Before:
  $ perf record -g -e syscalls:* ls
  $ perf report

(select an event and unfold, then zoom out and back, row cursor blocked)

    Children      Self  Command  Shared Object          Symbol
  ================================================================
  -  100.00%   100.00%  ls       libuClibc-0.9.33.2.so  [.] lstat64
  - lstat64
       16.67% 0x6469702e64
       16.67% 0x692d6f732e6f7364
       8.33% 0x442d00746f6f725f
       8.33% 0x746f006469
       8.33% 0x646c6f2e617461
       8.33% 0x646970
       8.33% 0x617461 <= [cursor may stop here, can't move down anymore]
       8.33% 0x7365
       8.33% 0x6469
       8.33% 0x65
  -   16.67%     0.00%  ls       [unknown]              [.]0x6469702e64
     0x6469702e64

When zoom into DSO or thread, nr_rows is not cleared which causes a
similar problem.

This patch recalculates hb->nr_callchain_rows and clears nr_rows to fix
the bug.

Signed-off-by: He Kuang <hekuang@huawei.com>
---
 tools/perf/ui/browsers/hists.c | 20 ++++++++++++++++++++
 tools/perf/util/hist.c         |  1 +
 2 files changed, 21 insertions(+)

diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
index 1106bb8..bef9ab0 100644
--- a/tools/perf/ui/browsers/hists.c
+++ b/tools/perf/ui/browsers/hists.c
@@ -42,6 +42,7 @@ static void hist_browser__update_nr_entries(struct hist_browser *hb);
 
 static struct rb_node *hists__filter_entries(struct rb_node *nd,
 					     float min_pcnt);
+static int __hist_browser__get_folding(struct hist_browser *browser);
 
 static bool hist_browser__has_filter(struct hist_browser *hb)
 {
@@ -57,6 +58,7 @@ static u32 hist_browser__nr_entries(struct hist_browser *hb)
 	else
 		nr_entries = hb->hists->nr_entries;
 
+	hb->nr_callchain_rows = __hist_browser__get_folding(hb);
 	return nr_entries + hb->nr_callchain_rows;
 }
 
@@ -353,6 +355,24 @@ static void hist_entry__set_folding(struct hist_entry *he, bool unfold)
 		he->nr_rows = 0;
 }
 
+static int
+__hist_browser__get_folding(struct hist_browser *browser)
+{
+	struct rb_node *nd;
+	struct hists *hists = browser->hists;
+	int unfolded_rows = 0;
+
+	for (nd = rb_first(&hists->entries);
+	     (nd = hists__filter_entries(nd, browser->min_pcnt)) != NULL;
+	     nd = rb_next(nd)) {
+		struct hist_entry *he = rb_entry(nd, struct hist_entry, rb_node);
+
+		if (he->ms.unfolded)
+			unfolded_rows += he->nr_rows;
+	}
+	return unfolded_rows;
+}
+
 static void
 __hist_browser__set_folding(struct hist_browser *browser, bool unfold)
 {
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