linux-vybrid_public/tools/perf/util/ui/browsers/hists.c

#define _GNU_SOURCE
#include <stdio.h>
#undef _GNU_SOURCE
#include "../libslang.h"
#include <stdlib.h>
#include <string.h>
#include <newt.h>
#include <linux/rbtree.h>

#include "../../hist.h"
#include "../../pstack.h"
#include "../../sort.h"
#include "../../util.h"

#include "../browser.h"
#include "../helpline.h"
#include "../util.h"
#include "map.h"

struct hist_browser {
	struct ui_browser   b;
	struct hists	    *hists;
	struct hist_entry   *he_selection;
	struct map_symbol   *selection;
};

static void hist_browser__refresh_dimensions(struct hist_browser *self)
{
	/* 3 == +/- toggle symbol before actual hist_entry rendering */
	self->b.width = 3 + (hists__sort_list_width(self->hists) +
			     sizeof("[k]"));
}

static void hist_browser__reset(struct hist_browser *self)
{
	self->b.nr_entries = self->hists->nr_entries;
	hist_browser__refresh_dimensions(self);
	ui_browser__reset_index(&self->b);
}

static char tree__folded_sign(bool unfolded)
{
	return unfolded ? '-' : '+';
}

static char map_symbol__folded(const struct map_symbol *self)
{
	return self->has_children ? tree__folded_sign(self->unfolded) : ' ';
}

static char hist_entry__folded(const struct hist_entry *self)
{
	return map_symbol__folded(&self->ms);
}

static char callchain_list__folded(const struct callchain_list *self)
{
	return map_symbol__folded(&self->ms);
}

static int callchain_node__count_rows_rb_tree(struct callchain_node *self)
{
	int n = 0;
	struct rb_node *nd;

	for (nd = rb_first(&self->rb_root); nd; nd = rb_next(nd)) {
		struct callchain_node *child = rb_entry(nd, struct callchain_node, rb_node);
		struct callchain_list *chain;
		char folded_sign = ' '; /* No children */

		list_for_each_entry(chain, &child->val, list) {
			++n;
			/* We need this because we may not have children */
			folded_sign = callchain_list__folded(chain);
			if (folded_sign == '+')
				break;
		}

		if (folded_sign == '-') /* Have children and they're unfolded */
			n += callchain_node__count_rows_rb_tree(child);
	}

	return n;
}

static int callchain_node__count_rows(struct callchain_node *node)
{
	struct callchain_list *chain;
	bool unfolded = false;
	int n = 0;

	list_for_each_entry(chain, &node->val, list) {
		++n;
		unfolded = chain->ms.unfolded;
	}

	if (unfolded)
		n += callchain_node__count_rows_rb_tree(node);

	return n;
}

static int callchain__count_rows(struct rb_root *chain)
{
	struct rb_node *nd;
	int n = 0;

	for (nd = rb_first(chain); nd; nd = rb_next(nd)) {
		struct callchain_node *node = rb_entry(nd, struct callchain_node, rb_node);
		n += callchain_node__count_rows(node);
	}

	return n;
}

static bool map_symbol__toggle_fold(struct map_symbol *self)
{
	if (!self->has_children)
		return false;

	self->unfolded = !self->unfolded;
	return true;
}

static void callchain_node__init_have_children_rb_tree(struct callchain_node *self)
{
	struct rb_node *nd = rb_first(&self->rb_root);

	for (nd = rb_first(&self->rb_root); nd; nd = rb_next(nd)) {
		struct callchain_node *child = rb_entry(nd, struct callchain_node, rb_node);
		struct callchain_list *chain;
		bool first = true;

		list_for_each_entry(chain, &child->val, list) {
			if (first) {
				first = false;
				chain->ms.has_children = chain->list.next != &child->val ||
							 !RB_EMPTY_ROOT(&child->rb_root);
			} else
				chain->ms.has_children = chain->list.next == &child->val &&
							 !RB_EMPTY_ROOT(&child->rb_root);
		}

		callchain_node__init_have_children_rb_tree(child);
	}
}

static void callchain_node__init_have_children(struct callchain_node *self)
{
	struct callchain_list *chain;

	list_for_each_entry(chain, &self->val, list)
		chain->ms.has_children = !RB_EMPTY_ROOT(&self->rb_root);

	callchain_node__init_have_children_rb_tree(self);
}

static void callchain__init_have_children(struct rb_root *self)
{
	struct rb_node *nd;

	for (nd = rb_first(self); nd; nd = rb_next(nd)) {
		struct callchain_node *node = rb_entry(nd, struct callchain_node, rb_node);
		callchain_node__init_have_children(node);
	}
}

static void hist_entry__init_have_children(struct hist_entry *self)
{
	if (!self->init_have_children) {
		self->ms.has_children = !RB_EMPTY_ROOT(&self->sorted_chain);
		callchain__init_have_children(&self->sorted_chain);
		self->init_have_children = true;
	}
}

static bool hist_browser__toggle_fold(struct hist_browser *self)
{
	if (map_symbol__toggle_fold(self->selection)) {
		struct hist_entry *he = self->he_selection;

		hist_entry__init_have_children(he);
		self->hists->nr_entries -= he->nr_rows;

		if (he->ms.unfolded)
			he->nr_rows = callchain__count_rows(&he->sorted_chain);
		else
			he->nr_rows = 0;
		self->hists->nr_entries += he->nr_rows;
		self->b.nr_entries = self->hists->nr_entries;

		return true;
	}

	/* If it doesn't have children, no toggling performed */
	return false;
}

static int hist_browser__run(struct hist_browser *self, const char *title)
{
	int key;
	int exit_keys[] = { 'a', '?', 'h', 'd', 'D', 't', NEWT_KEY_ENTER,
			    NEWT_KEY_RIGHT, NEWT_KEY_LEFT, 0, };
	char str[256], unit;
	unsigned long nr_events = self->hists->stats.nr_events[PERF_RECORD_SAMPLE];

	self->b.entries = &self->hists->entries;
	self->b.nr_entries = self->hists->nr_entries;

	hist_browser__refresh_dimensions(self);

	nr_events = convert_unit(nr_events, &unit);
	snprintf(str, sizeof(str), "Events: %lu%c                            ",
		 nr_events, unit);
	newtDrawRootText(0, 0, str);

	if (ui_browser__show(&self->b, title,
			     "Press '?' for help on key bindings") < 0)
		return -1;

	ui_browser__add_exit_keys(&self->b, exit_keys);

	while (1) {
		key = ui_browser__run(&self->b);

		switch (key) {
		case 'D': { /* Debug */
			static int seq;
			struct hist_entry *h = rb_entry(self->b.top,
							struct hist_entry, rb_node);
			ui_helpline__pop();
			ui_helpline__fpush("%d: nr_ent=(%d,%d), height=%d, idx=%d, fve: idx=%d, row_off=%d, nrows=%d",
					   seq++, self->b.nr_entries,
					   self->hists->nr_entries,
					   self->b.height,
					   self->b.index,
					   self->b.top_idx,
					   h->row_offset, h->nr_rows);
		}
			continue;
		case NEWT_KEY_ENTER:
			if (hist_browser__toggle_fold(self))
				break;
			/* fall thru */
		default:
			goto out;
		}
	}
out:
	ui_browser__hide(&self->b);
	return key;
}

static char *callchain_list__sym_name(struct callchain_list *self,
				      char *bf, size_t bfsize)
{
	if (self->ms.sym)
		return self->ms.sym->name;

	snprintf(bf, bfsize, "%#Lx", self->ip);
	return bf;
}

#define LEVEL_OFFSET_STEP 3

static int hist_browser__show_callchain_node_rb_tree(struct hist_browser *self,
						     struct callchain_node *chain_node,
						     u64 total, int level,
						     unsigned short row,
						     off_t *row_offset,
						     bool *is_current_entry)
{
	struct rb_node *node;
	int first_row = row, width, offset = level * LEVEL_OFFSET_STEP;
	u64 new_total, remaining;

	if (callchain_param.mode == CHAIN_GRAPH_REL)
		new_total = chain_node->children_hit;
	else
		new_total = total;

	remaining = new_total;
	node = rb_first(&chain_node->rb_root);
	while (node) {
		struct callchain_node *child = rb_entry(node, struct callchain_node, rb_node);
		struct rb_node *next = rb_next(node);
		u64 cumul = cumul_hits(child);
		struct callchain_list *chain;
		char folded_sign = ' ';
		int first = true;
		int extra_offset = 0;

		remaining -= cumul;

		list_for_each_entry(chain, &child->val, list) {
			char ipstr[BITS_PER_LONG / 4 + 1], *alloc_str;
			const char *str;
			int color;
			bool was_first = first;

			if (first)
				first = false;
			else
				extra_offset = LEVEL_OFFSET_STEP;

			folded_sign = callchain_list__folded(chain);
			if (*row_offset != 0) {
				--*row_offset;
				goto do_next;
			}

			alloc_str = NULL;
			str = callchain_list__sym_name(chain, ipstr, sizeof(ipstr));
			if (was_first) {
				double percent = cumul * 100.0 / new_total;

				if (asprintf(&alloc_str, "%2.2f%% %s", percent, str) < 0)
					str = "Not enough memory!";
				else
					str = alloc_str;
			}

			color = HE_COLORSET_NORMAL;
			width = self->b.width - (offset + extra_offset + 2);
			if (ui_browser__is_current_entry(&self->b, row)) {
				self->selection = &chain->ms;
				color = HE_COLORSET_SELECTED;
				*is_current_entry = true;
			}

			ui_browser__set_color(&self->b, color);
			ui_browser__gotorc(&self->b, row, 0);
			slsmg_write_nstring(" ", offset + extra_offset);
			slsmg_printf("%c ", folded_sign);
			slsmg_write_nstring(str, width);
			free(alloc_str);

			if (++row == self->b.height)
				goto out;
do_next:
			if (folded_sign == '+')
				break;
		}

		if (folded_sign == '-') {
			const int new_level = level + (extra_offset ? 2 : 1);
			row += hist_browser__show_callchain_node_rb_tree(self, child, new_total,
									 new_level, row, row_offset,
									 is_current_entry);
		}
		if (row == self->b.height)
			goto out;
		node = next;
	}
out:
	return row - first_row;
}

static int hist_browser__show_callchain_node(struct hist_browser *self,
					     struct callchain_node *node,
					     int level, unsigned short row,
					     off_t *row_offset,
					     bool *is_current_entry)
{
	struct callchain_list *chain;
	int first_row = row,
	     offset = level * LEVEL_OFFSET_STEP,
	     width = self->b.width - offset;
	char folded_sign = ' ';

	list_for_each_entry(chain, &node->val, list) {
		char ipstr[BITS_PER_LONG / 4 + 1], *s;
		int color;

		folded_sign = callchain_list__folded(chain);

		if (*row_offset != 0) {
			--*row_offset;
			continue;
		}

		color = HE_COLORSET_NORMAL;
		if (ui_browser__is_current_entry(&self->b, row)) {
			self->selection = &chain->ms;
			color = HE_COLORSET_SELECTED;
			*is_current_entry = true;
		}

		s = callchain_list__sym_name(chain, ipstr, sizeof(ipstr));
		ui_browser__gotorc(&self->b, row, 0);
		ui_browser__set_color(&self->b, color);
		slsmg_write_nstring(" ", offset);
		slsmg_printf("%c ", folded_sign);
		slsmg_write_nstring(s, width - 2);

		if (++row == self->b.height)
			goto out;
	}

	if (folded_sign == '-')
		row += hist_browser__show_callchain_node_rb_tree(self, node,
								 self->hists->stats.total_period,
								 level + 1, row,
								 row_offset,
								 is_current_entry);
out:
	return row - first_row;
}

static int hist_browser__show_callchain(struct hist_browser *self,
					struct rb_root *chain,
					int level, unsigned short row,
					off_t *row_offset,
					bool *is_current_entry)
{
	struct rb_node *nd;
	int first_row = row;

	for (nd = rb_first(chain); nd; nd = rb_next(nd)) {
		struct callchain_node *node = rb_entry(nd, struct callchain_node, rb_node);

		row += hist_browser__show_callchain_node(self, node, level,
							 row, row_offset,
							 is_current_entry);
		if (row == self->b.height)
			break;
	}

	return row - first_row;
}

static int hist_browser__show_entry(struct hist_browser *self,
				    struct hist_entry *entry,
				    unsigned short row)
{
	char s[256];
	double percent;
	int printed = 0;
	int color, width = self->b.width;
	char folded_sign = ' ';
	bool current_entry = ui_browser__is_current_entry(&self->b, row);
	off_t row_offset = entry->row_offset;

	if (current_entry) {
		self->he_selection = entry;
		self->selection = &entry->ms;
	}

	if (symbol_conf.use_callchain) {
		hist_entry__init_have_children(entry);
		folded_sign = hist_entry__folded(entry);
	}

	if (row_offset == 0) {
		hist_entry__snprintf(entry, s, sizeof(s), self->hists, NULL, false,
				     0, false, self->hists->stats.total_period);
		percent = (entry->period * 100.0) / self->hists->stats.total_period;

		color = HE_COLORSET_SELECTED;
		if (!current_entry) {
			if (percent >= MIN_RED)
				color = HE_COLORSET_TOP;
			else if (percent >= MIN_GREEN)
				color = HE_COLORSET_MEDIUM;
			else
				color = HE_COLORSET_NORMAL;
		}

		ui_browser__set_color(&self->b, color);
		ui_browser__gotorc(&self->b, row, 0);
		if (symbol_conf.use_callchain) {
			slsmg_printf("%c ", folded_sign);
			width -= 2;
		}
		slsmg_write_nstring(s, width);
		++row;
		++printed;
	} else
		--row_offset;

	if (folded_sign == '-' && row != self->b.height) {
		printed += hist_browser__show_callchain(self, &entry->sorted_chain,
							1, row, &row_offset,
							&current_entry);
		if (current_entry)
			self->he_selection = entry;
	}

	return printed;
}

static unsigned int hist_browser__refresh(struct ui_browser *self)
{
	unsigned row = 0;
	struct rb_node *nd;
	struct hist_browser *hb = container_of(self, struct hist_browser, b);

	if (self->top == NULL)
		self->top = rb_first(&hb->hists->entries);

	for (nd = self->top; nd; nd = rb_next(nd)) {
		struct hist_entry *h = rb_entry(nd, struct hist_entry, rb_node);

		if (h->filtered)
			continue;

		row += hist_browser__show_entry(hb, h, row);
		if (row == self->height)
			break;
	}

	return row;
}

static struct rb_node *hists__filter_entries(struct rb_node *nd)
{
	while (nd != NULL) {
		struct hist_entry *h = rb_entry(nd, struct hist_entry, rb_node);
		if (!h->filtered)
			return nd;

		nd = rb_next(nd);
	}

	return NULL;
}

static struct rb_node *hists__filter_prev_entries(struct rb_node *nd)
{
	while (nd != NULL) {
		struct hist_entry *h = rb_entry(nd, struct hist_entry, rb_node);
		if (!h->filtered)
			return nd;

		nd = rb_prev(nd);
	}

	return NULL;
}

static void ui_browser__hists_seek(struct ui_browser *self,
				   off_t offset, int whence)
{
	struct hist_entry *h;
	struct rb_node *nd;
	bool first = true;

	switch (whence) {
	case SEEK_SET:
		nd = hists__filter_entries(rb_first(self->entries));
		break;
	case SEEK_CUR:
		nd = self->top;
		goto do_offset;
	case SEEK_END:
		nd = hists__filter_prev_entries(rb_last(self->entries));
		first = false;
		break;
	default:
		return;
	}

	/*
	 * Moves not relative to the first visible entry invalidates its
	 * row_offset:
	 */
	h = rb_entry(self->top, struct hist_entry, rb_node);
	h->row_offset = 0;

	/*
	 * Here we have to check if nd is expanded (+), if it is we can't go
	 * the next top level hist_entry, instead we must compute an offset of
	 * what _not_ to show and not change the first visible entry.
	 *
	 * This offset increments when we are going from top to bottom and
	 * decreases when we're going from bottom to top.
	 *
	 * As we don't have backpointers to the top level in the callchains
	 * structure, we need to always print the whole hist_entry callchain,
	 * skipping the first ones that are before the first visible entry
	 * and stop when we printed enough lines to fill the screen.
	 */
do_offset:
	if (offset > 0) {
		do {
			h = rb_entry(nd, struct hist_entry, rb_node);
			if (h->ms.unfolded) {
				u16 remaining = h->nr_rows - h->row_offset;
				if (offset > remaining) {
					offset -= remaining;
					h->row_offset = 0;
				} else {
					h->row_offset += offset;
					offset = 0;
					self->top = nd;
					break;
				}
			}
			nd = hists__filter_entries(rb_next(nd));
			if (nd == NULL)
				break;
			--offset;
			self->top = nd;
		} while (offset != 0);
	} else if (offset < 0) {
		while (1) {
			h = rb_entry(nd, struct hist_entry, rb_node);
			if (h->ms.unfolded) {
				if (first) {
					if (-offset > h->row_offset) {
						offset += h->row_offset;
						h->row_offset = 0;
					} else {
						h->row_offset += offset;
						offset = 0;
						self->top = nd;
						break;
					}
				} else {
					if (-offset > h->nr_rows) {
						offset += h->nr_rows;
						h->row_offset = 0;
					} else {
						h->row_offset = h->nr_rows + offset;
						offset = 0;
						self->top = nd;
						break;
					}
				}
			}

			nd = hists__filter_prev_entries(rb_prev(nd));
			if (nd == NULL)
				break;
			++offset;
			self->top = nd;
			if (offset == 0) {
				/*
				 * Last unfiltered hist_entry, check if it is
				 * unfolded, if it is then we should have
				 * row_offset at its last entry.
				 */
				h = rb_entry(nd, struct hist_entry, rb_node);
				if (h->ms.unfolded)
					h->row_offset = h->nr_rows;
				break;
			}
			first = false;
		}
	} else {
		self->top = nd;
		h = rb_entry(nd, struct hist_entry, rb_node);
		h->row_offset = 0;
	}
}

static struct hist_browser *hist_browser__new(struct hists *hists)
{
	struct hist_browser *self = zalloc(sizeof(*self));

	if (self) {
		self->hists = hists;
		self->b.refresh = hist_browser__refresh;
		self->b.seek = ui_browser__hists_seek;
	}

	return self;
}

static void hist_browser__delete(struct hist_browser *self)
{
	free(self);
}

static struct hist_entry *hist_browser__selected_entry(struct hist_browser *self)
{
	return self->he_selection;
}

static struct thread *hist_browser__selected_thread(struct hist_browser *self)
{
	return self->he_selection->thread;
}

static int hist_browser__title(char *bf, size_t size, const char *ev_name,
			       const struct dso *dso, const struct thread *thread)
{
	int printed = 0;

	if (thread)
		printed += snprintf(bf + printed, size - printed,
				    "Thread: %s(%d)",
				    (thread->comm_set ?  thread->comm : ""),
				    thread->pid);
	if (dso)
		printed += snprintf(bf + printed, size - printed,
				    "%sDSO: %s", thread ? " " : "",
				    dso->short_name);
	return printed ?: snprintf(bf, size, "Event: %s", ev_name);
}

int hists__browse(struct hists *self, const char *helpline, const char *ev_name)
{
	struct hist_browser *browser = hist_browser__new(self);
	struct pstack *fstack;
	const struct thread *thread_filter = NULL;
	const struct dso *dso_filter = NULL;
	char msg[160];
	int key = -1;

	if (browser == NULL)
		return -1;

	fstack = pstack__new(2);
	if (fstack == NULL)
		goto out;

	ui_helpline__push(helpline);

	hist_browser__title(msg, sizeof(msg), ev_name,
			    dso_filter, thread_filter);

	while (1) {
		const struct thread *thread;
		const struct dso *dso;
		char *options[16];
		int nr_options = 0, choice = 0, i,
		    annotate = -2, zoom_dso = -2, zoom_thread = -2,
		    browse_map = -2;

		key = hist_browser__run(browser, msg);

		thread = hist_browser__selected_thread(browser);
		dso = browser->selection->map ? browser->selection->map->dso : NULL;

		switch (key) {
		case NEWT_KEY_F1:
			goto do_help;
		case NEWT_KEY_TAB:
		case NEWT_KEY_UNTAB:
			/*
			 * Exit the browser, let hists__browser_tree
			 * go to the next or previous
			 */
			goto out_free_stack;
		case 'a':
			if (browser->selection->map == NULL &&
			    browser->selection->map->dso->annotate_warned)
				continue;
			goto do_annotate;
		case 'd':
			goto zoom_dso;
		case 't':
			goto zoom_thread;
		case 'h':
		case '?':
do_help:
			ui__help_window("->        Zoom into DSO/Threads & Annotate current symbol\n"
					"<-        Zoom out\n"
					"a         Annotate current symbol\n"
					"h/?/F1    Show this window\n"
					"d         Zoom into current DSO\n"
					"t         Zoom into current Thread\n"
					"q/CTRL+C  Exit browser");
			continue;
		case NEWT_KEY_ENTER:
		case NEWT_KEY_RIGHT:
			/* menu */
			break;
		case NEWT_KEY_LEFT: {
			const void *top;

			if (pstack__empty(fstack))
				continue;
			top = pstack__pop(fstack);
			if (top == &dso_filter)
				goto zoom_out_dso;
			if (top == &thread_filter)
				goto zoom_out_thread;
			continue;
		}
		case NEWT_KEY_ESCAPE:
			if (!ui__dialog_yesno("Do you really want to exit?"))
				continue;
			/* Fall thru */
		default:
			goto out_free_stack;
		}

		if (browser->selection->sym != NULL &&
		    !browser->selection->map->dso->annotate_warned &&
		    asprintf(&options[nr_options], "Annotate %s",
			     browser->selection->sym->name) > 0)
			annotate = nr_options++;

		if (thread != NULL &&
		    asprintf(&options[nr_options], "Zoom %s %s(%d) thread",
			     (thread_filter ? "out of" : "into"),
			     (thread->comm_set ? thread->comm : ""),
			     thread->pid) > 0)
			zoom_thread = nr_options++;

		if (dso != NULL &&
		    asprintf(&options[nr_options], "Zoom %s %s DSO",
			     (dso_filter ? "out of" : "into"),
			     (dso->kernel ? "the Kernel" : dso->short_name)) > 0)
			zoom_dso = nr_options++;

		if (browser->selection->map != NULL &&
		    asprintf(&options[nr_options], "Browse map details") > 0)
			browse_map = nr_options++;

		options[nr_options++] = (char *)"Exit";

		choice = ui__popup_menu(nr_options, options);

		for (i = 0; i < nr_options - 1; ++i)
			free(options[i]);

		if (choice == nr_options - 1)
			break;

		if (choice == -1)
			continue;

		if (choice == annotate) {
			struct hist_entry *he;
do_annotate:
			if (browser->selection->map->dso->origin == DSO__ORIG_KERNEL) {
				browser->selection->map->dso->annotate_warned = 1;
				ui_helpline__puts("No vmlinux file found, can't "
						 "annotate with just a "
						 "kallsyms file");
				continue;
			}

			he = hist_browser__selected_entry(browser);
			if (he == NULL)
				continue;

			hist_entry__tui_annotate(he);
		} else if (choice == browse_map)
			map__browse(browser->selection->map);
		else if (choice == zoom_dso) {
zoom_dso:
			if (dso_filter) {
				pstack__remove(fstack, &dso_filter);
zoom_out_dso:
				ui_helpline__pop();
				dso_filter = NULL;
			} else {
				if (dso == NULL)
					continue;
				ui_helpline__fpush("To zoom out press <- or -> + \"Zoom out of %s DSO\"",
						   dso->kernel ? "the Kernel" : dso->short_name);
				dso_filter = dso;
				pstack__push(fstack, &dso_filter);
			}
			hists__filter_by_dso(self, dso_filter);
			hist_browser__title(msg, sizeof(msg), ev_name,
					    dso_filter, thread_filter);
			hist_browser__reset(browser);
		} else if (choice == zoom_thread) {
zoom_thread:
			if (thread_filter) {
				pstack__remove(fstack, &thread_filter);
zoom_out_thread:
				ui_helpline__pop();
				thread_filter = NULL;
			} else {
				ui_helpline__fpush("To zoom out press <- or -> + \"Zoom out of %s(%d) thread\"",
						   thread->comm_set ? thread->comm : "",
						   thread->pid);
				thread_filter = thread;
				pstack__push(fstack, &thread_filter);
			}
			hists__filter_by_thread(self, thread_filter);
			hist_browser__title(msg, sizeof(msg), ev_name,
					    dso_filter, thread_filter);
			hist_browser__reset(browser);
		}
	}
out_free_stack:
	pstack__delete(fstack);
out:
	hist_browser__delete(browser);
	return key;
}

int hists__tui_browse_tree(struct rb_root *self, const char *help)
{
	struct rb_node *first = rb_first(self), *nd = first, *next;
	int key = 0;

	while (nd) {
		struct hists *hists = rb_entry(nd, struct hists, rb_node);
		const char *ev_name = __event_name(hists->type, hists->config);

		key = hists__browse(hists, help, ev_name);
		switch (key) {
		case NEWT_KEY_TAB:
			next = rb_next(nd);
			if (next)
				nd = next;
			break;
		case NEWT_KEY_UNTAB:
			if (nd == first)
				continue;
			nd = rb_prev(nd);
		default:
			return key;
		}
	}

	return key;
}