perf top: Use all the lines in the screen

By querying the current number of rows, if the user specifies
the number of entries, use that instead. If the user uses the
'e' command to change the number of lines 0 will mean do it
automatically, any other number disables the auto resizing.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1258407027-384-2-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/builtin-top.c

@@ -60,7 +60,7 @@ static int			system_wide			=      0;
 static int			default_interval		=      0;
 
 static int			count_filter			=      5;
-static int			print_entries			=     15;
+static int			print_entries;
 
 static int			target_pid			=     -1;
 static int			inherit				=      0;
@@ -115,6 +115,36 @@ struct sym_entry {
  * Source functions
  */
 
+/* most GUI terminals set LINES (although some don't export it) */
+static int term_rows(void)
+{
+	char *lines_string = getenv("LINES");
+	int n_lines;
+
+	if (lines_string && (n_lines = atoi(lines_string)) > 0)
+		return n_lines;
+#ifdef TIOCGWINSZ
+	else {
+		struct winsize ws;
+		if (!ioctl(1, TIOCGWINSZ, &ws) && ws.ws_row)
+			return ws.ws_row;
+	}
+#endif
+	return 25;
+}
+
+static void update_print_entries(void)
+{
+	print_entries = term_rows();
+	if (print_entries > 9)
+		print_entries -= 9;
+}
+
+static void sig_winch_handler(int sig __used)
+{
+	update_print_entries();
+}
+
 static void parse_source(struct sym_entry *syme)
 {
 	struct symbol *sym;
@@ -668,6 +698,11 @@ static void handle_keypress(int c)
 			break;
 		case 'e':
 			prompt_integer(&print_entries, "Enter display entries (lines)");
+			if (print_entries == 0) {
+				update_print_entries();
+				signal(SIGWINCH, sig_winch_handler);
+			} else
+				signal(SIGWINCH, SIG_DFL);
 			break;
 		case 'E':
 			if (nr_counters > 1) {
@@ -1228,5 +1263,10 @@ int cmd_top(int argc, const char **argv, const char *prefix __used)
 	if (target_pid != -1 || profile_cpu != -1)
 		nr_cpus = 1;
 
+	if (print_entries == 0) {
+		update_print_entries();
+		signal(SIGWINCH, sig_winch_handler);
+	}
+
 	return __cmd_top();
 }