Motown: Add examples/media_test, a command line media player app.

examples/media_test/keystroke.cc

Index: examples/media_test/keystroke.cc
diff --git a/examples/media_test/keystroke.cc b/examples/media_test/keystroke.cc
new file mode 100644
index 0000000000000000000000000000000000000000..15ba3ae560e4bf69fb5c6d48d1f59c31fddf10d6
--- /dev/null
+++ b/examples/media_test/keystroke.cc
@@ -0,0 +1,44 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include <iostream>
+
+#include "examples/media_test/keystroke.h"
+
+namespace examples {
+
+bool eat_newline = false;
+bool upped_already = false;

[johngro, 2016/03/21 22:10:46]

This should either be hidden as private static members of a class, or made
static at the file scope level so that they do not leak out into the program's
namespace.

[dalesat, 2016/03/21 23:58:34]

Done.

+
+char Keystroke(void) {
+  const char *kUp = "\033[A";
+
+  fcntl(0, F_SETFL, fcntl(0, F_GETFL) | O_NONBLOCK);

[johngro, 2016/03/21 22:10:46]

you can say STDIN_FILENO instead of 0 here.  You will need to include unistd.h

[dalesat, 2016/03/21 23:58:34]

Done.

+  char buf[1];
+  if (read(0, buf, 1) > 0) {
+    if (!upped_already) {

[johngro, 2016/03/21 22:10:46]

so, this is terminal specific and is probably not going to work everywhere...

As a slightly more portable solution, I have some code I can give you which you
can use to put stdin into non-buffered, non-echoing, non-blocking mode.  Then
you can just call getchar.  The nasty part, however, is that you need to be sure
to hook various signals (ctrl-c for example) and put stuff back the way it was. 
Otherwise, you will need to reset your terminal to get character echoing back if
your program terminates uncleanly.

A better longer term TODO might be to use Mozart to get your keyboard input.  I
don't think that this is an option as of today, sadly, because Mozart assumes
that you are using base:: message loop type things, and will not play well with
code which expects you to be using the mojo:: message loop stuff.

[dalesat, 2016/03/21 23:58:34]

Acknowledged.

+      std::cerr << kUp << std::flush;

[johngro, 2016/03/21 22:10:46]

Why cerr and not cout?

[dalesat, 2016/03/21 23:58:34]

Force of habit. Fixed.

+      upped_already = true;
+    }
+
+    if (buf[0] == '\n') {
+      upped_already = false;
+      if (eat_newline) {
+        eat_newline = false;
+      } else {
+        return buf[0];
+      }
+    } else {
+      eat_newline = true;
+      return buf[0];
+    }
+  }
+  return 0;
+}
+
+}  // namespace examples