Piano: Rewrite application

Goals:
- Switch to a more typical LibGUI arrangement
- Separate GUI (MainWidget) and audio (AudioEngine)
- Improve on existing features while retaining the same feature set

Improvements:
- Each GUI element is a separate widget
- The wave (WaveWidget) scales with the window
- The piano roll (RollWidget) scales horizontally and scrolls vertically
- The piano (KeysWidget) fits as many notes as possible
- The knobs (KnobsWidget) are now sliders
- All mouse and key events are handled in constant time
- The octave can be changed while playing notes
- The same note can be played with the mouse, keyboard and roll at the
  same time, and the volume of the resulting note is scaled accordingly
- Note frequency constants use the maximum precision available in a
  double

1 files changed, 85 insertions, 0 deletions

diff --git a/Applications/Piano/AudioEngine.h b/Applications/Piano/AudioEngine.h
new file mode 100644
index 0000000000..14280a716f
--- /dev/null
+++ b/Applications/Piano/AudioEngine.h
@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2019-2020, William McPherson <willmcpherson2@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "Music.h"
+#include <AK/FixedArray.h>
+#include <AK/Noncopyable.h>
+#include <AK/Queue.h>
+
+class AudioEngine {
+    AK_MAKE_NONCOPYABLE(AudioEngine)
+    AK_MAKE_NONMOVABLE(AudioEngine)
+public:
+    AudioEngine();
+    ~AudioEngine();
+
+    const FixedArray<Sample>& buffer() const { return *m_front_buffer_ptr; }
+    int octave() const { return m_octave; }
+    int octave_base() const { return (m_octave - octave_min) * 12; }
+    int wave() const { return m_wave; }
+    int decay() const { return m_decay; }
+    int delay() const { return m_delay; }
+    int time() const { return m_time; }
+    int tick() const { return m_tick; }
+
+    void fill_buffer(FixedArray<Sample>& buffer);
+    void set_note(int note, Switch);
+    void set_note_current_octave(int note, Switch);
+    void set_octave(Direction);
+    void set_wave(int wave);
+    void set_wave(Direction);
+    void set_decay(int decay);
+    void set_delay(int delay);
+
+private:
+    double sine(size_t note);
+    double saw(size_t note);
+    double square(size_t note);
+    double triangle(size_t note);
+    double noise() const;
+
+    FixedArray<Sample> m_front_buffer { sample_count };
+    FixedArray<Sample> m_back_buffer { sample_count };
+    FixedArray<Sample>* m_front_buffer_ptr { &m_front_buffer };
+    FixedArray<Sample>* m_back_buffer_ptr { &m_back_buffer };
+
+    Queue<NonnullOwnPtr<FixedArray<Sample>>> m_delay_buffers;
+
+    u8 m_note_on[note_count] { 0 };
+    double m_power[note_count]; // Initialized lazily.
+    double m_pos[note_count];   // Initialized lazily.
+
+    int m_octave { 4 };
+    int m_wave { first_wave };
+    int m_decay { 0 };
+    int m_delay { 0 };
+
+    int m_time { 0 };
+    int m_tick { 8 };
+};