Piano: Add sampler

This commit adds basic support for importing, viewing and playing WAV
samples at different pitches.

Naming issues:
- We are using the Sample struct from Music.h, but also the Sample
  struct from LibAudio (Audio::Sample). This is a little confusing.

set_recorded_sample() finds the peak sample and then divides all the
samples by that peak to get a guaranteed min/max of -1/1. This is nice
because our other waves are also bound between these values and we can
just do the same stuff. This is why we're using Audio::Sample, because
it uses floats, whereas Music.h's Sample uses i16s. It's a little
annoying that we have to use a mixture of floats and doubles though.

For playback at lower frequencies, we're calculating in-between samples,
rather than just playing samples multiple times. Basically, you get the
current sample and add the difference between the current sample and the
next sample multiplied by the distance from the current sample. This is
like drawing the hypotenuse of a right-angled triangle.

Applications/Piano/AudioEngine.cpp

@@ -26,6 +26,7 @@
  */
 
 #include "AudioEngine.h"
+#include <LibAudio/WavLoader.h>
 #include <limits>
 #include <math.h>
 
@@ -94,6 +95,9 @@ void AudioEngine::fill_buffer(FixedArray<Sample>& buffer)
             case Wave::Noise:
                 val = (volume * m_power[note]) * noise();
                 break;
+            case Wave::RecordedSample:
+                val = (volume * m_power[note]) * recorded_sample(note);
+                break;
             default:
                 ASSERT_NOT_REACHED();
             }
@@ -143,6 +147,37 @@ void AudioEngine::reset()
     m_previous_column = horizontal_notes - 1;
 }
 
+String AudioEngine::set_recorded_sample(const StringView& path)
+{
+    Audio::WavLoader wav_loader(path);
+    if (wav_loader.has_error())
+        return String(wav_loader.error_string());
+    auto wav_buffer = wav_loader.get_more_samples(60 * sample_rate * sizeof(Sample)); // 1 minute maximum
+
+    if (!m_recorded_sample.is_empty())
+        m_recorded_sample.clear();
+    m_recorded_sample.resize(wav_buffer->sample_count());
+
+    float peak = 0;
+    for (int i = 0; i < wav_buffer->sample_count(); ++i) {
+        float left_abs = fabs(wav_buffer->samples()[i].left);
+        float right_abs = fabs(wav_buffer->samples()[i].right);
+        if (left_abs > peak)
+            peak = left_abs;
+        if (right_abs > peak)
+            peak = right_abs;
+    }
+
+    if (peak) {
+        for (int i = 0; i < wav_buffer->sample_count(); ++i) {
+            m_recorded_sample[i].left = wav_buffer->samples()[i].left / peak;
+            m_recorded_sample[i].right = wav_buffer->samples()[i].right / peak;
+        }
+    }
+
+    return String::empty();
+}
+
 // All of the information for these waves is on Wikipedia.
 
 double AudioEngine::sine(size_t note)
@@ -188,6 +223,21 @@ double AudioEngine::noise() const
     return w;
 }
 
+double AudioEngine::recorded_sample(size_t note)
+{
+    int t = m_pos[note];
+    if (t >= m_recorded_sample.size())
+        return 0;
+    double w = m_recorded_sample[t].left;
+    if (t + 1 < m_recorded_sample.size()) {
+        double t_fraction = m_pos[note] - t;
+        w += (m_recorded_sample[t + 1].left - m_recorded_sample[t].left) * t_fraction;
+    }
+    double recorded_sample_step = note_frequencies[note] / middle_c;
+    m_pos[note] += recorded_sample_step;
+    return w;
+}
+
 static inline double calculate_step(double distance, int milliseconds)
 {
     if (milliseconds == 0)

Applications/Piano/AudioEngine.h

@@ -31,6 +31,7 @@
 #include <AK/FixedArray.h>
 #include <AK/Noncopyable.h>
 #include <AK/Queue.h>
+#include <LibAudio/Buffer.h>
 
 class AudioEngine {
     AK_MAKE_NONCOPYABLE(AudioEngine)
@@ -40,6 +41,7 @@ public:
     ~AudioEngine();
 
     const FixedArray<Sample>& buffer() const { return *m_front_buffer_ptr; }
+    const Vector<Audio::Sample>& recorded_sample() const { return m_recorded_sample; }
     void reset();
     Switch roll_note(int y, int x) const { return m_roll_notes[y][x]; }
     int current_column() const { return m_current_column; }
@@ -55,6 +57,7 @@ public:
     int tick() const { return m_tick; }
 
     void fill_buffer(FixedArray<Sample>& buffer);
+    String set_recorded_sample(const StringView& path);
     void set_note(int note, Switch);
     void set_note_current_octave(int note, Switch);
     void set_roll_note(int y, int x, Switch);
@@ -73,6 +76,7 @@ private:
     double square(size_t note);
     double triangle(size_t note);
     double noise() const;
+    double recorded_sample(size_t note);
 
     void update_roll();
     void set_notes_from_roll();
@@ -86,6 +90,8 @@ private:
 
     Queue<NonnullOwnPtr<FixedArray<Sample>>> m_delay_buffers;
 
+    Vector<Audio::Sample> m_recorded_sample;
+
     u8 m_note_on[note_count] { 0 };
     double m_power[note_count] { 0 };
     double m_pos[note_count]; // Initialized lazily.

Applications/Piano/MainWidget.cpp

@@ -30,8 +30,10 @@
 #include "KeysWidget.h"
 #include "KnobsWidget.h"
 #include "RollWidget.h"
+#include "SamplerWidget.h"
 #include "WaveWidget.h"
 #include <LibGUI/BoxLayout.h>
+#include <LibGUI/TabWidget.h>
 
 MainWidget::MainWidget(AudioEngine& audio_engine)
     : m_audio_engine(audio_engine)
@@ -45,10 +47,16 @@ MainWidget::MainWidget(AudioEngine& audio_engine)
     m_wave_widget->set_size_policy(GUI::SizePolicy::Fill, GUI::SizePolicy::Fixed);
     m_wave_widget->set_preferred_size(0, 100);
 
-    m_roll_widget = RollWidget::construct(this, audio_engine);
+    m_roll_widget = RollWidget::construct(nullptr, audio_engine);
     m_roll_widget->set_size_policy(GUI::SizePolicy::Fill, GUI::SizePolicy::Fill);
     m_roll_widget->set_preferred_size(0, 300);
 
+    m_sampler_widget = SamplerWidget::construct(nullptr, audio_engine);
+
+    m_tab_widget = GUI::TabWidget::construct(this);
+    m_tab_widget->add_widget("Piano Roll", m_roll_widget);
+    m_tab_widget->add_widget("Sampler", m_sampler_widget);
+
     m_keys_and_knobs_container = GUI::Widget::construct(this);
     m_keys_and_knobs_container->set_layout(make<GUI::HorizontalBoxLayout>());
     m_keys_and_knobs_container->layout()->set_spacing(2);

Applications/Piano/MainWidget.h

@@ -33,9 +33,14 @@
 class AudioEngine;
 class WaveWidget;
 class RollWidget;
+class SamplerWidget;
 class KeysWidget;
 class KnobsWidget;
 
+namespace GUI {
+class TabWidget;
+}
+
 class MainWidget final : public GUI::Widget {
     C_OBJECT(MainWidget)
 public:
@@ -57,6 +62,8 @@ private:
 
     RefPtr<WaveWidget> m_wave_widget;
     RefPtr<RollWidget> m_roll_widget;
+    RefPtr<SamplerWidget> m_sampler_widget;
+    RefPtr<GUI::TabWidget> m_tab_widget;
     RefPtr<GUI::Widget> m_keys_and_knobs_container;
     RefPtr<KeysWidget> m_keys_widget;
     RefPtr<KnobsWidget> m_knobs_widget;

Applications/Piano/Makefile

@@ -3,6 +3,7 @@ OBJS = \
     MainWidget.o \
     WaveWidget.o \
     RollWidget.o \
+    SamplerWidget.o \
     KeysWidget.o \
     KnobsWidget.o \
     main.o

Applications/Piano/Music.h

@@ -67,6 +67,7 @@ enum Wave {
     Square,
     Saw,
     Noise,
+    RecordedSample,
 };
 
 constexpr const char* wave_strings[] = {
@@ -75,10 +76,11 @@ constexpr const char* wave_strings[] = {
     "Square",
     "Saw",
     "Noise",
+    "Sample",
 };
 
 constexpr int first_wave = Sine;
-constexpr int last_wave = Noise;
+constexpr int last_wave = RecordedSample;
 
 enum Envelope {
     Done,
@@ -110,6 +112,45 @@ constexpr KeyColor key_pattern[] = {
 const Color note_pressed_color(64, 64, 255);
 const Color column_playing_color(128, 128, 255);
 
+const Color wave_colors[] = {
+    // Sine
+    {
+        255,
+        192,
+        0,
+    },
+    // Triangle
+    {
+        35,
+        171,
+        35,
+    },
+    // Square
+    {
+        128,
+        160,
+        255,
+    },
+    // Saw
+    {
+        240,
+        100,
+        128,
+    },
+    // Noise
+    {
+        197,
+        214,
+        225,
+    },
+    // RecordedSample
+    {
+        227,
+        39,
+        39,
+    },
+};
+
 constexpr int notes_per_octave = 12;
 constexpr int white_keys_per_octave = 7;
 constexpr int black_keys_per_octave = 5;
@@ -217,6 +258,8 @@ constexpr double note_frequencies[] = {
 };
 constexpr int note_count = sizeof(note_frequencies) / sizeof(double);
 
+constexpr double middle_c = note_frequencies[36];
+
 }
 
 using namespace Music;

Applications/Piano/SamplerWidget.cpp

@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) 2020-2020, 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.
+ */
+
+#include "SamplerWidget.h"
+#include "AudioEngine.h"
+#include <LibGUI/BoxLayout.h>
+#include <LibGUI/Button.h>
+#include <LibGUI/FilePicker.h>
+#include <LibGUI/Label.h>
+#include <LibGUI/MessageBox.h>
+#include <LibGUI/Painter.h>
+
+WaveEditor::WaveEditor(GUI::Widget* parent, AudioEngine& audio_engine)
+    : GUI::Frame(parent)
+    , m_audio_engine(audio_engine)
+{
+    set_frame_thickness(2);
+    set_frame_shadow(Gfx::FrameShadow::Sunken);
+    set_frame_shape(Gfx::FrameShape::Container);
+}
+
+WaveEditor::~WaveEditor()
+{
+}
+
+int WaveEditor::sample_to_y(float percentage) const
+{
+    double portion_of_half_height = percentage * ((frame_inner_rect().height() - 1) / 2.0);
+    double y = (frame_inner_rect().height() / 2.0) + portion_of_half_height;
+    return y;
+}
+
+void WaveEditor::paint_event(GUI::PaintEvent& event)
+{
+    GUI::Frame::paint_event(event);
+
+    GUI::Painter painter(*this);
+    painter.fill_rect(frame_inner_rect(), Color::Black);
+
+    auto recorded_sample = m_audio_engine.recorded_sample();
+    if (recorded_sample.is_empty())
+        return;
+
+    double width_scale = static_cast<double>(frame_inner_rect().width()) / recorded_sample.size();
+
+    painter.translate(frame_thickness(), frame_thickness());
+
+    int prev_x = 0;
+    int prev_y = sample_to_y(recorded_sample[0].left);
+    painter.set_pixel({ prev_x, prev_y }, wave_colors[RecordedSample]);
+
+    for (int x = 1; x < recorded_sample.size(); ++x) {
+        int y = sample_to_y(recorded_sample[x].left);
+
+        Gfx::Point point1(prev_x * width_scale, prev_y);
+        Gfx::Point point2(x * width_scale, y);
+        painter.draw_line(point1, point2, wave_colors[RecordedSample]);
+
+        prev_x = x;
+        prev_y = y;
+    }
+}
+
+SamplerWidget::SamplerWidget(GUI::Widget* parent, AudioEngine& audio_engine)
+    : GUI::Frame(parent)
+    , m_audio_engine(audio_engine)
+{
+    set_frame_thickness(2);
+    set_frame_shadow(Gfx::FrameShadow::Sunken);
+    set_frame_shape(Gfx::FrameShape::Container);
+    set_layout(make<GUI::VerticalBoxLayout>());
+    layout()->set_margins({ 10, 10, 10, 10 });
+    layout()->set_spacing(10);
+    set_fill_with_background_color(true);
+
+    m_open_button_and_recorded_sample_name_container = GUI::Widget::construct(this);
+    m_open_button_and_recorded_sample_name_container->set_layout(make<GUI::HorizontalBoxLayout>());
+    m_open_button_and_recorded_sample_name_container->layout()->set_spacing(10);
+    m_open_button_and_recorded_sample_name_container->set_size_policy(GUI::SizePolicy::Fill, GUI::SizePolicy::Fixed);
+    m_open_button_and_recorded_sample_name_container->set_preferred_size(0, 24);
+
+    m_open_button = GUI::Button::construct(m_open_button_and_recorded_sample_name_container);
+    m_open_button->set_size_policy(GUI::SizePolicy::Fixed, GUI::SizePolicy::Fixed);
+    m_open_button->set_preferred_size(24, 24);
+    m_open_button->set_focusable(false);
+    m_open_button->set_icon(Gfx::Bitmap::load_from_file("/res/icons/16x16/open.png"));
+    m_open_button->on_click = [this](const auto&) {
+        Optional<String> open_path = GUI::FilePicker::get_open_filepath();
+        if (!open_path.has_value())
+            return;
+        String error_string = m_audio_engine.set_recorded_sample(open_path.value());
+        if (!error_string.is_empty()) {
+            GUI::MessageBox::show(String::format("Failed to load WAV file: %s", error_string.characters()), "Error", GUI::MessageBox::Type::Error);
+            return;
+        }
+        m_recorded_sample_name->set_text(open_path.value());
+        m_wave_editor->update();
+    };
+
+    m_recorded_sample_name = GUI::Label::construct("No sample loaded", m_open_button_and_recorded_sample_name_container);
+    m_recorded_sample_name->set_text_alignment(Gfx::TextAlignment::CenterLeft);
+
+    m_wave_editor = WaveEditor::construct(this, m_audio_engine);
+    m_wave_editor->set_size_policy(GUI::SizePolicy::Fill, GUI::SizePolicy::Fixed);
+    m_wave_editor->set_preferred_size(0, 100);
+}
+
+SamplerWidget::~SamplerWidget()
+{
+}

Applications/Piano/SamplerWidget.h

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2020-2020, 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 <LibGUI/Frame.h>
+
+namespace GUI {
+class Label;
+class Button;
+}
+
+class AudioEngine;
+
+class WaveEditor final : public GUI::Frame {
+    C_OBJECT(WaveEditor)
+public:
+    virtual ~WaveEditor() override;
+
+private:
+    WaveEditor(GUI::Widget* parent, AudioEngine&);
+
+    virtual void paint_event(GUI::PaintEvent&) override;
+
+    int sample_to_y(float percentage) const;
+
+    AudioEngine& m_audio_engine;
+};
+
+class SamplerWidget final : public GUI::Frame {
+    C_OBJECT(SamplerWidget)
+public:
+    virtual ~SamplerWidget() override;
+
+private:
+    SamplerWidget(GUI::Widget* parent, AudioEngine&);
+
+    AudioEngine& m_audio_engine;
+
+    RefPtr<GUI::Widget> m_open_button_and_recorded_sample_name_container;
+    RefPtr<GUI::Button> m_open_button;
+    RefPtr<GUI::Label> m_recorded_sample_name;
+    RefPtr<WaveEditor> m_wave_editor;
+};

Applications/Piano/WaveWidget.cpp

@@ -43,39 +43,6 @@ WaveWidget::~WaveWidget()
 {
 }
 
-static const Color wave_colors[] = {
-    // Sine
-    {
-        255,
-        192,
-        0,
-    },
-    // Triangle
-    {
-        35,
-        171,
-        35,
-    },
-    // Square
-    {
-        128,
-        160,
-        255,
-    },
-    // Saw
-    {
-        240,
-        100,
-        128,
-    },
-    // Noise
-    {
-        197,
-        214,
-        225,
-    },
-};
-
 int WaveWidget::sample_to_y(int sample) const
 {
     constexpr double sample_max = std::numeric_limits<i16>::max();