Piano: Add attack

Author: https://github.com/willmcpherson2
Commit: https://github.com/SerenityOS/serenity/commit/ab9475a3f31
Pull-request: https://github.com/SerenityOS/serenity/pull/1178

Applications/Piano/AudioEngine.cpp

@@ -32,6 +32,7 @@
 AudioEngine::AudioEngine()
 {
     set_sustain_impl(0);
+    set_attack(0);
     set_decay(0);
 }
 
@@ -45,12 +46,26 @@ void AudioEngine::fill_buffer(FixedArray<Sample>& buffer)
 
     for (size_t i = 0; i < buffer.size(); ++i) {
         for (size_t note = 0; note < note_count; ++note) {
-            if (!m_note_on[note])
+            switch (m_envelope[note]) {
+            case Done:
                 continue;
-
-            m_power[note] -= m_decay_step;
-            if (m_power[note] < m_sustain_level)
-                m_power[note] = m_sustain_level;
+            case Attack:
+                m_power[note] += m_attack_step;
+                if (m_power[note] >= 1) {
+                    m_power[note] = 1;
+                    m_envelope[note] = Decay;
+                }
+                break;
+            case Decay:
+                m_power[note] -= m_decay_step;
+                if (m_power[note] < m_sustain_level)
+                    m_power[note] = m_sustain_level;
+                break;
+            case Release:
+                break;
+            default:
+                ASSERT_NOT_REACHED();
+            }
 
             double val = 0;
             switch (m_wave) {
@@ -150,13 +165,15 @@ void AudioEngine::set_note(int note, Switch switch_note)
     if (switch_note == On) {
         if (m_note_on[note] == 0) {
             m_pos[note] = 0;
-            m_power[note] = 1;
+            m_envelope[note] = Attack;
         }
         ++m_note_on[note];
     } else {
         if (m_note_on[note] >= 1) {
-            if (m_note_on[note] == 1)
+            if (m_note_on[note] == 1) {
                 m_power[note] = 0;
+                m_envelope[note] = Done;
+            }
             --m_note_on[note];
         }
     }
@@ -209,6 +226,13 @@ static inline double calculate_step(double distance, int milliseconds)
     return step;
 }
 
+void AudioEngine::set_attack(int attack)
+{
+    ASSERT(attack >= 0);
+    m_attack = attack;
+    m_attack_step = calculate_step(1, m_attack);
+}
+
 void AudioEngine::set_decay(int decay)
 {
     ASSERT(decay >= 0);

Applications/Piano/AudioEngine.h

@@ -43,6 +43,7 @@ public:
     int octave() const { return m_octave; }
     int octave_base() const { return (m_octave - octave_min) * 12; }
     int wave() const { return m_wave; }
+    int attack() const { return m_attack; }
     int decay() const { return m_decay; }
     int sustain() const { return m_sustain; }
     int delay() const { return m_delay; }
@@ -55,6 +56,7 @@ public:
     void set_octave(Direction);
     void set_wave(int wave);
     void set_wave(Direction);
+    void set_attack(int attack);
     void set_decay(int decay);
     void set_sustain(int sustain);
     void set_delay(int delay);
@@ -76,11 +78,14 @@ private:
     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.
+    double m_power[note_count] { 0 };
+    double m_pos[note_count]; // Initialized lazily.
+    Envelope m_envelope[note_count] { Done };
 
     int m_octave { 4 };
     int m_wave { first_wave };
+    int m_attack;
+    double m_attack_step;
     int m_decay;
     double m_decay_step;
     int m_sustain;

Applications/Piano/KnobsWidget.cpp

@@ -50,6 +50,7 @@ KnobsWidget::KnobsWidget(GUI::Widget* parent, AudioEngine& audio_engine, MainWid
 
     m_octave_label = GUI::Label::construct("Octave", m_labels_container);
     m_wave_label = GUI::Label::construct("Wave", m_labels_container);
+    m_attack_label = GUI::Label::construct("Attack", m_labels_container);
     m_decay_label = GUI::Label::construct("Decay", m_labels_container);
     m_sustain_label = GUI::Label::construct("Sustain", m_labels_container);
     m_delay_label = GUI::Label::construct("Delay", m_labels_container);
@@ -61,6 +62,7 @@ KnobsWidget::KnobsWidget(GUI::Widget* parent, AudioEngine& audio_engine, MainWid
 
     m_octave_value = GUI::Label::construct(String::number(m_audio_engine.octave()), m_values_container);
     m_wave_value = GUI::Label::construct(wave_strings[m_audio_engine.wave()], m_values_container);
+    m_attack_value = GUI::Label::construct(String::number(m_audio_engine.attack()), m_values_container);
     m_decay_value = GUI::Label::construct(String::number(m_audio_engine.decay()), m_values_container);
     m_sustain_value = GUI::Label::construct(String::number(m_audio_engine.sustain()), m_values_container);
     m_delay_value = GUI::Label::construct(String::number(m_audio_engine.delay() / m_audio_engine.tick()), m_values_container);
@@ -93,6 +95,17 @@ KnobsWidget::KnobsWidget(GUI::Widget* parent, AudioEngine& audio_engine, MainWid
         m_wave_value->set_text(wave_strings[new_wave]);
     };
 
+    constexpr int max_attack = 1000;
+    m_attack_knob = GUI::Slider::construct(Orientation::Vertical, m_knobs_container);
+    m_attack_knob->set_range(0, max_attack);
+    m_attack_knob->set_value(max_attack - m_audio_engine.attack());
+    m_attack_knob->on_value_changed = [this](int value) {
+        int new_attack = max_attack - value;
+        m_audio_engine.set_attack(new_attack);
+        ASSERT(new_attack == m_audio_engine.attack());
+        m_attack_value->set_text(String::number(new_attack));
+    };
+
     constexpr int max_decay = 1000;
     m_decay_knob = GUI::Slider::construct(Orientation::Vertical, m_knobs_container);
     m_decay_knob->set_range(0, max_decay);

Applications/Piano/KnobsWidget.h

@@ -53,6 +53,7 @@ private:
     RefPtr<GUI::Widget> m_labels_container;
     RefPtr<GUI::Label> m_octave_label;
     RefPtr<GUI::Label> m_wave_label;
+    RefPtr<GUI::Label> m_attack_label;
     RefPtr<GUI::Label> m_decay_label;
     RefPtr<GUI::Label> m_sustain_label;
     RefPtr<GUI::Label> m_delay_label;
@@ -60,6 +61,7 @@ private:
     RefPtr<GUI::Widget> m_values_container;
     RefPtr<GUI::Label> m_octave_value;
     RefPtr<GUI::Label> m_wave_value;
+    RefPtr<GUI::Label> m_attack_value;
     RefPtr<GUI::Label> m_decay_value;
     RefPtr<GUI::Label> m_sustain_value;
     RefPtr<GUI::Label> m_delay_value;
@@ -67,6 +69,7 @@ private:
     RefPtr<GUI::Widget> m_knobs_container;
     RefPtr<GUI::Slider> m_octave_knob;
     RefPtr<GUI::Slider> m_wave_knob;
+    RefPtr<GUI::Slider> m_attack_knob;
     RefPtr<GUI::Slider> m_decay_knob;
     RefPtr<GUI::Slider> m_sustain_knob;
     RefPtr<GUI::Slider> m_delay_knob;

Applications/Piano/MainWidget.cpp

@@ -60,7 +60,7 @@ MainWidget::MainWidget(AudioEngine& audio_engine)
 
     m_knobs_widget = KnobsWidget::construct(m_keys_and_knobs_container, audio_engine, *this);
     m_knobs_widget->set_size_policy(GUI::SizePolicy::Fixed, GUI::SizePolicy::Fill);
-    m_knobs_widget->set_preferred_size(250, 0);
+    m_knobs_widget->set_preferred_size(300, 0);
 }
 
 MainWidget::~MainWidget()

Applications/Piano/Music.h

@@ -80,6 +80,13 @@ constexpr const char* wave_strings[] = {
 constexpr int first_wave = Sine;
 constexpr int last_wave = Noise;
 
+enum Envelope {
+    Done,
+    Attack,
+    Decay,
+    Release,
+};
+
 enum KeyColor {
     White,
     Black,