LibDSP: Introduce the Keyboard

This is a class for handling user MIDI input, which is combined by the
Track with roll note data if applicable.

4 files changed, 128 insertions, 0 deletions

diff --git a/Userland/Libraries/LibDSP/CMakeLists.txt b/Userland/Libraries/LibDSP/CMakeLists.txt
index a5de6f120e..34fa31957a 100644
--- a/Userland/Libraries/LibDSP/CMakeLists.txt
+++ b/Userland/Libraries/LibDSP/CMakeLists.txt
@@ -3,6 +3,7 @@ set(SOURCES
     Track.cpp
     Effects.cpp
     Synthesizers.cpp
+    Keyboard.cpp
 )
 
 serenity_lib(LibDSP dsp)
diff --git a/Userland/Libraries/LibDSP/Keyboard.cpp b/Userland/Libraries/LibDSP/Keyboard.cpp
new file mode 100644
index 0000000000..38483243a2
--- /dev/null
+++ b/Userland/Libraries/LibDSP/Keyboard.cpp
@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2021-2022, kleines Filmröllchen <filmroellchen@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "Keyboard.h"
+#include "Music.h"
+#include <AK/Error.h>
+#include <AK/NumericLimits.h>
+
+namespace LibDSP {
+
+void Keyboard::set_keyboard_note(u8 pitch, Keyboard::Switch note_switch)
+{
+    VERIFY(pitch < note_frequencies.size());
+
+    if (note_switch == Switch::Off) {
+        m_pressed_notes.remove(pitch);
+        return;
+    }
+
+    auto fake_note = RollNote {
+        .on_sample = m_transport->time(),
+        .off_sample = NumericLimits<u32>::max(),
+        .pitch = pitch,
+        .velocity = NumericLimits<i8>::max(),
+    };
+
+    m_pressed_notes.set(pitch, fake_note);
+}
+void Keyboard::set_keyboard_note_in_active_octave(i8 octave_offset, Switch note_switch)
+{
+    u8 real_note = octave_offset + (m_virtual_keyboard_octave - 1) * notes_per_octave;
+    set_keyboard_note(real_note, note_switch);
+}
+
+void Keyboard::change_virtual_keyboard_octave(Direction direction)
+{
+    if (direction == Direction::Up) {
+        if (m_virtual_keyboard_octave < octave_max)
+            ++m_virtual_keyboard_octave;
+    } else {
+        if (m_virtual_keyboard_octave > octave_min)
+            --m_virtual_keyboard_octave;
+    }
+}
+
+ErrorOr<void> Keyboard::set_virtual_keyboard_octave(u8 octave)
+{
+    if (octave <= octave_max && octave >= octave_min) {
+        m_virtual_keyboard_octave = octave;
+        return {};
+    }
+    return Error::from_string_literal("Octave out of range");
+}
+
+bool Keyboard::is_pressed(u8 pitch) const
+{
+    return m_pressed_notes.get(pitch).has_value() && m_pressed_notes.get(pitch)->is_playing(m_transport->time());
+}
+
+bool Keyboard::is_pressed_in_active_octave(i8 octave_offset) const
+{
+    return is_pressed(octave_offset + virtual_keyboard_octave_base());
+}
+
+}
diff --git a/Userland/Libraries/LibDSP/Keyboard.h b/Userland/Libraries/LibDSP/Keyboard.h
new file mode 100644
index 0000000000..fa69bd29b2
--- /dev/null
+++ b/Userland/Libraries/LibDSP/Keyboard.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2021-2022, kleines Filmröllchen <filmroellchen@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/NonnullRefPtr.h>
+#include <AK/RefCounted.h>
+#include <LibDSP/Music.h>
+#include <LibDSP/Transport.h>
+
+namespace LibDSP {
+
+class Keyboard : public RefCounted<Keyboard> {
+
+public:
+    enum class Direction : bool {
+        Down,
+        Up,
+    };
+    enum class Switch : bool {
+        Off,
+        On,
+    };
+
+    Keyboard(NonnullRefPtr<Transport> transport)
+        : m_transport(move(transport))
+    {
+    }
+
+    u8 virtual_keyboard_octave() const { return m_virtual_keyboard_octave; }
+    u8 virtual_keyboard_octave_base() const { return (m_virtual_keyboard_octave - octave_min) * 12; }
+    // Automatically clips the octave between the minimum and maximum.
+    void change_virtual_keyboard_octave(Direction);
+    // Errors out if the set octave is out of range.
+    ErrorOr<void> set_virtual_keyboard_octave(u8 octave);
+
+    void set_keyboard_note(u8 pitch, Switch note_switch);
+    void set_keyboard_note_in_active_octave(i8 octave_offset, Switch note_switch);
+
+    RollNotes const& notes() const { return m_pressed_notes; }
+    Optional<RollNote> note_at(u8 pitch) const { return m_pressed_notes.get(pitch); }
+    bool is_pressed(u8 pitch) const;
+    bool is_pressed_in_active_octave(i8 octave_offset) const;
+
+private:
+    u8 m_virtual_keyboard_octave { 4 };
+    RollNotes m_pressed_notes;
+
+    NonnullRefPtr<Transport> m_transport;
+
+    static constexpr int const octave_min = 1;
+    static constexpr int const octave_max = 7;
+};
+
+}
diff --git a/Userland/Libraries/LibDSP/Music.h b/Userland/Libraries/LibDSP/Music.h
index e82a57b789..884189a348 100644
--- a/Userland/Libraries/LibDSP/Music.h
+++ b/Userland/Libraries/LibDSP/Music.h
@@ -196,6 +196,7 @@ constexpr Array<double, 84> note_frequencies = {
     3951.0664100489994,
 };
 
+constexpr size_t const notes_per_octave = 12;
 constexpr double const middle_c = note_frequencies[36];
 
 }