Ladybird: Move Qt-specific classes and functions to a Qt subdirectory

This will help a lot with developing chromes for different UI frameworks
where we can see which helper classes and processes are really using Qt
vs just using it to get at helper data.

As a bonus, remove Qt dependency from WebDriver.

Ladybird/Qt/AudioThread.h

@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2023, Tim Flynn <trflynn89@serenityos.org>
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Endian.h>
+#include <AK/MemoryStream.h>
+#include <AK/Optional.h>
+#include <AK/Types.h>
+#include <LibAudio/Loader.h>
+#include <LibAudio/Sample.h>
+#include <LibCore/SharedCircularQueue.h>
+#include <QAudioFormat>
+#include <QAudioSink>
+#include <QByteArray>
+#include <QMediaDevices>
+#include <QThread>
+
+namespace Ladybird {
+
+static constexpr u32 UPDATE_RATE_MS = 10;
+
+struct AudioTask {
+    enum class Type {
+        Stop,
+        Play,
+        Pause,
+        Seek,
+        Volume,
+        RecreateAudioDevice,
+    };
+
+    Type type;
+    Optional<double> data {};
+};
+
+using AudioTaskQueue = Core::SharedSingleProducerCircularQueue<AudioTask>;
+
+class AudioThread final : public QThread { // We have to use QThread, otherwise internal Qt media QTimer objects do not work.
+    Q_OBJECT
+
+public:
+    static ErrorOr<NonnullOwnPtr<AudioThread>> create(NonnullRefPtr<Audio::Loader> loader);
+
+    ErrorOr<void> stop();
+
+    Duration duration() const { return m_duration; }
+
+    ErrorOr<void> queue_task(AudioTask task);
+
+Q_SIGNALS:
+    void playback_position_updated(Duration);
+
+private:
+    AudioThread(NonnullRefPtr<Audio::Loader> loader, AudioTaskQueue task_queue);
+
+    enum class Paused {
+        Yes,
+        No,
+    };
+
+    void run() override;
+
+    ErrorOr<Paused> play_next_samples(QAudioSink& audio_output, QIODevice& io_device);
+
+    void enqueue_samples(QAudioSink const& audio_output, QIODevice& io_device, FixedArray<Audio::Sample> samples);
+
+    template<typename T>
+    void write_sample(FixedMemoryStream& stream, float sample)
+    {
+        // The values that need to be written to the stream vary depending on the output channel format, and isn't
+        // particularly well documented. The value derivations performed below were adapted from a Qt example:
+        // https://code.qt.io/cgit/qt/qtmultimedia.git/tree/examples/multimedia/audiooutput/audiooutput.cpp?h=6.4.2#n46
+        LittleEndian<T> pcm;
+
+        if constexpr (IsSame<T, u8>)
+            pcm = static_cast<u8>((sample + 1.0f) / 2 * NumericLimits<u8>::max());
+        else if constexpr (IsSame<T, i16>)
+            pcm = static_cast<i16>(sample * NumericLimits<i16>::max());
+        else if constexpr (IsSame<T, i32>)
+            pcm = static_cast<i32>(sample * NumericLimits<i32>::max());
+        else if constexpr (IsSame<T, float>)
+            pcm = sample;
+        else
+            static_assert(DependentFalse<T>);
+
+        MUST(stream.write_value(pcm));
+    }
+
+    NonnullRefPtr<Audio::Loader> m_loader;
+    AudioTaskQueue m_task_queue;
+
+    QByteArray m_sample_buffer;
+
+    Duration m_duration;
+    Duration m_position;
+};
+
+}