LibWeb: Implement OscillatorNode.frequency

Which is an AudioParam clamped by the nyquist_frequency.

Tests/LibWeb/Text/expected/WebAudio/OscillatorNode.txt

@@ -8,3 +8,5 @@ Error creating node: 'InvalidStateError: Oscillator node type cannot be set to '
 oscillator node type: 'sine'
 Error: 'InvalidStateError: Oscillator node type cannot be set to 'custom'', type is: sine
 oscillator node type: 'triangle'
+[object AudioParam] current: 440, default: 440, min: -22050, max: 22050, rate: a-rate
+[object AudioParam] current: -52, default: 440, min: -22050, max: 22050, rate: a-rate

Tests/LibWeb/Text/input/WebAudio/OscillatorNode.html

@@ -1,5 +1,9 @@
 <script src="../include.js"></script>
 <script>
+    function dumpAudioParam(param) {
+        println(`${param} current: ${param.value}, default: ${param.defaultValue}, min: ${param.minValue}, max: ${param.maxValue}, rate: ${param.automationRate}`);
+    }
+
     test(() => {
         const audioContext = new OfflineAudioContext(1, 5000, 44100);
 
@@ -32,5 +36,11 @@
         }
         oscillator.type = 'triangle';
         println(`oscillator node type: '${oscillator.type}'`);
+
+        // Frequency attribute
+        let frequency = oscillator.frequency;
+        dumpAudioParam(frequency);
+        frequency.value = -52;
+        dumpAudioParam(frequency);
     });
 </script>

Userland/Libraries/LibWeb/WebAudio/AudioParam.cpp

@@ -13,6 +13,21 @@ namespace Web::WebAudio {
 
 JS_DEFINE_ALLOCATOR(AudioParam);
 
+AudioParam::AudioParam(JS::Realm& realm, float default_value, float min_value, float max_value, Bindings::AutomationRate automation_rate)
+    : Bindings::PlatformObject(realm)
+    , m_current_value(default_value)
+    , m_default_value(default_value)
+    , m_min_value(min_value)
+    , m_max_value(max_value)
+    , m_automation_rate(automation_rate)
+{
+}
+
+JS::NonnullGCPtr<AudioParam> AudioParam::create(JS::Realm& realm, float default_value, float min_value, float max_value, Bindings::AutomationRate automation_rate)
+{
+    return realm.vm().heap().allocate<AudioParam>(realm, realm, default_value, min_value, max_value, automation_rate);
+}
+
 AudioParam::~AudioParam() = default;
 
 // https://webaudio.github.io/web-audio-api/#dom-audioparam-value

Userland/Libraries/LibWeb/WebAudio/AudioParam.h

@@ -18,6 +18,8 @@ class AudioParam final : public Bindings::PlatformObject {
     JS_DECLARE_ALLOCATOR(AudioParam);
 
 public:
+    static JS::NonnullGCPtr<AudioParam> create(JS::Realm&, float default_value, float min_value, float max_value, Bindings::AutomationRate);
+
     virtual ~AudioParam() override;
 
     float value() const;
@@ -39,6 +41,8 @@ public:
     WebIDL::ExceptionOr<JS::NonnullGCPtr<AudioParam>> cancel_and_hold_at_time(double cancel_time);
 
 private:
+    AudioParam(JS::Realm&, float default_value, float min_value, float max_value, Bindings::AutomationRate);
+
     // https://webaudio.github.io/web-audio-api/#dom-audioparam-current-value-slot
     float m_current_value {}; //  [[current value]]
 

Userland/Libraries/LibWeb/WebAudio/OscillatorNode.cpp

@@ -6,6 +6,8 @@
 
 #include <LibWeb/Bindings/Intrinsics.h>
 #include <LibWeb/Bindings/OscillatorNodePrototype.h>
+#include <LibWeb/WebAudio/AudioParam.h>
+#include <LibWeb/WebAudio/BaseAudioContext.h>
 #include <LibWeb/WebAudio/OscillatorNode.h>
 
 namespace Web::WebAudio {
@@ -28,8 +30,9 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<OscillatorNode>> OscillatorNode::construct_
     return node;
 }
 
-OscillatorNode::OscillatorNode(JS::Realm& realm, JS::NonnullGCPtr<BaseAudioContext> context, OscillatorOptions const&)
+OscillatorNode::OscillatorNode(JS::Realm& realm, JS::NonnullGCPtr<BaseAudioContext> context, OscillatorOptions const& options)
     : AudioScheduledSourceNode(realm, context)
+    , m_frequency(AudioParam::create(realm, options.frequency, -context->nyquist_frequency(), context->nyquist_frequency(), Bindings::AutomationRate::ARate))
 {
 }
 
@@ -69,6 +72,7 @@ void OscillatorNode::initialize(JS::Realm& realm)
 void OscillatorNode::visit_edges(Cell::Visitor& visitor)
 {
     Base::visit_edges(visitor);
+    visitor.visit(m_frequency);
 }
 
 }

Userland/Libraries/LibWeb/WebAudio/OscillatorNode.h

@@ -33,6 +33,8 @@ public:
     Bindings::OscillatorType type() const;
     WebIDL::ExceptionOr<void> set_type(Bindings::OscillatorType);
 
+    JS::NonnullGCPtr<AudioParam const> frequency() const { return m_frequency; }
+
 protected:
     OscillatorNode(JS::Realm&, JS::NonnullGCPtr<BaseAudioContext>, OscillatorOptions const& = {});
 
@@ -44,6 +46,9 @@ private:
 
     // https://webaudio.github.io/web-audio-api/#dom-oscillatornode-type
     Bindings::OscillatorType m_type { Bindings::OscillatorType::Sine };
+
+    // https://webaudio.github.io/web-audio-api/#dom-oscillatornode-frequency
+    JS::NonnullGCPtr<AudioParam> m_frequency;
 };
 
 }

Userland/Libraries/LibWeb/WebAudio/OscillatorNode.idl

@@ -23,7 +23,7 @@ dictionary OscillatorOptions : AudioNodeOptions {
 interface OscillatorNode : AudioScheduledSourceNode {
     constructor(BaseAudioContext context, optional OscillatorOptions options = {});
     attribute OscillatorType type;
-    // FIXME: readonly attribute AudioParam frequency;
+    readonly attribute AudioParam frequency;
     // FIXME: readonly attribute AudioParam detune;
     // FIXME: undefined setPeriodicWave(PeriodicWave periodicWave);
 };