LibWeb: Implement AudioNode.channelCount

Author: https://github.com/gmta
Commit: https://github.com/LadybirdBrowser/ladybird/commit/cb212015505
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/1679

Userland/Libraries/LibWeb/WebAudio/AudioDestinationNode.cpp

@@ -7,9 +7,11 @@
 
 #include <LibWeb/Bindings/AudioDestinationNodePrototype.h>
 #include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/WebAudio/AudioContext.h>
 #include <LibWeb/WebAudio/AudioDestinationNode.h>
 #include <LibWeb/WebAudio/AudioNode.h>
 #include <LibWeb/WebAudio/BaseAudioContext.h>
+#include <LibWeb/WebAudio/OfflineAudioContext.h>
 
 namespace Web::WebAudio {
 
@@ -45,4 +47,25 @@ void AudioDestinationNode::visit_edges(Cell::Visitor& visitor)
     Base::visit_edges(visitor);
 }
 
+// https://webaudio.github.io/web-audio-api/#dom-audionode-channelcount
+WebIDL::ExceptionOr<void> AudioDestinationNode::set_channel_count(WebIDL::UnsignedLong channel_count)
+{
+    // The behavior depends on whether the destination node is the destination of an AudioContext
+    // or OfflineAudioContext:
+
+    // AudioContext: The channel count MUST be between 1 and maxChannelCount. An IndexSizeError
+    // exception MUST be thrown for any attempt to set the count outside this range.
+    if (is<AudioContext>(*context())) {
+        if (channel_count < 1 || channel_count > max_channel_count())
+            return WebIDL::IndexSizeError::create(realm(), "Channel index is out of range"_fly_string);
+    }
+
+    // OfflineAudioContext: The channel count cannot be changed. An InvalidStateError exception MUST
+    // be thrown for any attempt to change the value.
+    if (is<OfflineAudioContext>(*context()))
+        return WebIDL::InvalidStateError::create(realm(), "Cannot change channel count in an OfflineAudioContext"_fly_string);
+
+    return AudioNode::set_channel_count(channel_count);
+}
+
 }

Userland/Libraries/LibWeb/WebAudio/AudioDestinationNode.h

@@ -25,6 +25,7 @@ public:
     WebIDL::UnsignedLong max_channel_count();
     WebIDL::UnsignedLong number_of_inputs() override { return 1; }
     WebIDL::UnsignedLong number_of_outputs() override { return 1; }
+    WebIDL::ExceptionOr<void> set_channel_count(WebIDL::UnsignedLong) override;
 
     static JS::NonnullGCPtr<AudioDestinationNode> construct_impl(JS::Realm&, JS::NonnullGCPtr<BaseAudioContext>);
 

Userland/Libraries/LibWeb/WebAudio/AudioNode.cpp

@@ -101,15 +101,13 @@ void AudioNode::disconnect(JS::NonnullGCPtr<AudioParam> destination_param, WebID
 // https://webaudio.github.io/web-audio-api/#dom-audionode-channelcount
 WebIDL::ExceptionOr<void> AudioNode::set_channel_count(WebIDL::UnsignedLong channel_count)
 {
-    (void)channel_count;
-    return WebIDL::NotSupportedError::create(realm(), "FIXME: Implement AudioNode::set_channel_count(channel_count)"_fly_string);
-}
+    // If this value is set to zero or to a value greater than the implementation’s maximum number
+    // of channels the implementation MUST throw a NotSupportedError exception.
+    if (channel_count == 0 || channel_count > BaseAudioContext::MAX_NUMBER_OF_CHANNELS)
+        return WebIDL::NotSupportedError::create(realm(), "Invalid channel count"_fly_string);
 
-// https://webaudio.github.io/web-audio-api/#dom-audionode-channelcount
-WebIDL::UnsignedLong AudioNode::channel_count()
-{
-    dbgln("FIXME: Implement AudioNode::channel_count()");
-    return 2;
+    m_channel_count = channel_count;
+    return {};
 }
 
 // https://webaudio.github.io/web-audio-api/#dom-audionode-channelcountmode

Userland/Libraries/LibWeb/WebAudio/AudioNode.h

@@ -53,8 +53,10 @@ public:
     // https://webaudio.github.io/web-audio-api/#dom-audionode-numberofoutputs
     virtual WebIDL::UnsignedLong number_of_outputs() = 0;
 
-    WebIDL::ExceptionOr<void> set_channel_count(WebIDL::UnsignedLong);
-    WebIDL::UnsignedLong channel_count();
+    // https://webaudio.github.io/web-audio-api/#dom-audionode-channelcount
+    virtual WebIDL::ExceptionOr<void> set_channel_count(WebIDL::UnsignedLong);
+    virtual WebIDL::UnsignedLong channel_count() const { return m_channel_count; }
+
     WebIDL::ExceptionOr<void> set_channel_count_mode(Bindings::ChannelCountMode);
     Bindings::ChannelCountMode channel_count_mode();
     WebIDL::ExceptionOr<void> set_channel_interpretation(Bindings::ChannelInterpretation);
@@ -68,6 +70,7 @@ protected:
 
 private:
     JS::NonnullGCPtr<BaseAudioContext> m_context;
+    WebIDL::UnsignedLong m_channel_count { 2 };
     Bindings::ChannelCountMode m_channel_count_mode { Bindings::ChannelCountMode::Max };
     Bindings::ChannelInterpretation m_channel_interpretation { Bindings::ChannelInterpretation::Speakers };
 };