LibWeb: Implement AudioNode.channelCount

Author: https://github.com/gmta
Commit: cb21201550
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);
+}
+
 }