[HTML5] Refactor audio drivers. Implement AudioWorklet w/o threads.

Performances are not great in general, bad on Firefox, on Chrome, well,
it's an improvement compared to the way they broke ScriptProcessorNode.

I'm actually surprised this works, it involves so many allocations, but
there's no way around it when SharedArrayBuffer is not available :(.

platform/javascript/js/libs/library_godot_audio.js

@@ -159,6 +159,16 @@ const GodotAudio = {
 		return 1;
 	},
 
+	godot_audio_has_worklet__sig: 'i',
+	godot_audio_has_worklet: function () {
+		return (GodotAudio.ctx && GodotAudio.ctx.audioWorklet) ? 1 : 0;
+	},
+
+	godot_audio_has_script_processor__sig: 'i',
+	godot_audio_has_script_processor: function () {
+		return (GodotAudio.ctx && GodotAudio.ctx.createScriptProcessor) ? 1 : 0;
+	},
+
 	godot_audio_init__sig: 'iiiii',
 	godot_audio_init: function (p_mix_rate, p_latency, p_state_change, p_latency_update) {
 		const statechange = GodotRuntime.get_func(p_state_change);
@@ -209,6 +219,7 @@ const GodotAudioWorklet = {
 	$GodotAudioWorklet: {
 		promise: null,
 		worklet: null,
+		ring_buffer: null,
 
 		create: function (channels) {
 			const path = GodotConfig.locate_file('godot.audio.worklet.js');
@@ -239,6 +250,86 @@ const GodotAudioWorklet = {
 			});
 		},
 
+		start_no_threads: function (p_out_buf, p_out_size, out_callback, p_in_buf, p_in_size, in_callback) {
+			function RingBuffer() {
+				let wpos = 0;
+				let rpos = 0;
+				let pending_samples = 0;
+				const wbuf = new Float32Array(p_out_size);
+
+				function send(port) {
+					if (pending_samples === 0) {
+						return;
+					}
+					const buffer = GodotRuntime.heapSub(HEAPF32, p_out_buf, p_out_size);
+					const size = buffer.length;
+					const tot_sent = pending_samples;
+					out_callback(wpos, pending_samples);
+					if (wpos + pending_samples >= size) {
+						const high = size - wpos;
+						wbuf.set(buffer.subarray(wpos, size));
+						pending_samples -= high;
+						wpos = 0;
+					}
+					if (pending_samples > 0) {
+						wbuf.set(buffer.subarray(wpos, wpos + pending_samples), tot_sent - pending_samples);
+					}
+					port.postMessage({ 'cmd': 'chunk', 'data': wbuf.subarray(0, tot_sent) });
+					wpos += pending_samples;
+					pending_samples = 0;
+				}
+				this.receive = function (recv_buf) {
+					const buffer = GodotRuntime.heapSub(HEAPF32, p_in_buf, p_in_size);
+					const from = rpos;
+					let to_write = recv_buf.length;
+					let high = 0;
+					if (rpos + to_write >= p_in_size) {
+						high = p_in_size - rpos;
+						buffer.set(recv_buf.subarray(0, high), rpos);
+						to_write -= high;
+						rpos = 0;
+					}
+					if (to_write) {
+						buffer.set(recv_buf.subarray(high, to_write), rpos);
+					}
+					in_callback(from, recv_buf.length);
+					rpos += to_write;
+				};
+				this.consumed = function (size, port) {
+					pending_samples += size;
+					send(port);
+				};
+			}
+			GodotAudioWorklet.ring_buffer = new RingBuffer();
+			GodotAudioWorklet.promise.then(function () {
+				const node = GodotAudioWorklet.worklet;
+				const buffer = GodotRuntime.heapSlice(HEAPF32, p_out_buf, p_out_size);
+				node.connect(GodotAudio.ctx.destination);
+				node.port.postMessage({
+					'cmd': 'start_nothreads',
+					'data': [buffer, p_in_size],
+				});
+				node.port.onmessage = function (event) {
+					if (!GodotAudioWorklet.worklet) {
+						return;
+					}
+					if (event.data['cmd'] === 'read') {
+						const read = event.data['data'];
+						GodotAudioWorklet.ring_buffer.consumed(read, GodotAudioWorklet.worklet.port);
+					} else if (event.data['cmd'] === 'input') {
+						const buf = event.data['data'];
+						if (buf.length > p_in_size) {
+							GodotRuntime.error('Input chunk is too big');
+							return;
+						}
+						GodotAudioWorklet.ring_buffer.receive(buf);
+					} else {
+						GodotRuntime.error(event.data);
+					}
+				};
+			});
+		},
+
 		get_node: function () {
 			return GodotAudioWorklet.worklet;
 		},
@@ -262,9 +353,15 @@ const GodotAudioWorklet = {
 		},
 	},
 
-	godot_audio_worklet_create__sig: 'vi',
+	godot_audio_worklet_create__sig: 'ii',
 	godot_audio_worklet_create: function (channels) {
-		GodotAudioWorklet.create(channels);
+		try {
+			GodotAudioWorklet.create(channels);
+		} catch (e) {
+			GodotRuntime.error('Error starting AudioDriverWorklet', e);
+			return 1;
+		}
+		return 0;
 	},
 
 	godot_audio_worklet_start__sig: 'viiiii',
@@ -275,6 +372,13 @@ const GodotAudioWorklet = {
 		GodotAudioWorklet.start(in_buffer, out_buffer, state);
 	},
 
+	godot_audio_worklet_start_no_threads__sig: 'viiiiii',
+	godot_audio_worklet_start_no_threads: function (p_out_buf, p_out_size, p_out_callback, p_in_buf, p_in_size, p_in_callback) {
+		const out_callback = GodotRuntime.get_func(p_out_callback);
+		const in_callback = GodotRuntime.get_func(p_in_callback);
+		GodotAudioWorklet.start_no_threads(p_out_buf, p_out_size, out_callback, p_in_buf, p_in_size, in_callback);
+	},
+
 	godot_audio_worklet_state_wait__sig: 'iiii',
 	godot_audio_worklet_state_wait: function (p_state, p_idx, p_expected, p_timeout) {
 		Atomics.wait(HEAP32, (p_state >> 2) + p_idx, p_expected, p_timeout);
@@ -358,7 +462,15 @@ const GodotAudioScript = {
 
 	godot_audio_script_create__sig: 'iii',
 	godot_audio_script_create: function (buffer_length, channel_count) {
-		return GodotAudioScript.create(buffer_length, channel_count);
+		const buf_len = GodotRuntime.getHeapValue(buffer_length, 'i32');
+		try {
+			const out_len = GodotAudioScript.create(buf_len, channel_count);
+			GodotRuntime.setHeapValue(buffer_length, out_len, 'i32');
+		} catch (e) {
+			GodotRuntime.error('Error starting AudioDriverScriptProcessor', e);
+			return 1;
+		}
+		return 0;
 	},
 
 	godot_audio_script_start__sig: 'viiiii',