audio: Avoid using time.After on browsers for performance

audio/audio.go

@@ -430,7 +430,7 @@ func (p *Player) readToBuffer(length int) (int, error) {
 		if len(r.data) > 0 {
 			p.buf = append(p.buf, r.data...)
 		}
-	case <-time.After(15 * time.Millisecond):
+	case <-timeoutIfPossible(15 * time.Millisecond):
 		if l := length - len(p.buf); l > 0 {
 			empty := make([]uint8, l)
 			p.buf = append(p.buf, empty...)

audio/timeout_js.go

@@ -0,0 +1,27 @@
+// Copyright 2017 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build js
+
+package audio
+
+import (
+	"time"
+)
+
+func timeoutIfPossible(t time.Duration) <-chan time.Time {
+	// time.After uses setTimeout and causes performance problems.
+	// This function returns null and actually blocks forever.
+	return nil
+}

audio/timeout_notjs.go

@@ -0,0 +1,25 @@
+// Copyright 2017 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !js
+
+package audio
+
+import (
+	"time"
+)
+
+func timeoutIfPossible(t time.Duration) <-chan time.Time {
+	return time.After(t)
+}