Implement StereoPannerNode for robust stereo panning

Source/modules/webaudio/StereoPannerNode.h

Index: Source/modules/webaudio/StereoPannerNode.h
diff --git a/Source/platform/text/TextRunIterator.h b/Source/modules/webaudio/StereoPannerNode.h
similarity index 56%
copy from Source/platform/text/TextRunIterator.h
copy to Source/modules/webaudio/StereoPannerNode.h
index 0774b659a08244236f61d3b3b5cf728a6d078329..02b02e4278a5925be7926116a0d5be933f9ca761 100644
--- a/Source/platform/text/TextRunIterator.h
+++ b/Source/modules/webaudio/StereoPannerNode.h
@@ -1,4 +1,4 @@
-// Copyright (C) 2013 Google Inc. All rights reserved.
+// Copyright 2014 The Chromium Authors. All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
@@ -26,53 +26,49 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#ifndef TextRunIterator_h
-#define TextRunIterator_h
+#ifndef StereoPannerNode_h
+#define StereoPannerNode_h
 
-#include "platform/text/TextRun.h"
+#include "modules/webaudio/AudioNode.h"
+#include "modules/webaudio/AudioParam.h"
+#include "platform/audio/AudioBus.h"
+#include "platform/audio/Spatializer.h"
 
 namespace blink {
 
-class TextRunIterator {
+// StereoPannerNode is an AudioNode with one input and one output. It is
+// specifically designed for equal-power stereo panning.
+class StereoPannerNode final : public AudioNode {
+    DEFINE_WRAPPERTYPEINFO();
 public:
-    TextRunIterator()
-        : m_textRun(0)
-        , m_offset(0)
+    static StereoPannerNode* create(AudioContext* context, float sampleRate)
     {
+        return new StereoPannerNode(context, sampleRate);
     }
 
-    TextRunIterator(const TextRun* textRun, unsigned offset)
-        : m_textRun(textRun)
-        , m_offset(offset)
-    {
-    }
+    virtual ~StereoPannerNode();
 
-    TextRunIterator(const TextRunIterator& other)
-        : m_textRun(other.m_textRun)
-        , m_offset(other.m_offset)
-    {
-    }
+    virtual void dispose() override;
+    virtual void process(size_t framesToProcess) override;
+    virtual void initialize() override;
+    virtual void uninitialize() override;
 
-    unsigned offset() const { return m_offset; }
-    void increment() { m_offset++; }
-    bool atEnd() const { return !m_textRun || m_offset >= m_textRun->length(); }
-    UChar current() const { return (*m_textRun)[m_offset]; }
-    WTF::Unicode::Direction direction() const { return atEnd() ? WTF::Unicode::OtherNeutral : WTF::Unicode::direction(current()); }
-    bool atParagraphSeparator() const { return current() == '\n'; }
+    virtual double tailTime() const override { return 0; }
+    virtual double latencyTime() const override { return 0; }
 
-    bool operator==(const TextRunIterator& other)
-    {
-        return m_offset == other.m_offset && m_textRun == other.m_textRun;
-    }
+    virtual void trace(Visitor*) override;
 
-    bool operator!=(const TextRunIterator& other) { return !operator==(other); }
+    AudioParam* pan() { return m_pan.get(); }

[Raymond Toy, 2014/11/11 19:41:47]

Can this be const?

[hongchan, 2014/11/12 00:06:54]

The structure of this node is based on GainNode and PannerNode. GainNode has the
same statement with a different AudioParam name - but it doesn't have const. Do
you think should I add it here?

[Raymond Toy, 2014/11/12 00:16:44]

I think the style is to be const when possible, so if you can, make this const,
even if GainNode and PannerNode are not.

 
 private:
-    const TextRun* m_textRun;
-    int m_offset;
-};
+    StereoPannerNode(AudioContext*, float sampleRate);
 
+    Member<Spatializer> m_stereoPanner;
+    Member<AudioParam> m_pan;
+
+    AudioFloatArray m_sampleAccuratePanValues;
+};
 
 } // namespace blink
 
-#endif // TextRunIterator_h
+#endif // StereoPannerNode_h