Cleaning up PointerIdManager and add id re-mapping

third_party/WebKit/Source/core/events/PointerIdManager.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PointerIdManager_h
 #define PointerIdManager_h
 
+#include "core/CoreExport.h"
 #include "public/platform/WebPointerProperties.h"
 #include "wtf/Allocator.h"
-#include "wtf/ListHashSet.h"
+#include "wtf/HashMap.h"
 
 namespace blink {
 
 /**
-  Helper class for tracking the primary pointer id for each type of PointerEvents.
+  Helper class for tracking the pointer ids for each type of PointerEvents.
+  Using id re-mapping at this layer, this class makes sure that regardless of the
+  domain of the id (i.e. in touch or pen) the corresponding pointer event will have
+  a unique id amongst all pointer events as per pointer events' specification.
+  This class intended to behave the same as existing browsers as much as possible
+  for compatibility reasons. Particularly it behaves very similar to MS Edge to have
+  pointer event ids generated by mouse always equal 1 and those that are generated
+  by touch and pen will have increasing ids from 2.
 */
-class PointerIdManager {
+class CORE_EXPORT PointerIdManager {
     DISALLOW_NEW();
 public:
+    typedef unsigned MappedId;
+    typedef std::pair<WebPointerProperties::PointerType, unsigned> GeneratedPointer;
+    static const MappedId s_invalidId;
     PointerIdManager();
     ~PointerIdManager();
     void clear();
-    void add(WebPointerProperties::PointerType, unsigned);
-    void remove(WebPointerProperties::PointerType, unsigned);
-    bool isPrimary(WebPointerProperties::PointerType, unsigned);
+    MappedId add(const GeneratedPointer);
+    void remove(const GeneratedPointer);

[mustaq, 2015/11/20 20:13:53]

Two remove()s is confusing. just pass a ref to PointerIdManager and rawId. See
my comment in EventHandler.

+    void remove(const MappedId);
+    bool isPrimary(const MappedId) const;
+    MappedId getPrimaryId(const WebPointerProperties::PointerType) const;
+    WebPointerProperties::PointerType getType(const MappedId) const;
 
 private:
-    // TODO(crbug.com/537319): Switch to /one/ set of ids to guarantee uniqueness.
-    ListHashSet<unsigned> m_ids[static_cast<int>(WebPointerProperties::PointerType::LastEntry) + 1];
-    bool m_hasPrimaryId[static_cast<int>(WebPointerProperties::PointerType::LastEntry) + 1];
+    PointerIdManager::MappedId m_currentId;
+    HashMap<unsigned, MappedId, WTF::IntHash<unsigned>, WTF::UnsignedWithZeroKeyHashTraits<unsigned>> m_ids[static_cast<int>(WebPointerProperties::PointerType::LastEntry) + 1];
+    HashMap<MappedId, GeneratedPointer, WTF::IntHash<unsigned>, WTF::UnsignedWithZeroKeyHashTraits<unsigned>> m_reverseMapping;
+    MappedId m_primaryId[static_cast<int>(WebPointerProperties::PointerType::LastEntry) + 1];
 };
 
 } // namespace blink
 
 #endif // PointerIdManager_h