Do not increase the pointer id when type is eraser

third_party/WebKit/Source/core/events/PointerEventFactory.cpp

 // Copyright 2016 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.
 
 #include "core/events/PointerEventFactory.h"
 
 #include "core/frame/FrameView.h"
 #include "platform/geometry/FloatSize.h"
 
 namespace blink {
@@ skipping 172 matching lines @@
 
 // Mouse id is 1 to behave the same as MS Edge for compatibility reasons.
 const int PointerEventFactory::kMouseId = 1;
 
 void PointerEventFactory::SetIdTypeButtons(
     PointerEventInit& pointer_event_init,
     const WebPointerProperties& pointer_properties,
     unsigned buttons) {
   const WebPointerProperties::PointerType pointer_type =
       pointer_properties.pointer_type;
   const IncomingId incoming_id(pointer_type, pointer_properties.id);

[Navid Zolghadr, 2017/05/09 15:00:38]

How about this here?
const IncomingId incoming_id(pointer_type == kEraser ? kPen : pointer_type,
pointer_properties.id)

   int pointer_id = AddIdAndActiveButtons(incoming_id, buttons != 0);
 
   // Tweak the |buttons| to reflect pen eraser mode only if the pen is in
   // active buttons state w/o even considering the eraser button.
   // TODO(mustaq): Fix when the spec starts supporting hovering erasers.
   if (pointer_type == WebPointerProperties::PointerType::kEraser &&
       buttons != 0) {
     buttons |= static_cast<unsigned>(WebPointerProperties::Buttons::kEraser);
     buttons &= ~static_cast<unsigned>(WebPointerProperties::Buttons::kLeft);
   }
@@ skipping 272 matching lines @@
 }
 
 int PointerEventFactory::AddIdAndActiveButtons(const IncomingId p,
                                                bool is_active_buttons) {
   // Do not add extra mouse pointer as it was added in initialization
   if (p.GetPointerType() == WebPointerProperties::PointerType::kMouse) {
     pointer_id_mapping_.Set(kMouseId, PointerAttributes(p, is_active_buttons));
     return kMouseId;
   }
 
-  if (pointer_incoming_id_mapping_.Contains(p)) {
-    int mapped_id = pointer_incoming_id_mapping_.at(p);
-    pointer_id_mapping_.Set(mapped_id, PointerAttributes(p, is_active_buttons));
+  IncomingId incoming_id = p;
+  if (p.GetPointerType() == WebPointerProperties::PointerType::kEraser) {

[dtapuska, 2017/05/09 13:24:45]

Sorry this seems wrong to me. In that if we get an kEraser pointer type first
and then release it then you will end up incrementing the pointer ID. In that
the eraser pointer id != pen pointer id.

Can we just treat the creation of IncomingId if the type is kEraser as kPen?

+    const IncomingId pen_id =
+        IncomingId(WebPointerProperties::PointerType::kPen, p.RawId());
+    if (pointer_incoming_id_mapping_.Contains(pen_id))
+      incoming_id = pen_id;
+  }
+
+  if (pointer_incoming_id_mapping_.Contains(incoming_id)) {
+    int mapped_id = pointer_incoming_id_mapping_.at(incoming_id);
+    pointer_id_mapping_.Set(mapped_id,
+                            PointerAttributes(incoming_id, is_active_buttons));
     return mapped_id;
   }
-  int type_int = p.PointerTypeInt();
+  int type_int = incoming_id.PointerTypeInt();
   // We do not handle the overflow of m_currentId as it should be very rare
   int mapped_id = current_id_++;
   if (!id_count_[type_int])
     primary_id_[type_int] = mapped_id;
   id_count_[type_int]++;
-  pointer_incoming_id_mapping_.insert(p, mapped_id);
+  pointer_incoming_id_mapping_.insert(incoming_id, mapped_id);
   pointer_id_mapping_.insert(mapped_id,
-                             PointerAttributes(p, is_active_buttons));
+                             PointerAttributes(incoming_id, is_active_buttons));
   return mapped_id;
 }
 
 bool PointerEventFactory::Remove(const int mapped_id) {
   // Do not remove mouse pointer id as it should always be there
   if (mapped_id == kMouseId || !pointer_id_mapping_.Contains(mapped_id))
     return false;
 
   IncomingId p = pointer_id_mapping_.at(mapped_id).incoming_id;
   int type_int = p.PointerTypeInt();
@@ skipping 49 matching lines @@
     const WebPointerProperties& properties) const {
   if (properties.pointer_type == WebPointerProperties::PointerType::kMouse)
     return PointerEventFactory::kMouseId;
   IncomingId id(properties.pointer_type, properties.id);
   if (pointer_incoming_id_mapping_.Contains(id))
     return pointer_incoming_id_mapping_.at(id);
   return PointerEventFactory::kInvalidId;
 }
 
 }  // namespace blink