Correctly release the touch events on Lenovo Horizon device

ui/views/win/hwnd_message_handler.h

Index: ui/views/win/hwnd_message_handler.h
diff --git a/ui/views/win/hwnd_message_handler.h b/ui/views/win/hwnd_message_handler.h
index d2dc968b22a0579db935bc02d2d7e51c91f860cd..004fb880a469a4d50780e2f6798b0d1697a167eb 100644
--- a/ui/views/win/hwnd_message_handler.h
+++ b/ui/views/win/hwnd_message_handler.h
@@ -7,7 +7,7 @@
 
 #include <windows.h>
 
-#include <set>
+#include <array>
 #include <vector>
 
 #include "base/basictypes.h"
@@ -21,6 +21,7 @@
 #include "ui/base/ui_base_types.h"
 #include "ui/base/win/window_event_target.h"
 #include "ui/events/event.h"
+#include "ui/events/gesture_detection/motion_event.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/sequential_id_generator.h"
 #include "ui/gfx/win/window_impl.h"
@@ -208,7 +209,27 @@ class VIEWS_EXPORT HWNDMessageHandler :
   void SizeConstraintsChanged();
 
  private:
-  typedef std::set<DWORD> TouchIDs;
+  FRIEND_TEST_ALL_PREFIXES(HWNDMessageHandler, TestCorrectTouchInputList);
+  FRIEND_TEST_ALL_PREFIXES(HWNDMessageHandler, TestMissingTouchRelease);
+  FRIEND_TEST_ALL_PREFIXES(HWNDMessageHandler, TestMissingTouchPress);
+  FRIEND_TEST_ALL_PREFIXES(HWNDMessageHandler, TestMissingTouchPressAndRelease);
+
+  // We use InTouchList self-defined type to specify if the touch point from
+  // last message is in the current message or not.
+  enum class InTouchList { NotPresent, InPreviousMessage, InCurrentMessage };
+
+  // We need the touch location to release a touch point which is not in the
+  // current message.
+  struct TouchPoint {
+    gfx::Point location;
+    InTouchList in_touch_list;
+
+    TouchPoint() : in_touch_list(InTouchList::NotPresent) {}
+  };
+
+  using TouchEvents = std::vector<ui::TouchEvent>;
+  using TouchPointArray =
+      std::array<TouchPoint, ui::MotionEvent::MAX_TOUCH_POINT_COUNT>;
 
   // Overridden from internal::InputMethodDelegate:
   void DispatchKeyEventPostIME(const ui::KeyEvent& key) override;
@@ -458,7 +479,6 @@ class VIEWS_EXPORT HWNDMessageHandler :
   void OnWindowPosChanging(WINDOWPOS* window_pos);
   void OnWindowPosChanged(WINDOWPOS* window_pos);
 
-  typedef std::vector<ui::TouchEvent> TouchEvents;
   // Helper to handle the list of touch events passed in. We need this because
   // touch events on windows don't fire if we enter a modal loop in the context
   // of a touch event.
@@ -466,7 +486,7 @@ class VIEWS_EXPORT HWNDMessageHandler :
 
   // Resets the flag which indicates that we are in the context of a touch down
   // event.
-  void ResetTouchDownContext();
+  void DecrementTouchDownContext(int decrement);
 
   // Helper to handle mouse events.
   // The |message|, |w_param|, |l_param| parameters identify the Windows mouse
@@ -489,6 +509,23 @@ class VIEWS_EXPORT HWNDMessageHandler :
   // Provides functionality to transition a frame to DWM.
   void PerformDwmTransition();
 
+  void PrepareTouchEventList(TOUCHINPUT input[],
+                             int num_points,
+                             TouchEvents* touch_events);
+
+  // From one WM_TOUCH message, we will generate corresponding touch events.
+  void GenerateTouchEvent(DWORD input_dwID,
+                          const gfx::Point& point_location,
+                          ui::EventType touch_event_type,
+                          TouchEvents* touch_events);
+
+  // It will release the touch points which are no longer in the current message
+  // because the messages are sent inconsistently, and also set the touch points
+  // we have seen in the current message to be InPreviousMessage.
+  void UpdateTouchPointStates(TouchEvents* touch_events);
+
+  const TouchPointArray& touch_id_list() const { return touch_id_list_; }
+
   HWNDMessageHandlerDelegate* delegate_;
 
   scoped_ptr<FullscreenHandler> fullscreen_handler_;
@@ -522,9 +559,6 @@ class VIEWS_EXPORT HWNDMessageHandler :
   // area. We need this so we can correctly show the context menu on mouse-up.
   bool is_right_mouse_pressed_on_caption_;
 
-  // The set of touch devices currently down.
-  TouchIDs touch_ids_;
-
   // ScopedRedrawLock ----------------------------------------------------------
 
   // Represents the number of ScopedRedrawLocks active against this widget.
@@ -623,6 +657,16 @@ class VIEWS_EXPORT HWNDMessageHandler :
   // glass. Defaults to false.
   bool dwm_transition_desired_;
 
+  // The WM_TOUCH message at times sends inconsistent number of touch pointers,
+  // so we keep the IDs of touch pointers we have seen from last message, and
+  // compare with the current message in order to release the ones which are not
+  // in the current list, or send a touchpress when we see a new touch point.
+  // The index of the array is the touch_ID.
+  TouchPointArray touch_id_list_;
+
+  // Keep the count of the current active touch points.
+  int active_touch_point_count_;
+
   // A factory used to lookup appbar autohide edges.
   base::WeakPtrFactory<HWNDMessageHandler> autohide_factory_;