Pulls display related changes from mojo to chrome

mojo/services/view_manager/gesture_manager.h

Index: mojo/services/view_manager/gesture_manager.h
diff --git a/mojo/services/view_manager/gesture_manager.h b/mojo/services/view_manager/gesture_manager.h
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+++ b/mojo/services/view_manager/gesture_manager.h
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+// 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 SERVICES_VIEW_MANAGER_GESTURE_MANAGER_H_
+#define SERVICES_VIEW_MANAGER_GESTURE_MANAGER_H_
+
+#include <map>
+#include <set>
+
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/scoped_vector.h"
+
+namespace mojo {
+class Event;
+}
+
+namespace view_manager {
+
+class GestureManagerDelegate;
+class GestureManagerTest;
+class ServerView;
+
+struct GestureStateChange {
+  GestureStateChange();
+  ~GestureStateChange();
+
+  uint32_t chosen_gesture;
+  std::set<uint32_t> canceled_gestures;
+};
+
+using ChangeMap = std::map<const ServerView*, GestureStateChange>;
+
+// GestureManager handles incoming pointer events. It determines the set of
+// views (at most one per connection) that are interested in the event and
+// informs the delegate at the appropriate time.
+//
+// Each pointer may have any number of views associated with it, and each view
+// may have any number of gestures associated with it. Gesture are identified
+// the by the pair of the connection id of the view and the client supplied
+// gesture.  The same gesture may be used in multiple pointers (see example
+// below).
+//
+// Gestures have the following states:
+// . initial: Initial state for new gestures. From this state the gesture may
+//   become chosen or canceled. Once a gesture moves out of this state it can
+//   never go back.
+// . chosen: the gesture has been chosen. From this state the gesture may be
+//   canceled.
+// . canceled: the gesture has been canceled.
+// Gestures are active as long as they are included in the set of
+// |possible_gesture_ids|. Gestures can be removed at any time by removing the
+// gesture from |possible_gesture_ids|.
+//
+// A particular pointer has two distinct states:
+// . initial: none of the gestures associated with the pointer have been
+//   chosen.
+// . chosen: when a gesture associated with the pointer has been chosen.
+// Pointers are removed when a POINTER_UP or POINTER_CANCEL event is received.
+//
+// When a pointer is chosen all other gestures associated with the pointer are
+// implicitly canceled. If the chosen gesture is canceled the pointer remains
+// in the chosen state and no gestures can be chosen.
+//
+// Event propagation (ProcessEvent()) is handled in two distinct ways:
+// . Until a gesture has been chosen for the pointer, views are notified in
+//   order (deepest first). The next view (ancestor) is notified once
+//   SetGestures() has been invoked for the previous (descendant) view.
+// . Once a gesture has been chosen, then incoming events are immediately
+//   dispatched.
+//
+// The following example highlights various states and transitions:
+// . A POINTER_DOWN event is received for the pointer p1. The views that
+//   contain the location of the event (starting with the deepest) are v1, v2,
+//   v3 and v4. Both v1 and v2 have the property kViewManagerKeyWantsTouchEvents
+//   set, so only v1 and v2 are considered. v1 is the deepest view, so the
+//   touch event is set to it and only it first.
+// . v1 responds with possible gestures g1 and g2. v1 does not specify either
+//   of the gestures as chosen.
+// . As the response from v1 has been received and there is no chosen gesture
+//   the POINTER_DOWN event is sent to v2.
+// . v2 responds with gestures g3 and g4, neither of which are chosen.
+// . A POINTER_MOVE for p1 is received. As no gestures have been chosen event
+//   of the POINTER_MOVE continues with v1 first.
+// . v1 returns g1 and g2 as possible gestures and does not choose one.
+// . The POINTER_MOVE is sent to v2.
+// . v2 returns g3 and g4 as possible gestures and does not choose one.
+// At this point p1 has the possible gestures g1, g2, g3, g4. Gestures g1 and
+// g2 are associated with v1. Gestures g3 and g4 are associated with v2.
+// . A POINTER_DOWN event is received for the pointer p2. v1 and v2 again
+//   contain the location of the pointer. v1 is handed the event first.
+// . A POINTER_MOVE event is received for the pointer p2. As the response from
+//   v1 has not been received yet, the event is not sent yet (it is queued up).
+// . v1 responds to the POINTER_DOWN for p2 with g1 and g2 and chooses g1.
+// At this point g2, g3 and g4 are all canceled with g1 chosen. p2 is in the
+// chosen state, as is p1 (p1 enters the chosen state as it contains the chosen
+// gesture as well).
+// . The POINTER_DOWN event for p2 is sent to v2. As p2 is in the chosen state
+//   the POINTER_MOVE event that was queued up is sent to both v1 and v2 at the
+//   same time (no waiting for response).
+//
+// TODO(sky): add some sort of timeout to deal with hung processes.
+class GestureManager {
+ public:
+  using GestureAndConnectionId = uint64_t;
+
+  static const uint32_t kInvalidGestureId;
+
+  GestureManager(GestureManagerDelegate* delegate, const ServerView* root);
+  ~GestureManager();
+
+  // Processes the current event. See GestureManager description for details.
+  bool ProcessEvent(const mojo::Event& event);
+
+  // Sets the gestures for the specified view and pointer.
+  scoped_ptr<ChangeMap> SetGestures(
+      const ServerView* view,
+      int32_t pointer_id,
+      uint32_t chosen_gesture_id,
+      const std::set<uint32_t>& possible_gesture_ids,
+      const std::set<uint32_t>& canceled_gesture_ids);
+
+ private:
+  friend class GestureManagerTest;
+
+  class Gesture;
+  class Pointer;
+  struct PointerAndView;
+  class ScheduledDeleteProcessor;
+
+  // Returns the Pointer for |pointer_id|, or null if one doesn't exist.
+  Pointer* GetPointerById(int32_t pointer_id);
+
+  // Notification that |pointer| has no gestures. This deletes |pointer|.
+  void PointerHasNoGestures(Pointer* pointer);
+
+  // Returns the Gesture for the specified arguments, creating if necessary.
+  Gesture* GetGesture(const ServerView* view, uint32_t gesture_id);
+
+  // Called from Pointer when a gesture is associated with a pointer.
+  void AttachGesture(Gesture* gesture,
+                     Pointer* pointer,
+                     const ServerView* view);
+
+  // Called from Pointer when a gesture is no longer associated with a
+  // pointer.
+  void DetachGesture(Gesture* gesture,
+                     Pointer* pointer,
+                     const ServerView* view);
+
+  // Cancels the supplied gesture (if it isn't canceled already). Notifies all
+  // pointers containing |gesture| that |gesture| has been canceled.
+  void CancelGesture(Gesture* gesture,
+                     Pointer* pointer,
+                     const ServerView* view);
+
+  // Chooses the supplied gesture. Notifies all pointers containing |gesture|
+  // that |gesture| has been chosen.
+  void ChooseGesture(Gesture* gesture,
+                     Pointer* pointer,
+                     const ServerView* view);
+
+  // Deletes |pointer| after processing the current event. We delay deletion
+  // until after the event as immediate deletion can cause problems for Pointer
+  // (this is because the same Pointer may be on multiple frames of the stack).
+  void ScheduleDelete(Pointer* pointer);
+
+  GestureManagerDelegate* delegate_;
+  const ServerView* root_view_;
+
+  // Map for looking up gestures. Gestures are identified by the pair of
+  // connection id and supplied gesture id.
+  std::map<GestureAndConnectionId, Gesture*> gesture_map_;
+
+  ScopedVector<Pointer> active_pointers_;
+
+  // See comment in ScheduleDelete() for details.
+  ScopedVector<Pointer> pointers_to_delete_;
+
+  // Accumulates changes as the result of SetGestures().
+  scoped_ptr<ChangeMap> current_change_;
+
+  DISALLOW_COPY_AND_ASSIGN(GestureManager);
+};
+
+}  // namespace view_manager
+
+#endif  // SERVICES_VIEW_MANAGER_GESTURE_MANAGER_H_