Implementation of the Touch Exploration Mode - Part I (ui)

ui/chromeos/touch_exploration_controller.h

+// Copyright 2014 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 UI_CHROMEOS_TOUCH_EXPLORATION_CONTROLLER_H_
+#define UI_CHROMEOS_TOUCH_EXPLORATION_CONTROLLER_H_
+
+#include "base/values.h"
+#include "ui/chromeos/ui_chromeos_export.h"
+#include "ui/events/event_rewriter.h"
+#include "ui/gfx/geometry/point.h"
+
+namespace aura {
+class Window;
+}
+
+namespace ui {
+
+class Event;
+
+// TouchExplorationController is used in tandem with "Spoken Feedback" to
+// make the touch UI accessible. TouchExplorationController rewrites the
+// incoming touch events as follows:
+// - When one finger is touching the screen, touch events are converted to mouse
+//   moves. This is the "Touch Exploration Mode". (The idea is that mouse moves
+//   will be subsequently used by another component to move focus between UI
+//   elements, and the elements will be read out to the user.)
+// - When more than one finger is touching the screen, touches from the
+//   first (i.e. "oldest") finger are ignored, and the other touches go through
+//   as is.
+class UI_CHROMEOS_EXPORT TouchExplorationController :

[sadrul, 2014/04/30 18:51:15]

What is the expected ownership of this controller (i.e. is the caller expected
to retain ownership)? Does this controller requires the owner to destroy it
before the |root_window| is destroyed?

[mfomitchev, 2014/04/30 21:33:53]

Comment added to clarify.

+    public ui::EventRewriter {
+ public:
+  explicit TouchExplorationController(aura::Window* root_window);
+  virtual ~TouchExplorationController();
+
+ private:
+  // Overridden from ui::EventRewriter

[sadrul, 2014/04/30 18:51:15]

Overrides usually come at the end of the non-override functions in the same
block.

[mfomitchev, 2014/04/30 21:33:53]

Done.

+  virtual ui::EventRewriteStatus RewriteEvent(
+      const ui::Event& event, scoped_ptr<ui::Event>* rewritten_event) OVERRIDE;
+  virtual ui::EventRewriteStatus NextDispatchEvent(
+      const ui::Event& last_event, scoped_ptr<ui::Event>* new_event) OVERRIDE;
+
+  ui::Event* CreateMouseMoveEvent(gfx::Point location, int flags);

[sadrul, 2014/04/30 18:51:15]

const &Point(F)

This require the owner to take ownership of the created event, right? In that
case, the return type should be a scoped_ptr<Event>

[mfomitchev, 2014/04/30 21:33:53]

Done.

+
+  void EnterTouchToMouseMode();
+
+  // A set of touch ids for fingers currently touching the screen.
+  std::vector<int> touch_ids_;
+
+  // Map of touch ids to their last known location.
+  std::map<int, gfx::Point> touch_locations_;

[sadrul, 2014/04/30 18:51:15]

Can you use PointF here?

[mfomitchev, 2014/04/30 21:33:53]

Done.

+
+  // Initialized from RewriteEvent() and dispatched in NextDispatchEvent().
+  scoped_ptr<ui::Event> next_dispatch_event_;
+
+  aura::Window* root_window_;
+
+  DISALLOW_COPY_AND_ASSIGN(TouchExplorationController);
+};
+
+}  // namespace ui
+
+#endif  // UI_CHROMEOS_TOUCH_EXPLORATION_CONTROLLER_H_