Swipe Gestures for Accessibility

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/timer/timer.h"
 #include "base/values.h"
 #include "ui/chromeos/ui_chromeos_export.h"
 #include "ui/events/event.h"
 #include "ui/events/event_rewriter.h"
 #include "ui/events/gesture_detection/gesture_detector.h"
+#include "ui/events/gestures/gesture_provider_aura.h"
 #include "ui/gfx/geometry/point.h"
 
 namespace aura {
 class Window;
 }
 
 namespace ui {
 
 class Event;
 class EventHandler;
+class GestureEvent;
+class GestureProviderAura;
 class TouchEvent;
 
 // TouchExplorationController is used in tandem with "Spoken Feedback" to
-// make the touch UI accessible.
+// make the touch UI accessible. Gestures are mapped to accessible key

[dmazzoni, 2014/06/25 05:06:02]

This comment has a one-sentence intro, then a one-paragraph version, then a
detailed long version.

You should probably leave this one-sentence intro alone, but add one sentence
about gestures to the short version, and probably several sentences about
gestures to the long version. The fact that it sends key events is a temporarily
implementation detail, probably good for the long version only. In the short
version, focus on the user experience.

[lisayin, 2014/06/25 22:51:05]

Done.

+// shortcuts.
 //
 // ** Short version **
 //
 // At a high-level, single-finger events are used for accessibility -
 // exploring the screen gets turned into mouse moves (which can then be
 // spoken by an accessibility service running), a single tap while the user
 // is in touch exploration or a double-tap simulates a click, and gestures
 // can be used to send high-level accessibility commands.
 // When two or more fingers are pressed initially, from then on the events
 // are passed through, but with the initial finger removed - so if you swipe
@@ skipping 41 matching lines @@
 // continue to pass through events, allowing the user to start a scroll
 // with two fingers but finish it with one. Sometimes this requires rewriting
 // the touch ids.
 //
 // Once either touch exploration or passthrough mode has been activated,
 // it remains in that mode until all fingers have been released.
 //
 // The caller is expected to retain ownership of instances of this class and
 // destroy them before |root_window| is destroyed.
 class UI_CHROMEOS_EXPORT TouchExplorationController :
-    public ui::EventRewriter {
+ public ui::EventRewriter, public ui::GestureProviderAuraClient {
  public:
   explicit TouchExplorationController(aura::Window* root_window);
   virtual ~TouchExplorationController();
 
   void CallTapTimerNowForTesting();
   void SetEventHandlerForTesting(ui::EventHandler* event_handler_for_testing);
   bool IsInNoFingersDownStateForTesting() const;
+  bool IsInGestureInProgressStateForTesting() const;
 
  private:
   // Overridden from ui::EventRewriter
   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;
 
   // Event handlers based on the current state - see State, below.
   ui::EventRewriteStatus InNoFingersDown(
       const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event);
   ui::EventRewriteStatus InSingleTapPressed(
       const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event);
   ui::EventRewriteStatus InSingleTapOrTouchExploreReleased(
       const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event);
   ui::EventRewriteStatus InDoubleTapPressed(
       const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event);
   ui::EventRewriteStatus InTouchExploration(
       const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event);
+  ui::EventRewriteStatus InGestureInProgress(
+      const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event);
   ui::EventRewriteStatus InPassthroughMinusOne(
       const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event);
   ui::EventRewriteStatus InTouchExploreSecondPress(
       const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event);
+
   // This timer is started every time we get the first press event, and
   // it fires after the double-click timeout elapses (300 ms by default).
   // If the user taps and releases within 300 ms and doesn't press again,
   // we treat that as a single mouse move (touch exploration) event.
   void OnTapTimerFired();
 
   // Dispatch a new event outside of the event rewriting flow.
   void DispatchEvent(ui::Event* event);
 
+  // Overridden from GestureProviderAuraClient.
+  //
+  // The gesture provider keeps track of all the touch events after
+  // the user moves fast enough to trigger a gesture. After the user
+  // completes their gesture, this method will decide what keyboard
+  // input their gesture corresponded to.
+  void OnGestureEvent(ui::GestureEvent* gesture) OVERRIDE;
+
+  void OnSwipeEvent(ui::GestureEvent* swipe_gesture);
+
+  // Dispatches the keyboard short cut Shift+Search+<arrow key>
+  // outside the event rewritting flow.
+  void DispatchShiftSearchKeyEvent(const ui::KeyboardCode direction);
+
   scoped_ptr<ui::Event> CreateMouseMoveEvent(const gfx::PointF& location,
                                              int flags);
 
   void EnterTouchToMouseMode();
 
   // Set the state to NO_FINGERS_DOWN and reset any other fields to their
   // default value.
   void ResetToNoFingersDown();
 
   enum State {
@@ skipping 22 matching lines @@
     DOUBLE_TAP_PRESSED,
 
     // We're in touch exploration mode. Anything other than the first finger
     // is ignored, and movements of the first finger are rewritten as mouse
     // move events. This mode is entered if a single finger is pressed and
     // after the grace period the user hasn't added a second finger or
     // moved the finger outside of the slop region. We'll stay in this
     // mode until all fingers are lifted.
     TOUCH_EXPLORATION,
 
+    // If the user moves their finger faster than the threshold velocity after a
+    // single tap, the touch events that follow will be translated into gesture
+    // events. If the user successfully completes a gesture within the grace
+    // period, the gesture will be collected and sent to the GestureClient.

[dmazzoni, 2014/06/25 05:06:02]

"sent to the GestureClient" is an implementation detail. You should say that the
gesture will be interpreted and used to control the UI via discrete actions -
currently by synthesizing key events corresponding to each gesture.

[lisayin, 2014/06/25 22:51:05]

Done.

+    // Otherwise, the collected gestures are discarded and the state changes to
+    // touch_exploration.
+    GESTURE_IN_PROGRESS,
+
     // The user placed two or more fingers down within the grace period.
     // We're now in passthrough mode until all fingers are lifted. Initially
     // the first finger is ignored and other fingers are passed through
     // as-is. If a finger other than the initial one is the first to be
     // released, we rewrite the first finger with the touch id of the finger
     // that was released, from now on. The motivation for this is that if
     // the user starts a scroll with 2 fingers, they can release either one
     // and continue the scrolling.
     PASSTHROUGH_MINUS_ONE,
 
@@ skipping 42 matching lines @@
   base::OneShotTimer<TouchExplorationController> tap_timer_;
 
   // For testing only, an event handler to use for generated events
   // outside of the normal event rewriting flow.
   ui::EventHandler* event_handler_for_testing_;
 
   // A default gesture detector config, so we can share the same
   // timeout and pixel slop constants.
   ui::GestureDetector::Config gesture_detector_config_;
 
+  // Gesture Handler to interpret the touch events.
+  ui::GestureProviderAura gesture_provider_;
+
   // The previous state entered.
   State prev_state_;
 
   // A copy of the previous event passed.
   scoped_ptr<ui::TouchEvent> prev_event_;
 
   DISALLOW_COPY_AND_ASSIGN(TouchExplorationController);
 };
 
 }  // namespace ui
 
 #endif  // UI_CHROMEOS_TOUCH_EXPLORATION_CONTROLLER_H_