Touch emulator: create/destroy gesture provider on the fly.

content/browser/renderer_host/input/touch_emulator.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 CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EMULATOR_H_
 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EMULATOR_H_
 
 #include "content/browser/renderer_host/input/touch_emulator_client.h"
 #include "content/common/cursors/webcursor.h"
 #include "content/common/input/input_event_ack_state.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 #include "ui/events/gesture_detection/filtered_gesture_provider.h"
 #include "ui/gfx/size_f.h"
 
 namespace content {
 
 // Emulates touch input with mouse and keyboard.
 class CONTENT_EXPORT TouchEmulator : public ui::GestureProviderClient {
  public:
   explicit TouchEmulator(TouchEmulatorClient* client);
   ~TouchEmulator() override;
 
   void Enable();
   void Disable();
 
   // Note that TouchEmulator should always listen to touch events and their acks
   // (even in disabled state) to track native stream presence.
-  bool enabled() const { return enabled_; }
+  bool enabled() const { return !!gesture_provider_.get(); }

[jdduke (slow), 2014/12/30 16:37:19]

Does just "return gesture_provider_;" work?

[dgozman, 2015/01/14 14:14:27]

Done.

 
   // Returns |true| if the event was consumed. Consumed event should not
   // propagate any further.
   // TODO(dgozman): maybe pass latency info together with events.
   bool HandleMouseEvent(const blink::WebMouseEvent& event);
   bool HandleMouseWheelEvent(const blink::WebMouseWheelEvent& event);
   bool HandleKeyboardEvent(const blink::WebKeyboardEvent& event);
   bool HandleTouchEvent(const blink::WebTouchEvent& event);
 
   // Returns |true| if the event ack was consumed. Consumed ack should not
@@ skipping 25 matching lines @@
   void PinchBegin(const blink::WebGestureEvent& event);
   void PinchUpdate(const blink::WebGestureEvent& event);
   void PinchEnd(const blink::WebGestureEvent& event);
   void ScrollEnd(const blink::WebGestureEvent& event);
 
   // Offers the emulated event to |gesture_provider_|, conditionally forwarding
   // it to the client if appropriate.
   void HandleEmulatedTouchEvent(blink::WebTouchEvent event);
 
   TouchEmulatorClient* const client_;
-  ui::FilteredGestureProvider gesture_provider_;
 
+  // Emulator is enabled iff gesture provider is created.
   // Disabled emulator does only process touch acks left from previous
   // emulation. It does not intercept any events.
-  bool enabled_;
+  scoped_ptr<ui::FilteredGestureProvider> gesture_provider_;
 
   // While emulation is on, default cursor is touch. Pressing shift changes
   // cursor to the pinch one.
   WebCursor pointer_cursor_;
   WebCursor touch_cursor_;
   WebCursor pinch_cursor_;
   gfx::SizeF cursor_size_;
 
   // These are used to drop extra mouse move events coming too quickly, so
   // we don't handle too much touches in gesture provider.
@@ skipping 17 matching lines @@
   // The cumulative scale change from the start of pinch gesture.
   float pinch_scale_;
   bool pinch_gesture_active_;
 
   DISALLOW_COPY_AND_ASSIGN(TouchEmulator);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EMULATOR_H_