ui/events/blink/input_handler_proxy.h

// Copyright 2013 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_EVENTS_BLINK_INPUT_HANDLER_PROXY_H_
#define UI_EVENTS_BLINK_INPUT_HANDLER_PROXY_H_

#include <memory>

#include "base/containers/hash_tables.h"
#include "base/macros.h"
#include "cc/input/input_handler.h"
#include "third_party/WebKit/public/platform/WebGestureCurve.h"
#include "third_party/WebKit/public/platform/WebGestureCurveTarget.h"
#include "third_party/WebKit/public/platform/WebInputEvent.h"
#include "third_party/WebKit/public/web/WebActiveWheelFlingParameters.h"
#include "ui/events/blink/input_scroll_elasticity_controller.h"
#include "ui/events/blink/scoped_web_input_event.h"
#include "ui/events/blink/synchronous_input_handler_proxy.h"

namespace ui {

namespace test {
class InputHandlerProxyTest;
}

class InputHandlerProxyClient;
class InputScrollElasticityController;
class SynchronousInputHandler;
class SynchronousInputHandlerProxy;
struct DidOverscrollParams;

// This class is a proxy between the blink web input events for a WebWidget and
// the compositor's input handling logic. InputHandlerProxy instances live
// entirely on the compositor thread. Each InputHandler instance handles input
// events intended for a specific WebWidget.
class InputHandlerProxy
    : public cc::InputHandlerClient,
      public SynchronousInputHandlerProxy,
      public NON_EXPORTED_BASE(blink::WebGestureCurveTarget) {
 public:

  InputHandlerProxy(cc::InputHandler* input_handler,
                    InputHandlerProxyClient* client);
  ~InputHandlerProxy() override;

  InputScrollElasticityController* scroll_elasticity_controller() {
    return scroll_elasticity_controller_.get();
  }

  void set_smooth_scroll_enabled(bool value) { smooth_scroll_enabled_ = value; }

  enum EventDisposition {
    DID_HANDLE,
    DID_NOT_HANDLE,
    DID_HANDLE_NON_BLOCKING,
    DROP_EVENT
  };
  using EventDispositionCallback =
      base::Callback<void(EventDisposition,
                          ScopedWebInputEvent WebInputEvent,
                          const LatencyInfo&,
                          std::unique_ptr<ui::DidOverscrollParams>)>;
  void HandleInputEventWithLatencyInfo(
      ScopedWebInputEvent event,
      const LatencyInfo& latency_info,
      const EventDispositionCallback& callback);
  EventDisposition HandleInputEvent(const blink::WebInputEvent& event);

  // cc::InputHandlerClient implementation.
  void WillShutdown() override;
  void Animate(base::TimeTicks time) override;
  void MainThreadHasStoppedFlinging() override;
  void ReconcileElasticOverscrollAndRootScroll() override;
  void UpdateRootLayerStateForSynchronousInputHandler(
      const gfx::ScrollOffset& total_scroll_offset,
      const gfx::ScrollOffset& max_scroll_offset,
      const gfx::SizeF& scrollable_size,
      float page_scale_factor,
      float min_page_scale_factor,
      float max_page_scale_factor) override;

  // SynchronousInputHandlerProxy implementation.
  void SetOnlySynchronouslyAnimateRootFlings(
      SynchronousInputHandler* synchronous_input_handler) override;
  void SynchronouslyAnimate(base::TimeTicks time) override;
  void SynchronouslySetRootScrollOffset(
      const gfx::ScrollOffset& root_offset) override;
  void SynchronouslyZoomBy(float magnify_delta,
                           const gfx::Point& anchor) override;

  // blink::WebGestureCurveTarget implementation.
  bool scrollBy(const blink::WebFloatSize& offset,
                const blink::WebFloatSize& velocity) override;

  bool gesture_scroll_on_impl_thread_for_testing() const {
    return gesture_scroll_on_impl_thread_;
  }

 protected:
  void RecordMainThreadScrollingReasons(blink::WebGestureDevice device,
                                        uint32_t reasons);

 private:
  friend class test::InputHandlerProxyTest;

  // Helper functions for handling more complicated input events.
  EventDisposition HandleMouseWheel(
      const blink::WebMouseWheelEvent& event);
  EventDisposition ScrollByMouseWheel(
      const blink::WebMouseWheelEvent& event,
      cc::EventListenerProperties listener_properties);
  EventDisposition HandleGestureScrollBegin(
      const blink::WebGestureEvent& event);
  EventDisposition HandleGestureScrollUpdate(
      const blink::WebGestureEvent& event);
  EventDisposition HandleGestureScrollEnd(
      const blink::WebGestureEvent& event);
  EventDisposition HandleGestureFlingStart(
      const blink::WebGestureEvent& event);
  EventDisposition HandleTouchStart(const blink::WebTouchEvent& event);
  EventDisposition HandleTouchMove(const blink::WebTouchEvent& event);
  EventDisposition HandleTouchEnd(const blink::WebTouchEvent& event);

  // Returns true if the event should be suppressed due to to an active,
  // boost-enabled fling, in which case further processing should cease.
  bool FilterInputEventForFlingBoosting(const blink::WebInputEvent& event);

  // Schedule a time in the future after which a boost-enabled fling will
  // terminate without further momentum from the user (see |Animate()|).
  void ExtendBoostedFlingTimeout(const blink::WebGestureEvent& event);

  // Returns true if we scrolled by the increment.
  bool TouchpadFlingScroll(const blink::WebFloatSize& increment);

  // Returns true if we actually had an active fling to cancel, also notifying
  // the client that the fling has ended. Note that if a boosted fling is active
  // and suppressing an active scroll sequence, a synthetic GestureScrollBegin
  // will be injected to resume scrolling.
  bool CancelCurrentFling();

  // Returns true if we actually had an active fling to cancel.
  bool CancelCurrentFlingWithoutNotifyingClient();

  // Request a frame of animation from the InputHandler or
  // SynchronousInputHandler. They can provide that by calling Animate().
  void RequestAnimation();

  // Used to send overscroll messages to the browser.
  // |bundle_overscroll_params_with_ack| means overscroll message should be
  // bundled with triggering event response, and won't fire |DidOverscroll|.
  void HandleOverscroll(const gfx::Point& causal_event_viewport_point,
                        const cc::InputHandlerScrollResult& scroll_result,
                        bool bundle_overscroll_params_with_ack);

  // Whether to use a smooth scroll animation for this event.
  bool ShouldAnimate(bool has_precise_scroll_deltas) const;

  // Update the elastic overscroll controller with |gesture_event|.
  void HandleScrollElasticityOverscroll(
      const blink::WebGestureEvent& gesture_event,
      const cc::InputHandlerScrollResult& scroll_result);

  std::unique_ptr<blink::WebGestureCurve> fling_curve_;
  // Parameters for the active fling animation, stored in case we need to
  // transfer it out later.
  blink::WebActiveWheelFlingParameters fling_parameters_;

  InputHandlerProxyClient* client_;
  cc::InputHandler* input_handler_;

  // Time at which an active fling should expire due to a deferred cancellation
  // event. A call to |Animate()| after this time will end the fling.
  double deferred_fling_cancel_time_seconds_;

  // The last event that extended the lifetime of the boosted fling. If the
  // event was a scroll gesture, a GestureScrollBegin will be inserted if the
  // fling terminates (via |CancelCurrentFling()|).
  blink::WebGestureEvent last_fling_boost_event_;

  // When present, Animates are not requested to the InputHandler, but to this
  // SynchronousInputHandler instead. And all Animate() calls are expected to
  // happen via the SynchronouslyAnimate() call instead of coming directly from
  // the InputHandler.
  SynchronousInputHandler* synchronous_input_handler_;
  bool allow_root_animate_;

#ifndef NDEBUG
  bool expect_scroll_update_end_;
#endif
  bool gesture_scroll_on_impl_thread_;
  bool gesture_pinch_on_impl_thread_;
  // This is always false when there are no flings on the main thread, but
  // conservative in the sense that we might not be actually flinging when it is
  // true.
  bool fling_may_be_active_on_main_thread_;
  // The axes on which the current fling is allowed to scroll.  If a given fling
  // has overscrolled on a particular axis, further fling scrolls on that axis
  // will be disabled.
  bool disallow_horizontal_fling_scroll_;
  bool disallow_vertical_fling_scroll_;

  // Whether an active fling has seen an |Animate()| call. This is useful for
  // determining if the fling start time should be re-initialized.
  bool has_fling_animation_started_;

  // Non-zero only within the scope of |scrollBy|.
  gfx::Vector2dF current_fling_velocity_;

  // Used to animate rubber-band over-scroll effect on Mac.
  std::unique_ptr<InputScrollElasticityController>
      scroll_elasticity_controller_;

  bool smooth_scroll_enabled_;
  bool uma_latency_reporting_enabled_;

  // The merged result of the last touch start with previous touch starts.
  // This value will get returned for subsequent TouchMove events to allow
  // passive events not to block scrolling.
  int32_t touch_start_result_;

  base::TimeTicks last_fling_animate_time_;

  // Used to record overscroll notifications while an event is being
  // dispatched.  If the event causes overscroll, the overscroll metadata can be
  // bundled in the event ack, saving an IPC.  Note that we must continue
  // supporting overscroll IPC notifications due to fling animation updates.
  std::unique_ptr<DidOverscrollParams> current_overscroll_params_;

  DISALLOW_COPY_AND_ASSIGN(InputHandlerProxy);
};

}  // namespace ui

#endif  // UI_EVENTS_BLINK_INPUT_HANDLER_PROXY_H_