cc/input/input_handler.h

// Copyright 2011 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 CC_INPUT_INPUT_HANDLER_H_
#define CC_INPUT_INPUT_HANDLER_H_

#include <memory>

#include "base/time/time.h"
#include "cc/cc_export.h"
#include "cc/input/event_listener_properties.h"
#include "cc/input/main_thread_scrolling_reason.h"
#include "cc/input/overscroll_behavior.h"
#include "cc/input/scroll_state.h"
#include "cc/input/scrollbar.h"
#include "cc/input/touch_action.h"
#include "cc/metrics/events_metrics_manager.h"
#include "cc/paint/element_id.h"
#include "cc/trees/swap_promise_monitor.h"
#include "components/viz/common/frame_sinks/begin_frame_args.h"
#include "ui/events/types/scroll_input_type.h"
#include "ui/events/types/scroll_types.h"

namespace gfx {
class Point;
class ScrollOffset;
class SizeF;
class Vector2dF;
}  // namespace gfx

namespace ui {
class LatencyInfo;
}  // namespace ui

namespace cc {

class EventMetrics;
class ScrollElasticityHelper;

enum PointerResultType { kUnhandled = 0, kScrollbarScroll };

// These enum values are reported in UMA. So these values should never be
// removed or changed.
enum class ScrollBeginThreadState {
  kScrollingOnCompositor = 0,
  kScrollingOnCompositorBlockedOnMain = 1,
  kScrollingOnMain = 2,
  kMaxValue = kScrollingOnMain,
};

struct CC_EXPORT InputHandlerPointerResult {
  InputHandlerPointerResult() = default;
  // Tells what type of processing occurred in the input handler as a result of
  // the pointer event.
  PointerResultType type = kUnhandled;

  // Tells what scroll_units should be used.
  ui::ScrollGranularity scroll_units =
      ui::ScrollGranularity::kScrollByPrecisePixel;

  // If the input handler processed the event as a scrollbar scroll, it will
  // return a gfx::ScrollOffset that produces the necessary scroll. However,
  // it is still the client's responsibility to generate the gesture scrolls
  // instead of the input handler performing it as a part of handling the
  // pointer event (due to the latency attribution that happens at the
  // InputHandlerProxy level).
  gfx::ScrollOffset scroll_offset;

  // Used to determine which scroll_node needs to be scrolled. The primary
  // purpose of this is to avoid hit testing for gestures that already know
  // which scroller to target.
  ElementId target_scroller;
};

struct CC_EXPORT InputHandlerScrollResult {
  InputHandlerScrollResult() = default;
  // Did any layer scroll as a result this ScrollUpdate call?
  bool did_scroll = false;
  // Was any of the scroll delta argument to this ScrollUpdate call not used?
  bool did_overscroll_root = false;
  // The total overscroll that has been accumulated by all ScrollUpdate calls
  // that have had overscroll since the last ScrollBegin call. This resets upon
  // a ScrollUpdate with no overscroll.
  gfx::Vector2dF accumulated_root_overscroll;
  // The amount of the scroll delta argument to this ScrollUpdate call that was
  // not used for scrolling.
  gfx::Vector2dF unused_scroll_delta;
  // How the browser should handle the overscroll navigation based on the css
  // property scroll-boundary-behavior.
  OverscrollBehavior overscroll_behavior;
  // The current offset of the currently scrolling node. It is in DIP or
  // physical pixels depending on the use-zoom-for-dsf flag. If the currently
  // scrolling node is the viewport, this would be the sum of the scroll offsets
  // of the inner and outer node, representing the visual scroll offset.
  gfx::Vector2dF current_visual_offset;
};

class CC_EXPORT InputHandlerClient {
 public:
  InputHandlerClient(const InputHandlerClient&) = delete;
  virtual ~InputHandlerClient() = default;

  InputHandlerClient& operator=(const InputHandlerClient&) = delete;

  virtual void WillShutdown() = 0;
  virtual void Animate(base::TimeTicks time) = 0;
  virtual void ReconcileElasticOverscrollAndRootScroll() = 0;
  virtual 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) = 0;
  virtual void DeliverInputForBeginFrame(const viz::BeginFrameArgs& args) = 0;
  virtual void DeliverInputForHighLatencyMode() = 0;

 protected:
  InputHandlerClient() = default;
};

// The InputHandler is a way for the embedders to interact with the impl thread
// side of the compositor implementation. There is one InputHandler per
// LayerTreeHost. To use the input handler, implement the InputHanderClient
// interface and bind it to the handler on the compositor thread.
class CC_EXPORT InputHandler {
 public:
  // Note these are used in a histogram. Do not reorder or delete existing
  // entries.
  enum ScrollThread {
    SCROLL_ON_MAIN_THREAD = 0,
    SCROLL_ON_IMPL_THREAD,
    SCROLL_IGNORED,
    SCROLL_UNKNOWN,
    LAST_SCROLL_STATUS = SCROLL_UNKNOWN
  };

  InputHandler(const InputHandler&) = delete;
  InputHandler& operator=(const InputHandler&) = delete;

  struct ScrollStatus {
    ScrollStatus() = default;
    ScrollStatus(ScrollThread thread, uint32_t main_thread_scrolling_reasons)
        : thread(thread),
          main_thread_scrolling_reasons(main_thread_scrolling_reasons) {}
    ScrollStatus(ScrollThread thread,
                 uint32_t main_thread_scrolling_reasons,
                 bool needs_main_thread_hit_test)
        : thread(thread),
          main_thread_scrolling_reasons(main_thread_scrolling_reasons),
          needs_main_thread_hit_test(needs_main_thread_hit_test) {}
    ScrollThread thread = SCROLL_ON_IMPL_THREAD;
    uint32_t main_thread_scrolling_reasons =
        MainThreadScrollingReason::kNotScrollingOnMain;
    bool bubble = false;

    // Used only in scroll unification. Tells the caller that the input handler
    // detected a case where it cannot reliably target a scroll node and needs
    // the main thread to perform a hit test.
    bool needs_main_thread_hit_test = false;
  };

  enum class TouchStartOrMoveEventListenerType {
    NO_HANDLER,
    HANDLER,
    HANDLER_ON_SCROLLING_LAYER
  };

  // Binds a client to this handler to receive notifications. Only one client
  // can be bound to an InputHandler. The client must live at least until the
  // handler calls WillShutdown() on the client.
  virtual void BindToClient(InputHandlerClient* client) = 0;

  // Selects a ScrollNode to be "latched" for scrolling using the
  // |scroll_state| start position. The selected node remains latched until the
  // gesture is ended by a call to ScrollEnd.  Returns SCROLL_STARTED if a node
  // at the coordinates can be scrolled and was latched, SCROLL_ON_MAIN_THREAD
  // if the scroll event should instead be delegated to the main thread, or
  // SCROLL_IGNORED if there is nothing to be scrolled at the given
  // coordinates.
  virtual ScrollStatus ScrollBegin(ScrollState* scroll_state,
                                   ui::ScrollInputType type) = 0;

  // Similar to ScrollBegin, except the hit test is skipped and scroll always
  // targets at the root layer.
  virtual ScrollStatus RootScrollBegin(ScrollState* scroll_state,
                                       ui::ScrollInputType type) = 0;

  // Scroll the layer selected by |ScrollBegin| by given |scroll_state| delta.
  // Internally, the delta is transformed to local layer's coordinate space for
  // scrolls gestures that are direct manipulation (e.g. touch). If the
  // viewport is latched, and it can no longer scroll, the root overscroll
  // accumulated within this ScrollBegin() scope is reported in the return
  // value's |accumulated_overscroll| field. Should only be called if
  // ScrollBegin() returned SCROLL_STARTED.
  //
  // Is a no-op if no scroller was latched to in ScrollBegin and returns an
  // empty-initialized InputHandlerScrollResult.
  //
  // |delayed_by| is the delay from the event that caused the scroll. This is
  // taken into account when determining the duration of the animation if one
  // is created.
  virtual InputHandlerScrollResult ScrollUpdate(ScrollState* scroll_state,
                                                base::TimeDelta delayed_by) = 0;

  // Stop scrolling the selected layer. Must be called only if ScrollBegin()
  // returned SCROLL_STARTED. No-op if ScrollBegin wasn't called or didn't
  // result in a successful scroll latch. Snap to a snap position if
  // |should_snap| is true.
  virtual void ScrollEnd(bool should_snap) = 0;

  // Called to notify every time scroll-begin/end is attempted by an input
  // event.
  virtual void RecordScrollBegin(ui::ScrollInputType input_type,
                                 ScrollBeginThreadState scroll_start_state) = 0;
  virtual void RecordScrollEnd(ui::ScrollInputType input_type) = 0;

  virtual InputHandlerPointerResult MouseMoveAt(
      const gfx::Point& mouse_position) = 0;
  // TODO(arakeri): Pass in the modifier instead of a bool once the refactor
  // (crbug.com/1022097) is done. For details, see crbug.com/1016955.
  virtual InputHandlerPointerResult MouseDown(const gfx::PointF& mouse_position,
                                              bool shift_modifier) = 0;
  virtual InputHandlerPointerResult MouseUp(
      const gfx::PointF& mouse_position) = 0;
  virtual void MouseLeave() = 0;

  // Returns frame_element_id from the layer hit by the given point.
  // If the hit test failed, an invalid element ID is returned.
  virtual ElementId FindFrameElementIdAtPoint(
      const gfx::PointF& mouse_position) = 0;

  // Requests a callback to UpdateRootLayerStateForSynchronousInputHandler()
  // giving the current root scroll and page scale information.
  virtual void RequestUpdateForSynchronousInputHandler() = 0;

  // Called when the root scroll offset has been changed in the synchronous
  // input handler by the application (outside of input event handling). Offset
  // is expected in "content/page coordinates".
  virtual void SetSynchronousInputHandlerRootScrollOffset(
      const gfx::ScrollOffset& root_content_offset) = 0;

  virtual void PinchGestureBegin() = 0;
  virtual void PinchGestureUpdate(float magnify_delta,
                                  const gfx::Point& anchor) = 0;
  virtual void PinchGestureEnd(const gfx::Point& anchor, bool snap_to_min) = 0;

  // Request another callback to InputHandlerClient::Animate().
  virtual void SetNeedsAnimateInput() = 0;

  // Returns true if there is an active scroll on the viewport.
  virtual bool IsCurrentlyScrollingViewport() const = 0;

  virtual EventListenerProperties GetEventListenerProperties(
      EventListenerClass event_class) const = 0;

  // Returns true if |viewport_point| hits a wheel event handler region that
  // could block scrolling.
  virtual bool HasBlockingWheelEventHandlerAt(
      const gfx::Point& viewport_point) const = 0;

  // It returns the type of a touch start or move event listener at
  // |viewport_point|. Whether the page should be given the opportunity to
  // suppress scrolling by consuming touch events that started at
  // |viewport_point|, and whether |viewport_point| is on the currently
  // scrolling layer.
  // |out_touch_action| is assigned the allowed touch action for the
  // |viewport_point|. In the case there are no touch handlers or touch action
  // regions, |out_touch_action| is assigned TouchAction::kAuto since the
  // default touch action is auto.
  virtual TouchStartOrMoveEventListenerType
  EventListenerTypeForTouchStartOrMoveAt(const gfx::Point& viewport_point,
                                         TouchAction* out_touch_action) = 0;

  // Calling CreateLatencyInfoSwapPromiseMonitor() to get a scoped
  // LatencyInfoSwapPromiseMonitor. During the life time of the
  // LatencyInfoSwapPromiseMonitor, if SetNeedsRedraw() or SetNeedsRedrawRect()
  // is called on LayerTreeHostImpl, the original latency info will be turned
  // into a LatencyInfoSwapPromise.
  virtual std::unique_ptr<SwapPromiseMonitor>
  CreateLatencyInfoSwapPromiseMonitor(ui::LatencyInfo* latency) = 0;

  // During the lifetime of the returned EventsMetricsManager::ScopedMonitor, if
  // SetNeedsOneBeginImplFrame() or SetNeedsRedraw() are called on
  // LayerTreeHostImpl or a scroll animation is updated, |event_metrics| will be
  // saved for reporting event latency metrics. It is allowed to pass nullptr as
  // |event_metrics| in which case the return value would also be nullptr.
  virtual std::unique_ptr<EventsMetricsManager::ScopedMonitor>
  GetScopedEventMetricsMonitor(std::unique_ptr<EventMetrics> event_metrics) = 0;

  virtual ScrollElasticityHelper* CreateScrollElasticityHelper() = 0;

  // Called by the single-threaded UI Compositor to get or set the scroll offset
  // on the impl side. Returns false if |element_id| isn't in the active tree.
  virtual bool GetScrollOffsetForLayer(ElementId element_id,
                                       gfx::ScrollOffset* offset) = 0;
  virtual bool ScrollLayerTo(ElementId element_id,
                             const gfx::ScrollOffset& offset) = 0;

  virtual bool ScrollingShouldSwitchtoMainThread() = 0;

  // Sets the initial and target offset for scroll snapping for the currently
  // scrolling node and the given natural displacement. Also sets the target
  // element of the snap's scrolling animation.
  // |natural_displacement_in_viewport| is the estimated total scrolling for
  // the active scroll sequence.
  // Returns false if their is no position to snap to.
  virtual bool GetSnapFlingInfoAndSetAnimatingSnapTarget(
      const gfx::Vector2dF& natural_displacement_in_viewport,
      gfx::Vector2dF* initial_offset,
      gfx::Vector2dF* target_offset) = 0;

  // |did_finish| is true if the animation reached its target position (i.e.
  // it wasn't aborted).
  virtual void ScrollEndForSnapFling(bool did_finish) = 0;

  // Notifies when any input event is received, irrespective of whether it is
  // being handled by the InputHandler or not.
  virtual void NotifyInputEvent() = 0;

 protected:
  InputHandler() = default;
  virtual ~InputHandler() = default;
};

}  // namespace cc

#endif  // CC_INPUT_INPUT_HANDLER_H_