// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

/*
 * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
 * Copyright (C) 2006-2009 Google Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "components/input/web_input_event_builders_mac.h"

#import <ApplicationServices/ApplicationServices.h>
#import <Cocoa/Cocoa.h>
#include <stdint.h>

#include "base/apple/owned_objc.h"
#include "base/mac/mac_util.h"
#include "base/metrics/histogram_macros.h"
#include "base/notimplemented.h"
#include "base/strings/string_util.h"
#include "base/time/time.h"
#include "third_party/blink/public/common/input/web_input_event.h"
#include "ui/events/base_event_utils.h"
#include "ui/events/blink/blink_event_util.h"
#import "ui/events/cocoa/cocoa_event_utils.h"
#include "ui/events/event_utils.h"
#include "ui/events/keycodes/keyboard_code_conversion.h"
#include "ui/events/keycodes/keyboard_code_conversion_mac.h"

namespace input {

namespace {

inline NSString* FilterSpecialCharacter(NSString* str) {
  if ([str length] != 1)
    return str;
  unichar c = [str characterAtIndex:0];
  NSString* result = str;
  if (c == 0x7F) {
    // Backspace should be 8
    result = @"\x8";
  } else if (c >= 0xF700 && c <= 0xF7FF) {
    // Mac private use characters should be @"\0" (@"" won't work)
    // NSDeleteFunctionKey will also go into here
    // Use the range 0xF700~0xF7FF to match
    // http://www.opensource.apple.com/source/WebCore/WebCore-7601.1.55/platform/mac/KeyEventMac.mm
    result = @"\0";
  }
  return result;
}

inline NSString* TextFromEvent(NSEvent* event) {
  if ([event type] == NSEventTypeFlagsChanged)
    return @"";
  return FilterSpecialCharacter([event characters]);
}

inline NSString* UnmodifiedTextFromEvent(NSEvent* event) {
  if ([event type] == NSEventTypeFlagsChanged)
    return @"";
  return FilterSpecialCharacter([event charactersIgnoringModifiers]);
}

// End Apple code.
// ----------------------------------------------------------------------------

int ModifiersFromEvent(NSEvent* event) {
  int modifiers = 0;
  NSEventModifierFlags modifier_flags = [event modifierFlags];

  if (modifier_flags & NSEventModifierFlagControl)
    modifiers |= blink::WebInputEvent::kControlKey;
  if (modifier_flags & NSEventModifierFlagShift)
    modifiers |= blink::WebInputEvent::kShiftKey;
  if (modifier_flags & NSEventModifierFlagOption)
    modifiers |= blink::WebInputEvent::kAltKey;
  if (modifier_flags & NSEventModifierFlagCommand)
    modifiers |= blink::WebInputEvent::kMetaKey;
  if (modifier_flags & NSEventModifierFlagCapsLock)
    modifiers |= blink::WebInputEvent::kCapsLockOn;

  // The return value of 1 << 0 corresponds to the left mouse button,
  // 1 << 1 corresponds to the right mouse button,
  // 1 << n, n >= 2 correspond to other mouse buttons.
  NSUInteger pressed_buttons = [NSEvent pressedMouseButtons];

  if (pressed_buttons & (1 << 0))
    modifiers |= blink::WebInputEvent::kLeftButtonDown;
  if (pressed_buttons & (1 << 1))
    modifiers |= blink::WebInputEvent::kRightButtonDown;
  if (pressed_buttons & (1 << 2))
    modifiers |= blink::WebInputEvent::kMiddleButtonDown;
  if (pressed_buttons & (1 << 3))
    modifiers |= blink::WebInputEvent::kBackButtonDown;
  if (pressed_buttons & (1 << 4))
    modifiers |= blink::WebInputEvent::kForwardButtonDown;

  return modifiers;
}

struct EventLocationInfo {
  gfx::PointF position_in_screen;
  gfx::PointF position_in_widget;
  float movement_x;
  float movement_y;
  bool is_raw_movement_event = false;
};

EventLocationInfo GetWebEventLocationForEventInView(
    NSEvent* event,
    NSView* view,
    bool unaccelerated_movement = false) {
  EventLocationInfo result;

  NSPoint screen_local =
      [view.window convertPointToScreen:event.locationInWindow];
  NSScreen* primary_screen =
      (NSScreen.screens.count > 0) ? NSScreen.screens.firstObject : nil;

  // Flip y conditionally.
  result.position_in_screen.SetPoint(
      screen_local.x, primary_screen
                          ? primary_screen.frame.size.height - screen_local.y
                          : screen_local.y);

  NSPoint content_local = [view convertPoint:event.locationInWindow
                                    fromView:nil];
  // Flip y.
  result.position_in_widget.SetPoint(content_local.x,
                                     view.frame.size.height - content_local.y);

  CGEventRef cg_event = nullptr;
  if (unaccelerated_movement && (cg_event = event.CGEvent) != nullptr) {
    result.movement_x = CGEventGetIntegerValueField(
        cg_event, kCGEventUnacceleratedPointerMovementX);
    result.movement_y = CGEventGetIntegerValueField(
        cg_event, kCGEventUnacceleratedPointerMovementY);
    result.is_raw_movement_event = true;
  } else {
    result.movement_x = event.deltaX;
    result.movement_y = event.deltaY;
  }

  return result;
}

bool IsSystemKeyEvent(const blink::WebKeyboardEvent& event) {
  // Windows and Linux set |isSystemKey| if alt is down. Blink looks at this
  // flag to decide if it should handle a key or not. E.g. alt-left/right
  // shouldn't be used by Blink to scroll the current page, because we want
  // to get that key back for it to do history navigation. Hence, the
  // corresponding situation on OS X is to set this for cmd key presses.

  // cmd-b and and cmd-i are system wide key bindings that OS X doesn't
  // handle for us, so the editor handles them.
  int modifiers = event.GetModifiers() & blink::WebInputEvent::kInputModifiers;
  if (modifiers == blink::WebInputEvent::kMetaKey &&
      event.windows_key_code == ui::VKEY_B)
    return false;
  if (modifiers == blink::WebInputEvent::kMetaKey &&
      event.windows_key_code == ui::VKEY_I)
    return false;

  return event.GetModifiers() & blink::WebInputEvent::kMetaKey;
}

blink::WebMouseWheelEvent::Phase PhaseForNSEventPhase(
    NSEventPhase event_phase) {
  uint32_t phase = blink::WebMouseWheelEvent::kPhaseNone;
  if (event_phase & NSEventPhaseBegan)
    phase |= blink::WebMouseWheelEvent::kPhaseBegan;
  if (event_phase & NSEventPhaseStationary)
    phase |= blink::WebMouseWheelEvent::kPhaseStationary;
  if (event_phase & NSEventPhaseChanged)
    phase |= blink::WebMouseWheelEvent::kPhaseChanged;
  if (event_phase & NSEventPhaseEnded)
    phase |= blink::WebMouseWheelEvent::kPhaseEnded;
  if (event_phase & NSEventPhaseCancelled)
    phase |= blink::WebMouseWheelEvent::kPhaseCancelled;
  if (event_phase & NSEventPhaseMayBegin)
    phase |= blink::WebMouseWheelEvent::kPhaseMayBegin;
  return static_cast<blink::WebMouseWheelEvent::Phase>(phase);
}

blink::WebMouseWheelEvent::Phase PhaseForEvent(NSEvent* event) {
  NSEventPhase event_phase = [event phase];
  return PhaseForNSEventPhase(event_phase);
}

blink::WebMouseWheelEvent::Phase MomentumPhaseForEvent(NSEvent* event) {
  NSEventPhase event_momentum_phase = [event momentumPhase];
  return PhaseForNSEventPhase(event_momentum_phase);
}

ui::DomKey DomKeyFromEvent(NSEvent* event) {
  ui::DomKey key = ui::DomKeyFromNSEvent(event);
  if (key != ui::DomKey::NONE)
    return key;
  return ui::DomKey::UNIDENTIFIED;
}

blink::WebMouseEvent::Button ButtonFromPressedMouseButtons() {
  NSUInteger pressed_buttons = [NSEvent pressedMouseButtons];

  if (pressed_buttons & (1 << 0))
    return blink::WebMouseEvent::Button::kLeft;
  if (pressed_buttons & (1 << 1))
    return blink::WebMouseEvent::Button::kRight;
  if (pressed_buttons & (1 << 2))
    return blink::WebMouseEvent::Button::kMiddle;
  if (pressed_buttons & (1 << 3))
    return blink::WebMouseEvent::Button::kBack;
  if (pressed_buttons & (1 << 4))
    return blink::WebMouseEvent::Button::kForward;
  return blink::WebMouseEvent::Button::kNoButton;
}
blink::WebMouseEvent::Button ButtonFromButtonNumber(NSEvent* event) {
  NSUInteger button_number = [event buttonNumber];

  if (button_number == 1)
    return blink::WebMouseEvent::Button::kRight;
  if (button_number == 2)
    return blink::WebMouseEvent::Button::kMiddle;
  if (button_number == 3)
    return blink::WebMouseEvent::Button::kBack;
  if (button_number == 4)
    return blink::WebMouseEvent::Button::kForward;
  return blink::WebMouseEvent::Button::kNoButton;
}

blink::WebInputEvent::Type GesturePinchInputEventTypeFromPhase(
    NSEventPhase phase) {
  switch (phase) {
    case NSEventPhaseBegan:
      return blink::WebInputEvent::Type::kGesturePinchBegin;
    case NSEventPhaseStationary:
    case NSEventPhaseChanged:
      return blink::WebInputEvent::Type::kGesturePinchUpdate;
    case NSEventPhaseEnded:
    case NSEventPhaseCancelled:
      return blink::WebInputEvent::Type::kGesturePinchEnd;
    default:
      return blink::WebInputEvent::Type::kUndefined;
  }
}

}  // namespace

blink::WebKeyboardEvent WebKeyboardEventBuilder::Build(NSEvent* event) {
  ui::ComputeEventLatencyOS(base::apple::OwnedNSEvent(event));

  ui::DomCode dom_code = ui::DomCodeFromNSEvent(event);
  int modifiers =
      ModifiersFromEvent(event) | ui::DomCodeToWebInputEventModifiers(dom_code);

  if ((event.type != NSEventTypeFlagsChanged) && event.ARepeat) {
    modifiers |= blink::WebInputEvent::kIsAutoRepeat;
  }

  blink::WebKeyboardEvent result(
      ui::IsKeyUpEvent(event) ? blink::WebInputEvent::Type::kKeyUp
                              : blink::WebInputEvent::Type::kRawKeyDown,
      modifiers, ui::EventTimeStampFromSeconds(event.timestamp));

  // Some keys have the same meaning but different locations on the keyboard:
  // the left and right shift keys; the numeric keypad keys and their
  // counterparts in the number row; etc. A "located" keyboard code lets us
  // distinguish between keys with the same meaning. For example, VKEY_LSHIFT
  // and VKEY_RSHIFT are located keyboard codes and VKEY_SHIFT is their non-
  // located representation.
  //
  // When determining the windows_key_code, we want to use the non-located code
  // for some keys (Shift, etc.). We call ui::LocatedToNonLocatedKeyboardCode()
  // to perform this conversion. However, ui::LocatedToNonLocatedKeyboardCode()
  // converts more keys than we'd like. In particular, it returns the
  // non-located representations of number pad key codes. If we use these as
  // windows key codes, key presses in the number row and the number pad will be
  // indistinguishable (see https://crbug.com/1282730). To avoid this, when we
  // encounter a number pad key, we'll use the located key_code itself rather
  // than its non-located counterpart.
  ui::KeyboardCode key_code = ui::KeyboardCodeFromNSEvent(event);
  bool is_numeric_keypad_keycode =
      key_code >= ui::VKEY_NUMPAD0 && key_code <= ui::VKEY_NUMPAD9;
  result.windows_key_code = is_numeric_keypad_keycode
                                ? key_code
                                : ui::LocatedToNonLocatedKeyboardCode(key_code);

  result.native_key_code = [event keyCode];
  result.dom_code = static_cast<int>(dom_code);
  result.dom_key = DomKeyFromEvent(event);
  NSString* text_str = TextFromEvent(event);
  NSString* unmodified_str = UnmodifiedTextFromEvent(event);

  // Begin Apple code, copied from KeyEventMac.mm

  // Always use 13 for Enter/Return -- we don't want to use AppKit's
  // different character for Enter.
  if (result.windows_key_code == '\r') {
    text_str = @"\r";
    unmodified_str = @"\r";
  }

  // Always use 9 for tab -- we don't want to use AppKit's different character
  // for shift-tab.
  if (result.windows_key_code == 9) {
    text_str = @"\x9";
    unmodified_str = @"\x9";
  }

  // End Apple code.

  if ([text_str length] < blink::WebKeyboardEvent::kTextLengthCap &&
      [unmodified_str length] < blink::WebKeyboardEvent::kTextLengthCap) {
    [text_str getCharacters:reinterpret_cast<UniChar*>(&result.text[0])];
    [unmodified_str
        getCharacters:reinterpret_cast<UniChar*>(&result.unmodified_text[0])];
  } else
    NOTIMPLEMENTED();

  result.is_system_key = IsSystemKeyEvent(result);

  return result;
}

// WebMouseEvent --------------------------------------------------------------

blink::WebMouseEvent WebMouseEventBuilder::Build(
    NSEvent* event,
    NSView* view,
    blink::WebPointerProperties::PointerType pointerType,
    bool unacceleratedMovement) {
  ui::ComputeEventLatencyOS(base::apple::OwnedNSEvent(event));
  blink::WebInputEvent::Type event_type =
      blink::WebInputEvent::Type::kUndefined;
  int click_count = 0;
  blink::WebMouseEvent::Button button = blink::WebMouseEvent::Button::kNoButton;

  NSEventType type = [event type];
  switch (type) {
    case NSEventTypeMouseExited:
      event_type = blink::WebInputEvent::Type::kMouseLeave;
      break;
    case NSEventTypeLeftMouseDown:
      event_type = blink::WebInputEvent::Type::kMouseDown;
      click_count = [event clickCount];
      button = blink::WebMouseEvent::Button::kLeft;
      break;
    case NSEventTypeOtherMouseDown:
      event_type = blink::WebInputEvent::Type::kMouseDown;
      click_count = [event clickCount];
      button = ButtonFromButtonNumber(event);
      break;
    case NSEventTypeRightMouseDown:
      event_type = blink::WebInputEvent::Type::kMouseDown;
      click_count = [event clickCount];
      button = blink::WebMouseEvent::Button::kRight;
      break;
    case NSEventTypeLeftMouseUp:
      event_type = blink::WebInputEvent::Type::kMouseUp;
      click_count = [event clickCount];
      button = blink::WebMouseEvent::Button::kLeft;
      break;
    case NSEventTypeOtherMouseUp:
      event_type = blink::WebInputEvent::Type::kMouseUp;
      click_count = [event clickCount];
      button = ButtonFromButtonNumber(event);
      break;
    case NSEventTypeRightMouseUp:
      event_type = blink::WebInputEvent::Type::kMouseUp;
      click_count = [event clickCount];
      button = blink::WebMouseEvent::Button::kRight;
      break;
    case NSEventTypeMouseMoved:
    case NSEventTypeMouseEntered:
      event_type = blink::WebInputEvent::Type::kMouseMove;
      button = ButtonFromPressedMouseButtons();
      break;
    case NSEventTypeLeftMouseDragged:
      event_type = blink::WebInputEvent::Type::kMouseMove;
      button = blink::WebMouseEvent::Button::kLeft;
      break;
    case NSEventTypeOtherMouseDragged:
      event_type = blink::WebInputEvent::Type::kMouseMove;
      button = blink::WebMouseEvent::Button::kMiddle;
      break;
    case NSEventTypeRightMouseDragged:
      event_type = blink::WebInputEvent::Type::kMouseMove;
      button = blink::WebMouseEvent::Button::kRight;
      break;
    default:
      NOTIMPLEMENTED();
  }

  // Set id = 0 for all mouse events, disable multi-pen on mac for now.
  // NSEventTypeMouseExited and NSEventTypeMouseEntered events don't have
  // deviceID. Therefore pen exit and enter events can't get correct id.
  EventLocationInfo info =
      GetWebEventLocationForEventInView(event, view, unacceleratedMovement);
  blink::WebMouseEvent result(event_type, ModifiersFromEvent(event),
                              ui::EventTimeStampFromSeconds(event.timestamp),
                              0);
  result.click_count = click_count;
  result.button = button;
  result.SetPositionInScreen(info.position_in_screen);
  result.SetPositionInWidget(info.position_in_widget);
  result.movement_x = info.movement_x;
  result.movement_y = info.movement_y;
  result.is_raw_movement_event = info.is_raw_movement_event;
  result.pointer_type = pointerType;
  if ((type == NSEventTypeMouseExited || type == NSEventTypeMouseEntered) ||
      ([event subtype] != NSEventSubtypeTabletPoint &&
       [event subtype] != NSEventSubtypeTabletProximity)) {
    return result;
  }

  // Set stylus properties for events with a subtype of
  // NSEventSubtypeTabletPoint.
  NSEventSubtype subtype = [event subtype];
  if (subtype == NSEventSubtypeTabletPoint) {
    result.force = [event pressure];
    NSPoint tilt = [event tilt];
    result.tilt_x = tilt.x * 90.0f;
    // Pointer Events specification states that tiltY is positive when the
    // pen is tilted towards the user.
    // By default, in MacOS, the Y coordinate increases going up,
    // while in Chromium the Y coordinate increases going down.
    // https://developer.apple.com/library/archive/documentation/General/Conceptual/Devpedia-CocoaApp/CoordinateSystem.html
    // In this case (if the coordinate system is not flipped) tiltY needs to
    // be reversed to match Chromium's expectation that tiltY is positive
    // towards the user
    result.tilt_y = ([view isFlipped] ? 1.0 : (-1.0)) * tilt.y * 90.0f;
    result.tangential_pressure = [event tangentialPressure];
    // NSEvent spec doesn't specify the range of rotation, we make sure that
    // this value is in the range of [0,359].
    int twist = (int)[event rotation];
    twist = twist % 360;
    if (twist < 0)
      twist += 360;
    result.twist = twist;
  } else {
    event_type = [event isEnteringProximity]
                     ? blink::WebInputEvent::Type::kMouseMove
                     : blink::WebInputEvent::Type::kMouseLeave;
    result.SetType(event_type);
  }
  return result;
}

// WebMouseWheelEvent ---------------------------------------------------------

blink::WebMouseWheelEvent WebMouseWheelEventBuilder::Build(
    NSEvent* event,
    NSView* view) {
  ui::ComputeEventLatencyOS(base::apple::OwnedNSEvent(event));

  EventLocationInfo info = GetWebEventLocationForEventInView(event, view);
  blink::WebMouseWheelEvent result(
      blink::WebInputEvent::Type::kMouseWheel, ModifiersFromEvent(event),
      ui::EventTimeStampFromSeconds(event.timestamp));
  result.button = blink::WebMouseEvent::Button::kNoButton;
  result.SetPositionInScreen(info.position_in_screen);
  result.SetPositionInWidget(info.position_in_widget);
  result.movement_x = info.movement_x;
  result.movement_y = info.movement_y;
  result.is_raw_movement_event = info.is_raw_movement_event;

  // Of Mice and Men
  // ---------------
  //
  // There are three types of scroll data available on a scroll wheel CGEvent.
  // Apple's documentation ([1]) is rather vague in their differences, and not
  // terribly helpful in deciding which to use. This is what's really going on.
  //
  // First, these events behave very differently depending on whether a standard
  // wheel mouse is used (one that scrolls in discrete units) or a
  // trackpad/Mighty Mouse is used (which both provide continuous scrolling).
  // You must check to see which was used for the event by testing the
  // kCGScrollWheelEventIsContinuous field.
  //
  // Second, these events refer to "axes". Axis 1 is the y-axis, and axis 2 is
  // the x-axis.
  //
  // Third, there is a concept of mouse acceleration. Scrolling the same amount
  // of physical distance will give you different results logically depending on
  // whether you scrolled a little at a time or in one continuous motion. Some
  // fields account for this while others do not.
  //
  // Fourth, for trackpads there is a concept of chunkiness. When scrolling
  // continuously, events can be delivered in chunks. That is to say, lots of
  // scroll events with delta 0 will be delivered, and every so often an event
  // with a non-zero delta will be delivered, containing the accumulated deltas
  // from all the intermediate moves. [2]
  //
  // For notchy wheel mice (kCGScrollWheelEventIsContinuous == 0)
  // ------------------------------------------------------------
  //
  // kCGScrollWheelEventDeltaAxis*
  //   This is the rawest of raw events. For each mouse notch you get a value of
  //   +1/-1. This does not take acceleration into account and thus is less
  //   useful for building UIs.
  //
  // kCGScrollWheelEventPointDeltaAxis*
  //   This is smarter. In general, for each mouse notch you get a value of
  //   +1/-1, but this _does_ take acceleration into account, so you will get
  //   larger values on longer scrolls. This field would be ideal for building
  //   UIs except for one nasty bug: when the shift key is pressed, this set of
  //   fields fails to move the value into the axis2 field (the other two types
  //   of data do). This wouldn't be so bad except for the fact that while the
  //   number of axes is used in the creation of a CGScrollWheelEvent, there is
  //   no way to get that information out of the event once created.
  //
  // kCGScrollWheelEventFixedPtDeltaAxis*
  //   This is a fixed value, and for each mouse notch you get a value of
  //   +0.1/-0.1 (but, like above, scaled appropriately for acceleration). This
  //   value takes acceleration into account, and in fact is identical to the
  //   results you get from -[NSEvent delta*]. (That is, if you linked on Tiger
  //   or greater; see [2] for details.)
  //
  // A note about continuous devices
  // -------------------------------
  //
  // There are two devices that provide continuous scrolling events (trackpads
  // and Mighty Mouses) and they behave rather differently. The Mighty Mouse
  // behaves a lot like a regular mouse. There is no chunking, and the
  // FixedPtDelta values are the PointDelta values multiplied by 0.1. With the
  // trackpad, though, there is chunking. While the FixedPtDelta values are
  // reasonable (they occur about every fifth event but have values five times
  // larger than usual) the Delta values are unreasonable. They don't appear to
  // accumulate properly.
  //
  // For continuous devices (kCGScrollWheelEventIsContinuous != 0)
  // -------------------------------------------------------------
  //
  // kCGScrollWheelEventDeltaAxis*
  //   This provides values with no acceleration. With a trackpad, these values
  //   are chunked but each non-zero value does not appear to be cumulative.
  //   This seems to be a bug.
  //
  // kCGScrollWheelEventPointDeltaAxis*
  //   This provides values with acceleration. With a trackpad, these values are
  //   not chunked and are highly accurate.
  //
  // kCGScrollWheelEventFixedPtDeltaAxis*
  //   This provides values with acceleration. With a trackpad, these values are
  //   chunked but unlike Delta events are properly cumulative.
  //
  // Summary
  // -------
  //
  // In general the best approach to take is: determine if the event is
  // continuous. If it is not, then use the FixedPtDelta events (or just stick
  // with Cocoa events). They provide both acceleration and proper horizontal
  // scrolling. If the event is continuous, then doing pixel scrolling with the
  // PointDelta is the way to go. In general, avoid the Delta events. They're
  // the oldest (dating back to 10.4, before CGEvents were public) but they lack
  // acceleration and precision, making them useful only in specific edge cases.
  //
  // References
  // ----------
  //
  // [1]
  // <http://developer.apple.com/documentation/Carbon/Reference/QuartzEventServicesRef/Reference/reference.html>
  // [2] <http://developer.apple.com/releasenotes/Cocoa/AppKitOlderNotes.html>
  //     Scroll to the section headed "NSEventTypeScrollWheel events".
  //
  // P.S. The "smooth scrolling" option in the system preferences is utterly
  // unrelated to any of this.

  CGEventRef cg_event = [event CGEvent];
  DCHECK(cg_event);

  // Wheel ticks are supposed to be raw, unaccelerated values, one per physical
  // mouse wheel notch. The delta event is perfect for this (being a good
  // "specific edge case" as mentioned above). Trackpads, unfortunately, do
  // event chunking, and sending mousewheel events with 0 ticks causes some
  // websites to malfunction. Therefore, for all continuous input devices we use
  // the point delta data instead, since we cannot distinguish trackpad data
  // from data from any other continuous device.

  if (CGEventGetIntegerValueField(cg_event, kCGScrollWheelEventIsContinuous)) {
    result.delta_units = ui::ScrollGranularity::kScrollByPrecisePixel;
    result.delta_x = CGEventGetIntegerValueField(
        cg_event, kCGScrollWheelEventPointDeltaAxis2);
    result.delta_y = CGEventGetIntegerValueField(
        cg_event, kCGScrollWheelEventPointDeltaAxis1);
    result.wheel_ticks_x = result.delta_x / ui::kScrollbarPixelsPerCocoaTick;
    result.wheel_ticks_y = result.delta_y / ui::kScrollbarPixelsPerCocoaTick;
  } else {
    result.delta_x = [event deltaX] * ui::kScrollbarPixelsPerCocoaTick;
    result.delta_y = [event deltaY] * ui::kScrollbarPixelsPerCocoaTick;
    result.wheel_ticks_y =
        CGEventGetIntegerValueField(cg_event, kCGScrollWheelEventDeltaAxis1);
    result.wheel_ticks_x =
        CGEventGetIntegerValueField(cg_event, kCGScrollWheelEventDeltaAxis2);
  }

  result.phase = PhaseForEvent(event);
  result.momentum_phase = MomentumPhaseForEvent(event);

  return result;
}

blink::WebGestureEvent WebGestureEventBuilder::Build(NSEvent* event,
                                                     NSView* view) {
  blink::WebGestureEvent result;

  EventLocationInfo info = GetWebEventLocationForEventInView(event, view);
  result.SetPositionInScreen(info.position_in_screen);
  result.SetPositionInWidget(info.position_in_widget);

  result.SetModifiers(ModifiersFromEvent(event));
  result.SetTimeStamp(ui::EventTimeStampFromSeconds(event.timestamp));

  result.SetSourceDevice(blink::WebGestureDevice::kTouchpad);

  switch (event.type) {
    case NSEventTypeMagnify:
      result.SetType(GesturePinchInputEventTypeFromPhase(event.phase));
      result.data.pinch_update.scale = event.magnification + 1.0;
      result.SetNeedsWheelEvent(true);
      break;
    case NSEventTypeSmartMagnify:
      // Map the Cocoa "double-tap with two fingers" zoom gesture to regular
      // GestureDoubleTap, because the effect is similar to single-finger
      // double-tap zoom on mobile platforms. Note that tapCount is set to 1
      // because the gesture type already encodes that information.
      result.SetType(blink::WebInputEvent::Type::kGestureDoubleTap);
      result.data.tap.tap_count = 1;
      result.SetNeedsWheelEvent(true);
      break;
    default:
      NOTIMPLEMENTED();
  }

  return result;
}

// WebTouchEvent --------------------------------------------------------------

blink::WebTouchEvent WebTouchEventBuilder::Build(NSEvent* event, NSView* view) {
  blink::WebInputEvent::Type event_type =
      blink::WebInputEvent::Type::kUndefined;
  NSEventType type = [event type];
  blink::WebTouchPoint::State state =
      blink::WebTouchPoint::State::kStateUndefined;
  switch (type) {
    case NSEventTypeLeftMouseDown:
      event_type = blink::WebInputEvent::Type::kTouchStart;
      state = blink::WebTouchPoint::State::kStatePressed;
      break;
    case NSEventTypeLeftMouseUp:
      event_type = blink::WebInputEvent::Type::kTouchEnd;
      state = blink::WebTouchPoint::State::kStateReleased;
      break;
    case NSEventTypeLeftMouseDragged:
    case NSEventTypeRightMouseDragged:
    case NSEventTypeOtherMouseDragged:
    case NSEventTypeMouseMoved:
    case NSEventTypeRightMouseDown:
    case NSEventTypeOtherMouseDown:
    case NSEventTypeRightMouseUp:
    case NSEventTypeOtherMouseUp:
      event_type = blink::WebInputEvent::Type::kTouchMove;
      state = blink::WebTouchPoint::State::kStateMoved;
      break;
    default:
      NOTREACHED() << "Invalid types for touch events." << type;
  }

  blink::WebTouchEvent result(event_type, ModifiersFromEvent(event),
                              ui::EventTimeStampFromSeconds([event timestamp]));
  ui::ComputeEventLatencyOS(base::apple::OwnedNSEvent(event));
  result.hovering = event_type == blink::WebInputEvent::Type::kTouchEnd;
  result.unique_touch_event_id = ui::GetNextTouchEventId();
  result.touches_length = 1;

  EventLocationInfo info = GetWebEventLocationForEventInView(event, view);
  result.touches[0].SetPositionInScreen(info.position_in_screen);
  result.touches[0].SetPositionInWidget(info.position_in_widget);
  result.touches[0].movement_x = info.movement_x;
  result.touches[0].movement_y = info.movement_y;

  result.touches[0].state = state;
  result.touches[0].pointer_type =
      blink::WebPointerProperties::PointerType::kPen;
  result.touches[0].id = [event pointingDeviceID];
  result.touches[0].force = [event pressure];
  NSPoint tilt = [event tilt];
  result.touches[0].tilt_x = tilt.x * 90.0f;
  result.touches[0].tilt_y = tilt.y * 90.0f;
  result.touches[0].tangential_pressure = [event tangentialPressure];
  // NSEvent spec doesn't specify the range of rotation, we make sure that
  // this value is in the range of [0,359].
  int twist = (int)[event rotation];
  twist = twist % 360;
  if (twist < 0)
    twist += 360;
  result.touches[0].twist = twist;
  float rotation_angle = twist % 180;
  if (rotation_angle > 90)
    rotation_angle = 180.f - rotation_angle;
  result.touches[0].rotation_angle = rotation_angle;
  return result;
}

}  // namespace input