ash/events/accessibility_event_rewriter.cc

// Copyright 2020 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.

#include "ash/events/accessibility_event_rewriter.h"

#include "ash/accessibility/accessibility_controller_impl.h"
#include "ash/accessibility/point_scan_controller.h"
#include "ash/keyboard/keyboard_util.h"
#include "ash/magnifier/magnification_controller.h"
#include "ash/public/cpp/accessibility_event_rewriter_delegate.h"
#include "ash/shell.h"
#include "ui/chromeos/events/event_rewriter_chromeos.h"
#include "ui/events/devices/device_data_manager.h"
#include "ui/events/event.h"
#include "ui/events/event_utils.h"
#include "ui/events/types/event_type.h"

namespace ash {

namespace {

// Returns a ui::InputDeviceType given a Switch Access string device type.
ui::InputDeviceType GetInputDeviceType(
    const std::string& switch_access_device_type) {
  if (switch_access_device_type == kSwitchAccessInternalDevice)
    return ui::INPUT_DEVICE_INTERNAL;
  if (switch_access_device_type == kSwitchAccessUsbDevice)
    return ui::INPUT_DEVICE_USB;
  if (switch_access_device_type == kSwitchAccessBluetoothDevice)
    return ui::INPUT_DEVICE_BLUETOOTH;

  NOTREACHED();
  return ui::INPUT_DEVICE_UNKNOWN;
}
}  // namespace

AccessibilityEventRewriter::AccessibilityEventRewriter(
    ui::EventRewriterChromeOS* event_rewriter_chromeos,
    AccessibilityEventRewriterDelegate* delegate)
    : delegate_(delegate), event_rewriter_chromeos_(event_rewriter_chromeos) {
  Shell::Get()->accessibility_controller()->SetAccessibilityEventRewriter(this);
}

AccessibilityEventRewriter::~AccessibilityEventRewriter() {
  Shell::Get()->accessibility_controller()->SetAccessibilityEventRewriter(
      nullptr);
}

void AccessibilityEventRewriter::OnUnhandledSpokenFeedbackEvent(
    std::unique_ptr<ui::Event> event) const {
  DCHECK(event->IsKeyEvent()) << "Unexpected unhandled event type";
  // Send the event to the continuation for the most recent event rewritten by
  // ChromeVox, (that is, through its EventSource). Under the assumption that a
  // single AccessibilityEventRewriter is not registered to multiple
  // EventSources, this will be the same as this event's original source.
  const char* failure_reason = nullptr;
  if (chromevox_continuation_) {
    ui::EventDispatchDetails details =
        SendEvent(chromevox_continuation_, event.get());
    if (details.dispatcher_destroyed)
      failure_reason = "destroyed dispatcher";
    else if (details.target_destroyed)
      failure_reason = "destroyed target";
  } else if (chromevox_continuation_.WasInvalidated()) {
    failure_reason = "destroyed source";
  } else {
    failure_reason = "no prior rewrite";
  }
  if (failure_reason) {
    VLOG(0) << "Undispatched key " << event->AsKeyEvent()->key_code()
            << " due to " << failure_reason << ".";
  }
}

void AccessibilityEventRewriter::SetKeyCodesForSwitchAccessCommand(
    const std::map<int, std::set<std::string>>& key_codes,
    SwitchAccessCommand command) {
  // Remove all keys for the command.
  for (auto it = key_code_to_switch_access_command_.begin();
       it != key_code_to_switch_access_command_.end();) {
    if (it->second == command) {
      switch_access_key_codes_to_capture_.erase(it->first);
      it = key_code_to_switch_access_command_.erase(it);
    } else {
      it++;
    }
  }

  for (const auto& key_code : key_codes) {
    // Remove any preexisting key.
    switch_access_key_codes_to_capture_.erase(key_code.first);
    key_code_to_switch_access_command_.erase(key_code.first);

    // Map device types from Switch Access's internal representation.
    std::set<ui::InputDeviceType> device_types;
    for (const std::string& switch_access_device : key_code.second)
      device_types.insert(GetInputDeviceType(switch_access_device));

    switch_access_key_codes_to_capture_.insert({key_code.first, device_types});
    key_code_to_switch_access_command_.insert({key_code.first, command});
  }

  // Conflict resolution occurs up the stack (e.g. in the settings pages for
  // Switch Access).
}

bool AccessibilityEventRewriter::RewriteEventForChromeVox(
    const ui::Event& event,
    const Continuation continuation) {
  // Save continuation for |OnUnhandledSpokenFeedbackEvent()|.
  chromevox_continuation_ = continuation;

  if (!Shell::Get()->accessibility_controller()->spoken_feedback().enabled()) {
    return false;
  }

  if (event.IsKeyEvent()) {
    const ui::KeyEvent* key_event = event.AsKeyEvent();
    ui::EventRewriterChromeOS::MutableKeyState state(key_event);
    event_rewriter_chromeos_->RewriteModifierKeys(*key_event, &state);

    // Remove the Search modifier before asking for function keys to be
    // rewritten, then restore the flags. This allows ChromeVox to receive keys
    // mappings for raw f1-f12 as e.g. back, but also Search+f1-f12 as
    // Search+back (rather than just f1-f12).
    int original_flags = state.flags;
    state.flags = original_flags & ~ui::EF_COMMAND_DOWN;
    event_rewriter_chromeos_->RewriteFunctionKeys(*key_event, &state);
    state.flags = original_flags;

    std::unique_ptr<ui::Event> rewritten_event;
    ui::EventRewriterChromeOS::BuildRewrittenKeyEvent(*key_event, state,
                                                      &rewritten_event);
    const ui::KeyEvent* rewritten_key_event =
        rewritten_event.get()->AsKeyEvent();

    bool capture = chromevox_capture_all_keys_;

    // Always capture the Search key.
    capture |= rewritten_key_event->IsCommandDown() ||
               rewritten_key_event->key_code() == ui::VKEY_LWIN;

    // Don't capture tab as it gets consumed by Blink so never comes back
    // unhandled. In third_party/WebKit/Source/core/input/EventHandler.cpp, a
    // default tab handler consumes tab even when no focusable nodes are found;
    // it sets focus to Chrome and eats the event.
    if (rewritten_key_event->GetDomKey() == ui::DomKey::TAB)
      capture = false;

    delegate_->DispatchKeyEventToChromeVox(
        ui::Event::Clone(*rewritten_key_event), capture);
    return capture;
  }

  return false;
}

bool AccessibilityEventRewriter::RewriteEventForSwitchAccess(
    const ui::Event& event,
    const Continuation continuation) {
  if (!event.IsKeyEvent() || suspend_switch_access_key_handling_)
    return false;

  const ui::KeyEvent* key_event = event.AsKeyEvent();
  const auto& key =
      switch_access_key_codes_to_capture_.find(key_event->key_code());
  if (key == switch_access_key_codes_to_capture_.end())
    return false;

  int source_device_id = key_event->source_device_id();
  ui::InputDeviceType keyboard_type = ui::INPUT_DEVICE_UNKNOWN;
  for (const auto& keyboard :
       ui::DeviceDataManager::GetInstance()->GetKeyboardDevices()) {
    if (source_device_id == keyboard.id) {
      keyboard_type = keyboard.type;
      break;
    }
  }

  // An unknown |source_device_id| needs to pass this check as it's set that way
  // in tests.
  if (source_device_id != ui::ED_UNKNOWN_DEVICE &&
      key->second.count(keyboard_type) == 0) {
    return false;
  }

  if (key_event->type() == ui::ET_KEY_PRESSED) {
    AccessibilityControllerImpl* accessibility_controller =
        Shell::Get()->accessibility_controller();

    if (accessibility_controller->IsPointScanEnabled()) {
      PointScanController* point_scan_controller =
          accessibility_controller->GetPointScanController();
      base::Optional<gfx::PointF> point =
          point_scan_controller->OnPointSelect();
      if (point.has_value()) {
        delegate_->SendPointScanPoint(point.value());
      }
    } else {
      SwitchAccessCommand command =
          key_code_to_switch_access_command_[key_event->key_code()];
      delegate_->SendSwitchAccessCommand(command);
    }
  }
  return true;
}

bool AccessibilityEventRewriter::RewriteEventForMagnifier(
    const ui::Event& event,
    const Continuation continuation) {
  if (!event.IsKeyEvent())
    return false;

  const ui::KeyEvent* key_event = event.AsKeyEvent();

  if (!keyboard_util::IsArrowKeyCode(key_event->key_code()) ||
      !key_event->IsControlDown() || !key_event->IsAltDown()) {
    return false;
  }

  if (key_event->type() == ui::ET_KEY_PRESSED) {
    // If first time key is pressed (e.g. not repeat), start scrolling.
    if (!(key_event->flags() & ui::EF_IS_REPEAT))
      OnMagnifierKeyPressed(key_event);

    // Either way (first or repeat), capture key press.
    return true;
  }

  if (key_event->type() == ui::ET_KEY_RELEASED) {
    OnMagnifierKeyReleased(key_event);
    return true;
  }

  return false;
}

void AccessibilityEventRewriter::OnMagnifierKeyPressed(
    const ui::KeyEvent* event) {
  MagnificationController* controller =
      Shell::Get()->magnification_controller();
  switch (event->key_code()) {
    case ui::VKEY_UP:
      controller->SetScrollDirection(MagnificationController::SCROLL_UP);
      delegate_->SendMagnifierCommand(MagnifierCommand::kMoveUp);
      break;
    case ui::VKEY_DOWN:
      controller->SetScrollDirection(MagnificationController::SCROLL_DOWN);
      delegate_->SendMagnifierCommand(MagnifierCommand::kMoveDown);
      break;
    case ui::VKEY_LEFT:
      controller->SetScrollDirection(MagnificationController::SCROLL_LEFT);
      delegate_->SendMagnifierCommand(MagnifierCommand::kMoveLeft);
      break;
    case ui::VKEY_RIGHT:
      controller->SetScrollDirection(MagnificationController::SCROLL_RIGHT);
      delegate_->SendMagnifierCommand(MagnifierCommand::kMoveRight);
      break;
    default:
      NOTREACHED() << "Unexpected keyboard_code:" << event->key_code();
  }
}

void AccessibilityEventRewriter::OnMagnifierKeyReleased(
    const ui::KeyEvent* event) {
  MagnificationController* controller =
      Shell::Get()->magnification_controller();
  controller->SetScrollDirection(MagnificationController::SCROLL_NONE);
  delegate_->SendMagnifierCommand(MagnifierCommand::kMoveStop);
}

void AccessibilityEventRewriter::MaybeSendMouseEvent(const ui::Event& event) {
  // Mouse moves are the only pertinent event for accessibility component
  // extensions.
  if (send_mouse_events_ && event.type() == ui::ET_MOUSE_MOVED &&
      (Shell::Get()->magnification_controller()->IsEnabled() ||
       Shell::Get()->accessibility_controller()->spoken_feedback().enabled())) {
    delegate_->DispatchMouseEvent(ui::Event::Clone(event));
  }
}

ui::EventDispatchDetails AccessibilityEventRewriter::RewriteEvent(
    const ui::Event& event,
    const Continuation continuation) {
  bool captured = false;
  if (!delegate_)
    return SendEvent(continuation, &event);

  if (Shell::Get()->accessibility_controller()->IsSwitchAccessRunning()) {
    captured = RewriteEventForSwitchAccess(event, continuation);
  }

  if (!captured && Shell::Get()
                       ->accessibility_controller()
                       ->fullscreen_magnifier()
                       .enabled()) {
    captured = RewriteEventForMagnifier(event, continuation);
  }

  if (!captured) {
    captured = RewriteEventForChromeVox(event, continuation);
  }

  if (!captured) {
    MaybeSendMouseEvent(event);
  }

  return captured ? DiscardEvent(continuation)
                  : SendEvent(continuation, &event);
}

}  // namespace ash