Make Interaction Media Features MQ dynamic on Windows.

ui/events/devices/input_device_observer_win.cc

+// Copyright (c) 2017 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 "ui/events/devices/input_device_observer_win.h"
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/memory/singleton.h"
+#include "base/strings/string16.h"
+
+// This macro provides the implementation for the observer notification methods.
+#define NOTIFY_OBSERVERS(method_decl, observer_call)       \
+  void InputDeviceObserverWin::method_decl {               \
+    for (InputDeviceEventObserver & observer : observers_) \
+      observer.observer_call;                              \
+  }
+
+namespace ui {
+
+namespace {
+
+// The registry subkey that contains information about the state of the
+// detachable/convertible laptop, it tells if the device has an accessible
+// keyboard.
+// OEMs are expected to follow this guidelines to report docked/undocked state
+// https://msdn.microsoft.com/en-us/library/windows/hardware/dn922653(v=vs.85).aspx.

[mustaq, 2017/03/23 20:09:10]

Nit: Perhaps replace this URL with the redirected address you mentioned in
#msg29?

+const base::char16 kRegistryPriorityControl[] =
+    L"System\\CurrentControlSet\\Control\\PriorityControl";
+
+const base::char16 kRegistryConvertibleSlateModeKey[] = L"ConvertibleSlateMode";
+
+}  // namespace
+
+InputDeviceObserverWin::InputDeviceObserverWin() : weak_factory_(this) {
+  registry_key_.reset(new base::win::RegKey(
+      HKEY_LOCAL_MACHINE, kRegistryPriorityControl, KEY_NOTIFY | KEY_READ));
+
+  if (registry_key_->Valid()) {
+    slate_mode_enabled_ = IsSlateModeEnabled(registry_key_.get());
+    // Start watching the registry for changes.
+    base::win::RegKey::ChangeCallback callback =
+        base::Bind(&InputDeviceObserverWin::OnRegistryKeyChanged,
+                   weak_factory_.GetWeakPtr(), registry_key_.get());
+    registry_key_->StartWatching(callback);
+  }
+}
+
+InputDeviceObserverWin* InputDeviceObserverWin::GetInstance() {
+  return base::Singleton<
+      InputDeviceObserverWin,
+      base::LeakySingletonTraits<InputDeviceObserverWin>>::get();
+}
+
+InputDeviceObserverWin::~InputDeviceObserverWin() {}
+
+void InputDeviceObserverWin::OnRegistryKeyChanged(base::win::RegKey* key) {
+  if (!key)
+    return;
+
+  // |OnRegistryKeyChanged| is removed as an observer when the ChangeCallback is
+  // called, so we need to re-register.
+  key->StartWatching(base::Bind(&InputDeviceObserverWin::OnRegistryKeyChanged,
+                                base::Unretained(this), base::Unretained(key)));
+
+  bool new_slate_mode = IsSlateModeEnabled(key);
+  if (slate_mode_enabled_ == new_slate_mode)
+    return;
+
+  NotifyObserversTouchpadDeviceConfigurationChanged();
+  NotifyObserversMouseDeviceConfigurationChanged();
+  NotifyObserversKeyboardDeviceConfigurationChanged();
+  NotifyObserversTouchscreenDeviceConfigurationChanged();

[mustaq, 2017/03/23 20:09:10]

Another nit: now that you have focused the "watch" to only ConvertibleSlateMode
which includes only keyboard & touchpad, please omit other notifications (mouse
& touchscreen). For dynamic MQs, the end result would be the same since all
these 4 calls end up in |notifyRenderViewHost()|.

+  slate_mode_enabled_ = new_slate_mode;
+}
+
+bool InputDeviceObserverWin::IsSlateModeEnabled(base::win::RegKey* key) {
+  DWORD slate_enabled;
+  if (key->ReadValueDW(kRegistryConvertibleSlateModeKey, &slate_enabled) !=
+      ERROR_SUCCESS)
+    return false;
+  return slate_enabled == 1;
+}
+
+void InputDeviceObserverWin::AddObserver(InputDeviceEventObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void InputDeviceObserverWin::RemoveObserver(
+    InputDeviceEventObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+NOTIFY_OBSERVERS(NotifyObserversKeyboardDeviceConfigurationChanged(),
+                 OnKeyboardDeviceConfigurationChanged());
+
+NOTIFY_OBSERVERS(NotifyObserversMouseDeviceConfigurationChanged(),
+                 OnMouseDeviceConfigurationChanged());
+
+NOTIFY_OBSERVERS(NotifyObserversTouchpadDeviceConfigurationChanged(),
+                 OnTouchpadDeviceConfigurationChanged());
+
+NOTIFY_OBSERVERS(NotifyObserversTouchscreenDeviceConfigurationChanged(),
+                 OnTouchscreenDeviceConfigurationChanged());
+
+}  // namespace ui