The on screen keyboard on Windows 8+ should not obscure the input field.

ui/base/win/osk_display_manager.cc

+// Copyright 2016 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/base/win/osk_display_manager.h"
+
+#include <windows.h>
+#include <shellapi.h>
+#include <shlobj.h>
+#include <shobjidl.h>  // Must be before propkey.
+
+#include "base/bind.h"
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/message_loop/message_loop.h"
+#include "base/strings/string_util.h"
+#include "base/win/registry.h"
+#include "base/win/scoped_co_mem.h"
+#include "base/win/win_util.h"
+#include "base/win/windows_version.h"
+#include "ui/base/win/osk_display_observer.h"
+#include "ui/display/win/dpi.h"
+#include "ui/gfx/geometry/dip_util.h"
+
+namespace ui {
+
+static const int kCheckOSKDelayMs = 1000;

[grt (UTC plus 2), 2016/05/20 14:56:35]

put these privates in an unnamed namespace and omit "static"

[grt (UTC plus 2), 2016/05/20 14:56:35]

nit: use constexpr for compile-time constants
(https://google.github.io/styleguide/cppguide.html#Use_of_constexpr)

[grt (UTC plus 2), 2016/05/20 20:29:24]

ping

[ananta, 2016/05/20 20:54:17]

Done.

[ananta, 2016/05/20 20:54:17]

Done.

[ananta, 2016/05/20 20:54:17]

Done.

[ananta, 2016/05/20 20:54:17]

Done.

+static const int kDismissKeyboardRetryTimeoutMs = 100;
+static const int kDismissKeyboardMaxRetries = 5;
+
+static const wchar_t kOSKClassName[] = L"IPTip_Main_Window";
+
+const wchar_t kWindows8OSKRegPath[] =
+    L"Software\\Classes\\CLSID\\{054AAE20-4BEA-4347-8A35-64A533254A9D}"
+    L"\\LocalServer32";
+
+// This class provides functionality to detect when the on screen keyboard
+// is displayed and move the main window up if it is obscured by the keyboard.
+class OnScreenKeyboardDetector {
+ public:
+  OnScreenKeyboardDetector();
+  ~OnScreenKeyboardDetector();
+
+  // Schedules a delayed task which detects if the on screen keyboard was
+  // displayed.
+  void DetectKeyboard(HWND main_window);
+
+  // Dismisses the on screen keyboard. If a call to display the keyboard was
+  // made, this function waits for the keyboard to become visible by retrying
+  // upto a maximum of kDismissKeyboardMaxRetries.
+  bool DismissKeyboard();
+
+  // Add/Remove keyboard observers.
+  // Please note that this class does not track the |observer| destruction. It
+  // is upto the classes which set up these observers to remove them when they
+  // are destroyed.
+  void AddObserver(OnScreenKeyboardObserver* observer);
+  void RemoveObserver(OnScreenKeyboardObserver* observer);
+
+ private:
+  // Executes as a task and detects if the on screen keyboard is displayed.
+  // The |check_for_activation| parameter controls whether the function detects
+  // whether the keyboard wad displayed or hidden.
+  // Once the OSK is detected, this task runs periodically for the duration for
+  // which the OSK is visible.
+  void CheckOSKState(bool check_for_activation);
+
+  // Notifies observers that the keyboard was displayed.
+  // A recurring task CheckOSKState() is started to detect when the OSK
+  // disappears.
+  void HandleKeyboardVisible();
+
+  // Notifies observers that the keyboard was hidden.
+  // The observer list is cleared out after this notification.
+  void HandleKeyboardHidden();
+
+  // Removes all observers from the list.
+  void ClearObservers();
+
+  // The main window which displays the on screen keyboard.
+  HWND main_window_ = nullptr;
+
+  // Tracks if the keyboard was displayed.
+  bool osk_visible_notification_received_ = false;
+
+  // The keyboard dimensions in pixels.
+  gfx::Rect osk_rect_pixels_;
+
+  // Set to true if a call to DetectKeyboard() was made.
+  bool keyboard_detect_requested_ = false;
+
+  // Contains the number of attempts made to dismiss the keyboard. Please refer
+  // to the DismissKeyboard() function for more information.
+  int keyboard_dismiss_retry_count_ = 0;
+
+  base::ObserverList<OnScreenKeyboardObserver, false> observers_;
+
+  // Should be the last member in the class. Helps ensure that tasks spawned
+  // by this class instance are canceled when it is destroyed.
+  base::WeakPtrFactory<OnScreenKeyboardDetector> keyboard_detector_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(OnScreenKeyboardDetector);
+};
+
+// OnScreenKeyboardDetector member definitions.
+OnScreenKeyboardDetector::OnScreenKeyboardDetector()
+    : keyboard_detector_factory_(this) {}
+
+OnScreenKeyboardDetector::~OnScreenKeyboardDetector() {}
+
+void OnScreenKeyboardDetector::DetectKeyboard(HWND main_window) {
+  main_window_ = main_window;
+  keyboard_detect_requested_ = true;
+  // The keyboard is displayed by TabTip.exe which is launched via a
+  // ShellExecute call in the
+  // OnScreenKeyboardDisplayManager::DisplayVirtualKeyboard() function. We use
+  // a delayed task to check if the keyboard is visible because of the possible
+  // delay between the ShellExecute call and the keyboard becoming visible.
+  base::MessageLoop::current()->PostDelayedTask(
+      FROM_HERE, base::Bind(&OnScreenKeyboardDetector::CheckOSKState,
+                            keyboard_detector_factory_.GetWeakPtr(), true),
+      base::TimeDelta::FromMilliseconds(kCheckOSKDelayMs));
+}
+
+bool OnScreenKeyboardDetector::DismissKeyboard() {
+  // We dismiss the virtual keyboard by generating the ESC keystroke
+  // programmatically.
+  HWND osk = ::FindWindow(kOSKClassName, nullptr);
+  if (::IsWindow(osk) && ::IsWindowEnabled(osk)) {
+    keyboard_detect_requested_ = false;
+    keyboard_dismiss_retry_count_ = 0;
+    HandleKeyboardHidden();
+    PostMessage(osk, WM_SYSCOMMAND, SC_CLOSE, 0);
+    return true;
+  } else if (keyboard_detect_requested_) {
+    if (keyboard_dismiss_retry_count_ < kDismissKeyboardMaxRetries) {
+      keyboard_dismiss_retry_count_++;
+      // Please refer to the comments in the DetectKeyboard() function for more
+      // information as to why we need a delayed task here.
+      base::MessageLoop::current()->PostDelayedTask(
+          FROM_HERE, base::Bind(base::IgnoreResult(
+                                    &OnScreenKeyboardDetector::DismissKeyboard),
+                                keyboard_detector_factory_.GetWeakPtr()),
+          base::TimeDelta::FromMilliseconds(kDismissKeyboardRetryTimeoutMs));
+    } else {
+      keyboard_dismiss_retry_count_ = 0;
+    }
+  }
+  return false;
+}
+
+void OnScreenKeyboardDetector::AddObserver(OnScreenKeyboardObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void OnScreenKeyboardDetector::RemoveObserver(
+    OnScreenKeyboardObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+void OnScreenKeyboardDetector::CheckOSKState(bool check_for_activation) {
+  HWND osk = ::FindWindow(kOSKClassName, nullptr);
+  if (!::IsWindow(osk))
+    return;
+
+  RECT osk_rect = {};
+  ::GetWindowRect(osk, &osk_rect);
+
+  if (check_for_activation) {
+    if (::IsWindowVisible(osk) && ::IsWindowEnabled(osk)) {
+      if (!osk_visible_notification_received_)
+        HandleKeyboardVisible();
+    } else {
+      DVLOG(1) << "OSK did not come up in 1 second. Something wrong.";
+    }
+  } else {
+    // Three cases here.
+    // 1. OSK was hidden because the user dismissed it.
+    // 2. We are no longer in the foreground.
+    // 3. The OSK is still visible.
+    // In the first case we just have to notify the observers that the OSK was
+    // hidden.
+    // In the second case we need to dismiss the OSK which internally will
+    // notify the observers about the OSK being hidden.
+    if (!::IsWindowEnabled(osk)) {
+      if (osk_visible_notification_received_) {
+        if (main_window_ == ::GetForegroundWindow()) {
+          DVLOG(1) << "OSK window hidden while we are in the foreground.";
+          HandleKeyboardHidden();
+        }
+      }
+    } else if (main_window_ != ::GetForegroundWindow()) {
+      if (osk_visible_notification_received_) {
+        DVLOG(1) << "We are no longer in the foreground. Dismising OSK.";
+        DismissKeyboard();
+      }
+    } else {
+      base::MessageLoop::current()->PostDelayedTask(
+          FROM_HERE, base::Bind(&OnScreenKeyboardDetector::CheckOSKState,
+                                keyboard_detector_factory_.GetWeakPtr(), false),
+          base::TimeDelta::FromMilliseconds(kCheckOSKDelayMs));
+    }
+  }
+}
+
+void OnScreenKeyboardDetector::HandleKeyboardVisible() {
+  DCHECK(!osk_visible_notification_received_);
+  osk_visible_notification_received_ = true;
+
+  FOR_EACH_OBSERVER(OnScreenKeyboardObserver, observers_,
+                    OnKeyboardVisible(osk_rect_pixels_));
+
+  // Now that the keyboard is visible, run the task to detect if it was hidden.
+  base::MessageLoop::current()->PostDelayedTask(
+      FROM_HERE, base::Bind(&OnScreenKeyboardDetector::CheckOSKState,
+                            keyboard_detector_factory_.GetWeakPtr(), false),
+      base::TimeDelta::FromMilliseconds(kCheckOSKDelayMs));
+}
+
+void OnScreenKeyboardDetector::HandleKeyboardHidden() {
+  osk_visible_notification_received_ = false;
+  FOR_EACH_OBSERVER(OnScreenKeyboardObserver, observers_,
+                    OnKeyboardHidden(osk_rect_pixels_));
+  ClearObservers();
+}
+
+void OnScreenKeyboardDetector::ClearObservers() {
+  base::ObserverListBase<OnScreenKeyboardObserver>::Iterator iter(&observers_);
+  for (OnScreenKeyboardObserver* observer = iter.GetNext(); observer;
+       observer = iter.GetNext()) {
+    RemoveObserver(observer);
+  }
+}
+
+// OnScreenKeyboardDisplayManager member definitions.
+OnScreenKeyboardDisplayManager::OnScreenKeyboardDisplayManager() {}
+
+OnScreenKeyboardDisplayManager::~OnScreenKeyboardDisplayManager() {}
+
+OnScreenKeyboardDisplayManager* OnScreenKeyboardDisplayManager::GetInstance() {
+  return base::Singleton<

[grt (UTC plus 2), 2016/05/20 14:56:35]

since the only access of the singleton is from within this one function and you
want to leak the instance on exit, base::Singleton is overkill. if all callers
will be on the same thread (i.e., the UI thread), then you are safe with:
...::GetInstance() {
  static OnScreenKeyboardDisplayManager* instance = nullptr;
  if (!instance) {
    instance = new OnScreenKeyboardDisplayManager;
    ANNOTATE_LEAKING_OBJECT_PTR(instance);
  }
  return instance;
}

otherwise, if callers may be on multiple threads, you can go with:
...::GetInstance() {
  static LazyInstance<OnScreenKeyboardDisplayManager> instance =
LAZY_INSTANCE_INITIALIZER;
  return instance.Pointer();
}

[ananta, 2016/05/20 19:32:55]

Done.

+      OnScreenKeyboardDisplayManager,
+      base::LeakySingletonTraits<OnScreenKeyboardDisplayManager>>::get();
+}
+
+bool OnScreenKeyboardDisplayManager::DisplayVirtualKeyboard(
+    OnScreenKeyboardObserver* observer) {
+  if (base::win::GetVersion() < base::win::VERSION_WIN8)
+    return false;
+
+  if (base::win::IsKeyboardPresentOnSlate(nullptr))
+    return false;
+
+  if (osk_path_.empty()) {
+    // We need to launch TabTip.exe from the location specified under the
+    // LocalServer32 key for the {{054AAE20-4BEA-4347-8A35-64A533254A9D}}
+    // CLSID.
+    // TabTip.exe is typically found at
+    // c:\program files\common files\microsoft shared\ink on English Windows.
+    // We don't want to launch TabTip.exe from
+    // c:\program files (x86)\common files\microsoft shared\ink. This path is
+    // normally found on 64 bit Windows.
+    base::win::RegKey key(HKEY_LOCAL_MACHINE, kWindows8OSKRegPath,
+                          KEY_READ | KEY_WOW64_64KEY);
+    DWORD osk_path_length = 1024;
+    if (key.ReadValue(NULL, base::WriteInto(&osk_path_, osk_path_length),
+                      &osk_path_length, NULL) != ERROR_SUCCESS) {
+      DLOG(WARNING) << "Failed to read on screen keyboard path from registry";
+      return false;
+    }
+
+    osk_path_.resize(base::string16::traits_type::length(osk_path_.c_str()));
+
+    osk_path_ = base::ToLowerASCII(osk_path_);
+
+    size_t common_program_files_offset =
+        osk_path_.find(L"%commonprogramfiles%");
+    // Typically the path to TabTip.exe read from the registry will start with
+    // %CommonProgramFiles% which needs to be replaced with the corrsponding
+    // expanded string.
+    // If the path does not begin with %CommonProgramFiles% we use it as is.
+    if (common_program_files_offset != base::string16::npos) {
+      // Preserve the beginning quote in the path.
+      osk_path_.erase(common_program_files_offset,
+                      wcslen(L"%commonprogramfiles%"));
+      // The path read from the registry contains the %CommonProgramFiles%
+      // environment variable prefix. On 64 bit Windows the SHGetKnownFolderPath
+      // function returns the common program files path with the X86 suffix for
+      // the FOLDERID_ProgramFilesCommon value.
+      // To get the correct path to TabTip.exe we first read the environment
+      // variable CommonProgramW6432 which points to the desired common
+      // files path. Failing that we fallback to the SHGetKnownFolderPath API.
+
+      // We then replace the %CommonProgramFiles% value with the actual common
+      // files path found in the process.
+      base::string16 common_program_files_path;
+      DWORD buffer_size =
+          GetEnvironmentVariable(L"CommonProgramW6432", nullptr, 0);
+      if (buffer_size) {
+        GetEnvironmentVariable(
+            L"CommonProgramW6432",
+            base::WriteInto(&common_program_files_path, buffer_size),
+            buffer_size);
+        DCHECK(!common_program_files_path.empty());
+      } else {
+        base::win::ScopedCoMem<wchar_t> common_program_files;
+        if (FAILED(SHGetKnownFolderPath(FOLDERID_ProgramFilesCommon, 0, nullptr,
+                                        &common_program_files))) {
+          return false;
+        }
+        common_program_files_path = common_program_files;
+      }
+
+      osk_path_.insert(common_program_files_offset, common_program_files_path);
+    }
+  }
+
+  HINSTANCE ret = ::ShellExecuteW(nullptr, L"", osk_path_.c_str(), nullptr,
+                                  nullptr, SW_SHOW);
+
+  bool success = reinterpret_cast<intptr_t>(ret) > 32;
+  if (success) {
+    // If multiple calls to DisplayVirtualKeyboard occur one after the other,
+    // the last observer would be the one to get notifications.
+    keyboard_detector_.reset(new OnScreenKeyboardDetector);
+    if (observer)
+      keyboard_detector_->AddObserver(observer);
+    keyboard_detector_->DetectKeyboard(::GetForegroundWindow());
+  }
+  return success;
+}
+
+bool OnScreenKeyboardDisplayManager::DismissVirtualKeyboard() {
+  if (base::win::GetVersion() < base::win::VERSION_WIN8)
+    return false;
+
+  bool ret = false;

[grt (UTC plus 2), 2016/05/20 14:56:35]

nit:
  return keyboard_detector_ ? keyboard_detector_->DismissKeyboard() : false;

[ananta, 2016/05/20 19:32:55]

Done.

+  if (keyboard_detector_.get())
+    ret = keyboard_detector_->DismissKeyboard();
+  return ret;
+}
+
+}  // namespace ui