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

base/win/osk_display_manager.cc

Index: base/win/osk_display_manager.cc
diff --git a/base/win/osk_display_manager.cc b/base/win/osk_display_manager.cc
new file mode 100644
index 0000000000000000000000000000000000000000..4b0017cf41c6eae42157d31d88718711673dc70b
--- /dev/null
+++ b/base/win/osk_display_manager.cc
@@ -0,0 +1,256 @@
+// Copyright (c) 2016 The Chromium Authors. All rights reserved.

[grt (UTC plus 2), 2016/05/18 15:41:19]

(c)

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "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"
+
+namespace base {
+namespace win {
+
+static const int kCheckOSKDelayMs = 1000;
+static const wchar_t kOSKClassName[] = L"IPTip_Main_Window";
+
+const wchar_t kWindows8OSKRegPath[] =
+    L"Software\\Classes\\CLSID\\{054AAE20-4BEA-4347-8A35-64A533254A9D}"
+    L"\\LocalServer32";
+
+OnScreenKeyboardDetector::OnScreenKeyboardDetector()
+    : main_window_(nullptr),
+      keyboard_detector_factory_(this),
+      osk_visible_notification_received_(false) {
+  memset(&osk_rect_, 0, sizeof(osk_rect_));
+}
+
+OnScreenKeyboardDetector::~OnScreenKeyboardDetector() {
+  ClearObservers();

[grt (UTC plus 2), 2016/05/18 15:41:19]

is this needed? can you just let the list self-destruct without emptying it (and
set the check_empty template param to false in the .h)?

[ananta, 2016/05/19 01:57:11]

Done.

+}
+
+void OnScreenKeyboardDetector::DetectKeyboard(HWND main_window) {
+  main_window_ = main_window;
+  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)) {
+    HandleKeyboardHidden();
+    PostMessage(osk, WM_SYSCOMMAND, SC_CLOSE, 0);
+    return true;
+  }
+  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;
+
+  ::GetWindowRect(osk, &osk_rect_);
+  if (check_for_activation) {
+    if (::IsWindowVisible(osk) && ::IsWindowEnabled(osk)) {
+      if (!osk_visible_notification_received_) {

[grt (UTC plus 2), 2016/05/18 15:41:19]

nit: omit braces

[ananta, 2016/05/19 01:57:11]

Done.

+        HandleKeyboardVisible();
+      }
+    } else {
+      DVLOG(1) << "OSK did not come up in 1 second. Something wrong.";
+    }
+  } else {
+    // Two cases here.

[grt (UTC plus 2), 2016/05/18 15:41:19]

looks like the code handles three cases. could you document the PostDelayedTask
case here, too?

[ananta, 2016/05/19 01:57:12]

Done.

+    // OSK was hidden because the user dismissed it.
+    // We are no longer in the foreground.
+    // 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();
+        ClearObservers();
+      }
+    } 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_));
+
+  // 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_));
+}
+
+void OnScreenKeyboardDetector::ClearObservers() {
+  base::ObserverListBase<OnScreenKeyboardObserver>::Iterator iter(&observers_);
+  for (OnScreenKeyboardObserver* observer = iter.GetNext(); observer;
+    observer = iter.GetNext()) {
+    RemoveObserver(observer);
+  }
+}
+
+OnScreenKeyboardDisplayManager* OnScreenKeyboardDisplayManager::GetInstance() {
+  return base::Singleton<OnScreenKeyboardDisplayManager,

[grt (UTC plus 2), 2016/05/18 15:41:19]

is a leaky lazy instance appropriate here?

[ananta, 2016/05/19 01:57:11]

That would work as well. Changed.

+      base::StaticMemorySingletonTraits<
+          OnScreenKeyboardDisplayManager>>::get();
+}
+
+bool OnScreenKeyboardDisplayManager::DisplayVirtualKeyboard(
+    OnScreenKeyboardObserver* observer) {
+  if (GetVersion() < VERSION_WIN8)
+    return false;
+
+  if (IsKeyboardPresentOnSlate(nullptr))
+    return false;
+
+  static LazyInstance<string16>::Leaky osk_path = LAZY_INSTANCE_INITIALIZER;

[grt (UTC plus 2), 2016/05/18 15:41:19]

OnScreenKeyboardDisplayManager is a singleton. why does the path need to be a
local lazy instance rather than an instance member of the class?

[ananta, 2016/05/19 01:57:11]

Yes. Moved this function into a class without inspecting the code fully. Thanks
for finding this. Changed.

+
+  if (osk_path.Get().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.
+    RegKey key(HKEY_LOCAL_MACHINE, kWindows8OSKRegPath,
+      KEY_READ | KEY_WOW64_64KEY);
+    DWORD osk_path_length = 1024;
+    if (key.ReadValue(NULL,
+      WriteInto(&osk_path.Get(), osk_path_length),

[grt (UTC plus 2), 2016/05/18 15:41:19]

note that WriteInto doesn't update the size of the string, so osk_path.size()
will return 1024 at this point, and operations will look at the full size of the
buffer. i propose trimming the string with something like
osk_path.resize(base::string16::traits_type::length(osk_path.c_str()));

[ananta, 2016/05/19 01:57:12]

Done.

+      &osk_path_length,
+      NULL) != ERROR_SUCCESS) {
+      DLOG(WARNING) << "Failed to read on screen keyboard path from registry";
+      return false;
+    }
+    size_t common_program_files_offset =
+      osk_path.Get().find(L"%CommonProgramFiles%");

[grt (UTC plus 2), 2016/05/18 15:41:20]

case-insensitive?

+    // 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 != string16::npos) {
+      // Preserve the beginning quote in the path.
+      osk_path.Get().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.
+      string16 common_program_files_path;
+      std::unique_ptr<wchar_t[]> common_program_files_wow6432;
+      DWORD buffer_size =
+        GetEnvironmentVariable(L"CommonProgramW6432", NULL, 0);

[grt (UTC plus 2), 2016/05/18 15:41:19]

nullptr

[ananta, 2016/05/19 01:57:12]

Done.

+      if (buffer_size) {
+        common_program_files_wow6432.reset(new wchar_t[buffer_size]);
+        GetEnvironmentVariable(L"CommonProgramW6432",
+          common_program_files_wow6432.get(),

[grt (UTC plus 2), 2016/05/18 15:41:20]

WriteInto(&common_program_files_path, buffer_size)?

[ananta, 2016/05/19 01:57:11]

Thanks. done.

+          buffer_size);
+        common_program_files_path = common_program_files_wow6432.get();
+        DCHECK(!common_program_files_path.empty());
+      }
+      else {
+        ScopedCoMem<wchar_t> common_program_files;
+        if (FAILED(SHGetKnownFolderPath(FOLDERID_ProgramFilesCommon, 0, NULL,

[grt (UTC plus 2), 2016/05/18 15:41:19]

nullptr

[ananta, 2016/05/19 01:57:11]

Done.

+          &common_program_files))) {
+          return false;
+        }
+        common_program_files_path = common_program_files;
+      }
+
+      osk_path.Get().insert(1, common_program_files_path);

[grt (UTC plus 2), 2016/05/18 15:41:19]

1 -> common_program_files_offset?

[ananta, 2016/05/19 01:57:12]

Yes. done.

+    }
+  }
+
+  HINSTANCE ret = ::ShellExecuteW(NULL,

[grt (UTC plus 2), 2016/05/18 15:41:19]

nullptr all the things ;-)

[ananta, 2016/05/19 01:57:12]

Done.

+    L"",
+    osk_path.Get().c_str(),
+    NULL,
+    NULL,
+    SW_SHOW);
+
+  bool success = reinterpret_cast<intptr_t>(ret) > 32;
+  if (success) {
+    keyboard_detector_.reset(new OnScreenKeyboardDetector);

[grt (UTC plus 2), 2016/05/18 15:41:20]

since this is a singleton, two callers to DisplayVirtualKeyboard will stomp on
one another. is this what you really want?

[ananta, 2016/05/19 01:57:11]

It does not matter in this use case as the callers are on the UI thread and
hence will be serialized.

+    if (observer)
+      keyboard_detector_->AddObserver(observer);
+    keyboard_detector_->DetectKeyboard(::GetForegroundWindow());
+  }
+  return success;
+}
+
+bool OnScreenKeyboardDisplayManager::DismissVirtualKeyboard(
+    OnScreenKeyboardObserver* observer) {
+  if (GetVersion() < VERSION_WIN8)
+    return false;
+
+  DCHECK(keyboard_detector_.get());
+  bool ret = keyboard_detector_->DismissKeyboard();
+  if (observer)
+    keyboard_detector_->RemoveObserver(observer);
+  return ret;
+}
+
+}  // namespace win
+}  // namespace base
+