Added a system caret used for accessibility on Windows.

ui/views/win/hwnd_message_handler.cc

 // Copyright (c) 2012 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/views/win/hwnd_message_handler.h"
 
 #include <dwmapi.h>
 #include <oleacc.h>
 #include <shellapi.h>
 #include <tchar.h>
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/debug/alias.h"
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
+#include "base/win/scoped_comptr.h"
 #include "base/win/scoped_gdi_object.h"
 #include "base/win/windows_version.h"
+#include "ui/accessibility/platform/ax_fake_caret_win.h"
+#include "ui/accessibility/platform/ax_platform_node_win.h"
+#include "ui/base/ime/input_method.h"
+#include "ui/base/ime/text_input_client.h"
+#include "ui/base/ime/text_input_type.h"
 #include "ui/base/view_prop.h"
 #include "ui/base/win/internal_constants.h"
 #include "ui/base/win/lock_state.h"
 #include "ui/base/win/mouse_wheel_util.h"
 #include "ui/base/win/shell.h"
 #include "ui/base/win/touch_input.h"
 #include "ui/display/win/dpi.h"
 #include "ui/display/win/screen_win.h"
 #include "ui/events/event.h"
 #include "ui/events/event_constants.h"
@@ skipping 342 matching lines @@
                  GetProcAddress(GetModuleHandle(L"user32.dll"),
                                 "EnableChildWindowDpiMessage"));
     }();
     if (enable_child_window_dpi_message_func)
       enable_child_window_dpi_message_func(hwnd(), TRUE);
   }
 
   prop_window_target_.reset(new ui::ViewProp(hwnd(),
                             ui::WindowEventTarget::kWin32InputEventTarget,
                             static_cast<ui::WindowEventTarget*>(this)));
+  delegate_->AddInputMethodObserver(this);
 
   // Direct Manipulation is enabled on Windows 10+. The CreateInstance function
   // returns NULL if Direct Manipulation is not available.
   direct_manipulation_helper_ =
       gfx::win::DirectManipulationHelper::CreateInstance();
   if (direct_manipulation_helper_)
     direct_manipulation_helper_->Initialize(hwnd());
 
   // Disable pen flicks (http://crbug.com/506977)
   base::win::DisableFlicks(hwnd());
@@ skipping 524 matching lines @@
     // DefWindowProc() may have destroyed the window and/or us in a nested
     // message loop.
     if (!ref || !::IsWindow(window))
       return result;
   }
 
   if (delegate_) {
     delegate_->PostHandleMSG(message, w_param, l_param);
     if (message == WM_NCDESTROY) {
       RestoreEnabledIfNecessary();
+      delegate_->RemoveInputMethodObserver(this);

[sky, 2017/06/19 15:00:14]

Why do you need to remove the observer here? More specifically, can it be
removed from the destructor?

+      DestroyFakeCaret();

[sky, 2017/06/19 15:00:14]

Similarly why does the fake care need to be destroyed here, why not the
destructor?

       delegate_->HandleDestroyed();
     }
   }
 
   if (message == WM_ACTIVATE && IsTopLevelWindow(window))
     PostProcessActivateMessage(LOWORD(w_param), !!HIWORD(w_param),
                                reinterpret_cast<HWND>(l_param));
   return result;
 }
 
+void HWNDMessageHandler::OnCaretBoundsChanged(
+    const ui::TextInputClient* client) {
+  if (!client || client->GetTextInputType() == ui::TEXT_INPUT_TYPE_NONE)
+    return;
+
+  if (!ax_fake_caret_)
+    ax_fake_caret_ = std::make_unique<ui::AXFakeCaretWin>(hwnd());
+
+  const gfx::Rect dip_caret_bounds(client->GetCaretBounds());
+  gfx::Rect caret_bounds =
+      display::win::ScreenWin::DIPToScreenRect(hwnd(), dip_caret_bounds);
+  // Collapse any selection.
+  caret_bounds.set_width(1);
+  ax_fake_caret_->MoveCaretTo(caret_bounds);
+}
+
+void HWNDMessageHandler::OnTextInputTypeChanged(
+    const ui::TextInputClient* client) {
+  if (!client || client->GetTextInputType() == ui::TEXT_INPUT_TYPE_NONE) {
+    DestroyFakeCaret();
+    return;
+  }
+
+  OnCaretBoundsChanged(client);
+}
+
+void HWNDMessageHandler::OnInputMethodDestroyed(
+    const ui::InputMethod* input_method) {
+  DestroyFakeCaret();
+}
+
 LRESULT HWNDMessageHandler::HandleMouseMessage(unsigned int message,
                                                WPARAM w_param,
                                                LPARAM l_param,
                                                bool* handled) {
   // Don't track forwarded mouse messages. We expect the caller to track the
   // mouse.
   base::WeakPtr<HWNDMessageHandler> ref(weak_factory_.GetWeakPtr());
   LRESULT ret = HandleMouseEventInternal(message, w_param, l_param, false);
   *handled = IsMsgHandled();
   return ret;
@@ skipping 564 matching lines @@
 
   // Only the lower 32 bits of l_param are valid when checking the object id
   // because it sometimes gets sign-extended incorrectly (but not always).
   DWORD obj_id = static_cast<DWORD>(static_cast<DWORD_PTR>(l_param));
 
   // Accessibility readers will send an OBJID_CLIENT message
   if (static_cast<DWORD>(OBJID_CLIENT) == obj_id) {
     // Retrieve MSAA dispatch object for the root view.
     base::win::ScopedComPtr<IAccessible> root(
         delegate_->GetNativeViewAccessible());
-
-    // Create a reference that MSAA will marshall to the client.
     reference_result = LresultFromObject(IID_IAccessible, w_param,
         static_cast<IAccessible*>(root.Detach()));
+  } else if (::GetFocus() == hwnd() && ax_fake_caret_ &&
+             static_cast<DWORD>(OBJID_CARET) == obj_id) {
+    base::win::ScopedComPtr<IAccessible> fake_caret_accessible =
+        ax_fake_caret_->GetCaret();
+    reference_result = LresultFromObject(IID_IAccessible, w_param,
+                                         fake_caret_accessible.Detach());
   }
 
   return reference_result;
 }
 
 LRESULT HWNDMessageHandler::OnImeMessages(UINT message,
                                           WPARAM w_param,
                                           LPARAM l_param) {
   LRESULT result = 0;
   base::WeakPtr<HWNDMessageHandler> ref(weak_factory_.GetWeakPtr());
@@ skipping 703 matching lines @@
   // Ignore size/move/maximize in fullscreen mode.
   if (IsFullscreen() && (((notification_code & sc_mask) == SC_SIZE) ||
                          ((notification_code & sc_mask) == SC_MOVE) ||
                          ((notification_code & sc_mask) == SC_MAXIMIZE)))
     return;
   if (delegate_->GetFrameMode() == FrameMode::CUSTOM_DRAWN) {
     if ((notification_code & sc_mask) == SC_MINIMIZE ||
         (notification_code & sc_mask) == SC_MAXIMIZE ||
         (notification_code & sc_mask) == SC_RESTORE) {
       delegate_->ResetWindowControls();
+      DestroyFakeCaret();
     } else if ((notification_code & sc_mask) == SC_MOVE ||
                (notification_code & sc_mask) == SC_SIZE) {
       if (!IsVisible()) {
         // Circumvent ScopedRedrawLocks and force visibility before entering a
         // resize or move modal loop to get continuous sizing/moving feedback.
         SetWindowLong(hwnd(), GWL_STYLE,
                       GetWindowLong(hwnd(), GWL_STYLE) | WS_VISIBLE);
       }
+      DestroyFakeCaret();
     }
   }
 
   // Handle SC_KEYMENU, which means that the user has pressed the ALT
   // key and released it, so we should focus the menu bar.
   if ((notification_code & sc_mask) == SC_KEYMENU && point.x() == 0) {
     int modifiers = ui::EF_NONE;
     if (ui::win::IsShiftPressed())
       modifiers |= ui::EF_SHIFT_DOWN;
     if (ui::win::IsCtrlPressed())
@@ skipping 641 matching lines @@
   // not treat this like a fullscreen window.
   MONITORINFO monitor_info = {sizeof(monitor_info)};
   GetMonitorInfo(MonitorFromWindow(hwnd(), MONITOR_DEFAULTTOPRIMARY),
                  &monitor_info);
   gfx::Rect shrunk_rect(monitor_info.rcMonitor);
   shrunk_rect.set_height(shrunk_rect.height() - 1);
   background_fullscreen_hack_ = true;
   SetBoundsInternal(shrunk_rect, false);
 }
 
+void HWNDMessageHandler::DestroyFakeCaret() {
+  ax_fake_caret_ = nullptr;
+}
+
 }  // namespace views