src/win32/base/win32_window_util.cc

// Copyright 2010-2015, Google Inc.
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#include "win32/base/win32_window_util.h"

#define _ATL_NO_AUTOMATIC_NAMESPACE
#define _WTL_NO_AUTOMATIC_NAMESPACE
#define _ATL_NO_HOSTING
// Workaround against KB813540
#include <atlbase_mozc.h>
#include <atlapp.h>
#include <atlwin.h>
#include <atlstr.h>

#include <memory>

#include "base/logging.h"
#include "base/port.h"
#include "base/system_util.h"
#include "base/win_util.h"

namespace mozc {
namespace win32 {
namespace {

using ATL::CWindow;
using ATL::CStringW;
using std::unique_ptr;

wstring SafeGetWindowText(HWND window_handle) {
  if (!::IsWindow(window_handle)) {
    return wstring();
  }

  const int text_len_without_null = GetWindowTextLength(window_handle);
  if (text_len_without_null <= 0) {
    return wstring();
  }

  const size_t buffer_len = text_len_without_null + 1;
  unique_ptr<wchar_t[]> buffer(new wchar_t[buffer_len]);

  const int copied_len_without_null = GetWindowText(
      window_handle, buffer.get(), buffer_len);

  if (copied_len_without_null <= 0) {
    return wstring();
  }

  return wstring(buffer.get(), copied_len_without_null);
}

}  // namespace

wstring WindowUtil::GetWindowClassName(HWND window_handle) {
  // Maximum length of WindowClass is assumed to be 256.
  // http://msdn.microsoft.com/en-us/library/ms633576.aspx
  wchar_t buffer[256 + 1] = {};
  const size_t num_copied_without_null = ::GetClassNameW(
      window_handle, buffer, arraysize(buffer));
  if (num_copied_without_null + 1 >= arraysize(buffer)) {
    return L"";
  }
  return wstring(buffer, num_copied_without_null);
}

// static
bool WindowUtil::ChangeMessageFilter(HWND window_handle, UINT message) {
  typedef BOOL (WINAPI *FPChangeWindowMessageFilter)(UINT, DWORD);
  typedef BOOL (WINAPI *FPChangeWindowMessageFilterEx)(
      HWND, UINT, DWORD, LPVOID);

  // Following constants are not available unless we change the WINVER
  // higher enough.
  const int kMessageFilterAdd = 1;    // MSGFLT_ADD    (WINVER >=0x0600)
  const int kMessageFilterAllow = 1;  // MSGFLT_ALLOW  (WINVER >=0x0601)

  // Skip windows XP.
  // ChangeWindowMessageFilter is only available on Windows Vista or Later
  if (!SystemUtil::IsVistaOrLater()) {
    LOG(ERROR) << "Skip ChangeWindowMessageFilter on Windows XP";
    return true;
  }

  const HMODULE lib = WinUtil::GetSystemModuleHandle(L"user32.dll");
  if (lib == nullptr) {
    LOG(ERROR) << L"GetModuleHandle for user32.dll failed.";
    return false;
  }

  // Windows 7+
  // http://msdn.microsoft.com/en-us/library/dd388202.aspx
  FPChangeWindowMessageFilterEx change_window_message_filter_ex
      = reinterpret_cast<FPChangeWindowMessageFilterEx>(
          ::GetProcAddress(lib, "ChangeWindowMessageFilterEx"));
  if (change_window_message_filter_ex != nullptr) {
    // Windows 7+ only
    if (!(*change_window_message_filter_ex)(
            window_handle, message, kMessageFilterAllow, nullptr)) {
      // Note: this actually fails in Internet Explorer 10 on Windows 8
      // with ERROR_ACCESS_DENIED (0x5).
      const int error = ::GetLastError();
      VLOG(1) << L"ChangeWindowMessageFilterEx failed. error = " << error;
      return false;
    }
    return true;
  }

  // Windows Vista
  FPChangeWindowMessageFilter change_window_message_filter
      = reinterpret_cast<FPChangeWindowMessageFilter>(
          ::GetProcAddress(lib, "ChangeWindowMessageFilter"));
  if (change_window_message_filter == nullptr) {
    const int error = ::GetLastError();
    LOG(ERROR) << L"GetProcAddress failed. error = " << error;
    return false;
  }

  DCHECK(change_window_message_filter != nullptr);
  if (!(*change_window_message_filter)(message, kMessageFilterAdd)) {
    const int error = ::GetLastError();
    LOG(ERROR) << L"ChangeWindowMessageFilter failed. error = " << error;
    return false;
  }

  return true;
}

}  // namespace win32
}  // namespace mozc