modules/desktop_capture/win/full_screen_win_application_handler.cc

/*
 *  Copyright (c) 2019 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include "modules/desktop_capture/win/full_screen_win_application_handler.h"

#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <cwchar>
#include <cwctype>
#include <iterator>
#include <memory>
#include <string>
#include <vector>

#include "absl/strings/ascii.h"
#include "absl/strings/match.h"
#include "absl/strings/string_view.h"
#include "modules/desktop_capture/desktop_capturer.h"
#include "modules/desktop_capture/full_screen_application_handler.h"
#include "rtc_base/logging.h"  // For RTC_LOG_GLE
#include "rtc_base/string_utils.h"
#include "system_wrappers/include/metrics.h"

void RecordFullScreenDetectorResult(FullScreenDetectorResult result) {
  RTC_HISTOGRAM_ENUMERATION(
      "WebRTC.Screenshare.FullScreenDetectorResult", static_cast<int>(result),
      static_cast<int>(FullScreenDetectorResult::kMaxValue));
}

namespace webrtc {
namespace {

// Utility function to verify that `window` has class name equal to `class_name`
bool CheckWindowClassName(HWND window, const wchar_t* class_name) {
  const size_t classNameLength = wcslen(class_name);

  // https://docs.microsoft.com/en-us/windows/win32/api/winuser/ns-winuser-wndclassa
  // says lpszClassName field in WNDCLASS is limited by 256 symbols, so we don't
  // need to have a buffer bigger than that.
  constexpr size_t kMaxClassNameLength = 256;
  WCHAR buffer[kMaxClassNameLength];

  const int length = ::GetClassNameW(window, buffer, kMaxClassNameLength);
  if (length <= 0) {
    return false;
  }

  if (static_cast<size_t>(length) != classNameLength) {
    return false;
  }
  return wcsncmp(buffer, class_name, classNameLength) == 0;
}

bool IsFullScreenWindow(HWND wnd) {
  // Get the monitor info of the display monitor where the window is.
  MONITORINFO monitor_info = {sizeof(monitor_info)};
  if (!::GetMonitorInfo(::MonitorFromWindow(wnd, MONITOR_DEFAULTTONEAREST),
                        &monitor_info)) {
    return false;
  }

  // Verifies if the window rectangle is same as the monitor.
  RECT wnd_rect;
  if (!::GetWindowRect(wnd, &wnd_rect) ||
      !::EqualRect(&wnd_rect, &monitor_info.rcMonitor)) {
    return false;
  }

  // Check if the window style does not have WS_OVERLAPPEDWINDOW as the full
  // screen window should not have a title bar or border.
  return !(::GetWindowLongPtr(wnd, GWL_STYLE) & WS_OVERLAPPEDWINDOW);
}

std::string WindowText(HWND window) {
  size_t len = ::GetWindowTextLength(window);
  if (len == 0) {
    return std::string();
  }

  std::vector<wchar_t> buffer(len + 1, 0);
  size_t copied = ::GetWindowTextW(window, buffer.data(), buffer.size());
  if (copied == 0) {
    return std::string();
  }
  return ToUtf8(buffer.data(), copied);
}

DWORD WindowProcessId(HWND window) {
  DWORD dwProcessId = 0;
  ::GetWindowThreadProcessId(window, &dwProcessId);
  return dwProcessId;
}

std::wstring FileNameFromPath(const std::wstring& path) {
  auto found = path.rfind(L"\\");
  if (found == std::string::npos) {
    return path;
  }
  return path.substr(found + 1);
}

// Returns windows which belong to given process id
// `sources` is a full list of available windows
// `processId` is a process identifier (window owner)
// `window_to_exclude` is a window to be exluded from result
DesktopCapturer::SourceList GetProcessWindows(
    const DesktopCapturer::SourceList& sources,
    DWORD processId,
    HWND window_to_exclude) {
  DesktopCapturer::SourceList result;
  std::copy_if(sources.begin(), sources.end(), std::back_inserter(result),
               [&](DesktopCapturer::Source source) {
                 const HWND source_hwnd = reinterpret_cast<HWND>(source.id);
                 return window_to_exclude != source_hwnd &&
                        WindowProcessId(source_hwnd) == processId;
               });
  return result;
}
}  // namespace

FullScreenPowerPointHandler::FullScreenPowerPointHandler(
    DesktopCapturer::SourceId sourceId)
    : FullScreenApplicationHandler(sourceId),
      was_slide_show_created_after_capture_started_(false),
      full_screen_detector_result_(FullScreenDetectorResult::kUnknown) {}

DesktopCapturer::SourceId FullScreenPowerPointHandler::FindFullScreenWindow(
    const DesktopCapturer::SourceList& window_list,
    int64_t timestamp) const {
  if (!UseHeuristicFullscreenPowerPointWindows() || window_list.empty()) {
    return 0;
  }

  HWND original_window = reinterpret_cast<HWND>(GetSourceId());
  if (GetWindowType(original_window) != WindowType::kEditor) {
    return 0;
  }

  DesktopCapturer::SourceList powerpoint_windows = GetProcessWindows(
      window_list, WindowProcessId(original_window), original_window);

  // No relevant windows with the same process id as the `original_window` were
  // found.
  if (powerpoint_windows.empty()) {
    was_slide_show_created_after_capture_started_ = true;
    return 0;
  }

  bool do_same_title_editors_exist = false;
  bool does_slide_show_exist = false;
  DesktopCapturer::SourceId full_screen_slide_show_id = 0;
  const std::string original_document_title =
      GetDocumentTitleFromEditor(original_window);
  auto result = full_screen_detector_result_;
  for (const auto& source : powerpoint_windows) {
    HWND window = reinterpret_cast<HWND>(source.id);

    // If another PowerPoint editor window with the same title exists, then we
    // don't use the heuristic as we don't know which editor has opened the
    // slide show.
    if (GetWindowType(window) == WindowType::kEditor &&
        GetDocumentTitleFromEditor(window) == original_document_title) {
      do_same_title_editors_exist = true;
      result = FullScreenDetectorResult::kFailureDueToSameTitleWindows;
    }

    // Looking for fullscreen slide show window for the corresponding editor
    // document.
    if (GetWindowType(window) == WindowType::kSlideShow &&
        GetDocumentTitleFromSlideShow(window) == original_document_title) {
      does_slide_show_exist = true;
      full_screen_slide_show_id = source.id;
    }
  }
  if (does_slide_show_exist) {
    if (!was_slide_show_created_after_capture_started_) {
      full_screen_slide_show_id = 0;
      result = FullScreenDetectorResult::kFailureDueToSlideShowWasNotChosen;
    } else if (do_same_title_editors_exist) {
      full_screen_slide_show_id = 0;
      result = FullScreenDetectorResult::kFailureDueToSameTitleWindows;
    } else {
      result = FullScreenDetectorResult::kSuccess;
    }
  } else {
    was_slide_show_created_after_capture_started_ = true;
  }

  if (full_screen_detector_result_ != result) {
    full_screen_detector_result_ = result;
    RecordFullScreenDetectorResult(result);
  }
  return full_screen_slide_show_id;
}

void FullScreenPowerPointHandler::SetSlideShowCreationStateForTest(
    bool fullscreen_slide_show_started_after_capture_start) {
  was_slide_show_created_after_capture_started_ =
      fullscreen_slide_show_started_after_capture_start;
}

FullScreenPowerPointHandler::WindowType
FullScreenPowerPointHandler::GetWindowType(HWND window) const {
  if (IsEditorWindow(window)) {
    return WindowType::kEditor;
  } else if (IsSlideShowWindow(window)) {
    return WindowType::kSlideShow;
  }

  return WindowType::kOther;
}

constexpr static char kDocumentTitleSeparator = '-';

std::string FullScreenPowerPointHandler::GetDocumentTitleFromEditor(
    HWND window) const {
  std::string title = WindowText(window);
  return std::string(absl::StripAsciiWhitespace(absl::string_view(title).substr(
      0, title.rfind(kDocumentTitleSeparator))));
}

std::string FullScreenPowerPointHandler::GetDocumentTitleFromSlideShow(
    HWND window) const {
  std::string title = WindowText(window);
  size_t position = title.find(kDocumentTitleSeparator);
  if (position != std::string::npos) {
    title = absl::StripAsciiWhitespace(
        absl::string_view(title).substr(position + 1, std::wstring::npos));
  }

  size_t left_bracket_pos = title.find("[");
  size_t right_bracket_pos = title.rfind("]");
  if (left_bracket_pos == std::string::npos ||
      right_bracket_pos == std::string::npos ||
      right_bracket_pos <= left_bracket_pos) {
    return title;
  }

  return std::string(absl::StripAsciiWhitespace(title.substr(
      left_bracket_pos + 1, right_bracket_pos - left_bracket_pos - 1)));
}

bool FullScreenPowerPointHandler::IsEditorWindow(HWND window) const {
  return CheckWindowClassName(window, L"PPTFrameClass");
}

bool FullScreenPowerPointHandler::IsSlideShowWindow(HWND window) const {
  return CheckWindowClassName(window, L"screenClass") &&
         IsFullScreenWindow(window);
}

class OpenOfficeApplicationHandler : public FullScreenApplicationHandler {
 public:
  explicit OpenOfficeApplicationHandler(DesktopCapturer::SourceId sourceId)
      : FullScreenApplicationHandler(sourceId) {}

  DesktopCapturer::SourceId FindFullScreenWindow(
      const DesktopCapturer::SourceList& window_list,
      int64_t timestamp) const override {
    if (window_list.empty()) {
      return 0;
    }

    DWORD process_id = WindowProcessId(reinterpret_cast<HWND>(GetSourceId()));

    DesktopCapturer::SourceList app_windows =
        GetProcessWindows(window_list, process_id, nullptr);

    DesktopCapturer::SourceList document_windows;
    std::copy_if(
        app_windows.begin(), app_windows.end(),
        std::back_inserter(document_windows),
        [this](const DesktopCapturer::Source& x) { return IsEditorWindow(x); });

    // Check if we have only one document window, otherwise it's not possible
    // to securely match a document window and a slide show window which has
    // empty title.
    if (document_windows.size() != 1) {
      return 0;
    }

    // Check if document window has been selected as a source
    if (document_windows.front().id != GetSourceId()) {
      return 0;
    }

    // Check if we have a slide show window.
    auto slide_show_window =
        std::find_if(app_windows.begin(), app_windows.end(),
                     [this](const DesktopCapturer::Source& x) {
                       return IsSlideShowWindow(x);
                     });

    if (slide_show_window == app_windows.end()) {
      return 0;
    }

    return slide_show_window->id;
  }

 private:
  bool IsEditorWindow(const DesktopCapturer::Source& source) const {
    if (source.title.empty()) {
      return false;
    }

    return CheckWindowClassName(reinterpret_cast<HWND>(source.id), L"SALFRAME");
  }

  bool IsSlideShowWindow(const DesktopCapturer::Source& source) const {
    // Check title size to filter out a Presenter Control window which shares
    // window class with Slide Show window but has non empty title.
    if (!source.title.empty()) {
      return false;
    }

    return CheckWindowClassName(reinterpret_cast<HWND>(source.id),
                                L"SALTMPSUBFRAME");
  }
};

std::wstring GetPathByWindowId(HWND window_id) {
  DWORD process_id = WindowProcessId(window_id);
  HANDLE process =
      ::OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION, FALSE, process_id);
  if (process == NULL) {
    return L"";
  }
  DWORD path_len = MAX_PATH;
  WCHAR path[MAX_PATH];
  std::wstring result;
  if (::QueryFullProcessImageNameW(process, 0, path, &path_len)) {
    result = std::wstring(path, path_len);
  } else {
    RTC_LOG_GLE(LS_ERROR) << "QueryFullProcessImageName failed.";
  }

  ::CloseHandle(process);
  return result;
}

std::unique_ptr<FullScreenApplicationHandler>
CreateFullScreenWinApplicationHandler(DesktopCapturer::SourceId source_id) {
  std::unique_ptr<FullScreenApplicationHandler> result;
  HWND hwnd = reinterpret_cast<HWND>(source_id);
  std::wstring exe_path = GetPathByWindowId(hwnd);
  std::wstring file_name = FileNameFromPath(exe_path);
  std::transform(file_name.begin(), file_name.end(), file_name.begin(),
                 std::towupper);

  if (file_name == L"POWERPNT.EXE") {
    result = std::make_unique<FullScreenPowerPointHandler>(source_id);
  } else if (file_name == L"SOFFICE.BIN" &&
             absl::EndsWith(WindowText(hwnd), "OpenOffice Impress")) {
    result = std::make_unique<OpenOfficeApplicationHandler>(source_id);
  }

  return result;
}

}  // namespace webrtc