blob: fe696eba67de880e29db77c13d2caa843dfc2e34 [file] [log] [blame]
* Copyright (c) 2014 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 "webrtc/modules/desktop_capture/cropping_window_capturer.h"
#include "webrtc/base/win32.h"
#include "webrtc/modules/desktop_capture/win/scoped_gdi_object.h"
#include "webrtc/modules/desktop_capture/win/screen_capture_utils.h"
#include "webrtc/modules/desktop_capture/win/window_capture_utils.h"
#include "webrtc/system_wrappers/include/logging.h"
namespace webrtc {
namespace {
// Used to pass input/output data during the EnumWindow call for verifying if
// the selected window is on top.
struct TopWindowVerifierContext {
TopWindowVerifierContext(HWND selected_window, HWND excluded_window)
: selected_window(selected_window),
selected_window_process_id(0) {}
HWND selected_window;
HWND excluded_window;
bool is_top_window;
DWORD selected_window_process_id;
DesktopRect selected_window_rect;
// The function is called during EnumWindow for every window enumerated and is
// responsible for verifying if the selected window is on top.
BOOL CALLBACK TopWindowVerifier(HWND hwnd, LPARAM param) {
TopWindowVerifierContext* context =
if (hwnd == context->selected_window) {
context->is_top_window = true;
return FALSE;
// Ignore the excluded window.
if (hwnd == context->excluded_window) {
return TRUE;
// Ignore hidden or minimized window.
if (IsIconic(hwnd) || !IsWindowVisible(hwnd)) {
return TRUE;
// Ignore descendant/owned windows since we want to capture them.
// This check does not work for tooltips and context menus. Drop down menus
// and popup windows are fine.
if (GetAncestor(hwnd, GA_ROOTOWNER) == context->selected_window) {
return TRUE;
// If |hwnd| has no title and belongs to the same process, assume it's a
// tooltip or context menu from the selected window and ignore it.
const size_t kTitleLength = 32;
WCHAR window_title[kTitleLength];
GetWindowText(hwnd, window_title, kTitleLength);
if (wcsnlen_s(window_title, kTitleLength) == 0) {
DWORD enumerated_process;
GetWindowThreadProcessId(hwnd, &enumerated_process);
if (!context->selected_window_process_id) {
if (context->selected_window_process_id == enumerated_process) {
return TRUE;
// Check if the enumerated window intersects with the selected window.
RECT enumerated_rect;
if (!GetWindowRect(hwnd, &enumerated_rect)) {
// Bail out if failed to get the window area.
context->is_top_window = false;
return FALSE;
DesktopRect intersect_rect = context->selected_window_rect;
DesktopRect enumerated_desktop_rect =
// If intersection is not empty, the selected window is not on top.
if (!intersect_rect.is_empty()) {
context->is_top_window = false;
return FALSE;
// Otherwise, keep enumerating.
return TRUE;
class CroppingWindowCapturerWin : public CroppingWindowCapturer {
const DesktopCaptureOptions& options)
: CroppingWindowCapturer(options) {}
bool ShouldUseScreenCapturer() override;
DesktopRect GetWindowRectInVirtualScreen() override;
// The region from GetWindowRgn in the desktop coordinate if the region is
// rectangular, or the rect from GetWindowRect if the region is not set.
DesktopRect window_region_rect_;
AeroChecker aero_checker_;
bool CroppingWindowCapturerWin::ShouldUseScreenCapturer() {
if (!rtc::IsWindows8OrLater() && aero_checker_.IsAeroEnabled())
return false;
// Check if the window is a translucent layered window.
HWND selected = reinterpret_cast<HWND>(selected_window());
LONG window_ex_style = GetWindowLong(selected, GWL_EXSTYLE);
if (window_ex_style & WS_EX_LAYERED) {
COLORREF color_ref_key = 0;
BYTE alpha = 0;
DWORD flags = 0;
// GetLayeredWindowAttributes fails if the window was setup with
// UpdateLayeredWindow. We have no way to know the opacity of the window in
// that case. This happens for Stiky Note (crbug/412726).
if (!GetLayeredWindowAttributes(selected, &color_ref_key, &alpha, &flags))
return false;
// UpdateLayeredWindow is the only way to set per-pixel alpha and will cause
// the previous GetLayeredWindowAttributes to fail. So we only need to check
// the window wide color key or alpha.
if ((flags & LWA_COLORKEY) || ((flags & LWA_ALPHA) && (alpha < 255)))
return false;
TopWindowVerifierContext context(
selected, reinterpret_cast<HWND>(excluded_window()));
RECT selected_window_rect;
if (!GetWindowRect(selected, &selected_window_rect)) {
return false;
context.selected_window_rect = DesktopRect::MakeLTRB(
// Get the window region and check if it is rectangular.
win::ScopedGDIObject<HRGN, win::DeleteObjectTraits<HRGN> >
scoped_hrgn(CreateRectRgn(0, 0, 0, 0));
int region_type = GetWindowRgn(selected, scoped_hrgn.Get());
// Do not use the screen capturer if the region is empty or not rectangular.
if (region_type == COMPLEXREGION || region_type == NULLREGION)
return false;
if (region_type == SIMPLEREGION) {
RECT region_rect;
GetRgnBox(scoped_hrgn.Get(), &region_rect);
DesktopRect rgn_rect =
window_region_rect_ = context.selected_window_rect;
// Check if the window is occluded by any other window, excluding the child
// windows, context menus, and |excluded_window_|.
EnumWindows(&TopWindowVerifier, reinterpret_cast<LPARAM>(&context));
return context.is_top_window;
DesktopRect CroppingWindowCapturerWin::GetWindowRectInVirtualScreen() {
DesktopRect original_rect;
DesktopRect window_rect;
HWND hwnd = reinterpret_cast<HWND>(selected_window());
if (!GetCroppedWindowRect(hwnd, &window_rect, &original_rect)) {
LOG(LS_WARNING) << "Failed to get window info: " << GetLastError();
return window_rect;
// Convert |window_rect| to be relative to the top-left of the virtual screen.
DesktopRect screen_rect(GetScreenRect(kFullDesktopScreenId, L""));
return window_rect;
} // namespace
// static
CroppingWindowCapturer::Create(const DesktopCaptureOptions& options) {
return new CroppingWindowCapturerWin(options);
} // namespace webrtc