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// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#include "qgdiwindowcapture_p.h"
#include "qvideoframe.h"
#include <QtMultimedia/private/qsurfacecapturegrabber_p.h>
#include "private/qcapturablewindow_p.h"
#include "private/qmemoryvideobuffer_p.h"
#include "private/qvideoframe_p.h"
#include <qt_windows.h>
#include <QtCore/qloggingcategory.h>
Q_STATIC_LOGGING_CATEGORY(qLcGdiWindowCapture, "qt.multimedia.ffmpeg.gdiwindowcapture");
QT_BEGIN_NAMESPACE
class QGdiWindowCapture::Grabber : public QSurfaceCaptureGrabber
{
public:
static std::unique_ptr<Grabber> create(QGdiWindowCapture &capture, HWND hWnd)
{
auto hdcWindow = GetDC(hWnd);
if (!hdcWindow) {
capture.updateError(QPlatformSurfaceCapture::Error::CaptureFailed,
QLatin1String("Cannot create a window drawing context"));
return nullptr;
}
auto hdcMem = CreateCompatibleDC(hdcWindow);
if (!hdcMem) {
capture.updateError(QPlatformSurfaceCapture::Error::CaptureFailed,
QLatin1String("Cannot create a compatible drawing context"));
return nullptr;
}
std::unique_ptr<Grabber> result(new Grabber(capture, hWnd, hdcWindow, hdcMem));
if (!result->update())
return nullptr;
result->start();
return result;
}
~Grabber() override
{
stop();
if (m_hBitmap)
DeleteObject(m_hBitmap);
if (m_hdcMem)
DeleteDC(m_hdcMem);
if (m_hdcWindow)
ReleaseDC(m_hwnd, m_hdcWindow);
}
QVideoFrameFormat format() const { return m_format; }
private:
Grabber(QGdiWindowCapture &capture, HWND hWnd, HDC hdcWindow, HDC hdcMem)
: QSurfaceCaptureGrabber(),
m_hwnd(hWnd),
m_hdcWindow(hdcWindow),
m_hdcMem(hdcMem)
{
addFrameCallback(&capture, &QGdiWindowCapture::newVideoFrame);
connect(this, &Grabber::errorUpdated, &capture, &QGdiWindowCapture::updateError);
const auto vrefresh = GetDeviceCaps(hdcWindow, VREFRESH);
const auto defaultRate = vrefresh > 0
? qMin(static_cast<qreal>(vrefresh), DefaultScreenCaptureFrameRate)
: DefaultScreenCaptureFrameRate;
setFrameRate(capture.frameRate().value_or(defaultRate));
}
bool update()
{
RECT windowRect{};
if (!GetWindowRect(m_hwnd, &windowRect)) {
updateError(QPlatformSurfaceCapture::Error::CaptureFailed,
QLatin1String("Cannot get window size"));
return false;
}
const QSize size{ windowRect.right - windowRect.left, windowRect.bottom - windowRect.top };
if (m_format.isValid() && size == m_format.frameSize() && m_hBitmap)
return true;
if (m_hBitmap)
DeleteObject(std::exchange(m_hBitmap, nullptr));
if (size.isEmpty()) {
m_format = {};
updateError(QPlatformSurfaceCapture::Error::CaptureFailed,
QLatin1String("Invalid window size"));
return false;
}
m_hBitmap = CreateCompatibleBitmap(m_hdcWindow, size.width(), size.height());
if (!m_hBitmap) {
m_format = {};
updateError(QPlatformSurfaceCapture::Error::CaptureFailed,
QLatin1String("Cannot create a compatible bitmap"));
return false;
}
QVideoFrameFormat format(size, QVideoFrameFormat::Format_BGRX8888);
format.setStreamFrameRate(activeFrameRate());
m_format = format;
return true;
}
QVideoFrame grabFrame() override
{
if (!update())
return {};
const auto oldBitmap = SelectObject(m_hdcMem, m_hBitmap);
auto deselect = qScopeGuard([&]() { SelectObject(m_hdcMem, oldBitmap); });
const auto size = m_format.frameSize();
if (!BitBlt(m_hdcMem, 0, 0, size.width(), size.height(), m_hdcWindow, 0, 0, SRCCOPY)) {
updateError(QPlatformSurfaceCapture::Error::CaptureFailed,
QLatin1String("Cannot copy image to the compatible DC"));
return {};
}
BITMAPINFO info{};
auto &header = info.bmiHeader;
header.biSize = sizeof(BITMAPINFOHEADER);
header.biWidth = size.width();
header.biHeight = -size.height(); // negative height to ensure top-down orientation
header.biPlanes = 1;
header.biBitCount = 32;
header.biCompression = BI_RGB;
const auto bytesPerLine = size.width() * 4;
QByteArray array(size.height() * bytesPerLine, Qt::Uninitialized);
const auto copiedHeight = GetDIBits(m_hdcMem, m_hBitmap, 0, size.height(), array.data(), &info, DIB_RGB_COLORS);
if (copiedHeight != size.height()) {
qCWarning(qLcGdiWindowCapture) << copiedHeight << "lines have been copied, expected:" << size.height();
// In practice, it might fail randomly first time after start. So we don't consider it as an error.
// TODO: investigate reasons and properly handle the error
// updateError(QPlatformSurfaceCapture::CaptureFailed,
// QLatin1String("Cannot get raw image data"));
return {};
}
if (header.biWidth != size.width() || header.biHeight != -size.height()
|| header.biPlanes != 1 || header.biBitCount != 32 || header.biCompression != BI_RGB) {
updateError(QPlatformSurfaceCapture::Error::CaptureFailed,
QLatin1String("Output bitmap info is unexpected"));
return {};
}
return QVideoFramePrivate::createFrame(
std::make_unique<QMemoryVideoBuffer>(std::move(array), bytesPerLine), m_format);
}
private:
HWND m_hwnd = {};
QVideoFrameFormat m_format;
HDC m_hdcWindow = {};
HDC m_hdcMem = {};
HBITMAP m_hBitmap = {};
};
QGdiWindowCapture::QGdiWindowCapture() : QPlatformSurfaceCapture(WindowSource{}) { }
QGdiWindowCapture::~QGdiWindowCapture() = default;
QVideoFrameFormat QGdiWindowCapture::frameFormat() const
{
return m_grabber ? m_grabber->format() : QVideoFrameFormat();
}
bool QGdiWindowCapture::setActiveInternal(bool active)
{
if (active == static_cast<bool>(m_grabber))
return true;
if (m_grabber) {
m_grabber.reset();
} else {
auto window = source<WindowSource>();
auto handle = QCapturableWindowPrivate::handle(window);
m_grabber = Grabber::create(*this, reinterpret_cast<HWND>(handle ? handle->id : 0));
}
return static_cast<bool>(m_grabber) == active;
}
QT_END_NAMESPACE