qohosplatformbackingstore.cpp

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// Copyright (C) 2025 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 "qohosplatformbackingstore.h"
#include "qohosplatformscreen.h"
#include "render/qohossurface.h"
#include <native_buffer/native_buffer.h>
#include <native_window/buffer_handle.h>
#include <native_window/external_window.h>
#include <qarkui/vsync.h>
#include <qohosutils.h>
#include <render/qohosview.h>
#include <QtCore/private/qcore_ohos_p.h>
#include <QtCore/private/qohoslogger_p.h>
#include <QtCore/qendian.h>
#include <algorithm>
#include <cstdint>
#include <cstring>
#include <iterator>
#include <tuple>
 
QT_BEGIN_NAMESPACE
 
namespace
{
 
constexpr std::int32_t ohNativeWindowErrorCodeSuccess = 0;
 
std::uint64_t getNativeWindowBufferQueueSize(::OHNativeWindow *nativeWindow)
{
    std::int32_t bufferQueueSize;
    auto getBufferQueueSizeResult = ::OH_NativeWindow_NativeWindowHandleOpt(
        nativeWindow, ::NativeWindowOperation::GET_BUFFERQUEUE_SIZE, &bufferQueueSize);
    if (Q_UNLIKELY(getBufferQueueSizeResult != ohNativeWindowErrorCodeSuccess)) {
        qOhosReportFatalErrorAndAbort(
            "%s: failed to get buffer queue size with error code: %d",
            Q_FUNC_INFO, getBufferQueueSizeResult);
    }
    return bufferQueueSize;
}
 
std::size_t qImageBytesPerPixel(const QImage &image)
{
    const auto bitsPerPixel = image.depth();
    const auto bytesPerPixel = bitsPerPixel / 8;
    return bytesPerPixel;
}
 
QSpan<uchar> qImageScanLine(QImage &image, int y)
{
    return QSpan(image.scanLine(y), image.width() * qImageBytesPerPixel(image));
}
 
void copyImageRow(QSpan<const uchar> srcRow, QSpan<uchar> dstRow)
{
    const auto sizeToCopy = std::min(srcRow.size(), dstRow.size());
    std::memcpy(dstRow.data(), srcRow.data(), sizeToCopy);
}
 
void copyImage(
    QOhosPlatformBackingStore::QImageView srcImage, QImage &dstImage, const QRegion &region, const QPoint &dstOffset)
{
    const auto intersectedRegion =
        region.intersected(QRect({}, srcImage.size()))
        .intersected(QRect({}, dstImage.size()).translated(-dstOffset));
 
    for (const auto &rect : intersectedRegion) {
        const auto xSrc = rect.x() * srcImage.bytesPerPixel();
        const auto widthSrc = rect.width() * srcImage.bytesPerPixel();
        const auto xDst = (rect.x() + dstOffset.x()) * qImageBytesPerPixel(dstImage);
        const auto widthDst = rect.width() * qImageBytesPerPixel(dstImage);
 
        for (int row = 0; row < rect.height(); ++row) {
            const int srcY = rect.y() + row;
            const int dstY = srcY + dstOffset.y();
            const auto srcRow = srcImage.constScanLine(srcY).subspan(xSrc, widthSrc);
            auto dstRow = qImageScanLine(dstImage, dstY).subspan(xDst, widthDst);
            copyImageRow(srcRow, dstRow);
        }
    }
}
 
void debugDrawFlushedQRegion(QImage &dstImage, const QRegion &region)
{
    static const QColor debugBoxColor("#7F00FF00");
 
    QPainter painter(&dstImage);
    painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
    for (const QRect &rect : region)
        painter.fillRect(rect, debugBoxColor);
}
 
std::vector<::Region::Rect> makeOhosRegionRectsForFlush(
    const QRegion &region, const QPoint &rootWindowOffset, const QSize &dstImageSize)
{
    std::vector<::Region::Rect> rects;
    if (!region.isEmpty()) {
        std::transform(
            region.begin(), region.end(), std::back_inserter(rects),
            [&](const auto &qrect) {
                return ::Region::Rect{
                    .x = qrect.x() + rootWindowOffset.x(),
                    .y = (dstImageSize.height() - qrect.y()) + rootWindowOffset.y() - qrect.height(),
                    .w = static_cast<std::uint32_t>(qrect.width()),
                    .h = static_cast<std::uint32_t>(qrect.height()),
                };
            });
    }
    return rects;
}
 
std::function<void()> makeVSyncFrameRequestFunc(
    QtOhos::QThreadSafeRef<QWindow> qWindowRef, ::OHNativeWindow *nativeWindow,
    QOhosConsumer<QWindow *> qtThreadFlushFunc)
{
    auto sharedQtThreadFlushFunc = QtOhos::moveToSharedPtr(std::move(qtThreadFlushFunc));
    return QOhosJsThreadGateway::eval(
        [&](QOhosJsState &) {
            auto sharedFrameRequestFunc = QtOhos::makeProxyWithJsThreadDeleter(
                QtOhos::moveToSharedPtr(
                    QArkUi::makeVSyncFrameRequester(
                        nativeWindow,
                        [qWindowRef, sharedQtThreadFlushFunc]() {
                            qWindowRef.visitInQtThreadIfAlive(
                                [sharedQtThreadFlushFunc](QWindow &qWindow) {
                                    (*sharedQtThreadFlushFunc)(&qWindow);
                                });
                            })));
 
            return [sharedFrameRequestFunc]() {
                (*sharedFrameRequestFunc)();
            };
        },
        Q_FUNC_INFO);
}
 
QPoint extractNegativeOffset(const QPoint &offset)
{
    return QPoint(
        std::max(0, -offset.x()),
        std::max(0, -offset.y()));
}
 
}
 
QOhosPlatformBackingStore::QOhosPlatformBackingStore(QWindow *window, const CreateInfo &createInfo)
    : QRasterBackingStore(window)
    , m_debugDrawFlushedRegion(createInfo.debugDrawFlushedRegion)
    , m_vsyncEnabled(createInfo.enableVsync)
    , m_flushFunc(
        std::make_shared<std::function<void(QWindow *)>>(
            [this](QWindow *qWindow) {
                flushImmediate(qWindow);
            }))
    , m_windowContextManager(createInfo.enableVsync, m_flushFunc)
{
}
 
void QOhosPlatformBackingStore::flush(QWindow *window, const QRegion &region, const QPoint &offset)
{
    if (m_reinitializeContextManager) {
        m_windowContextManager = WindowContextManager(m_vsyncEnabled, m_flushFunc);
        m_reinitializeContextManager = false;
    }
 
    auto *platformWindow = QOhosPlatformWindow::fromQWindowOrNull(window);
    auto *surface = platformWindow != nullptr ? platformWindow->ownedSurfaceOrNull() : nullptr;
    auto bounds = region.translated(offset).boundingRect() & m_image.rect();
 
    if (bounds.isEmpty())
        return;
 
    if (surface == nullptr) {
        qOhosPrintfDebug("Window %p has no surface", window);
        return;
    }
 
    m_windowContextManager
        .getOrCreateWindowContext(window, surface->nativeWindow())
        .flushData().updateDirtyRegionAndScheduleFlush(region, offset);
}
 
void QOhosPlatformBackingStore::resize(const QSize &size, const QRegion &staticContents)
{
    m_reinitializeContextManager = (size != m_requestedSize);
    QRasterBackingStore::resize(size, staticContents);
}
 
QImage::Format QOhosPlatformBackingStore::format() const
{
    return QOhosSurface::mapNativeBufferFormatToQImageFormatOrFail(QOhosSurface::bufferFormat);
}
 
QOhosPlatformBackingStore::QImageView::QImageView(const QImage &srcImage, const QRect &subRect)
    : m_srcImage(srcImage)
    , m_subRect(subRect)
{
    auto imageRect = QRect(QPoint{}, m_srcImage.size());
    if (!imageRect.contains(m_subRect)) {
        qOhosReportFatalErrorAndAbort(
            "image rect: (%d, %d, %d, %d) does not contain sub-rect: (%d, %d, %d, %d)",
            imageRect.x(), imageRect.y(), imageRect.width(), imageRect.height(),
            m_subRect.x(), m_subRect.y(), m_subRect.width(), m_subRect.height());
    }
 
    constexpr auto minAcceptedImageDepth = 8;
    if (srcImage.depth() < minAcceptedImageDepth)
        qOhosReportFatalErrorAndAbort("QImageView is not supported for <8bpp QImages");
}
 
std::size_t QOhosPlatformBackingStore::QImageView::bytesPerPixel() const
{
    return qImageBytesPerPixel(m_srcImage);
}
 
QSpan<const uchar> QOhosPlatformBackingStore::QImageView::constScanLine(int i) const
{
    Q_ASSERT(i >= 0 && i < m_subRect.height());
    auto srcScanLine = QSpan(
        m_srcImage.constScanLine(m_subRect.y() + i), m_srcImage.bytesPerLine());
    return srcScanLine.subspan(
        m_subRect.x() * bytesPerPixel(), bytesPerLine());
}
 
std::size_t QOhosPlatformBackingStore::QImageView::bytesPerLine() const
{
    return bytesPerPixel() * m_subRect.width();
}
 
QSize QOhosPlatformBackingStore::QImageView::size() const
{
    return m_subRect.size();
}
 
QOhosPlatformBackingStore::BufferRegionHandler::BufferRegionHandler(::OHNativeWindow *nativeWindow)
    : m_bufferQueueSize(getNativeWindowBufferQueueSize(nativeWindow))
{
}
 
std::optional<QRegion> QOhosPlatformBackingStore::BufferRegionHandler::mergeRegionForBufferHandle(
    ::BufferHandle *bufferHandle,
    QRegion region) const
{
    const auto it = m_buffersToFlushSequenceIds.find(bufferHandle);
    if (it == m_buffersToFlushSequenceIds.end())
        return std::nullopt;
 
    std::uint64_t numberOfRegions = m_flushSequenceId - it->second;
    if (numberOfRegions > m_bufferQueueSize)
        return std::nullopt;
 
    for (auto it = m_lastFlushedRegions.cend() - numberOfRegions; it != m_lastFlushedRegions.cend(); ++it)
        region = region.united(*it);
 
    return region;
}
 
void QOhosPlatformBackingStore::BufferRegionHandler::storeRegionForBufferHandle(
    ::BufferHandle *bufferHandle,
    const QRegion &region)
{
    m_buffersToFlushSequenceIds[bufferHandle] = m_flushSequenceId;
 
    if (m_buffersToFlushSequenceIds.size() > m_bufferQueueSize) {
        m_buffersToFlushSequenceIds.clear();
        m_lastFlushedRegions.clear();
        m_flushSequenceId = 0;
        return;
    }
 
    m_lastFlushedRegions.push_back(region);
    if (m_lastFlushedRegions.size() > m_bufferQueueSize)
        m_lastFlushedRegions.pop_front();
 
    ++m_flushSequenceId;
}
 
QOhosPlatformBackingStore::FlushData::FlushData(std::function<void()> flushRequestFunc)
    : m_flushRequestFunc(std::move(flushRequestFunc))
{
}
 
std::pair<QRegion, QPoint> QOhosPlatformBackingStore::FlushData::fetchAndReset()
{
    return std::make_pair(
        std::exchange(m_mergedRegionForFlush, QRegion {}),
        std::exchange(m_lastWindowOffset, QPoint {}));
}
 
void QOhosPlatformBackingStore::FlushData::updateDirtyRegionAndScheduleFlush(
    const QRegion &region, const QPoint &rootWindowOffset)
{
    m_mergedRegionForFlush = m_mergedRegionForFlush.united(region);
    m_lastWindowOffset = rootWindowOffset;
    m_flushRequestFunc();
}
 
QOhosPlatformBackingStore::WindowContext::WindowContext(
    ::OHNativeWindow *nativeWindow, std::function<void()> flushRequestFunc)
    : m_bufferRegionHandler(std::make_unique<BufferRegionHandler>(nativeWindow))
    , m_flushData(std::move(flushRequestFunc))
{
}
 
QOhosPlatformBackingStore::BufferRegionHandler &
QOhosPlatformBackingStore::WindowContext::bufferRegionHandler()
{
    return *m_bufferRegionHandler;
}
 
QOhosPlatformBackingStore::FlushData &QOhosPlatformBackingStore::WindowContext::flushData()
{
    return m_flushData;
}
 
QOhosPlatformBackingStore::WindowContextManager::WindowContextManager(
    bool vsyncEnabled,
    std::shared_ptr<std::function<void(QWindow *)>> flushImmediateFunc)
    : m_flushFunc(flushImmediateFunc)
    , m_vsyncEnabled(vsyncEnabled)
{
}
 
QOhosPlatformBackingStore::WindowContext &
QOhosPlatformBackingStore::WindowContextManager::getOrCreateWindowContext(
    QWindow *window,
    ::OHNativeWindow *nativeWindow)
{
    auto handlerIter = m_windowContexts.find(window);
    if (handlerIter == m_windowContexts.end()) {
 
        std::function<void()> flushFunc;
 
        if (m_vsyncEnabled) {
            auto weakQtFlushFunc = QtOhos::makeWeakPtr(m_flushFunc);
            auto qWindowRef = QtOhos::makeQThreadSafeRef(window);
            flushFunc = makeVSyncFrameRequestFunc(
                qWindowRef, nativeWindow,
                [weakQtFlushFunc](QWindow *qWindow) {
                    auto sharedQtThreadFlushFunc = weakQtFlushFunc.lock();
                    if (sharedQtThreadFlushFunc)
                        (*sharedQtThreadFlushFunc)(qWindow);
                });
        } else {
            flushFunc = [window, flushFunc = m_flushFunc]() {
                (*flushFunc)(window);
            };
        }
 
        std::tie(handlerIter, std::ignore) = m_windowContexts.emplace(
            window, std::make_unique<WindowContext>(
                nativeWindow, std::move(flushFunc)));
    }
    return *(handlerIter->second);
}
 
bool QOhosPlatformBackingStore::scroll(const QRegion &area, int dx, int dy)
{
    Q_GUI_EXPORT void qt_scrollRectInImage(QImage &img, const QRect &rect, const QPoint &offset);
 
    const qreal devicePixelRatio = m_image.devicePixelRatio();
    const QPoint delta(
        static_cast<int>(dx * devicePixelRatio),
        static_cast<int>(dy * devicePixelRatio));
 
    for (const QRect &rect : area) {
        qt_scrollRectInImage(
            m_image,
            QRect(rect.topLeft() * devicePixelRatio, rect.size() * devicePixelRatio), delta);
    }
 
    return true;
}
 
void QOhosPlatformBackingStore::beginPaint(const QRegion &region)
{
    auto previousImageSize = m_image.size();
    QRasterBackingStore::beginPaint(region);
    bool imageWasResized = previousImageSize != m_image.size();
    if (imageWasResized)
        m_windowContextManager = WindowContextManager(m_vsyncEnabled, m_flushFunc);
}
 
void QOhosPlatformBackingStore::flushImmediate(QWindow *window)
{
    auto *platformWindow = QOhosPlatformWindow::fromQWindowOrNull(window);
    auto *surface = platformWindow != nullptr ? platformWindow->ownedSurfaceOrNull() : nullptr;
 
    if (surface == nullptr) {
        qOhosPrintfDebug("Window %p has no surface", window);
        return;
    }
 
    bool isRootWindow = window == this->window();
 
    ::OHNativeWindow *nativeWindow = surface->nativeWindow();
 
    auto &windowContext = m_windowContextManager.getOrCreateWindowContext(window, nativeWindow);
    QRegion region;
    QPoint rootWindowOffset;
    std::tie(region, rootWindowOffset) = windowContext.flushData().fetchAndReset();
 
    if (region.isEmpty())
        return;
 
    auto &bufferRegionHandler = m_windowContextManager
        .getOrCreateWindowContext(window, nativeWindow).bufferRegionHandler();
 
    auto srcImageRect = isRootWindow
        ? QRect({}, m_image.size())
        : QRect(rootWindowOffset, platformWindow->geometry().size()).intersected(QRect({}, m_image.size()));
    if (srcImageRect.isEmpty()) {
        qOhosPrintfDebug("Cannot get source image rect, ignore flush call");
        return;
    }
 
    QImageView srcImage = QImageView(m_image, srcImageRect);
 
    const auto rootWindowRegionToFlush = region
        .translated(rootWindowOffset)
        .intersected(srcImageRect)
        .translated(-rootWindowOffset);
 
    surface->paintOnNativeWindowSurface(
        [&](QImage &dstImage, ::BufferHandle *bufferHandle) {
            if (srcImage.bytesPerPixel() != qImageBytesPerPixel(dstImage)) {
                qOhosReportFatalErrorAndAbort(
                    "%s: bytes per pixel in src and dst image mismatch. Image formats are not the same.", Q_FUNC_INFO);
            }
 
            const auto& mergedRegionOpt = bufferRegionHandler.mergeRegionForBufferHandle(bufferHandle, rootWindowRegionToFlush);
            const auto dstImageOffset = extractNegativeOffset(rootWindowOffset);
            const auto windowVisibleRegion = QRegion(QRect(dstImageOffset, srcImage.size()));
            const auto requestedRegion = mergedRegionOpt.value_or(windowVisibleRegion);
            const auto sourceRegionToFlush = requestedRegion.translated(-dstImageOffset);
            copyImage(srcImage, dstImage, sourceRegionToFlush, dstImageOffset);
 
            if (m_debugDrawFlushedRegion)
                debugDrawFlushedQRegion(dstImage, rootWindowRegionToFlush);
 
            return makeOhosRegionRectsForFlush(
                mergedRegionOpt.value_or(QRegion()), isRootWindow ? QPoint{} : rootWindowOffset, dstImage.size());
        },
        [&](::BufferHandle *bufferHandle) {
            bufferRegionHandler.storeRegionForBufferHandle(bufferHandle, rootWindowRegionToFlush);
        });
 
    if (isRootWindow) {
        auto *view = platformWindow->ownedViewOrNull();
        if (view != nullptr)
            view->handleSurfaceContentsUpdated();
    }
}
 
QT_END_NAMESPACE