整合QML和Skia（gpu后端）

Question

我正在尝试将Skia与QML结合使用。我从QQuickPaintedItem继承。我已经修改了示例http://doc.qt.io/qt-5/qtquick-customitems-painteditem-example.html，以将QQuickPaintedItem::FramebufferObject用作renderTarget。我正在尝试根据SkSurface的现有纹理创建QQuickPaintedItem。我总是空着。请让我知道是否可以使用QML项目中的现有纹理并将其用于Skia渲染。

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include "textballoon.h"

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

    QGuiApplication app(argc, argv);


    QQmlApplicationEngine engine;
    qmlRegisterType<TextBalloon>("com.sanjay.check", 1, 0, "TextBalloon");
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    if (engine.rootObjects().isEmpty())
        return -1;

    return app.exec();
}

project.pro文件

QT += quick
CONFIG += c++11

# The following define makes your compiler emit warnings if you use
# any feature of Qt which as been marked deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
        main.cpp \
    textballoon.cpp

RESOURCES += qml.qrc

# Additional import path used to resolve QML modules in Qt Creator's code model
QML_IMPORT_PATH =

# Additional import path used to resolve QML modules just for Qt Quick Designer
QML_DESIGNER_IMPORT_PATH =

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

HEADERS += \
    textballoon.h

INCLUDEPATH +=\
/home/sanju/skia/include/core \
/home/sanju/skia/src/core \
/home/sanju/skia/include/private \
/home/sanju/skia/include/config \
#/home/sanju/skia/tools/ \
/home/sanju/skia/include/gpu \
/home/sanju/skia/src/gpu \
/home/sanju/skia/src/gpu/gl \
#/home/sanju/skia/include/effects \
/home/sanju/skia/include/encode \
/home/sanju/skia/include/utils \

unix:!macx: LIBS += -L$$PWD/../../skia/out/Release/ -lskia

INCLUDEPATH += $$PWD/../../skia/out/Release
DEPENDPATH += $$PWD/../../skia/out/Release

这是我修改后的textballoon.cpp文件

#include "GrContext.h"
#include "gl/GrGLTypes.h"
//#include "GrGLTexture.h"

#include "textballoon.h"

#include "gl/GrGLInterface.h"
#include "SkData.h"
#include "SkImage.h"
#include "SkStream.h"
#include "SkSurface.h"
//#include "GrGpu.h"
#include "GrBackendSurface.h"
//#include "GrContextPriv.h"
//#include "GrGpu.h"

#include <QtDebug>
//! [0]
TextBalloon::TextBalloon(QQuickItem *parent)
    : QQuickPaintedItem(parent)
    , rightAligned(false)
{
    setRenderTarget(QQuickPaintedItem::FramebufferObject);
    setRightAligned(true);

    QObject::connect(this, &QQuickPaintedItem::widthChanged, this, [this]() {
        //        qDebug() << "textureChanged";
        this->dirty = true;
    });
}
//! [0]

//! [1]
void TextBalloon::paint(QPainter *painter)
{
    QBrush brush(QColor("#007430"));

    painter->setBrush(brush);
    painter->setPen(Qt::NoPen);
    painter->setRenderHint(QPainter::Antialiasing);

    QSizeF itemSize = size();
    painter->drawRoundedRect(0, 0, itemSize.width(), itemSize.height() - 10, 10, 10);

    if (rightAligned)
    {
        const QPointF points[3] = {
            QPointF(itemSize.width() - 10.0, itemSize.height() - 10.0),
            QPointF(itemSize.width() - 20.0, itemSize.height()),
            QPointF(itemSize.width() - 30.0, itemSize.height() - 10.0),
        };
        painter->drawConvexPolygon(points, 3);
    }
    else
    {
        const QPointF points[3] = {
            QPointF(10.0, itemSize.height() - 10.0),
            QPointF(20.0, itemSize.height()),
            QPointF(30.0, itemSize.height() - 10.0),
        };
        painter->drawConvexPolygon(points, 3);
    }

    if(textureProvider())
    {
        sk_sp<const GrGLInterface> interface = nullptr;
        // Leaving interface as null makes Skia extract pointers to OpenGL functions for the current
        // context in a platform-specific way. Alternatively, you may create your own GrGLInterface and
        // initialize it however you like to attach to an alternate OpenGL implementation or intercept
        // Skia's OpenGL calls.
        sk_sp<GrContext> context = GrContext::MakeGL(interface);
        if (!context) {
            SkDebugf("GrContext::MakeGL returned null\n");
        }

        //            GrGpu* gpu = context->contextPriv().getGpu();

        QSGTexture* texture = textureProvider()->texture();
        if(texture)
        {
            qDebug() << "Texture exist";
            QSurfaceFormat format = QSurfaceFormat::defaultFormat();
            QSize size = texture->textureSize();
            qDebug() << size;


            qDebug() << "Texture id " << texture->textureId() << " alpha channel " << texture->hasAlphaChannel()
                     << "FORMAT RGB" << format.depthBufferSize() << " sample size " << format.samples();


            GrGLTextureInfo info;
            info.fID = texture->textureId();
            info.fFormat = SkColorType::kUnknown_SkColorType;
            GrBackendTexture grTexture(size.width(),
                                       size.height(),
                                       texture->hasMipmaps()? GrMipMapped::kYes : GrMipMapped::kNo,
                                       info);

            GrGLFramebufferInfo fboInfo;
            fboInfo.fFBOID = texture->textureId();

            auto surface =  SkSurface::MakeFromBackendTexture(context.get(),
                                                              grTexture,
                                                              GrSurfaceOrigin::kTopLeft_GrSurfaceOrigin,
                                                              0,
                                                              SkColorType::kUnknown_SkColorType,
                                                              nullptr,
                                                              nullptr);

//            GrGLFramebufferInfo fboInfo;
//            fboInfo.fFBOID = texture->textureId();

//            GrBackendRenderTarget backendTarget(size.width(),
//                                                size.height(),
//                                                0,
//                                                0,
//                                                fboInfo);
//            auto surface =  SkSurface::MakeFromBackendRenderTarget(context.get(),
//                                                              backendTarget,
//                                                              GrSurfaceOrigin::kTopLeft_GrSurfaceOrigin,
//                                                              SkColorType::kUnknown_SkColorType,
//                                                              nullptr,
//                                                              nullptr);
            if(surface)
            {
                qDebug() << "Surface created";
            }
        }
    }
}
//! [1]

bool TextBalloon::isRightAligned()
{
    return this->rightAligned;
}

void TextBalloon::setRightAligned(bool rightAligned)
{
    this->rightAligned = rightAligned;
}