paintdriver-ex-1.cpp

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// Copyright (C) 2025 The Qt Company Ltd.

// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

#include <QtCanvasPainter/qcanvaspainter.h>

#include <QtCanvasPainter/qcanvaspainterfactory.h>

#include <QtCanvasPainter/qcanvasrhipaintdriver.h>

#include <QtGui/qguiapplication.h>

#include <QtGui/qimage.h>

#include <rhi/qrhi.h>

#include <memory>

static std::unique_ptr<QRhi> rhi; // In real code: QRhi::create(impl, &params)

//![0]

int main(int argc, char *argv[])

    QGuiApplication app(argc, argv);

    // std::unique_ptr<QRhi> rhi(QRhi::create(...));

    std::unique_ptr<QRhiTexture> tex(rhi->newTexture(QRhiTexture::RGBA8, QSize(1280, 720), 1,

                                     QRhiTexture::RenderTarget | QRhiTexture::UsedAsTransferSource));

    tex->create();

    std::unique_ptr<QRhiRenderBuffer> ds(rhi->newRenderBuffer(QRhiRenderBuffer::DepthStencil, QSize(1280, 720)));

    ds->create();

    QRhiTextureRenderTargetDescription rtDesc;

    rtDesc.setColorAttachments({ tex.get() });

    rtDesc.setDepthStencilBuffer(ds.get());

    std::unique_ptr<QRhiTextureRenderTarget> rt(rhi->newTextureRenderTarget(rtDesc));

    std::unique_ptr<QRhiRenderPassDescriptor> rp(rt->newCompatibleRenderPassDescriptor());

    rt->setRenderPassDescriptor(rp.get());

    rt->create();

    std::unique_ptr<QCanvasPainterFactory> factory(new QCanvasPainterFactory);

    QCanvasPainter *painter = factory->create(rhi.get());

    QCanvasRhiPaintDriver *pd = factory->paintDriver();

    QRhiCommandBuffer *cb;

    QRhiReadbackResult readbackResult;

    rhi->beginOffscreenFrame(&cb);

    pd->resetForNewFrame();

        pd->beginPaint(cb, rt.get());

        painter->beginPath();

        painter->circle(640, 360, 180);

        painter->setFillStyle(Qt::red);

        painter->fill();

        pd->endPaint();

        QRhiResourceUpdateBatch *u = rhi->nextResourceUpdateBatch();

        u->readBackTexture({ tex.get() }, &readbackResult);

        cb->resourceUpdate(u);

    rhi->endOffscreenFrame();

    QImage image(reinterpret_cast<const uchar *>(readbackResult.data.constData()),

                    readbackResult.pixelSize.width(),

                    readbackResult.pixelSize.height(),

                    QImage::Format_RGBA8888);

    if (rhi->isYUpInFramebuffer())

        image.flip();

    image.save("result.png");

    return 0;

//![0]