qquickrhiitem_intro.cpp

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// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
#include <QtQuick/QQuickRhiItem>
#include <rhi/qrhi.h>
 
class ExampleRhiItemRenderer : public QQuickRhiItemRenderer
{
public:
    void initialize(QRhiCommandBuffer *cb) override;
    void synchronize(QQuickRhiItem *item) override;
    void render(QRhiCommandBuffer *cb) override;
 
private:
    QRhi *m_rhi = nullptr;
    std::unique_ptr<QRhiBuffer> m_vbuf;
    std::unique_ptr<QRhiBuffer> m_ubuf;
    std::unique_ptr<QRhiShaderResourceBindings> m_srb;
    std::unique_ptr<QRhiGraphicsPipeline> m_pipeline;
    QMatrix4x4 m_viewProjection;
    float m_angle = 0.0f;
};
 
class ExampleRhiItem : public QQuickRhiItem
{
    Q_OBJECT
    QML_NAMED_ELEMENT(ExampleRhiItem)
    Q_PROPERTY(float angle READ angle WRITE setAngle NOTIFY angleChanged)
 
public:
    QQuickRhiItemRenderer *createRenderer() override;
 
    float angle() const { return m_angle; }
    void setAngle(float a);
 
signals:
    void angleChanged();
 
private:
    float m_angle = 0.0f;
};
 
QQuickRhiItemRenderer *ExampleRhiItem::createRenderer()
{
    return new ExampleRhiItemRenderer;
}
 
void ExampleRhiItem::setAngle(float a)
{
    if (m_angle == a)
        return;
 
    m_angle = a;
    emit angleChanged();
    update();
}
 
void ExampleRhiItemRenderer::synchronize(QQuickRhiItem *rhiItem)
{
    ExampleRhiItem *item = static_cast<ExampleRhiItem *>(rhiItem);
    if (item->angle() != m_angle)
        m_angle = item->angle();
}
 
static QShader getShader(const QString &name)
{
    QFile f(name);
    return f.open(QIODevice::ReadOnly) ? QShader::fromSerialized(f.readAll()) : QShader();
}
 
static float vertexData[] = {
    0.0f,   0.5f,   1.0f, 0.0f, 0.0f,
    -0.5f,  -0.5f,   0.0f, 1.0f, 0.0f,
    0.5f,  -0.5f,   0.0f, 0.0f, 1.0f,
};
 
void ExampleRhiItemRenderer::initialize(QRhiCommandBuffer *cb)
{
    if (m_rhi != rhi()) {
        m_pipeline.reset();
        m_rhi = rhi();
    }
 
    if (!m_pipeline) {
        m_vbuf.reset(m_rhi->newBuffer(QRhiBuffer::Immutable, QRhiBuffer::VertexBuffer, sizeof(vertexData)));
        m_vbuf->create();
 
        m_ubuf.reset(m_rhi->newBuffer(QRhiBuffer::Dynamic, QRhiBuffer::UniformBuffer, 64));
        m_ubuf->create();
 
        m_srb.reset(m_rhi->newShaderResourceBindings());
        m_srb->setBindings({
            QRhiShaderResourceBinding::uniformBuffer(0, QRhiShaderResourceBinding::VertexStage, m_ubuf.get()),
        });
        m_srb->create();
 
        m_pipeline.reset(m_rhi->newGraphicsPipeline());
        m_pipeline->setShaderStages({
            { QRhiShaderStage::Vertex, getShader(QLatin1String(":/shaders/color.vert.qsb")) },
            { QRhiShaderStage::Fragment, getShader(QLatin1String(":/shaders/color.frag.qsb")) }
        });
        QRhiVertexInputLayout inputLayout;
        inputLayout.setBindings({
            { 5 * sizeof(float) }
        });
        inputLayout.setAttributes({
            { 0, 0, QRhiVertexInputAttribute::Float2, 0 },
            { 0, 1, QRhiVertexInputAttribute::Float3, 2 * sizeof(float) }
        });
        m_pipeline->setVertexInputLayout(inputLayout);
        m_pipeline->setShaderResourceBindings(m_srb.get());
        m_pipeline->setRenderPassDescriptor(renderTarget()->renderPassDescriptor());
        m_pipeline->create();
 
        QRhiResourceUpdateBatch *resourceUpdates = m_rhi->nextResourceUpdateBatch();
        resourceUpdates->uploadStaticBuffer(m_vbuf.get(), vertexData);
        cb->resourceUpdate(resourceUpdates);
    }
 
    const QSize outputSize = renderTarget()->pixelSize();
    m_viewProjection = m_rhi->clipSpaceCorrMatrix();
    m_viewProjection.perspective(45.0f, outputSize.width() / (float) outputSize.height(), 0.01f, 1000.0f);
    m_viewProjection.translate(0, 0, -4);
}
 
void ExampleRhiItemRenderer::render(QRhiCommandBuffer *cb)
{
    QRhiResourceUpdateBatch *resourceUpdates = m_rhi->nextResourceUpdateBatch();
    QMatrix4x4 modelViewProjection = m_viewProjection;
    modelViewProjection.rotate(m_angle, 0, 1, 0);
    resourceUpdates->updateDynamicBuffer(m_ubuf.get(), 0, 64, modelViewProjection.constData());
 
    const QColor clearColor = QColor::fromRgbF(0.4f, 0.7f, 0.0f, 1.0f);
    cb->beginPass(renderTarget(), clearColor, { 1.0f, 0 }, resourceUpdates);
 
    cb->setGraphicsPipeline(m_pipeline.get());
    const QSize outputSize = renderTarget()->pixelSize();
    cb->setViewport(QRhiViewport(0, 0, outputSize.width(), outputSize.height()));
    cb->setShaderResources();
    const QRhiCommandBuffer::VertexInput vbufBinding(m_vbuf.get(), 0);
    cb->setVertexInput(0, 1, &vbufBinding);
    cb->draw(3);
 
    cb->endPass();
}