1 files changed, 151 insertions, 0 deletions
diff --git a/src/gui/doc/snippets/rhioffscreen/main.cpp b/src/gui/doc/snippets/rhioffscreen/main.cpp
new file mode 100644
index 0000000000..c2c6f74dc1
--- /dev/null
+++ b/src/gui/doc/snippets/rhioffscreen/main.cpp
@@ -0,0 +1,151 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+//! [0]
+#include <QGuiApplication>
+#include <QImage>
+#include <QFile>
+#include <rhi/qrhi.h>
+
+int main(int argc, char **argv)
+{
+    QGuiApplication app(argc, argv);
+
+#if QT_CONFIG(vulkan)
+    QVulkanInstance inst;
+#endif
+    std::unique_ptr<QRhi> rhi;
+#if defined(Q_OS_WIN)
+    QRhiD3D12InitParams params;
+    rhi.reset(QRhi::create(QRhi::D3D12, &params));
+#elif QT_CONFIG(metal)
+    QRhiMetalInitParams params;
+    rhi.reset(QRhi::create(QRhi::Metal, &params));
+#elif QT_CONFIG(vulkan)
+    inst.setExtensions(QRhiVulkanInitParams::preferredInstanceExtensions());
+    if (inst.create()) {
+        QRhiVulkanInitParams params;
+        params.inst = &inst;
+        rhi.reset(QRhi::create(QRhi::Vulkan, &params));
+    } else {
+        qFatal("Failed to create Vulkan instance");
+    }
+#endif
+    if (rhi)
+        qDebug() << rhi->backendName() << rhi->driverInfo();
+    else
+        qFatal("Failed to initialize RHI");
+
+    float rotation = 0.0f;
+    float opacity = 1.0f;
+    int opacityDir = 1;
+
+    std::unique_ptr<QRhiTexture> tex(rhi->newTexture(QRhiTexture::RGBA8,
+                                                     QSize(1280, 720),
+                                                     1,
+                                                     QRhiTexture::RenderTarget | QRhiTexture::UsedAsTransferSource));
+    tex->create();
+    std::unique_ptr<QRhiTextureRenderTarget> rt(rhi->newTextureRenderTarget({ tex.get() }));
+    std::unique_ptr<QRhiRenderPassDescriptor> rp(rt->newCompatibleRenderPassDescriptor());
+    rt->setRenderPassDescriptor(rp.get());
+    rt->create();
+
+    QMatrix4x4 viewProjection = rhi->clipSpaceCorrMatrix();
+    viewProjection.perspective(45.0f, 1280 / 720.f, 0.01f, 1000.0f);
+    viewProjection.translate(0, 0, -4);
+
+    static float vertexData[] = { // Y up, CCW
+        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,
+    };
+
+    std::unique_ptr<QRhiBuffer> vbuf(rhi->newBuffer(QRhiBuffer::Immutable,
+                                                    QRhiBuffer::VertexBuffer,
+                                                    sizeof(vertexData)));
+    vbuf->create();
+
+    std::unique_ptr<QRhiBuffer> ubuf(rhi->newBuffer(QRhiBuffer::Dynamic,
+                                                    QRhiBuffer::UniformBuffer,
+                                                    64 + 4));
+    ubuf->create();
+
+    std::unique_ptr<QRhiShaderResourceBindings> srb(rhi->newShaderResourceBindings());
+    srb->setBindings({
+        QRhiShaderResourceBinding::uniformBuffer(0,
+                                                 QRhiShaderResourceBinding::VertexStage | QRhiShaderResourceBinding::FragmentStage,
+                                                 ubuf.get())
+    });
+    srb->create();
+
+    std::unique_ptr<QRhiGraphicsPipeline> ps(rhi->newGraphicsPipeline());
+    QRhiGraphicsPipeline::TargetBlend premulAlphaBlend;
+    premulAlphaBlend.enable = true;
+    ps->setTargetBlends({ premulAlphaBlend });
+    static auto getShader = [](const QString &name) {
+        QFile f(name);
+        return f.open(QIODevice::ReadOnly) ? QShader::fromSerialized(f.readAll()) : QShader();
+    };
+    ps->setShaderStages({
+        { QRhiShaderStage::Vertex, getShader(QLatin1String("color.vert.qsb")) },
+        { QRhiShaderStage::Fragment, getShader(QLatin1String("color.frag.qsb")) }
+    });
+    QRhiVertexInputLayout inputLayout;
+    inputLayout.setBindings({
+        { 5 * sizeof(float) }
+    });
+    inputLayout.setAttributes({
+        { 0, 0, QRhiVertexInputAttribute::Float2, 0 },
+        { 0, 1, QRhiVertexInputAttribute::Float3, 2 * sizeof(float) }
+    });
+    ps->setVertexInputLayout(inputLayout);
+    ps->setShaderResourceBindings(srb.get());
+    ps->setRenderPassDescriptor(rp.get());
+    ps->create();
+
+    QRhiCommandBuffer *cb;
+    for (int frame = 0; frame < 20; ++frame) {
+        rhi->beginOffscreenFrame(&cb);
+
+        QRhiResourceUpdateBatch *u = rhi->nextResourceUpdateBatch();
+        if (frame == 0)
+            u->uploadStaticBuffer(vbuf.get(), vertexData);
+
+        QMatrix4x4 mvp = viewProjection;
+        mvp.rotate(rotation, 0, 1, 0);
+        u->updateDynamicBuffer(ubuf.get(), 0, 64, mvp.constData());
+        rotation += 5.0f;
+
+        u->updateDynamicBuffer(ubuf.get(), 64, 4, &opacity);
+        opacity += opacityDir * 0.2f;
+        if (opacity < 0.0f || opacity > 1.0f) {
+            opacityDir *= -1;
+            opacity = qBound(0.0f, opacity, 1.0f);
+        }
+
+        cb->beginPass(rt.get(), Qt::green, { 1.0f, 0 }, u);
+        cb->setGraphicsPipeline(ps.get());
+        cb->setViewport({ 0, 0, 1280, 720 });
+        cb->setShaderResources();
+        const QRhiCommandBuffer::VertexInput vbufBinding(vbuf.get(), 0);
+        cb->setVertexInput(0, 1, &vbufBinding);
+        cb->draw(3);
+        QRhiReadbackResult readbackResult;
+        u = rhi->nextResourceUpdateBatch();
+        u->readBackTexture({ tex.get() }, &readbackResult);
+        cb->endPass(u);
+
+        rhi->endOffscreenFrame();
+
+        QImage image(reinterpret_cast<const uchar *>(readbackResult.data.constData()),
+                     readbackResult.pixelSize.width(),
+                     readbackResult.pixelSize.height(),
+                     QImage::Format_RGBA8888_Premultiplied);
+        if (rhi->isYUpInFramebuffer())
+            image = image.mirrored();
+        image.save(QString::asprintf("frame%d.png", frame));
+    }
+
+    return 0;
+}
+//! [0]