rhi: Autotest rendering a triangle

Also improve (docs and runtime checks) and test the minimum set
of required data to create a graphics pipeline.

Task-number: QTBUG-78971
Change-Id: If5c14f1ab1ff3cf70f168fde585f05fc9d28ec91
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

src/gui/rhi/qrhi.cpp

@@ -3084,9 +3084,13 @@ QDebug operator<<(QDebug dbg, const QRhiShaderResourceBindings &srb)
     \inmodule QtGui
     \brief Graphics pipeline state resource.
 
+    \note Setting the shader stages is mandatory. There must be at least one
+    stage, and there must be a vertex stage.
+
     \note Setting the shader resource bindings is mandatory. The referenced
     QRhiShaderResourceBindings must already be built by the time build() is
-    called.
+    called. Associating with a QRhiShaderResourceBindings that has no bindings
+    is also valid, as long as no shader in any stage expects any resources.
 
     \note Setting the render pass descriptor is mandatory. To obtain a
     QRhiRenderPassDescriptor that can be passed to setRenderPassDescriptor(),
@@ -3095,8 +3099,6 @@ QDebug operator<<(QDebug dbg, const QRhiShaderResourceBindings &srb)
 
     \note Setting the vertex input layout is mandatory.
 
-    \note Setting the shader stages is mandatory.
-
     \note sampleCount() defaults to 1 and must match the sample count of the
     render target's color and depth stencil attachments.
 
@@ -3912,6 +3914,46 @@ quint32 QRhiImplementation::approxByteSizeForTexture(QRhiTexture::Format format,
     return approxSize;
 }
 
+bool QRhiImplementation::sanityCheckGraphicsPipeline(QRhiGraphicsPipeline *ps)
+{
+    if (ps->cbeginShaderStages() == ps->cendShaderStages()) {
+        qWarning("Cannot build a graphics pipeline without any stages");
+        return false;
+    }
+
+    bool hasVertexStage = false;
+    for (auto it = ps->cbeginShaderStages(), itEnd = ps->cendShaderStages(); it != itEnd; ++it) {
+        if (!it->shader().isValid()) {
+            qWarning("Empty shader passed to graphics pipeline");
+            return false;
+        }
+        if (it->type() == QRhiShaderStage::Vertex) {
+            hasVertexStage = true;
+            const QRhiVertexInputLayout inputLayout = ps->vertexInputLayout();
+            if (inputLayout.cbeginAttributes() == inputLayout.cendAttributes()) {
+                qWarning("Vertex stage present without any vertex inputs");
+                return false;
+            }
+        }
+    }
+    if (!hasVertexStage) {
+        qWarning("Cannot build a graphics pipeline without a vertex stage");
+        return false;
+    }
+
+    if (!ps->renderPassDescriptor()) {
+        qWarning("Cannot build a graphics pipeline without a QRhiRenderPassDescriptor");
+        return false;
+    }
+
+    if (!ps->shaderResourceBindings()) {
+        qWarning("Cannot build a graphics pipeline without QRhiShaderResourceBindings");
+        return false;
+    }
+
+    return true;
+}
+
 /*!
     \internal
  */

src/gui/rhi/qrhi_p.h

@@ -72,7 +72,6 @@ class QRhiCommandBuffer;
 class QRhiResourceUpdateBatch;
 class QRhiResourceUpdateBatchPrivate;
 class QRhiProfiler;
-class QRhiShaderResourceBindingPrivate;
 
 class Q_GUI_EXPORT QRhiDepthStencilClearValue
 {

src/gui/rhi/qrhi_p_p.h

@@ -205,6 +205,8 @@ public:
         cleanupCallbacks.append(callback);
     }
 
+    bool sanityCheckGraphicsPipeline(QRhiGraphicsPipeline *ps);
+
     QRhi *q;
 
     static const int MAX_SHADER_CACHE_ENTRIES = 128;

src/gui/rhi/qrhid3d11.cpp

@@ -3491,6 +3491,8 @@ bool QD3D11GraphicsPipeline::build()
         release();
 
     QRHI_RES_RHI(QRhiD3D11);
+    if (!rhiD->sanityCheckGraphicsPipeline(this))
+        return false;
 
     D3D11_RASTERIZER_DESC rastDesc;
     memset(&rastDesc, 0, sizeof(rastDesc));

src/gui/rhi/qrhigles2.cpp

@@ -3690,6 +3690,9 @@ bool QGles2GraphicsPipeline::build()
     if (!rhiD->ensureContext())
         return false;
 
+    if (!rhiD->sanityCheckGraphicsPipeline(this))
+        return false;
+
     drawMode = toGlTopology(m_topology);
 
     program = rhiD->f->glCreateProgram();

src/gui/rhi/qrhimetal.mm

@@ -3139,6 +3139,8 @@ bool QMetalGraphicsPipeline::build()
         release();
 
     QRHI_RES_RHI(QRhiMetal);
+    if (!rhiD->sanityCheckGraphicsPipeline(this))
+        return false;
 
     // same binding space for vertex and constant buffers - work it around
     const int firstVertexBinding = QRHI_RES(QMetalShaderResourceBindings, m_shaderResourceBindings)->maxBinding + 1;

src/gui/rhi/qrhinull.cpp

@@ -805,6 +805,10 @@ void QNullGraphicsPipeline::release()
 
 bool QNullGraphicsPipeline::build()
 {
+    QRHI_RES_RHI(QRhiNull);
+    if (!rhiD->sanityCheckGraphicsPipeline(this))
+        return false;
+
     return true;
 }
 

src/gui/rhi/qrhivulkan.cpp

@@ -5886,6 +5886,9 @@ bool QVkGraphicsPipeline::build()
         release();
 
     QRHI_RES_RHI(QRhiVulkan);
+    if (!rhiD->sanityCheckGraphicsPipeline(this))
+        return false;
+
     if (!rhiD->ensurePipelineCache())
         return false;
 

tests/auto/gui/rhi/qrhi/data/simple.frag

@@ -0,0 +1,8 @@
+#version 440
+
+layout(location = 0) out vec4 fragColor;
+
+void main()
+{
+    fragColor = vec4(1.0, 0.0, 0.0, 1.0);
+}

tests/auto/gui/rhi/qrhi/data/simple.vert

@@ -0,0 +1,10 @@
+#version 440
+
+layout(location = 0) in vec4 position;
+
+out gl_PerVertex { vec4 gl_Position; };
+
+void main()
+{
+    gl_Position = position;
+}

tests/auto/gui/rhi/qrhi/data/texture.frag

@@ -1,12 +0,0 @@
-#version 440
-
-layout(location = 0) in vec2 v_texcoord;
-
-layout(location = 0) out vec4 fragColor;
-
-layout(binding = 1) uniform sampler2D tex;
-
-void main()
-{
-    fragColor = texture(tex, v_texcoord);
-}

tests/auto/gui/rhi/qrhi/data/texture.vert

@@ -1,18 +0,0 @@
-#version 440
-
-layout(location = 0) in vec4 position;
-layout(location = 1) in vec2 texcoord;
-
-layout(location = 0) out vec2 v_texcoord;
-
-layout(std140, binding = 0) uniform buf {
-    mat4 mvp;
-} ubuf;
-
-out gl_PerVertex { vec4 gl_Position; };
-
-void main()
-{
-    v_texcoord = texcoord;
-    gl_Position = ubuf.mvp * position;
-}

tests/auto/gui/rhi/qrhi/tst_qrhi.cpp

@@ -81,6 +81,10 @@ private slots:
     void resourceUpdateBatchRGBATextureCopy();
     void resourceUpdateBatchRGBATextureMip_data();
     void resourceUpdateBatchRGBATextureMip();
+    void invalidPipeline_data();
+    void invalidPipeline();
+    void renderToTextureSimple_data();
+    void renderToTextureSimple();
 
 private:
     struct {
@@ -980,5 +984,222 @@ void tst_QRhi::resourceUpdateBatchRGBATextureMip()
     }
 }
 
+static QShader loadShader(const char *name)
+{
+    QFile f(QString::fromUtf8(name));
+    if (f.open(QIODevice::ReadOnly)) {
+        const QByteArray contents = f.readAll();
+        return QShader::fromSerialized(contents);
+    }
+    return QShader();
+}
+
+void tst_QRhi::invalidPipeline_data()
+{
+    rhiTestData();
+}
+
+void tst_QRhi::invalidPipeline()
+{
+    QFETCH(QRhi::Implementation, impl);
+    QFETCH(QRhiInitParams *, initParams);
+
+    QScopedPointer<QRhi> rhi(QRhi::create(impl, initParams, QRhi::Flags(), nullptr));
+    if (!rhi)
+        QSKIP("QRhi could not be created, skipping testing empty shader");
+
+    QScopedPointer<QRhiTexture> texture(rhi->newTexture(QRhiTexture::RGBA8, QSize(256, 256), 1, QRhiTexture::RenderTarget));
+    QVERIFY(texture->build());
+    QScopedPointer<QRhiTextureRenderTarget> rt(rhi->newTextureRenderTarget({ texture.data() }));
+    QScopedPointer<QRhiRenderPassDescriptor> rpDesc(rt->newCompatibleRenderPassDescriptor());
+    rt->setRenderPassDescriptor(rpDesc.data());
+    QVERIFY(rt->build());
+
+    QRhiCommandBuffer *cb = nullptr;
+    QVERIFY(rhi->beginOffscreenFrame(&cb) == QRhi::FrameOpSuccess);
+    QVERIFY(cb);
+
+    QScopedPointer<QRhiShaderResourceBindings> srb(rhi->newShaderResourceBindings());
+    QVERIFY(srb->build());
+
+    QRhiVertexInputLayout inputLayout;
+    inputLayout.setBindings({ { 2 * sizeof(float) } });
+    inputLayout.setAttributes({ { 0, 0, QRhiVertexInputAttribute::Float2, 0 } });
+
+    // no stages
+    QScopedPointer<QRhiGraphicsPipeline> pipeline(rhi->newGraphicsPipeline());
+    pipeline->setVertexInputLayout(inputLayout);
+    pipeline->setShaderResourceBindings(srb.data());
+    pipeline->setRenderPassDescriptor(rpDesc.data());
+    QVERIFY(!pipeline->build());
+
+    QShader vs;
+    QShader fs;
+
+    // no shaders in the stages
+    pipeline.reset(rhi->newGraphicsPipeline());
+    pipeline->setShaderStages({ { QRhiShaderStage::Vertex, vs }, { QRhiShaderStage::Fragment, fs } });
+    pipeline->setVertexInputLayout(inputLayout);
+    pipeline->setShaderResourceBindings(srb.data());
+    pipeline->setRenderPassDescriptor(rpDesc.data());
+    QVERIFY(!pipeline->build());
+
+    vs = loadShader(":/data/simple.vert.qsb");
+    QVERIFY(vs.isValid());
+    fs = loadShader(":/data/simple.frag.qsb");
+    QVERIFY(fs.isValid());
+
+    // no vertex stage
+    pipeline.reset(rhi->newGraphicsPipeline());
+    pipeline->setShaderStages({ { QRhiShaderStage::Fragment, fs } });
+    pipeline->setVertexInputLayout(inputLayout);
+    pipeline->setShaderResourceBindings(srb.data());
+    pipeline->setRenderPassDescriptor(rpDesc.data());
+    QVERIFY(!pipeline->build());
+
+    // no vertex inputs
+    pipeline.reset(rhi->newGraphicsPipeline());
+    pipeline->setShaderStages({ { QRhiShaderStage::Vertex, vs }, { QRhiShaderStage::Fragment, fs } });
+    pipeline->setRenderPassDescriptor(rpDesc.data());
+    pipeline->setShaderResourceBindings(srb.data());
+    QVERIFY(!pipeline->build());
+
+    // no renderpass descriptor
+    pipeline.reset(rhi->newGraphicsPipeline());
+    pipeline->setShaderStages({ { QRhiShaderStage::Vertex, vs }, { QRhiShaderStage::Fragment, fs } });
+    pipeline->setVertexInputLayout(inputLayout);
+    pipeline->setShaderResourceBindings(srb.data());
+    QVERIFY(!pipeline->build());
+
+    // no shader resource bindings
+    pipeline.reset(rhi->newGraphicsPipeline());
+    pipeline->setShaderStages({ { QRhiShaderStage::Vertex, vs }, { QRhiShaderStage::Fragment, fs } });
+    pipeline->setVertexInputLayout(inputLayout);
+    pipeline->setRenderPassDescriptor(rpDesc.data());
+    QVERIFY(!pipeline->build());
+
+    // correct
+    pipeline.reset(rhi->newGraphicsPipeline());
+    pipeline->setShaderStages({ { QRhiShaderStage::Vertex, vs }, { QRhiShaderStage::Fragment, fs } });
+    pipeline->setVertexInputLayout(inputLayout);
+    pipeline->setRenderPassDescriptor(rpDesc.data());
+    pipeline->setShaderResourceBindings(srb.data());
+    QVERIFY(pipeline->build());
+}
+
+void tst_QRhi::renderToTextureSimple_data()
+{
+    rhiTestData();
+}
+
+void tst_QRhi::renderToTextureSimple()
+{
+    QFETCH(QRhi::Implementation, impl);
+    QFETCH(QRhiInitParams *, initParams);
+
+    QScopedPointer<QRhi> rhi(QRhi::create(impl, initParams, QRhi::Flags(), nullptr));
+    if (!rhi)
+        QSKIP("QRhi could not be created, skipping testing rendering");
+
+    const QSize outputSize(1920, 1080);
+    QScopedPointer<QRhiTexture> texture(rhi->newTexture(QRhiTexture::RGBA8, outputSize, 1,
+                                                        QRhiTexture::RenderTarget | QRhiTexture::UsedAsTransferSource));
+    QVERIFY(texture->build());
+
+    QScopedPointer<QRhiTextureRenderTarget> rt(rhi->newTextureRenderTarget({ texture.data() }));
+    QScopedPointer<QRhiRenderPassDescriptor> rpDesc(rt->newCompatibleRenderPassDescriptor());
+    rt->setRenderPassDescriptor(rpDesc.data());
+    QVERIFY(rt->build());
+
+    QRhiCommandBuffer *cb = nullptr;
+    QVERIFY(rhi->beginOffscreenFrame(&cb) == QRhi::FrameOpSuccess);
+    QVERIFY(cb);
+
+    QRhiResourceUpdateBatch *updates = rhi->nextResourceUpdateBatch();
+
+    static const float vertices[] = {
+        -1.0f, -1.0f,
+        1.0f, -1.0f,
+        0.0f, 1.0f
+    };
+    QScopedPointer<QRhiBuffer> vbuf(rhi->newBuffer(QRhiBuffer::Immutable, QRhiBuffer::VertexBuffer, sizeof(vertices)));
+    QVERIFY(vbuf->build());
+    updates->uploadStaticBuffer(vbuf.data(), vertices);
+
+    QScopedPointer<QRhiShaderResourceBindings> srb(rhi->newShaderResourceBindings());
+    QVERIFY(srb->build());
+
+    QScopedPointer<QRhiGraphicsPipeline> pipeline(rhi->newGraphicsPipeline());
+    QShader vs = loadShader(":/data/simple.vert.qsb");
+    QVERIFY(vs.isValid());
+    QShader fs = loadShader(":/data/simple.frag.qsb");
+    QVERIFY(fs.isValid());
+    pipeline->setShaderStages({ { QRhiShaderStage::Vertex, vs }, { QRhiShaderStage::Fragment, fs } });
+    QRhiVertexInputLayout inputLayout;
+    inputLayout.setBindings({ { 2 * sizeof(float) } });
+    inputLayout.setAttributes({ { 0, 0, QRhiVertexInputAttribute::Float2, 0 } });
+    pipeline->setVertexInputLayout(inputLayout);
+    pipeline->setShaderResourceBindings(srb.data());
+    pipeline->setRenderPassDescriptor(rpDesc.data());
+
+    QVERIFY(pipeline->build());
+
+    cb->beginPass(rt.data(), Qt::blue, { 1.0f, 0 }, updates);
+    cb->setGraphicsPipeline(pipeline.data());
+    cb->setViewport({ 0, 0, float(outputSize.width()), float(outputSize.height()) });
+    QRhiCommandBuffer::VertexInput vbindings(vbuf.data(), 0);
+    cb->setVertexInput(0, 1, &vbindings);
+    cb->draw(3);
+
+    QRhiReadbackResult readResult;
+    QImage result;
+    readResult.completed = [&readResult, &result] {
+        result = QImage(reinterpret_cast<const uchar *>(readResult.data.constData()),
+                        readResult.pixelSize.width(), readResult.pixelSize.height(),
+                        QImage::Format_RGBA8888_Premultiplied); // non-owning, no copy needed because readResult outlives result
+    };
+    QRhiResourceUpdateBatch *readbackBatch = rhi->nextResourceUpdateBatch();
+    readbackBatch->readBackTexture({ texture.data() }, &readResult);
+    cb->endPass(readbackBatch);
+
+    rhi->endOffscreenFrame();
+    // Offscreen frames are synchronous, so the readback is guaranteed to
+    // complete at this point. This would not be the case with swapchain-based
+    // frames.
+    QCOMPARE(result.size(), texture->pixelSize());
+
+    if (impl == QRhi::Null)
+        return;
+
+    // Now we have a red rectangle on blue background.
+    const int y = 100;
+    const quint32 *p = reinterpret_cast<const quint32 *>(result.constScanLine(y));
+    int x = result.width() - 1;
+    int redCount = 0;
+    int blueCount = 0;
+    const int maxFuzz = 1;
+    while (x-- >= 0) {
+        const QRgb c(*p++);
+        if (qRed(c) >= (255 - maxFuzz) && qGreen(c) == 0 && qBlue(c) == 0)
+            ++redCount;
+        else if (qRed(c) == 0 && qGreen(c) == 0 && qBlue(c) >= (255 - maxFuzz))
+            ++blueCount;
+        else
+            QFAIL("Encountered a pixel that is neither red or blue");
+    }
+
+    QCOMPARE(redCount + blueCount, texture->pixelSize().width());
+
+    // The triangle is "pointing up" in the resulting image with OpenGL
+    // (because Y is up both in normalized device coordinates and in images)
+    // and Vulkan (because Y is down in both and the vertex data was specified
+    // with Y up in mind), but "pointing down" with D3D (because Y is up in NDC
+    // but down in images).
+    if (rhi->isYUpInFramebuffer() == rhi->isYUpInNDC())
+        QVERIFY(redCount < blueCount);
+    else
+        QVERIFY(redCount > blueCount);
+}
+
 #include <tst_qrhi.moc>
 QTEST_MAIN(tst_QRhi)