xorblender.cpp Example File

scenegraph/twotextureproviders/xorblender.cpp
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#include "xorblender.h" #include <QtCore/QPointer> #include <QtGui/QOpenGLContext> #include <QtGui/QOpenGLFunctions> #include <QtQuick/QSGSimpleMaterial> #include <QtQuick/QSGTexture> #include <QtQuick/QSGGeometryNode> #include <QtQuick/QSGTextureProvider> /* This example could just as well have been implemented all in QML using * a ShaderEffect, and for 90% of all usecases, using a ShaderEffect will * be sufficient. This example exists to illustrate how to consume * texture providers from C++ and how to use multiple texture sources in * a custom material. */ struct XorBlendState { QSGTexture *texture1; QSGTexture *texture2; }; class XorBlendShader : public QSGSimpleMaterialShader<XorBlendState> { QSG_DECLARE_SIMPLE_SHADER(XorBlendShader, XorBlendState) public: const char *vertexShader() const override { return "attribute highp vec4 aVertex; \n" "attribute highp vec2 aTexCoord; \n" "uniform highp mat4 qt_Matrix; \n" "varying highp vec2 vTexCoord; \n" "void main() { \n" " gl_Position = qt_Matrix * aVertex; \n" " vTexCoord = aTexCoord; \n" "}"; } const char *fragmentShader() const override { return "uniform lowp float qt_Opacity; \n" "uniform lowp sampler2D uSource1; \n" "uniform lowp sampler2D uSource2; \n" "varying highp vec2 vTexCoord; \n" "void main() { \n" " lowp vec4 p1 = texture2D(uSource1, vTexCoord); \n" " lowp vec4 p2 = texture2D(uSource2, vTexCoord); \n" " gl_FragColor = (p1 * (1.0 - p2.a) + p2 * (1.0 - p1.a)) * qt_Opacity; \n" "}"; } QList<QByteArray> attributes() const override { return QList<QByteArray>() << "aVertex" << "aTexCoord"; } void updateState(const XorBlendState *state, const XorBlendState *) override { QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions(); // We bind the textures in inverse order so that we leave the updateState // function with GL_TEXTURE0 as the active texture unit. This is maintain // the "contract" that updateState should not mess up the GL state beyond // what is needed for this material. f->glActiveTexture(GL_TEXTURE1); state->texture2->bind(); f->glActiveTexture(GL_TEXTURE0); state->texture1->bind(); } void resolveUniforms() override { // The texture units never change, only the texturess we bind to them so // we set these once and for all here. program()->setUniformValue("uSource1", 0); // GL_TEXTURE0 program()->setUniformValue("uSource2", 1); // GL_TEXTURE1 } }; /* The rendering is split into two nodes. The top-most node is not actually * rendering anything, but is responsible for managing the texture providers. * The XorNode also has a geometry node internally which it uses to render * the texture providers using the XorBlendShader when all providers and * textures are all present. * * The texture providers are updated solely on the render thread (when rendering * is happening on a separate thread). This is why we are using preprocess * and direct signals between the the texture providers and the node rather * than updating state in updatePaintNode. */ class XorNode : public QObject, public QSGNode { Q_OBJECT public: XorNode(QSGTextureProvider *p1, QSGTextureProvider *p2) : m_provider1(p1) , m_provider2(p2) { setFlag(QSGNode::UsePreprocess, true); // Set up material so it is all set for later.. m_material = XorBlendShader::createMaterial(); m_material->state()->texture1 = nullptr; m_material->state()->texture2 = nullptr; m_material->setFlag(QSGMaterial::Blending); m_node.setMaterial(m_material); m_node.setFlag(QSGNode::OwnsMaterial); // Set up geometry, actual vertices will be initialized in updatePaintNode m_node.setGeometry(new QSGGeometry(QSGGeometry::defaultAttributes_TexturedPoint2D(), 4)); m_node.setFlag(QSGNode::OwnsGeometry); // If this node is used as in a shader effect source, we need to propegate // changes that will occur in this node outwards. connect(m_provider1.data(), &QSGTextureProvider::textureChanged, this, &XorNode::textureChange, Qt::DirectConnection); connect(m_provider2.data(), &QSGTextureProvider::textureChanged, this, &XorNode::textureChange, Qt::DirectConnection); } void preprocess() override { XorBlendState *state = m_material->state(); // Update the textures from the providers, calling into QSGDynamicTexture if required if (m_provider1) { state->texture1 = m_provider1->texture(); if (QSGDynamicTexture *dt1 = qobject_cast<QSGDynamicTexture *>(state->texture1)) dt1->updateTexture(); } if (m_provider2) { state->texture2 = m_provider2->texture(); if (QSGDynamicTexture *dt2 = qobject_cast<QSGDynamicTexture *>(state->texture2)) dt2->updateTexture(); } // Remove node from the scene graph if it is there and either texture is missing... if (m_node.parent() && (!state->texture1 || !state->texture2)) removeChildNode(&m_node); // Add it if it is not already there and both textures are present.. else if (!m_node.parent() && state->texture1 && state->texture2) appendChildNode(&m_node); } void setRect(const QRectF &rect) { // Update geometry if it has changed and mark the change in the scene graph. if (m_rect != rect) { m_rect = rect; QSGGeometry::updateTexturedRectGeometry(m_node.geometry(), m_rect, QRectF(0, 0, 1, 1)); m_node.markDirty(QSGNode::DirtyGeometry); } } public slots: void textureChange() { // When our sources change, we will look different, so signal the change to the // scene graph. markDirty(QSGNode::DirtyMaterial); } private: QRectF m_rect; QSGSimpleMaterial<XorBlendState> *m_material; QSGGeometryNode m_node; QPointer<QSGTextureProvider> m_provider1; QPointer<QSGTextureProvider> m_provider2; }; XorBlender::XorBlender(QQuickItem *parent) : QQuickItem(parent) , m_source1(nullptr) , m_source2(nullptr) , m_source1Changed(false) , m_source2Changed(false) { setFlag(ItemHasContents, true); } void XorBlender::setSource1(QQuickItem *i) { if (i == m_source1) return; m_source1 = i; emit source1Changed(m_source1); m_source1Changed = true; update(); } void XorBlender::setSource2(QQuickItem *i) { if (i == m_source2) return; m_source2 = i; emit source2Changed(m_source2); m_source2Changed = true; update(); } QSGNode *XorBlender::updatePaintNode(QSGNode *old, UpdatePaintNodeData *) { // Check if our input is valid and abort if not, deleting the old node. bool abort = false; if (!m_source1 || !m_source1->isTextureProvider()) { qDebug() << "source1 is missing or not a texture provider"; abort = true; } if (!m_source2 || !m_source2->isTextureProvider()) { qDebug() << "source2 is missing or not a texture provider"; abort = true; } if (abort) { delete old; return nullptr; } XorNode *node = static_cast<XorNode *>(old); // If the sources have changed, recreate the nodes if (m_source1Changed || m_source2Changed) { delete node; node = nullptr; m_source1Changed = false; m_source2Changed = false; } // Create a new XorNode for us to render with. if (!node) node = new XorNode(m_source1->textureProvider(), m_source2->textureProvider()); // Update the geometry of the node to match the new bounding rect node->setRect(boundingRect()); return node; } #include "xorblender.moc"

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