squircle.cpp Example File | Qt Quick 5.12.9

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- Scene Graph - OpenGL Under QML
- squircle.cpp Example File
- Qt 5.12.9 Reference Documentation

# squircle.cpp Example File

scenegraph/openglunderqml/squircle.cpp

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     #include "squircle.h"

     #include <QtQuick/qquickwindow.h>
     #include <QtGui/QOpenGLShaderProgram>
     #include <QtGui/QOpenGLContext>

     Squircle::Squircle()
         : m_t(0)
         , m_renderer(nullptr)
     {
         connect(this, &QQuickItem::windowChanged, this, &Squircle::handleWindowChanged);
     }

     void Squircle::setT(qreal t)
     {
         if (t == m_t)
             return;
         m_t = t;
         emit tChanged();
         if (window())
             window()->update();
     }

     void Squircle::handleWindowChanged(QQuickWindow *win)
     {
         if (win) {
             connect(win, &QQuickWindow::beforeSynchronizing, this, &Squircle::sync, Qt::DirectConnection);
             connect(win, &QQuickWindow::sceneGraphInvalidated, this, &Squircle::cleanup, Qt::DirectConnection);
             // If we allow QML to do the clearing, they would clear what we paint
             // and nothing would show.
             win->setClearBeforeRendering(false);
         }
     }

     void Squircle::cleanup()
     {
         if (m_renderer) {
             delete m_renderer;
             m_renderer = nullptr;
         }
     }

     SquircleRenderer::~SquircleRenderer()
     {
         delete m_program;
     }

     void Squircle::sync()
     {
         if (!m_renderer) {
             m_renderer = new SquircleRenderer();
             connect(window(), &QQuickWindow::beforeRendering, m_renderer, &SquircleRenderer::paint, Qt::DirectConnection);
         }
         m_renderer->setViewportSize(window()->size() * window()->devicePixelRatio());
         m_renderer->setT(m_t);
         m_renderer->setWindow(window());
     }

     void SquircleRenderer::paint()
     {
         if (!m_program) {
             initializeOpenGLFunctions();

             m_program = new QOpenGLShaderProgram();
             m_program->addCacheableShaderFromSourceCode(QOpenGLShader::Vertex,
                                                         "attribute highp vec4 vertices;"
                                                         "varying highp vec2 coords;"
                                                         "void main() {"
                                                         "    gl_Position = vertices;"
                                                         "    coords = vertices.xy;"
                                                         "}");
             m_program->addCacheableShaderFromSourceCode(QOpenGLShader::Fragment,
                                                         "uniform lowp float t;"
                                                         "varying highp vec2 coords;"
                                                         "void main() {"
                                                         "    lowp float i = 1. - (pow(abs(coords.x), 4.) + pow(abs(coords.y), 4.));"
                                                         "    i = smoothstep(t - 0.8, t + 0.8, i);"
                                                         "    i = floor(i * 20.) / 20.;"
                                                         "    gl_FragColor = vec4(coords * .5 + .5, i, i);"
                                                         "}");

             m_program->bindAttributeLocation("vertices", 0);
             m_program->link();

         }
         m_program->bind();

         m_program->enableAttributeArray(0);

         float values[] = {
             -1, -1,
             1, -1,
             -1, 1,
             1, 1
         };
         m_program->setAttributeArray(0, GL_FLOAT, values, 2);
         m_program->setUniformValue("t", (float) m_t);

         glViewport(0, 0, m_viewportSize.width(), m_viewportSize.height());

         glDisable(GL_DEPTH_TEST);

         glClearColor(0, 0, 0, 1);
         glClear(GL_COLOR_BUFFER_BIT);

         glEnable(GL_BLEND);
         glBlendFunc(GL_SRC_ALPHA, GL_ONE);

         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

         m_program->disableAttributeArray(0);
         m_program->release();

         // Not strictly needed for this example, but generally useful for when
         // mixing with raw OpenGL.
         m_window->resetOpenGLState();
     }