threadedqopenglwidget example: Split out class Renderer

This makes the code clearer and decouples it from the
GLWidget.

As a drive-by, add a global shortcut to close.

Pick-to: 6.3 6.2
Change-Id: I3469d29bc367acc17c5f8acf9d46219259b8315b
Reviewed-by: Laszlo Agocs <[email protected]>

1 files changed, 314 insertions, 0 deletions

diff --git a/examples/opengl/threadedqopenglwidget/renderer.cpp b/examples/opengl/threadedqopenglwidget/renderer.cpp
new file mode 100644
index 00000000000..f1b4e21e503
--- /dev/null
+++ b/examples/opengl/threadedqopenglwidget/renderer.cpp
@@ -0,0 +1,314 @@
+/****************************************************************************
+**
+** Copyright (C) 2022 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "renderer.h"
+#include <qmath.h>
+#include <QOpenGLWidget>
+#include <QGuiApplication>
+
+static const char VERTEX_SHADER[] = R"(attribute highp vec4 vertex;
+attribute mediump vec3 normal;
+uniform mediump mat4 matrix;
+varying mediump vec4 color;
+void main(void)
+{
+    vec3 toLight = normalize(vec3(0.0, 0.3, 1.0));
+    float angle = max(dot(normal, toLight), 0.0);
+    vec3 col = vec3(0.40, 1.0, 0.0);
+    color = vec4(col * 0.2 + col * 0.8 * angle, 1.0);
+    color = clamp(color, 0.0, 1.0);
+    gl_Position = matrix * vertex;
+}
+)";
+
+static const char FRAGMENT_SHADER[] = R"(varying mediump vec4 color;
+void main(void)
+{
+    gl_FragColor = color;
+}
+)";
+
+Renderer::Renderer(QOpenGLWidget *w) :
+    m_glwidget(w)
+{
+}
+
+void Renderer::paintQtLogo()
+{
+    vbo.bind();
+    program.setAttributeBuffer(vertexAttr, GL_FLOAT, 0, 3);
+    program.setAttributeBuffer(normalAttr, GL_FLOAT, vertices.count() * 3 * sizeof(GLfloat), 3);
+    vbo.release();
+
+    program.enableAttributeArray(vertexAttr);
+    program.enableAttributeArray(normalAttr);
+
+    glDrawArrays(GL_TRIANGLES, 0, vertices.size());
+
+    program.disableAttributeArray(normalAttr);
+    program.disableAttributeArray(vertexAttr);
+}
+
+// Some OpenGL implementations have serious issues with compiling and linking
+// shaders on multiple threads concurrently. Avoid this.
+Q_GLOBAL_STATIC(QMutex, initMutex)
+
+void Renderer::render()
+{
+    if (m_exiting)
+        return;
+
+    QOpenGLContext *ctx = m_glwidget->context();
+    if (!ctx) // QOpenGLWidget not yet initialized
+        return;
+
+    // Grab the context.
+    m_grabMutex.lock();
+    emit contextWanted();
+    m_grabCond.wait(&m_grabMutex);
+    QMutexLocker lock(&m_renderMutex);
+    m_grabMutex.unlock();
+
+    if (m_exiting)
+        return;
+
+    Q_ASSERT(ctx->thread() == QThread::currentThread());
+
+    // Make the context (and an offscreen surface) current for this thread. The
+    // QOpenGLWidget's fbo is bound in the context.
+    m_glwidget->makeCurrent();
+
+    if (!m_inited) {
+        m_inited = true;
+        initializeOpenGLFunctions();
+
+        QMutexLocker initLock(initMutex());
+        QOpenGLShader *vshader = new QOpenGLShader(QOpenGLShader::Vertex, this);
+        vshader->compileSourceCode(VERTEX_SHADER);
+
+        QOpenGLShader *fshader = new QOpenGLShader(QOpenGLShader::Fragment, this);
+        fshader->compileSourceCode(FRAGMENT_SHADER);
+
+        program.addShader(vshader);
+        program.addShader(fshader);
+        program.link();
+
+        vertexAttr = program.attributeLocation("vertex");
+        normalAttr = program.attributeLocation("normal");
+        matrixUniform = program.uniformLocation("matrix");
+
+        m_fAngle = 0;
+        m_fScale = 1;
+        createGeometry();
+
+        vbo.create();
+        vbo.bind();
+        const int verticesSize = vertices.count() * 3 * sizeof(GLfloat);
+        vbo.allocate(verticesSize * 2);
+        vbo.write(0, vertices.constData(), verticesSize);
+        vbo.write(verticesSize, normals.constData(), verticesSize);
+
+        m_elapsed.start();
+    }
+
+    //qDebug("%p elapsed %lld", QThread::currentThread(), m_elapsed.restart());
+
+    glClearColor(0.1f, 0.2f, 0.2f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+    glFrontFace(GL_CW);
+    glCullFace(GL_FRONT);
+    glEnable(GL_CULL_FACE);
+    glEnable(GL_DEPTH_TEST);
+
+    QMatrix4x4 modelview;
+    modelview.rotate(m_fAngle, 0.0f, 1.0f, 0.0f);
+    modelview.rotate(m_fAngle, 1.0f, 0.0f, 0.0f);
+    modelview.rotate(m_fAngle, 0.0f, 0.0f, 1.0f);
+    modelview.scale(m_fScale);
+    modelview.translate(0.0f, -0.2f, 0.0f);
+
+    program.bind();
+    program.setUniformValue(matrixUniform, modelview);
+    paintQtLogo();
+    program.release();
+
+    glDisable(GL_DEPTH_TEST);
+    glDisable(GL_CULL_FACE);
+
+    m_fAngle += 1.0f;
+
+    // Make no context current on this thread and move the QOpenGLWidget's
+    // context back to the gui thread.
+    m_glwidget->doneCurrent();
+    ctx->moveToThread(qGuiApp->thread());
+
+    // Schedule composition. Note that this will use QueuedConnection, meaning
+    // that update() will be invoked on the gui thread.
+    QMetaObject::invokeMethod(m_glwidget, "update");
+}
+
+void Renderer::createGeometry()
+{
+    vertices.clear();
+    normals.clear();
+
+    qreal x1 = +0.06f;
+    qreal y1 = -0.14f;
+    qreal x2 = +0.14f;
+    qreal y2 = -0.06f;
+    qreal x3 = +0.08f;
+    qreal y3 = +0.00f;
+    qreal x4 = +0.30f;
+    qreal y4 = +0.22f;
+
+    quad(x1, y1, x2, y2, y2, x2, y1, x1);
+    quad(x3, y3, x4, y4, y4, x4, y3, x3);
+
+    extrude(x1, y1, x2, y2);
+    extrude(x2, y2, y2, x2);
+    extrude(y2, x2, y1, x1);
+    extrude(y1, x1, x1, y1);
+    extrude(x3, y3, x4, y4);
+    extrude(x4, y4, y4, x4);
+    extrude(y4, x4, y3, x3);
+
+    const int NumSectors = 100;
+    const qreal sectorAngle = 2 * qreal(M_PI) / NumSectors;
+
+    for (int i = 0; i < NumSectors; ++i) {
+        qreal angle = i * sectorAngle;
+        qreal sinAngle = sin(angle);
+        qreal cosAngle = cos(angle);
+        qreal x5 = 0.30 * sinAngle;
+        qreal y5 = 0.30 * cosAngle;
+        qreal x6 = 0.20 * sinAngle;
+        qreal y6 = 0.20 * cosAngle;
+
+        angle += sectorAngle;
+        sinAngle = sin(angle);
+        cosAngle = cos(angle);
+        qreal x7 = 0.20 * sinAngle;
+        qreal y7 = 0.20 * cosAngle;
+        qreal x8 = 0.30 * sinAngle;
+        qreal y8 = 0.30 * cosAngle;
+
+        quad(x5, y5, x6, y6, x7, y7, x8, y8);
+
+        extrude(x6, y6, x7, y7);
+        extrude(x8, y8, x5, y5);
+    }
+
+    for (qsizetype i = 0; i < vertices.size(); ++i)
+        vertices[i] *= 2.0f;
+}
+
+void Renderer::quad(qreal x1, qreal y1, qreal x2, qreal y2, qreal x3, qreal y3, qreal x4, qreal y4)
+{
+    vertices << QVector3D(x1, y1, -0.05f);
+    vertices << QVector3D(x2, y2, -0.05f);
+    vertices << QVector3D(x4, y4, -0.05f);
+
+    vertices << QVector3D(x3, y3, -0.05f);
+    vertices << QVector3D(x4, y4, -0.05f);
+    vertices << QVector3D(x2, y2, -0.05f);
+
+    QVector3D n = QVector3D::normal
+        (QVector3D(x2 - x1, y2 - y1, 0.0f), QVector3D(x4 - x1, y4 - y1, 0.0f));
+
+    normals << n;
+    normals << n;
+    normals << n;
+
+    normals << n;
+    normals << n;
+    normals << n;
+
+    vertices << QVector3D(x4, y4, 0.05f);
+    vertices << QVector3D(x2, y2, 0.05f);
+    vertices << QVector3D(x1, y1, 0.05f);
+
+    vertices << QVector3D(x2, y2, 0.05f);
+    vertices << QVector3D(x4, y4, 0.05f);
+    vertices << QVector3D(x3, y3, 0.05f);
+
+    n = QVector3D::normal
+        (QVector3D(x2 - x4, y2 - y4, 0.0f), QVector3D(x1 - x4, y1 - y4, 0.0f));
+
+    normals << n;
+    normals << n;
+    normals << n;
+
+    normals << n;
+    normals << n;
+    normals << n;
+}
+
+void Renderer::extrude(qreal x1, qreal y1, qreal x2, qreal y2)
+{
+    vertices << QVector3D(x1, y1, +0.05f);
+    vertices << QVector3D(x2, y2, +0.05f);
+    vertices << QVector3D(x1, y1, -0.05f);
+
+    vertices << QVector3D(x2, y2, -0.05f);
+    vertices << QVector3D(x1, y1, -0.05f);
+    vertices << QVector3D(x2, y2, +0.05f);
+
+    QVector3D n = QVector3D::normal
+        (QVector3D(x2 - x1, y2 - y1, 0.0f), QVector3D(0.0f, 0.0f, -0.1f));
+
+    normals << n;
+    normals << n;
+    normals << n;
+
+    normals << n;
+    normals << n;
+    normals << n;
+}