Organize QtOpenGLWidgets documentation

Move snippets to the right place, and give the widgets class a place to
live.

QtOpenGLWidgets is just a library, not a separate module, but we need a
module page that the class can refer to for correct build instructions.

Change-Id: I6d955ad3c4cd1003a828cc1f256deb6e7fb50ec4
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

7 files changed, 544 insertions, 5 deletions

diff --git a/src/opengl/doc/qtopengl.qdocconf b/src/opengl/doc/qtopengl.qdocconf
index 6153e97e04..857ad46c8f 100644
--- a/src/opengl/doc/qtopengl.qdocconf
+++ b/src/opengl/doc/qtopengl.qdocconf
@@ -11,8 +11,10 @@ project = QtOpenGL
 # <rootdir>/examples.
 # Paths are relative to the  location of this file.
 
-headerdirs += ..
+headerdirs += .. \
+              ../../openglwidgets
 sourcedirs  += .. \
+               ../../openglwidgets \
                ../../../examples/opengl/doc/src
 exampledirs += ../../../examples/opengl \
                . \
diff --git a/src/opengl/doc/snippets/code/doc_gui_widgets_qopenglwidget.cpp b/src/opengl/doc/snippets/code/doc_gui_widgets_qopenglwidget.cpp
new file mode 100644
index 0000000000..633a413b4f
--- /dev/null
+++ b/src/opengl/doc/snippets/code/doc_gui_widgets_qopenglwidget.cpp
@@ -0,0 +1,209 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the documentation 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."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+//! [0]
+class MyGLWidget : public QOpenGLWidget
+{
+public:
+    MyGLWidget(QWidget *parent) : QOpenGLWidget(parent) { }
+
+protected:
+    void initializeGL() override
+    {
+        // Set up the rendering context, load shaders and other resources, etc.:
+        QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
+        f->glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
+        ...
+    }
+
+    void resizeGL(int w, int h) override
+    {
+        // Update projection matrix and other size related settings:
+        m_projection.setToIdentity();
+        m_projection.perspective(45.0f, w / float(h), 0.01f, 100.0f);
+        ...
+    }
+
+    void paintGL() override
+    {
+        // Draw the scene:
+        QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
+        f->glClear(GL_COLOR_BUFFER_BIT);
+        ...
+    }
+
+};
+//! [0]
+
+//! [1]
+class MyGLWidget : public QOpenGLWidget, protected QOpenGLFunctions
+{
+    ...
+    void initializeGL() override
+    {
+        initializeOpenGLFunctions();
+        glClearColor(...);
+        ...
+    }
+    ...
+};
+//! [1]
+
+//! [2]
+QOpenGLWidget *widget = new QOpenGLWidget(parent);
+QSurfaceFormat format;
+format.setDepthBufferSize(24);
+format.setStencilBufferSize(8);
+format.setVersion(3, 2);
+format.setProfile(QSurfaceFormat::CoreProfile);
+widget->setFormat(format); // must be called before the widget or its parent window gets shown
+//! [2]
+
+//! [3]
+    ...
+    void paintGL() override
+    {
+        QOpenGLFunctions_3_2_Core *f = QOpenGLContext::currentContext()->versionFunctions<QOpenGLFunctions_3_2_Core>();
+        ...
+        f->glDrawArraysInstanced(...);
+        ...
+    }
+    ...
+//! [3]
+
+//! [4]
+class MyGLWidget : public QOpenGLWidget
+{
+    ...
+
+private:
+    QOpenGLVertexArrayObject m_vao;
+    QOpenGLBuffer m_vbo;
+    QOpenGLShaderProgram *m_program;
+    QOpenGLShader *m_shader;
+    QOpenGLTexture *m_texture;
+};
+
+MyGLWidget::MyGLWidget()
+    : m_program(0), m_shader(0), m_texture(0)
+{
+    // No OpenGL resource initialization is done here.
+}
+
+MyGLWidget::~MyGLWidget()
+{
+    // Make sure the context is current and then explicitly
+    // destroy all underlying OpenGL resources.
+    makeCurrent();
+
+    delete m_texture;
+    delete m_shader;
+    delete m_program;
+
+    m_vbo.destroy();
+    m_vao.destroy();
+
+    doneCurrent();
+}
+
+void MyGLWidget::initializeGL()
+{
+    m_vao.create();
+    if (m_vao.isCreated())
+        m_vao.bind();
+
+    m_vbo.create();
+    m_vbo.bind();
+    m_vbo.allocate(...);
+
+    m_texture = new QOpenGLTexture(QImage(...));
+
+    m_shader = new QOpenGLShader(...);
+    m_program = new QOpenGLShaderProgram(...);
+
+    ...
+}
+//! [4]
+
+//! [5]
+void MyGLWidget::initializeGL()
+{
+    // context() and QOpenGLContext::currentContext() are equivalent when called from initializeGL or paintGL.
+    connect(context(), &QOpenGLContext::aboutToBeDestroyed, this, &MyGLWidget::cleanup);
+}
+
+void MyGLWidget::cleanup()
+{
+    makeCurrent();
+    delete m_texture;
+    m_texture = 0;
+    ...
+    doneCurrent();
+}
+//! [5]
+
+//! [6]
+int main(int argc, char **argv)
+{
+    QApplication app(argc, argv);
+
+    QSurfaceFormat format;
+    format.setDepthBufferSize(24);
+    format.setStencilBufferSize(8);
+    format.setVersion(3, 2);
+    format.setProfile(QSurfaceFormat::CoreProfile);
+    QSurfaceFormat::setDefaultFormat(format);
+
+    MyWidget widget;
+    widget.show();
+
+    return app.exec();
+}
+//! [6]
diff --git a/src/opengl/doc/snippets/code/src_gui_opengl_qopenglbuffer.cpp b/src/opengl/doc/snippets/code/src_gui_opengl_qopenglbuffer.cpp
new file mode 100644
index 0000000000..bd768b1ed7
--- /dev/null
+++ b/src/opengl/doc/snippets/code/src_gui_opengl_qopenglbuffer.cpp
@@ -0,0 +1,68 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the documentation 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 <QtOpenGL/QOpenGLBuffer>
+
+namespace src_gui_opengl_qopenglbuffer {
+void wrapper() {
+
+//! [0]
+QOpenGLBuffer buffer1(QOpenGLBuffer::IndexBuffer);
+buffer1.create();
+
+QOpenGLBuffer buffer2 = buffer1;
+//! [0]
+
+
+//! [1]
+QOpenGLBuffer::release(QOpenGLBuffer::VertexBuffer);
+//! [1]
+
+} // wrapper
+} // src_gui_opengl_qopenglbuffer
diff --git a/src/opengl/doc/snippets/code/src_gui_opengl_qopengldebug.cpp b/src/opengl/doc/snippets/code/src_gui_opengl_qopengldebug.cpp
new file mode 100644
index 0000000000..241450c23a
--- /dev/null
+++ b/src/opengl/doc/snippets/code/src_gui_opengl_qopengldebug.cpp
@@ -0,0 +1,133 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the documentation 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 <QOpenGLContext>
+#include <QSurfaceFormat>
+#include <QWidget>
+#include <QtOpenGL/QOpenGLDebugLogger>
+
+namespace src_gui_opengl_qopengldebug {
+struct LogHandler : public QObject
+{
+    Q_OBJECT
+public slots:
+    static bool handleLoggedMessage() { return true; };
+};
+struct SnippetWrapper : public QObject
+{
+    Q_OBJECT
+    void wrapper1(LogHandler *receiver);
+    const QWidget *receiver;
+};
+
+void wrapper0() {
+
+//! [0]
+GLenum error = GL_NO_ERROR;
+do {
+    error = glGetError();
+    if (error != GL_NO_ERROR) {
+        // handle the error
+    }
+} while (error != GL_NO_ERROR);
+//! [0]
+
+
+//! [1]
+QSurfaceFormat format;
+// asks for a OpenGL 3.2 debug context using the Core profile
+format.setMajorVersion(3);
+format.setMinorVersion(2);
+format.setProfile(QSurfaceFormat::CoreProfile);
+format.setOption(QSurfaceFormat::DebugContext);
+
+QOpenGLContext *context = new QOpenGLContext;
+context->setFormat(format);
+context->create();
+//! [1]
+
+} // wrapper0
+
+
+void SnippetWrapper::wrapper1(LogHandler *receiver) {
+//! [2]
+QOpenGLContext *ctx = QOpenGLContext::currentContext();
+QOpenGLDebugLogger *logger = new QOpenGLDebugLogger(this);
+
+logger->initialize(); // initializes in the current context, i.e. ctx
+//! [2]
+
+
+//! [3]
+ctx->hasExtension(QByteArrayLiteral("GL_KHR_debug"));
+//! [3]
+
+
+//! [4]
+const QList<QOpenGLDebugMessage> messages = logger->loggedMessages();
+for (const QOpenGLDebugMessage &message : messages)
+    qDebug() << message;
+//! [4]
+
+
+//! [5]
+connect(logger, &QOpenGLDebugLogger::messageLogged, receiver, &LogHandler::handleLoggedMessage);
+logger->startLogging();
+//! [5]
+
+
+//! [6]
+QOpenGLDebugMessage message =
+    QOpenGLDebugMessage::createApplicationMessage(QStringLiteral("Custom message"));
+
+logger->logMessage(message);
+//! [6]
+
+} // SnippetWrapper::wrapper1
+} // src_gui_opengl_qopengldebug
diff --git a/src/opengl/doc/snippets/code/src_gui_qopenglshaderprogram.cpp b/src/opengl/doc/snippets/code/src_gui_qopenglshaderprogram.cpp
new file mode 100644
index 0000000000..131936ed3f
--- /dev/null
+++ b/src/opengl/doc/snippets/code/src_gui_qopenglshaderprogram.cpp
@@ -0,0 +1,116 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the documentation 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 <QColor>
+#include <QString>
+#include <QtOpenGL/QOpenGLShader>
+
+namespace src_gui_qopenglshaderprogram {
+QString code;
+QObject *context = nullptr;
+QRectF rect() { return QRectF(); }
+
+void wrapper() {
+//! [0]
+QOpenGLShader shader(QOpenGLShader::Vertex);
+shader.compileSourceCode(code);
+
+QOpenGLShaderProgram program(context);
+program.addShader(&shader);
+program.link();
+
+program.bind();
+//! [0]
+
+//! [1]
+program.addShaderFromSourceCode(QOpenGLShader::Vertex,
+    "attribute highp vec4 vertex;\n"
+    "uniform highp mat4 matrix;\n"
+    "void main(void)\n"
+    "{\n"
+    "   gl_Position = matrix * vertex;\n"
+    "}");
+program.addShaderFromSourceCode(QOpenGLShader::Fragment,
+    "uniform mediump vec4 color;\n"
+    "void main(void)\n"
+    "{\n"
+    "   gl_FragColor = color;\n"
+    "}");
+program.link();
+program.bind();
+
+int vertexLocation = program.attributeLocation("vertex");
+int matrixLocation = program.uniformLocation("matrix");
+int colorLocation = program.uniformLocation("color");
+//! [1]
+
+//! [2]
+static GLfloat const triangleVertices[] = {
+    60.0f,  10.0f,  0.0f,
+    110.0f, 110.0f, 0.0f,
+    10.0f,  110.0f, 0.0f
+};
+
+QColor color(0, 255, 0, 255);
+
+QMatrix4x4 pmvMatrix;
+pmvMatrix.ortho(rect());
+
+program.enableAttributeArray(vertexLocation);
+program.setAttributeArray(vertexLocation, triangleVertices, 3);
+program.setUniformValue(matrixLocation, pmvMatrix);
+program.setUniformValue(colorLocation, color);
+
+glDrawArrays(GL_TRIANGLES, 0, 3);
+
+program.disableAttributeArray(vertexLocation);
+//! [2]
+
+} // wrapper
+} // src_gui_qopenglshaderprogram
diff --git a/src/opengl/doc/src/qtopengl-index.qdoc b/src/opengl/doc/src/qtopengl-index.qdoc
index 53f1599c1b..a655a3e20f 100644
--- a/src/opengl/doc/src/qtopengl-index.qdoc
+++ b/src/opengl/doc/src/qtopengl-index.qdoc
@@ -31,9 +31,6 @@
     \brief The Qt OpenGL module offers classes that make it easy to
     use OpenGL in Qt applications.
 
-    \warning This module should not be used anymore for new code. Please
-    use the corresponding OpenGL classes in \l{Qt GUI}.
-
     \section1 Introduction
 
     OpenGL is a standard API for rendering 3D graphics. OpenGL only
diff --git a/src/opengl/doc/src/qtopengl-module.qdoc b/src/opengl/doc/src/qtopengl-module.qdoc
index 0ba78ed5dc..0d1c9e687f 100644
--- a/src/opengl/doc/src/qtopengl-module.qdoc
+++ b/src/opengl/doc/src/qtopengl-module.qdoc
@@ -35,5 +35,19 @@
     \brief The Qt OpenGL module offers classes that make it easy to
     use OpenGL in Qt applications.
 
-    \warning This module should not be used anymore for new code.
+    The \l{Qt OpenGL Widgets C++ Classes}{Qt OpenGL Widgets} library provides
+    a C++ widget class for rendering OpenGL graphics into widgets UIs.
+
+    \generatelist classesbymodule QtOpenGLWidgets
+*/
+
+/*
+    This "module" only exists so that classes in that separate library have
+    the correct build system documentation.
+*/
+/*!
+    \module QtOpenGLWidgets
+    \title Qt OpenGL Widgets C++ Classes
+    \qtcmakepackage OpenGLWidgets
+    \qtvariable openglwidgets
 */