Modernize the OpenGL examples

Change them to use QOpenGLWidget and QOpenGLTexture.
Advocate also the usage of VBOs.

Hopeless examples, that rely on the fixed pipeline and will
not compile or work in ES and dynamic builds, are moved to
a "legacy" directory. The documentation pages for these are
removed. This long due change avoids the confusion newcomers
experience when trying to get started with Qt 5 and OpenGL.

hellowindow's behavior is changed to open a single window only
by default. The old default behavior, that opened three windows
on platforms that supported both MultipleWindows & ThreadedOpenGL,
can be requested by passing --multiple. --single is removed since it
is the default now. This plays much nicer with drivers that have
issues with threading.

In addition, say hello to hellogl2.

This is the old hellogl example updated to use QOpenGLWidget and
OpenGL 2. It also has a mainwindow with multiple (un)dockable widgets
containing the OpenGL widgets. This helps testing the behavior when
the top-level of the QOpenGLWidget changes and provides a very
important example of how to do proper resource management in this case.
(must use aboutToBeDestroyed() of the context, since the context goes
away and is replaced by a new one on every dock/undock)

As a bonus, the logo is now real 3D, no more orthographic nonsense.

Launch with --multisample to request 4x MSAA.

Launch with --coreprofile to request 3.2 Core. In this particular example
the shaders are present in both versions and there is a VAO so the application
is functional with core profile contexts.

Change-Id: Id780a80cb0708ef164cc172450ed74050f065596
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>

6 files changed, 81 insertions, 73 deletions

diff --git a/examples/opengl/cube/cube.pro b/examples/opengl/cube/cube.pro
index 85272bc471..b9416f1a9d 100644
--- a/examples/opengl/cube/cube.pro
+++ b/examples/opengl/cube/cube.pro
@@ -5,20 +5,17 @@ TEMPLATE = app
 
 SOURCES += main.cpp
 
-qtHaveModule(opengl) {
-    QT += opengl
+SOURCES += \
+    mainwidget.cpp \
+    geometryengine.cpp
 
-    SOURCES += mainwidget.cpp \
-       geometryengine.cpp
+HEADERS += \
+    mainwidget.h \
+    geometryengine.h
 
-    HEADERS += \
-        mainwidget.h \
-        geometryengine.h
-
-    RESOURCES += \
-        shaders.qrc \
-        textures.qrc
-}
+RESOURCES += \
+    shaders.qrc \
+    textures.qrc
 
 # install
 target.path = $$[QT_INSTALL_EXAMPLES]/opengl/cube
diff --git a/examples/opengl/cube/geometryengine.cpp b/examples/opengl/cube/geometryengine.cpp
index 0a34213084..618a080c37 100644
--- a/examples/opengl/cube/geometryengine.cpp
+++ b/examples/opengl/cube/geometryengine.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -49,29 +49,27 @@ struct VertexData
     QVector2D texCoord;
 };
 
+//! [0]
 GeometryEngine::GeometryEngine()
+    : indexBuf(QOpenGLBuffer::IndexBuffer)
 {
-}
-
-GeometryEngine::~GeometryEngine()
-{
-    glDeleteBuffers(2, vboIds);
-}
-
-void GeometryEngine::init()
-{
-    initializeGLFunctions();
+    initializeOpenGLFunctions();
 
-//! [0]
     // Generate 2 VBOs
-    glGenBuffers(2, vboIds);
-
-//! [0]
+    arrayBuf.create();
+    indexBuf.create();
 
     // Initializes cube geometry and transfers it to VBOs
     initCubeGeometry();
 }
 
+GeometryEngine::~GeometryEngine()
+{
+    arrayBuf.destroy();
+    indexBuf.destroy();
+}
+//! [0]
+
 void GeometryEngine::initCubeGeometry()
 {
     // For cube we would need only 8 vertices but we have to
@@ -133,21 +131,21 @@ void GeometryEngine::initCubeGeometry()
 
 //! [1]
     // Transfer vertex data to VBO 0
-    glBindBuffer(GL_ARRAY_BUFFER, vboIds[0]);
-    glBufferData(GL_ARRAY_BUFFER, 24 * sizeof(VertexData), vertices, GL_STATIC_DRAW);
+    arrayBuf.bind();
+    arrayBuf.allocate(vertices, 24 * sizeof(VertexData));
 
     // Transfer index data to VBO 1
-    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboIds[1]);
-    glBufferData(GL_ELEMENT_ARRAY_BUFFER, 34 * sizeof(GLushort), indices, GL_STATIC_DRAW);
+    indexBuf.bind();
+    indexBuf.allocate(indices, 34 * sizeof(GLushort));
 //! [1]
 }
 
 //! [2]
-void GeometryEngine::drawCubeGeometry(QGLShaderProgram *program)
+void GeometryEngine::drawCubeGeometry(QOpenGLShaderProgram *program)
 {
     // Tell OpenGL which VBOs to use
-    glBindBuffer(GL_ARRAY_BUFFER, vboIds[0]);
-    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboIds[1]);
+    arrayBuf.bind();
+    indexBuf.bind();
 
     // Offset for position
     quintptr offset = 0;
@@ -155,7 +153,7 @@ void GeometryEngine::drawCubeGeometry(QGLShaderProgram *program)
     // Tell OpenGL programmable pipeline how to locate vertex position data
     int vertexLocation = program->attributeLocation("a_position");
     program->enableAttributeArray(vertexLocation);
-    glVertexAttribPointer(vertexLocation, 3, GL_FLOAT, GL_FALSE, sizeof(VertexData), (const void *)offset);
+    program->setAttributeBuffer(vertexLocation, GL_FLOAT, offset, 3, sizeof(VertexData));
 
     // Offset for texture coordinate
     offset += sizeof(QVector3D);
@@ -163,7 +161,7 @@ void GeometryEngine::drawCubeGeometry(QGLShaderProgram *program)
     // Tell OpenGL programmable pipeline how to locate vertex texture coordinate data
     int texcoordLocation = program->attributeLocation("a_texcoord");
     program->enableAttributeArray(texcoordLocation);
-    glVertexAttribPointer(texcoordLocation, 2, GL_FLOAT, GL_FALSE, sizeof(VertexData), (const void *)offset);
+    program->setAttributeBuffer(texcoordLocation, GL_FLOAT, offset, 2, sizeof(VertexData));
 
     // Draw cube geometry using indices from VBO 1
     glDrawElements(GL_TRIANGLE_STRIP, 34, GL_UNSIGNED_SHORT, 0);
diff --git a/examples/opengl/cube/geometryengine.h b/examples/opengl/cube/geometryengine.h
index fe90c436c6..0b51ebf5f2 100644
--- a/examples/opengl/cube/geometryengine.h
+++ b/examples/opengl/cube/geometryengine.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -41,22 +41,23 @@
 #ifndef GEOMETRYENGINE_H
 #define GEOMETRYENGINE_H
 
-#include <QGLFunctions>
-#include <QGLShaderProgram>
+#include <QOpenGLFunctions>
+#include <QOpenGLShaderProgram>
+#include <QOpenGLBuffer>
 
-class GeometryEngine : protected QGLFunctions
+class GeometryEngine : protected QOpenGLFunctions
 {
 public:
     GeometryEngine();
     virtual ~GeometryEngine();
 
-    void init();
-    void drawCubeGeometry(QGLShaderProgram *program);
+    void drawCubeGeometry(QOpenGLShaderProgram *program);
 
 private:
     void initCubeGeometry();
 
-    GLuint vboIds[2];
+    QOpenGLBuffer arrayBuf;
+    QOpenGLBuffer indexBuf;
 };
 
 #endif // GEOMETRYENGINE_H
diff --git a/examples/opengl/cube/main.cpp b/examples/opengl/cube/main.cpp
index a414fad023..73363da016 100644
--- a/examples/opengl/cube/main.cpp
+++ b/examples/opengl/cube/main.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -40,6 +40,7 @@
 
 #include <QApplication>
 #include <QLabel>
+#include <QSurfaceFormat>
 
 #ifndef QT_NO_OPENGL
 #include "mainwidget.h"
@@ -48,6 +49,11 @@
 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
+
+    QSurfaceFormat format;
+    format.setDepthBufferSize(24);
+    QSurfaceFormat::setDefaultFormat(format);
+
     app.setApplicationName("cube");
     app.setApplicationVersion("0.1");
 #ifndef QT_NO_OPENGL
diff --git a/examples/opengl/cube/mainwidget.cpp b/examples/opengl/cube/mainwidget.cpp
index 5c1cd28b54..b5a7a972d1 100644
--- a/examples/opengl/cube/mainwidget.cpp
+++ b/examples/opengl/cube/mainwidget.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -45,14 +45,21 @@
 #include <math.h>
 
 MainWidget::MainWidget(QWidget *parent) :
-    QGLWidget(parent),
+    QOpenGLWidget(parent),
+    geometries(0),
+    texture(0),
     angularSpeed(0)
 {
 }
 
 MainWidget::~MainWidget()
 {
-    deleteTexture(texture);
+    // Make sure the context is current when deleting the texture
+    // and the buffers.
+    makeCurrent();
+    delete texture;
+    delete geometries;
+    doneCurrent();
 }
 
 //! [0]
@@ -95,16 +102,18 @@ void MainWidget::timerEvent(QTimerEvent *)
         // Update rotation
         rotation = QQuaternion::fromAxisAndAngle(rotationAxis, angularSpeed) * rotation;
 
-        // Update scene
-        updateGL();
+        // Request an update
+        update();
     }
 }
 //! [1]
 
 void MainWidget::initializeGL()
 {
-    initializeGLFunctions();
-    qglClearColor(Qt::black);
+    initializeOpenGLFunctions();
+
+    glClearColor(0, 0, 0, 1);
+
     initShaders();
     initTextures();
 
@@ -116,7 +125,7 @@ void MainWidget::initializeGL()
     glEnable(GL_CULL_FACE);
 //! [2]
 
-    geometries.init();
+    geometries = new GeometryEngine;
 
     // Use QBasicTimer because its faster than QTimer
     timer.start(12, this);
@@ -126,11 +135,11 @@ void MainWidget::initializeGL()
 void MainWidget::initShaders()
 {
     // Compile vertex shader
-    if (!program.addShaderFromSourceFile(QGLShader::Vertex, ":/vshader.glsl"))
+    if (!program.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/vshader.glsl"))
         close();
 
     // Compile fragment shader
-    if (!program.addShaderFromSourceFile(QGLShader::Fragment, ":/fshader.glsl"))
+    if (!program.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/fshader.glsl"))
         close();
 
     // Link shader pipeline
@@ -147,28 +156,23 @@ void MainWidget::initShaders()
 void MainWidget::initTextures()
 {
     // Load cube.png image
-    glEnable(GL_TEXTURE_2D);
-    texture = bindTexture(QImage(":/cube.png"));
+    texture = new QOpenGLTexture(QImage(":/cube.png").mirrored());
 
     // Set nearest filtering mode for texture minification
-    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    texture->setMinificationFilter(QOpenGLTexture::Nearest);
 
     // Set bilinear filtering mode for texture magnification
-    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    texture->setMagnificationFilter(QOpenGLTexture::Linear);
 
     // Wrap texture coordinates by repeating
     // f.ex. texture coordinate (1.1, 1.2) is same as (0.1, 0.2)
-    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
-    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
+    texture->setWrapMode(QOpenGLTexture::Repeat);
 }
 //! [4]
 
 //! [5]
 void MainWidget::resizeGL(int w, int h)
 {
-    // Set OpenGL viewport to cover whole widget
-    glViewport(0, 0, w, h);
-
     // Calculate aspect ratio
     qreal aspect = qreal(w) / qreal(h ? h : 1);
 
@@ -188,6 +192,8 @@ void MainWidget::paintGL()
     // Clear color and depth buffer
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
+    texture->bind();
+
 //! [6]
     // Calculate model view transformation
     QMatrix4x4 matrix;
@@ -202,5 +208,5 @@ void MainWidget::paintGL()
     program.setUniformValue("texture", 0);
 
     // Draw cube geometry
-    geometries.drawCubeGeometry(&program);
+    geometries->drawCubeGeometry(&program);
 }
diff --git a/examples/opengl/cube/mainwidget.h b/examples/opengl/cube/mainwidget.h
index 92b3aabf46..8aff8f7714 100644
--- a/examples/opengl/cube/mainwidget.h
+++ b/examples/opengl/cube/mainwidget.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -43,18 +43,18 @@
 
 #include "geometryengine.h"
 
-#include <QGLWidget>
-#include <QGLFunctions>
+#include <QOpenGLWidget>
+#include <QOpenGLFunctions>
 #include <QMatrix4x4>
 #include <QQuaternion>
 #include <QVector2D>
 #include <QBasicTimer>
-#include <QGLShaderProgram>
-
+#include <QOpenGLShaderProgram>
+#include <QOpenGLTexture>
 
 class GeometryEngine;
 
-class MainWidget : public QGLWidget, protected QGLFunctions
+class MainWidget : public QOpenGLWidget, protected QOpenGLFunctions
 {
     Q_OBJECT
 
@@ -76,10 +76,10 @@ protected:
 
 private:
     QBasicTimer timer;
-    QGLShaderProgram program;
-    GeometryEngine geometries;
+    QOpenGLShaderProgram program;
+    GeometryEngine *geometries;
 
-    GLuint texture;
+    QOpenGLTexture *texture;
 
     QMatrix4x4 projection;