Move opengl/wid/net example docs to proper folders.

Change-Id: I846439a9cf7ad965ed27a00f98dbc4ff97abe73b
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Martin Smith <martin.smith@digia.com>

1 files changed, 128 insertions, 0 deletions

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+/****************************************************************************
+**
+** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:FDL$
+** GNU Free Documentation License
+** Alternatively, this file may be used under the terms of the GNU Free
+** Documentation License version 1.3 as published by the Free Software
+** Foundation and appearing in the file included in the packaging of
+** this file.
+**
+** Other Usage
+** Alternatively, this file may be used in accordance with the terms
+** and conditions contained in a signed written agreement between you
+** and Nokia.
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+    \example hellogl_es
+    \title Hello GL ES Example
+
+    The Hello GL ES example is the \l{Hello GL Example} ported to OpenGL ES.
+    It also included some effects from the OpenGL \l{Overpainting Example}.
+
+    \image hellogl-es-example.png
+
+    A complete introduction to OpenGL ES and a description of all differences
+    between OpenGL and OpenGL ES is out of the scope of this document; but
+    we will describe some of the major issues and differences.
+
+    Since Hello GL ES is a direct port of standard OpenGL code, it is a fairly
+    good example for porting OpenGL code to OpenGL ES.
+
+    \tableofcontents
+
+    \section1 Using QGLWidget
+
+    QGLWidget can be used for OpenGL ES similar to the way it is used with
+    standard OpenGL; but there are some differences. We use EGL 1.0 to embedd
+    the OpenGL ES window within the native window manager. In
+    QGLWidget::initializeGL() we initialize OpenGL ES.
+
+    \section1 Porting OpenGL to OpenGL ES
+
+    Since OpenGL ES is missing the immediate mode and does not support quads,
+    we have to create triangle arrays.
+
+    We create a quad by adding vertices to a QList of vertices. We create both
+    sides of the quad and hardcode a distance of 0.05f. We also compute the
+    correct normal for each face and store them in another QList.
+
+    \snippet hellogl_es/glwidget.cpp 0
+
+    And then we convert the complete list of vertexes and the list of normals
+    into the native OpenGL ES format that we can use with the OpenGL ES API.
+
+    \snippet hellogl_es/glwidget.cpp 1
+
+    In \c paintQtLogo() we draw the triangle array using OpenGL ES. We use
+    q_vertexTypeEnum to abstract the fact that our vertex and normal arrays
+    are either in float or in fixed point format.
+
+    \snippet hellogl_es/glwidget.cpp 2
+
+    \section1 Using QGLPainter
+
+    Since the \c QGLPainter is slower for OpenGL ES we paint the bubbles with
+    the rasterizer and cache them in a QImage. This happends only once during
+    the initialiazation.
+
+    \snippet hellogl_es/bubble.cpp 0
+
+    For each bubble this QImage is then drawn to the QGLWidget by using the
+    according QPainter with transparency enabled.
+
+    \snippet hellogl_es/bubble.cpp 1
+
+    Another difference beetwen OpenGL and OpenGL ES is that OpenGL ES does not
+    support glPushAttrib(GL_ALL_ATTRIB_BITS). So we have to restore all the
+    OpenGL states ourselves, after we created the QPainter in
+    GLWidget::paintGL().
+
+    \snippet hellogl_es/glwidget.cpp 3
+
+    Setting up up the model view matrix and setting the right OpenGL states is
+    done in the same way as for standard OpenGL.
+
+    \snippet hellogl_es/glwidget.cpp 4
+
+    Now we have to restore the OpenGL state for the QPainter. This is not done
+    automatically for OpenGL ES.
+
+    \snippet hellogl_es/glwidget.cpp 5
+
+    Now we use the QPainter to draw the transparent bubbles.
+
+    \snippet hellogl_es/glwidget.cpp 6
+
+    In the end, we calculate the framerate and display it using the QPainter
+    again.
+
+    \snippet hellogl_es/glwidget.cpp 7
+
+    After we finished all the drawing operations we swap the screen buffer.
+
+    \snippet hellogl_es/glwidget.cpp 8
+
+    \section1 Summary
+
+    Similar to the \l{Hello GL Example}, we subclass QGLWidget to render
+    a 3D scene using OpenGL ES calls. QGLWidget is a subclass of QWidget.
+    Hence, its \l{QGLWidget}'s subclasses can be placed in layouts and
+    provided with interactive features just like normal custom widgets.
+
+    QGLWidget allows pure OpenGL ES rendering to be mixed with QPainter calls,
+    but care must be taken to maintain the state of the OpenGL ES
+    implementation.
+*/