Make QOpenGLWidget public

QOpenGLWidget is now public.

In addition Qt::WA_AlwaysStackOnTop is introduced to support the
special case of semi-transparent QOpenGLWidget or QQuickWidget on
top of regular widgets.

hellogl_es2 becomes the qopenglwidget example. This example performs
painting both via QPainter and native GL commands and has the OpenGL
widget combined with other, normal widgets.

The widget stack receives some changes when it comes to renderToTexture
widgets like QQuickWidget and QOpenGLWidget. Calling update() will now
result in a paint event, which is essential for QOpenGLWidget since we
want it to behave like a regular widget. The dirty region handling is
extended specially for such widgets due to performance reasons.
(an OpenGL content update must not result in any backingstore painting,
and is thus handled as a different kind of dirtiness)

[ChangeLog] Added QOpenGLWidget. This widget serves as a replacement for QGLWidget.

Task-number: QTBUG-36899
Task-number: QTBUG-40086
Change-Id: Ibf7f82fea99b39edfffd2fc088e7e0eadbca25cf
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>

1 files changed, 109 insertions, 0 deletions

diff --git a/src/widgets/doc/snippets/code/doc_gui_widgets_qopenglwidget.cpp b/src/widgets/doc/snippets/code/doc_gui_widgets_qopenglwidget.cpp
new file mode 100644
index 0000000000..bc279e4406
--- /dev/null
+++ b/src/widgets/doc/snippets/code/doc_gui_widgets_qopenglwidget.cpp
@@ -0,0 +1,109 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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 Digia Plc and its Subsidiary(-ies) 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()
+    {
+        // 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)
+    {
+        // 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()
+    {
+        // Draw the scene:
+        QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
+        f->glClear(GL_COLOR_BUFFER_BIT);
+        ...
+    }
+
+};
+//! [0]
+
+//! [1]
+class MyGLWidget : public QOpenGLWidget, protected QOpenGLFunctions
+{
+    ...
+    void initializeGL()
+    {
+        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()
+    {
+        QOpenGLFunctions_3_2_Core *f = QOpenGLContext::currentContext()->versionFunctions<QOpenGLFunctions_3_2_Core>();
+        ...
+        f->glDrawArraysInstanced(...);
+        ...
+    }
+    ...
+//! [3]