Add an example for creating OpenGL contexts

Besides serving as an example for performing OpenGL rendering inside
a window container in a way that it works across all GL versions,
this is an extremely useful tool for developers and users alike
since it allows quick and easy checking of what sort of context a
particular driver returns for a particular QSurfaceFormat.

NB! Depending on the OpenGL driver, some surprises can be expected.
The handling of core/compatibility profiles, the fwdcompat bit,
the supported GLSL versions, etc. tend to be somewhat different
across the different OpenGL implementations.

Task-number: QTBUG-37071
Change-Id: Iae4328e66cd0bb19f74a77fefef93ea5a3221e31
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

1 files changed, 82 insertions, 0 deletions

diff --git a/examples/opengl/contextinfo/renderwindow.h b/examples/opengl/contextinfo/renderwindow.h
new file mode 100644
index 0000000000..36b15fd22b
--- /dev/null
+++ b/examples/opengl/contextinfo/renderwindow.h
@@ -0,0 +1,82 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the examples 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."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef RENDERWINDOW_H
+#define RENDERWINDOW_H
+
+#include <QWindow>
+#include <QOpenGLVertexArrayObject>
+#include <QOpenGLBuffer>
+
+QT_FORWARD_DECLARE_CLASS(QOpenGLContext)
+QT_FORWARD_DECLARE_CLASS(QOpenGLShaderProgram)
+
+class RenderWindow : public QWindow
+{
+    Q_OBJECT
+
+public:
+    RenderWindow(const QSurfaceFormat &format);
+    QOpenGLContext *context() { return m_context; }
+    void exposeEvent(QExposeEvent *) Q_DECL_OVERRIDE;
+    void setForceGLSL110(bool enable) { m_forceGLSL110 = enable; }
+
+signals:
+    void ready();
+    void error(const QString &msg);
+
+private slots:
+    void render();
+
+private:
+    void init();
+    void setupVertexAttribs();
+
+    QOpenGLContext *m_context;
+    bool m_initialized;
+    bool m_forceGLSL110;
+    QOpenGLShaderProgram *m_program;
+    int m_posAttr, m_colAttr, m_matrixUniform;
+    QOpenGLVertexArrayObject m_vao;
+    QOpenGLBuffer m_vbo;
+    float m_angle;
+};
+
+#endif // RENDERWINDOW_H