Add public and QPA APIs for adapting existing OpenGL contexts

For now only xcb on GLX is supported. Other platforms will follow later.

Add also some missing documentation for the platform OpenGL context factory
functions.

[ChangeLog] QOpenGLContext is now able to adopt existing native contexts.

Task-number: QTBUG-37552
Change-Id: I5dd959f102df178f646b2df5989203b5dc6de376
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>

3 files changed, 166 insertions, 0 deletions

diff --git a/src/platformheaders/nativecontexts/nativecontexts.pri b/src/platformheaders/nativecontexts/nativecontexts.pri
new file mode 100644
index 0000000000..dcbeae2b0f
--- /dev/null
+++ b/src/platformheaders/nativecontexts/nativecontexts.pri
@@ -0,0 +1 @@
+HEADERS += $$PWD/qglxnativecontext.h
diff --git a/src/platformheaders/nativecontexts/qglxnativecontext.h b/src/platformheaders/nativecontexts/qglxnativecontext.h
new file mode 100644
index 0000000000..e3dd547a8f
--- /dev/null
+++ b/src/platformheaders/nativecontexts/qglxnativecontext.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 plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** 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 Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QGLXNATIVECONTEXT_H
+#define QGLXNATIVECONTEXT_H
+
+#include <X11/Xlib.h>
+#include <GL/glx.h>
+
+QT_BEGIN_NAMESPACE
+
+struct QGLXNativeContext
+{
+    QGLXNativeContext()
+        : m_context(0),
+          m_display(0),
+          m_window(0),
+          m_visualId(0)
+    { }
+
+    QGLXNativeContext(GLXContext ctx, Display *dpy = 0, Window wnd = 0, VisualID vid = 0)
+        : m_context(ctx),
+          m_display(dpy),
+          m_window(wnd),
+          m_visualId(vid)
+    { }
+
+    GLXContext context() const { return m_context; }
+    Display *display() const { return m_display; }
+    Window window() const { return m_window; }
+    VisualID visualId() const { return m_visualId; }
+
+private:
+    GLXContext m_context;
+    Display *m_display;
+    Window m_window;
+    VisualID m_visualId;
+};
+
+QT_END_NAMESPACE
+
+Q_DECLARE_METATYPE(QGLXNativeContext)
+
+#endif // QGLXNATIVECONTEXT_H
diff --git a/src/platformheaders/nativecontexts/qglxnativecontext.qdoc b/src/platformheaders/nativecontexts/qglxnativecontext.qdoc
new file mode 100644
index 0000000000..14c6d37c0e
--- /dev/null
+++ b/src/platformheaders/nativecontexts/qglxnativecontext.qdoc
@@ -0,0 +1,83 @@
+/****************************************************************************
+**
+** 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.
+**
+** $QT_BEGIN_LICENSE:FDL$
+** 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 Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** GNU Free Documentation License Usage
+** 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.  Please review the following information to ensure
+** the GNU Free Documentation License version 1.3 requirements
+** will be met: http://www.gnu.org/copyleft/fdl.html.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+  \class QGLXNativeContext
+  \inmodule QtPlatformHeaders
+  \since 5.4
+
+  \brief A class encapsulating a GLXContext and related native handles.
+
+  \note Only context() is guaranteed to be valid. The other handles may be all \c 0. They are
+  useful however when QOpenGLContext::setNativeHandle() is used to adopt a legacy context
+  created by glXCreateContext. To adopt such a context, either the Window or VisualID
+  that had been used to create the context needs to be known, otherwise the adoption will
+  fail. For modern contexts created with an FBConfig, these are not necessary, the
+  GLXContext itself is sufficient. The Display is optional.
+
+  \note As of Qt 5.4 there is no binary compatibility guarantee for this class, meaning
+  that an application using it is only guaranteed to work with the Qt version it was
+  developed against.
+
+  \sa QOpenGLContext::setNativeHandle(), QOpenGLContext::nativeHandle()
+ */
+
+/*!
+  \fn GLXContext QGLXNativeContext::context() const
+
+  \return the GLXContext.
+ */
+
+/*!
+  \fn Display *QGLXNativeContext::display() const
+
+  \return a pointer to the X11 display or \c NULL if not available.
+ */
+
+/*!
+  \fn Window QGLXNativeContext::window() const
+
+  \return the X11 Window or \c 0 if not available.
+ */
+
+/*!
+  \fn VisualID QGLXNativeContext::visualId() const
+
+  \return the X11 visual ID or \c 0 if not available.
+ */
+
+/*!
+  \fn QGLXNativeContext::QGLXNativeContext()
+
+  Construct a new instance with no handles.
+ */
+
+/*!
+  \fn QGLXNativeContext::QGLXNativeContext(GLXContext ctx, Display *dpy = 0, Window wnd = 0, VisualID vid = 0)
+
+  Constructs a new instance with the provided \a ctx, \a dpy, \a wnd, \a vid handles.
+ */