Make QGLFramebufferObject work again using new QGLPaintDevice API

This patch also refactors QGL2PaintEngineEx::ensureActive() and the
logic which handles multiple paint engines rendering to the same
QGLContext. In a nut-shell:

* QGLPaintDevice::beginPaint() stores the currently bound FBO
* QGLPaintDevice::ensureActiveTarget() makes sure that GL rendering will
  end up in the paint device (I.e. the right context is current and the
  right FBO is bound). If a different context or FBO was bound, it is
  _not_ remembered.
* QGLPaintDevice::endPaint() restores whatever FBO was bound when
  beginPaint() was called.

This logic allows interleaved painter rendering to multiple FBOs and
contexts to work as expected. It also allows a stacked begin/end to work
properly when it's mixed with native GL rendering (as far as current
render target is concerened. GL state clobbering is obviously a
different topic).

QGLPaintDevice::context() also had to be made virtual as there's no good
place to call setContext. This might be possible to change in the future
though.

Finally, to make this work, QGLFramebufferObjectPrivate had to be moved
into it's own private header.

1 files changed, 151 insertions, 0 deletions

diff --git a/src/opengl/qglframebufferobject_p.h b/src/opengl/qglframebufferobject_p.h
new file mode 100644
index 0000000000..65fcf540c7
--- /dev/null
+++ b/src/opengl/qglframebufferobject_p.h
@@ -0,0 +1,151 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtOpenGL module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** 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, Nokia gives you certain
+** additional rights.  These rights are described in the Nokia Qt LGPL
+** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
+** package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QGLFRAMEBUFFEROBJECT_P_H
+#define QGLFRAMEBUFFEROBJECT_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists for the convenience
+// of the QLibrary class.  This header file may change from
+// version to version without notice, or even be removed.
+//
+// We mean it.
+//
+
+QT_BEGIN_NAMESPACE
+
+QT_BEGIN_INCLUDE_NAMESPACE
+
+#include <qglframebufferobject.h>
+#include <private/qglpaintdevice_p.h>
+#include <private/qgl_p.h>
+
+QT_END_INCLUDE_NAMESPACE
+
+#ifndef QT_OPENGL_ES
+#define DEFAULT_FORMAT GL_RGBA8
+#else
+#define DEFAULT_FORMAT GL_RGBA
+#endif
+
+class QGLFramebufferObjectFormatPrivate
+{
+public:
+    QGLFramebufferObjectFormatPrivate()
+        : ref(1),
+          samples(0),
+          attachment(QGLFramebufferObject::NoAttachment),
+          target(GL_TEXTURE_2D),
+          internal_format(DEFAULT_FORMAT)
+    {
+    }
+    QGLFramebufferObjectFormatPrivate
+            (const QGLFramebufferObjectFormatPrivate *other)
+        : ref(1),
+          samples(other->samples),
+          attachment(other->attachment),
+          target(other->target),
+          internal_format(other->internal_format)
+    {
+    }
+    bool equals(const QGLFramebufferObjectFormatPrivate *other)
+    {
+        return samples == other->samples &&
+               attachment == other->attachment &&
+               target == other->target &&
+               internal_format == other->internal_format;
+    }
+
+    QAtomicInt ref;
+    int samples;
+    QGLFramebufferObject::Attachment attachment;
+    GLenum target;
+    GLenum internal_format;
+};
+
+class QGLFBOGLPaintDevice : public QGLPaintDevice
+{
+public:
+    virtual QPaintEngine* paintEngine() const {return fbo->paintEngine();}
+    virtual QSize size() const {return fbo->size();}
+    virtual QGLContext* context() const {return const_cast<QGLContext *>(QGLContext::currentContext());}
+    void setFBO(QGLFramebufferObject* f) {fbo = f; }
+    virtual void ensureActiveTarget();
+    virtual void beginPaint();
+    virtual void endPaint();
+
+private:
+    bool wasBound;
+    QGLFramebufferObject* fbo;
+};
+
+class QGLFramebufferObjectPrivate
+{
+public:
+    QGLFramebufferObjectPrivate() : depth_stencil_buffer(0), valid(false), ctx(0), previous_fbo(0), engine(0) {}
+    ~QGLFramebufferObjectPrivate() {}
+
+    void init(QGLFramebufferObject *q, const QSize& sz,
+              QGLFramebufferObject::Attachment attachment,
+              GLenum internal_format, GLenum texture_target, GLint samples = 0);
+    bool checkFramebufferStatus() const;
+    GLuint texture;
+    GLuint fbo;
+    GLuint depth_stencil_buffer;
+    GLuint color_buffer;
+    GLenum target;
+    QSize size;
+    QGLFramebufferObjectFormat format;
+    uint valid : 1;
+    QGLFramebufferObject::Attachment fbo_attachment;
+    QGLContextGroup *ctx; // for Windows extension ptrs
+    GLuint previous_fbo;
+    mutable QPaintEngine *engine;
+    QGLFBOGLPaintDevice glDevice;
+};
+
+
+QT_END_NAMESPACE
+
+#endif // QGLFRAMEBUFFEROBJECT_P_H