VirtualBox/include/VBoxFrameBuffer.h

	VBoxFrameBuffer.h revision 6c2957acd397b02b27ba1c1a4f90863823a3b6f4
/** @file
 *
 * VBox frontends: Qt GUI ("VirtualBox"):
 * VBoxFrameBuffer class and subclasses declarations
 */

/*
 * Copyright (C) 2006-2007 Sun Microsystems, Inc.
 *
 * This file is part of VirtualBox Open Source Edition (OSE), as
 * available from http://www.virtualbox.org. This file is free software;
 * you can redistribute it and/or modify it under the terms of the GNU
 * General Public License (GPL) as published by the Free Software
 * Foundation, in version 2 as it comes in the "COPYING" file of the
 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
 * Clara, CA 95054 USA or visit http://www.sun.com if you need
 * additional information or have any questions.
 */

#ifndef ___VBoxFrameBuffer_h___
#define ___VBoxFrameBuffer_h___

#include "COMDefs.h"
#include <iprt/critsect.h>

/* Qt includes */
#include <QImage>
#include <QPixmap>
#include <QMutex>
#include <QPaintEvent>
#include <QMoveEvent>
#if defined (VBOX_GUI_USE_QGL)
#include <QGLWidget>
#endif

#if defined (VBOX_GUI_USE_SDL)
#include <SDL.h>
#include <signal.h>
#endif

#if defined (Q_WS_WIN) && defined (VBOX_GUI_USE_DDRAW)
// VBox/cdefs.h defines these:
#undef LOWORD
#undef HIWORD
#undef LOBYTE
#undef HIBYTE
#include <ddraw.h>
#endif

class VBoxConsoleView;

/////////////////////////////////////////////////////////////////////////////

/**
 *  Frame buffer resize event.
 */
class VBoxResizeEvent : public QEvent
{
public:

    VBoxResizeEvent (ulong aPixelFormat, uchar *aVRAM,
                     ulong aBitsPerPixel, ulong aBytesPerLine,
                     ulong aWidth, ulong aHeight) :
        QEvent ((QEvent::Type) VBoxDefs::ResizeEventType),
        mPixelFormat (aPixelFormat), mVRAM (aVRAM), mBitsPerPixel (aBitsPerPixel),
        mBytesPerLine (aBytesPerLine), mWidth (aWidth), mHeight (aHeight) {}
    ulong pixelFormat() { return mPixelFormat; }
    uchar *VRAM() { return mVRAM; }
    ulong bitsPerPixel() { return mBitsPerPixel; }
    ulong bytesPerLine() { return mBytesPerLine; }
    ulong width() { return mWidth; }
    ulong height() { return mHeight; }

private:

    ulong mPixelFormat;
    uchar *mVRAM;
    ulong mBitsPerPixel;
    ulong mBytesPerLine;
    ulong mWidth;
    ulong mHeight;
};

/**
 *  Frame buffer repaint event.
 */
class VBoxRepaintEvent : public QEvent
{
public:
    VBoxRepaintEvent (int x, int y, int w, int h) :
        QEvent ((QEvent::Type) VBoxDefs::RepaintEventType),
        ex (x), ey (y), ew (w), eh (h)
    {}
    int x() { return ex; }
    int y() { return ey; }
    int width() { return ew; }
    int height() { return eh; }
private:
    int ex, ey, ew, eh;
};

/**
 *  Frame buffer set region event.
 */
class VBoxSetRegionEvent : public QEvent
{
public:
    VBoxSetRegionEvent (const QRegion &aReg)
        : QEvent ((QEvent::Type) VBoxDefs::SetRegionEventType)
        , mReg (aReg) {}
    QRegion region() { return mReg; }
private:
    QRegion mReg;
};

#ifdef VBOX_WITH_VIDEOHWACCEL
class VBoxVHWACommandProcessEvent : public QEvent
{
public:
    VBoxVHWACommandProcessEvent (struct _VBOXVHWACMD * pCmd)
        : QEvent ((QEvent::Type) VBoxDefs::VHWACommandProcessType)
        , mpCmd (pCmd) {}
    struct _VBOXVHWACMD * command() { return mpCmd; }
private:
    struct _VBOXVHWACMD * mpCmd;
};

#endif

/////////////////////////////////////////////////////////////////////////////

/**
 *  Common IFramebuffer implementation for all methods used by GUI to maintain
 *  the VM display video memory.
 *
 *  Note that although this class can be called from multiple threads
 *  (in particular, the GUI thread and EMT) it doesn't protect access to every
 *  data field using its mutex lock. This is because all synchronization between
 *  the GUI and the EMT thread is supposed to be done using the
 *  IFramebuffer::NotifyUpdate() and IFramebuffer::RequestResize() methods
 *  (in particular, the \a aFinished parameter of these methods is responsible
 *  for the synchronization). These methods are always called on EMT and
 *  therefore always follow one another but never in parallel.
 *
 *  Using this object's mutex lock (exposed also in IFramebuffer::Lock() and
 *  IFramebuffer::Unlock() implementations) usually makes sense only if some
 *  third-party thread (i.e. other than GUI or EMT) needs to make sure that
 *  *no* VM display update or resize event can occur while it is accessing
 *  IFramebuffer properties or the underlying display memory storage area.
 *
 *  See IFramebuffer documentation for more info.
 */

class VBoxFrameBuffer : VBOX_SCRIPTABLE_IMPL(IFramebuffer)
{
public:

    VBoxFrameBuffer (VBoxConsoleView *aView);
    virtual ~VBoxFrameBuffer();

    NS_DECL_ISUPPORTS

#if defined (Q_OS_WIN32)

    STDMETHOD_(ULONG, AddRef)()
    {
        return ::InterlockedIncrement (&refcnt);
    }

    STDMETHOD_(ULONG, Release)()
    {
        long cnt = ::InterlockedDecrement (&refcnt);
        if (cnt == 0)
            delete this;
        return cnt;
    }

    STDMETHOD(QueryInterface) (REFIID riid , void **ppObj)
    {
        if (riid == IID_IUnknown) {
            *ppObj = this;
            AddRef();
            return S_OK;
        }
        if (riid == IID_IFramebuffer) {
            *ppObj = this;
            AddRef();
            return S_OK;
        }
        *ppObj = NULL;
        return E_NOINTERFACE;
    }

#endif

    // IFramebuffer COM methods
    STDMETHOD(COMGETTER(Address)) (BYTE **aAddress);
    STDMETHOD(COMGETTER(Width)) (ULONG *aWidth);
    STDMETHOD(COMGETTER(Height)) (ULONG *aHeight);
    STDMETHOD(COMGETTER(BitsPerPixel)) (ULONG *aBitsPerPixel);
    STDMETHOD(COMGETTER(BytesPerLine)) (ULONG *aBytesPerLine);
    STDMETHOD(COMGETTER(PixelFormat)) (ULONG *aPixelFormat);
    STDMETHOD(COMGETTER(UsesGuestVRAM)) (BOOL *aUsesGuestVRAM);
    STDMETHOD(COMGETTER(HeightReduction)) (ULONG *aHeightReduction);
    STDMETHOD(COMGETTER(Overlay)) (IFramebufferOverlay **aOverlay);
    STDMETHOD(COMGETTER(WinId)) (ULONG64 *winId);

    STDMETHOD(Lock)();
    STDMETHOD(Unlock)();

    STDMETHOD(RequestResize) (ULONG aScreenId, ULONG aPixelFormat,
                              BYTE *aVRAM, ULONG aBitsPerPixel, ULONG aBytesPerLine,
                              ULONG aWidth, ULONG aHeight,
                              BOOL *aFinished);

    STDMETHOD(VideoModeSupported) (ULONG aWidth, ULONG aHeight, ULONG aBPP,
                                   BOOL *aSupported);

    STDMETHOD(GetVisibleRegion)(BYTE *aRectangles, ULONG aCount, ULONG *aCountCopied);
    STDMETHOD(SetVisibleRegion)(BYTE *aRectangles, ULONG aCount);

    STDMETHOD(ProcessVHWACommand)(BYTE *pCommand);

    ulong width() { return mWdt; }
    ulong height() { return mHgt; }

    virtual ulong pixelFormat()
    {
        return FramebufferPixelFormat_FOURCC_RGB;
    }

    virtual bool usesGuestVRAM()
    {
        return false;
    }

    void lock() { RTCritSectEnter(&mCritSect); }
    void unlock() { RTCritSectLeave(&mCritSect); }

    virtual uchar *address() = 0;
    virtual ulong bitsPerPixel() = 0;
    virtual ulong bytesPerLine() = 0;

    /**
     *  Called on the GUI thread (from VBoxConsoleView) when some part of the
     *  VM display viewport needs to be repainted on the host screen.
     */
    virtual void paintEvent (QPaintEvent *pe) = 0;

    /**
     *  Called on the GUI thread (from VBoxConsoleView) after it gets a
     *  VBoxResizeEvent posted from the RequestResize() method implementation.
     */
    virtual void resizeEvent (VBoxResizeEvent *re)
    {
        mWdt = re->width();
        mHgt = re->height();
    }

    /**
     *  Called on the GUI thread (from VBoxConsoleView) when the VM console
     *  window is moved.
     */
    virtual void moveEvent (QMoveEvent * /*me*/ ) {}

#ifdef VBOX_WITH_VIDEOHWACCEL
    /* this method is called from the GUI thread
     * to perform the actual Video HW Acceleration command processing */
    virtual void doProcessVHWACommand(struct _VBOXVHWACMD * pCommand);
#endif

protected:

    VBoxConsoleView *mView;
    RTCRITSECT mCritSect;
    int mWdt;
    int mHgt;
    uint64_t mWinId;

#if defined (Q_OS_WIN32)
private:
    long refcnt;
#endif
};

/////////////////////////////////////////////////////////////////////////////

#if defined (VBOX_GUI_USE_QIMAGE)

class VBoxQImageFrameBuffer : public VBoxFrameBuffer
{
public:

    VBoxQImageFrameBuffer (VBoxConsoleView *aView);

    STDMETHOD(NotifyUpdate) (ULONG aX, ULONG aY,
                             ULONG aW, ULONG aH);

    ulong pixelFormat() { return mPixelFormat; }
    bool usesGuestVRAM() { return mUsesGuestVRAM; }

    uchar *address() { return mImg.bits(); }
    ulong bitsPerPixel() { return mImg.depth(); }
    ulong bytesPerLine() { return mImg.bytesPerLine(); }

    void paintEvent (QPaintEvent *pe);
    void resizeEvent (VBoxResizeEvent *re);

private:

    QPixmap mPM;
    QImage mImg;
    ulong mPixelFormat;
    bool mUsesGuestVRAM;
};

#endif

/////////////////////////////////////////////////////////////////////////////

#if defined (VBOX_GUI_USE_QGL)
class VBoxVHWADirtyRect
{
public:
    VBoxVHWADirtyRect() :
        mIsClear(true)
    {}

    VBoxVHWADirtyRect(const QRect & aRect)
    {
        if(aRect.isEmpty())
        {
            mIsClear = false;
            mRect = aRect;
        }
        else
        {
            mIsClear = true;
        }
    }

    bool isClear() const { return mIsClear; }

    void add(const QRect & aRect)
    {
        if(aRect.isEmpty())
            return;

        mRect = mIsClear ? aRect : mRect.united(aRect);
        mIsClear = false;
    }

    void set(const QRect & aRect)
    {
        if(aRect.isEmpty())
        {
            mIsClear = true;
        }
        else
        {
            mRect = aRect;
            mIsClear = false;
        }
    }

    void clear() { mIsClear = true; }

    const QRect & rect() const {return mRect;}

    bool intersects(const QRect & aRect) const {return mIsClear ? false : mRect.intersects(aRect);}

    bool intersects(const VBoxVHWADirtyRect & aRect) const {return mIsClear ? false : aRect.intersects(mRect);}

    QRect united(const QRect & aRect) const {return mIsClear ? aRect : aRect.united(mRect);}

    bool contains(const QRect & aRect) const {return mIsClear ? false : aRect.contains(mRect);}

    void subst(const VBoxVHWADirtyRect & aRect) { if(!mIsClear && aRect.contains(mRect)) clear(); }

private:
    QRect mRect;
    bool mIsClear;
};

class VBoxVHWASurfaceBase
{
public:
    VBoxVHWASurfaceBase(GLsizei aWidth, GLsizei aHeight,
            GLint aInternalFormat, GLenum aFormat, GLenum aType);

    virtual ~VBoxVHWASurfaceBase();

    virtual void init(uchar *pvMem);

    virtual void uninit();

    static void globalInit();

    int blt(const QRect * aDstRect, VBoxVHWASurfaceBase * aSrtSurface, const QRect * aSrcRect);

    int lock(const QRect * pRect, uint32_t flags);

    int unlock();

    virtual void makeCurrent() = 0;

    void paint(const QRect * aRect);

    void performDisplay() { Assert(mDisplayInitialized); glCallList(mDisplay); }

    static ulong calcBytesPerPixel(GLenum format, GLenum type);

    static GLsizei makePowerOf2(GLsizei val);

    bool    addressAlocated() const { return mFreeAddress; }
    uchar * address(){ return mAddress; }
    uchar * pointAddress(int x, int y) { return mAddress + y*mBytesPerLine + x*mBytesPerPixel; }
    ulong   memSize(){ return mBytesPerLine * mRect.height(); }

    ulong width()  { return mRect.width();  }
    ulong height() { return mRect.height(); }

    GLenum format() {return mFormat; }
    GLint  internalFormat() { return mInternalFormat; }
    GLenum type() { return mType; }
    ulong  bytesPerPixel() { return mBytesPerPixel; }
    ulong  bytesPerLine() { return mBytesPerLine; }

    /* clients should treat the returned texture as read-only */
    GLuint textureSynched(const QRect * aRect) { synchTexture(aRect); return mTexture; }

    void setAddress(uchar * addr);

    const QRect& rect() {return mRect;}

    virtual bool isPrimary() = 0;
private:
    void initDisplay();
    void deleteDisplay();
    void updateTexture(const QRect * aRect);
    void synchTexture(const QRect * aRect);
    void synchMem(const QRect * aRect);

    QRect mRect;

    GLuint mDisplay;
    bool mDisplayInitialized;

    uchar * mAddress;
    GLuint mTexture;

    GLenum mFormat;
    GLint  mInternalFormat;
    GLenum mType;
//    ulong  mDisplayWidth;
//    ulong  mDisplayHeight;
    ulong  mBytesPerPixel;
    ulong  mBytesPerLine;

    int mLockCount;
    /* memory buffer not reflected in fm and texture, e.g if memory buffer is replaced or in case of lock/unlock  */
    VBoxVHWADirtyRect mUpdateMemRect;
    /*in case of blit we blit from another surface's texture, so our current texture gets durty  */
    VBoxVHWADirtyRect mUpdateFB2TexRect;
    /*in case of blit the memory buffer does not get updated until we need it, e.g. for paint or lock operations */
    VBoxVHWADirtyRect mUpdateFB2MemRect;

    bool mFreeAddress;
};

class VBoxVHWASurfacePrimary : public VBoxVHWASurfaceBase
{
public:
    VBoxVHWASurfacePrimary(GLsizei aWidth, GLsizei aHeight,
            GLint aInternalFormat, GLenum aFormat, GLenum aType,
            class VBoxGLWidget *pWidget) :
                VBoxVHWASurfaceBase(aWidth, aHeight,
                        aInternalFormat, aFormat, aType),
                mWidget(pWidget)
    {}

    bool isPrimary() {return true;}
    void makeCurrent();
private:
    class VBoxGLWidget *mWidget;
};

class VBoxGLWidget : public QGLWidget
{
public:
    VBoxGLWidget (QWidget *aParent)
        : QGLWidget (aParent),
        pDisplay(NULL),
        mRe(NULL),
        mpIntersectionRect(NULL),
        mBitsPerPixel(0),
        mPixelFormat(0),
        mUsesGuestVRAM(false)
    {
//        /* No need for background drawing */
//        setAttribute (Qt::WA_OpaquePaintEvent);
    }

    ulong vboxPixelFormat() { return mPixelFormat; }
    bool vboxUsesGuestVRAM() { return mUsesGuestVRAM; }

    uchar *vboxAddress() { return pDisplay ? pDisplay->address() : NULL; }
    ulong vboxBitsPerPixel() { return mBitsPerPixel; }
    ulong vboxBytesPerLine() { return pDisplay ? pDisplay->bytesPerLine() : NULL; }

    void vboxPaintEvent (QPaintEvent *pe);
    void vboxResizeEvent (VBoxResizeEvent *re);

    VBoxVHWASurfacePrimary * vboxGetSurface() { return pDisplay; }
protected:
//    void resizeGL (int height, int width);

    void paintGL();

    void initializeGL();

private:
//    void vboxDoInitDisplay();
//    void vboxDoDeleteDisplay();
//    void vboxDoPerformDisplay() { Assert(mDisplayInitialized); glCallList(mDisplay); }

    void vboxDoResize(VBoxResizeEvent *re);
    void vboxDoPaint(const QRect *rec);
    VBoxVHWASurfacePrimary * pDisplay;

    VBoxResizeEvent *mRe;
    const QRect *mpIntersectionRect;
    ulong  mBitsPerPixel;
    ulong  mPixelFormat;
    bool   mUsesGuestVRAM;
};


class VBoxQGLFrameBuffer : public VBoxFrameBuffer
{
public:

    VBoxQGLFrameBuffer (VBoxConsoleView *aView);

    STDMETHOD(NotifyUpdate) (ULONG aX, ULONG aY,
                             ULONG aW, ULONG aH);

#ifdef VBOX_WITH_VIDEOHWACCEL
    STDMETHOD(ProcessVHWACommand)(BYTE *pCommand);
#endif

    ulong pixelFormat() { return vboxWidget()->vboxPixelFormat(); }
    bool usesGuestVRAM() { return vboxWidget()->vboxUsesGuestVRAM(); }

    uchar *address() { return vboxWidget()->vboxAddress(); }
    ulong bitsPerPixel() { return vboxWidget()->vboxBitsPerPixel(); }
    ulong bytesPerLine() { return vboxWidget()->vboxBytesPerLine(); }

    uchar *vramAddressFromOffset(uint64_t offset);

    void paintEvent (QPaintEvent *pe);
    void resizeEvent (VBoxResizeEvent *re);
#ifdef VBOX_WITH_VIDEOHWACCEL
    void doProcessVHWACommand(struct _VBOXVHWACMD * pCommand);
#endif

private:
#ifdef VBOX_WITH_VIDEOHWACCEL
    void checkUpdateAddress (VBoxVHWASurfaceBase * pSurface, uint64_t offset)
    {
        if (pSurface->addressAlocated())
        {
            uchar * addr = vramAddressFromOffset(offset);
            if(addr)
            {
                pSurface->setAddress(addr);
            }
        }
    }
    int vhwaSurfaceCanCreate(struct _VBOXVHWACMD_SURF_CANCREATE *pCmd);
    int vhwaSurfaceCreate(struct _VBOXVHWACMD_SURF_CREATE *pCmd);
    int vhwaSurfaceDestroy(struct _VBOXVHWACMD_SURF_DESTROY *pCmd);
    int vhwaSurfaceLock(struct _VBOXVHWACMD_SURF_LOCK *pCmd);
    int vhwaSurfaceUnlock(struct _VBOXVHWACMD_SURF_UNLOCK *pCmd);
    int vhwaSurfaceBlt(struct _VBOXVHWACMD_SURF_BLT *pCmd);
    int vhwaQueryInfo1(struct _VBOXVHWACMD_QUERYINFO1 *pCmd);
    int vhwaQueryInfo2(struct _VBOXVHWACMD_QUERYINFO2 *pCmd);
#endif
    void vboxMakeCurrent();
    VBoxGLWidget * vboxWidget();
};


#endif

/////////////////////////////////////////////////////////////////////////////

#if defined (VBOX_GUI_USE_SDL)

class VBoxSDLFrameBuffer : public VBoxFrameBuffer
{
public:

    VBoxSDLFrameBuffer (VBoxConsoleView *aView);
    virtual ~VBoxSDLFrameBuffer();

    STDMETHOD(NotifyUpdate) (ULONG aX, ULONG aY,
                             ULONG aW, ULONG aH);

    uchar *address()
    {
        SDL_Surface *surf = mSurfVRAM ? mSurfVRAM : mScreen;
        return surf ? (uchar *) (uintptr_t) surf->pixels : 0;
    }

    ulong bitsPerPixel()
    {
        SDL_Surface *surf = mSurfVRAM ? mSurfVRAM : mScreen;
        return surf ? surf->format->BitsPerPixel : 0;
    }

    ulong bytesPerLine()
    {
        SDL_Surface *surf = mSurfVRAM ? mSurfVRAM : mScreen;
        return surf ? surf->pitch : 0;
    }

    ulong pixelFormat()
    {
        return mPixelFormat;
    }

    bool usesGuestVRAM()
    {
        return mSurfVRAM != NULL;
    }

    void paintEvent (QPaintEvent *pe);
    void resizeEvent (VBoxResizeEvent *re);

private:

    SDL_Surface *mScreen;
    SDL_Surface *mSurfVRAM;

    ulong mPixelFormat;
};

#endif

/////////////////////////////////////////////////////////////////////////////

#if defined (VBOX_GUI_USE_DDRAW)

class VBoxDDRAWFrameBuffer : public VBoxFrameBuffer
{
public:

    VBoxDDRAWFrameBuffer (VBoxConsoleView *aView);
    virtual ~VBoxDDRAWFrameBuffer();

    STDMETHOD(NotifyUpdate) (ULONG aX, ULONG aY,
                             ULONG aW, ULONG aH);

    uchar *address() { return (uchar *) mSurfaceDesc.lpSurface; }
    ulong bitsPerPixel() { return mSurfaceDesc.ddpfPixelFormat.dwRGBBitCount; }
    ulong bytesPerLine() { return (ulong) mSurfaceDesc.lPitch; }

    ulong pixelFormat() { return mPixelFormat; };

    bool usesGuestVRAM() { return mUsesGuestVRAM; }

    void paintEvent (QPaintEvent *pe);
    void resizeEvent (VBoxResizeEvent *re);
    void moveEvent (QMoveEvent *me);

private:

    void releaseObjects();

    bool createSurface (ULONG aPixelFormat, uchar *pvVRAM,
                        ULONG aBitsPerPixel, ULONG aBytesPerLine,
                        ULONG aWidth, ULONG aHeight);
    void deleteSurface();
    void drawRect (ULONG x, ULONG y, ULONG w, ULONG h);
    void getWindowPosition (void);

    LPDIRECTDRAW7        mDDRAW;
    LPDIRECTDRAWCLIPPER  mClipper;
    LPDIRECTDRAWSURFACE7 mSurface;
    DDSURFACEDESC2       mSurfaceDesc;
    LPDIRECTDRAWSURFACE7 mPrimarySurface;

    ulong mPixelFormat;

    bool mUsesGuestVRAM;

    int mWndX;
    int mWndY;

    bool mSynchronousUpdates;
};

#endif

/////////////////////////////////////////////////////////////////////////////

#if defined (Q_WS_MAC) && defined (VBOX_GUI_USE_QUARTZ2D)

#include <Carbon/Carbon.h>

class VBoxQuartz2DFrameBuffer : public VBoxFrameBuffer
{
public:

    VBoxQuartz2DFrameBuffer (VBoxConsoleView *aView);
    virtual ~VBoxQuartz2DFrameBuffer ();

    STDMETHOD (NotifyUpdate) (ULONG aX, ULONG aY,
                              ULONG aW, ULONG aH);
    STDMETHOD (SetVisibleRegion) (BYTE *aRectangles, ULONG aCount);

    uchar *address() { return mDataAddress; }
    ulong bitsPerPixel() { return CGImageGetBitsPerPixel (mImage); }
    ulong bytesPerLine() { return CGImageGetBytesPerRow (mImage); }
    ulong pixelFormat() { return mPixelFormat; };
    bool usesGuestVRAM() { return mBitmapData == NULL; }

    const CGImageRef imageRef() const { return mImage; }

    void paintEvent (QPaintEvent *pe);
    void resizeEvent (VBoxResizeEvent *re);

private:

    void clean();

    uchar *mDataAddress;
    void *mBitmapData;
    ulong mPixelFormat;
    CGImageRef mImage;
    typedef struct
    {
        /** The size of this structure expressed in rcts entries. */
        ULONG allocated;
        /** The number of entries in the rcts array. */
        ULONG used;
        /** Variable sized array of the rectangle that makes up the region. */
        CGRect rcts[1];
    } RegionRects;
    /** The current valid region, all access is by atomic cmpxchg or atomic xchg.
     *
     * The protocol for updating and using this has to take into account that
     * the producer (SetVisibleRegion) and consumer (paintEvent) are running
     * on different threads. Therefore the producer will create a new RegionRects
     * structure before atomically replace the existing one. While the consumer
     * will read the value by atomically replace it by NULL, and then when its
     * done try restore it by cmpxchg. If the producer has already put a new
     * region there, it will be discarded (see mRegionUnused).
     */
    RegionRects volatile *mRegion;
    /** For keeping the unused region and thus avoid some RTMemAlloc/RTMemFree calls.
     * This is operated with atomic cmpxchg and atomic xchg. */
    RegionRects volatile *mRegionUnused;
};

#endif /* Q_WS_MAC && VBOX_GUI_USE_QUARTZ2D */

#endif // !___VBoxFrameBuffer_h___