/****************************************************************************
**
** Implementation of some internal classes
**
** Created : 010427
**
** Copyright (C) 1992-2008 Trolltech ASA.  All rights reserved.
**
** This file is part of the kernel module of the Qt GUI Toolkit.
**
** This file may be used under the terms of the GNU General
** Public License versions 2.0 or 3.0 as published by the Free
** Software Foundation and appearing in the files LICENSE.GPL2
** and LICENSE.GPL3 included in the packaging of this file.
** Alternatively you may (at your option) use any later version
** of the GNU General Public License if such license has been
** publicly approved by Trolltech ASA (or its successors, if any)
** and the KDE Free Qt Foundation.
**
** Please review the following information to ensure GNU General
** Public Licensing requirements will be met:
** http://trolltech.com/products/qt/licenses/licensing/opensource/.
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
** or contact the sales department at sales@trolltech.com.
**
** This file may be used under the terms of the Q Public License as
** defined by Trolltech ASA and appearing in the file LICENSE.QPL
** included in the packaging of this file.  Licensees holding valid Qt
** Commercial licenses may use this file in accordance with the Qt
** Commercial License Agreement provided with the Software.
**
** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
** herein.
**
**********************************************************************/

#include "private/qinternal_p.h"
#include "qwidget.h"
#include "qpixmap.h"
#include "qpainter.h"
#include "qcleanuphandler.h"

// Modern systems (year 2011) have very large screens in excess of 1000 pixels wide
// Some may even have screens in excess of 4000 pixels wide(!)
// Prevent drawing artifacts on such screens
#define USE_HUGE_QT_SHARED_DOUBLE_BUFFERS 1

static QPixmap* qdb_shared_pixmap = 0;
static QPixmap *qdb_force_pixmap = 0;
static QSharedDoubleBuffer* qdb_owner = 0;

QCleanupHandler<QPixmap> qdb_pixmap_cleanup;

#ifdef Q_WS_MACX
bool QSharedDoubleBuffer::dblbufr = FALSE;
#else
bool QSharedDoubleBuffer::dblbufr = TRUE;
#endif


/*
  hardLimitWidth/Height: if >= 0, the maximum number of pixels that
  get double buffered.

  sharedLimitWidth/Height: if >= 0, the maximum number of pixels the
  shared double buffer can keep.

  For x with sharedLimitSize < x <= hardLimitSize, temporary buffers
  are constructed.
 */
static const int hardLimitWidth = -1;
static const int hardLimitHeight = -1;
#if defined( Q_WS_QWS ) || defined( Q_WS_MAC9 )
// Small in Qt/Embedded / Mac9 - 5K on 32bpp
static const int sharedLimitWidth = 64;
static const int sharedLimitHeight = 20;
#else
#ifdef USE_HUGE_QT_SHARED_DOUBLE_BUFFERS
// 24M on 32bpp
static const int sharedLimitWidth = 6400;
static const int sharedLimitHeight = 1000;
#else
// 240K on 32bpp
static const int sharedLimitWidth = 640;
static const int sharedLimitHeight = 100;
#endif
#endif

// *******************************************************************
// QSharedDoubleBufferCleaner declaration and implementation
// *******************************************************************

/* \internal
   This class is responsible for cleaning up the pixmaps created by the
   QSharedDoubleBuffer class.  When QSharedDoubleBuffer creates a
   pixmap larger than the shared limits, this class deletes it after a
   specified amount of time.

   When the large pixmap is created/used, you must call start(). If the
   large pixmap is ever deleted, you must call stop().  The start()
   method always restarts the timer, so if the large pixmap is
   constantly in use, the timer will never fire, and the pixmap will
   not be constantly created and destroyed.
*/

static const int shared_double_buffer_cleanup_timeout = 30000; // 30 seconds

// declaration

class QSharedDoubleBufferCleaner : public QObject
{
public:
    QSharedDoubleBufferCleaner( void );

    void start( void );
    void stop( void );

    void doCleanup( void );

    bool event( QEvent *e );

private:
    int timer_id;
};

// implementation

/* \internal
   Creates a QSharedDoubleBufferCleaner object. The timer is not
   started when creating the object.
*/
QSharedDoubleBufferCleaner::QSharedDoubleBufferCleaner( void )
    : QObject( 0, "internal shared double buffer cleanup object" ),
      timer_id( -1 )
{
}

/* \internal
   Starts the cleanup timer.  Any previously running timer is stopped.
*/
void QSharedDoubleBufferCleaner::start( void )
{
    stop();
    timer_id = startTimer( shared_double_buffer_cleanup_timeout );
}

/* \internal
   Stops the cleanup timer, if it is running.
*/
void QSharedDoubleBufferCleaner::stop( void )
{
    if ( timer_id != -1 )
	killTimer( timer_id );
    timer_id = -1;
}

/* \internal
 */
void QSharedDoubleBufferCleaner::doCleanup( void )
{
    qdb_pixmap_cleanup.remove( &qdb_force_pixmap );
    delete qdb_force_pixmap;
    qdb_force_pixmap = 0;
}

/* \internal
   Event handler reimplementation.  Calls doCleanup() when the timer
   fires.
*/
bool QSharedDoubleBufferCleaner::event( QEvent *e )
{
    if ( e->type() != QEvent::Timer )
	return FALSE;

    QTimerEvent *event = (QTimerEvent *) e;
    if ( event->timerId() == timer_id ) {
	doCleanup();
	stop();
    }
#ifdef QT_CHECK_STATE
    else {
	qWarning( "QSharedDoubleBufferCleaner::event: invalid timer event received." );
	return FALSE;
    }
#endif // QT_CHECK_STATE

    return TRUE;
}

// static instance
static QSharedDoubleBufferCleaner *static_cleaner = 0;
QSingleCleanupHandler<QSharedDoubleBufferCleaner> cleanup_static_cleaner;

inline static QSharedDoubleBufferCleaner *staticCleaner()
{
    if ( ! static_cleaner ) {
	static_cleaner = new QSharedDoubleBufferCleaner();
	cleanup_static_cleaner.set( &static_cleaner );
    }
    return static_cleaner;
}


// *******************************************************************
// QSharedDoubleBuffer implementation
// *******************************************************************

/* \internal
   \enum DoubleBufferFlags

   \value InitBG initialize the background of the double buffer.

   \value Force disable shared buffer size limits.

   \value Default InitBG and Force are used by default.
*/

/* \internal
   \enum DoubleBufferState

   \value Active indicates that the buffer may be used.

   \value BufferActive indicates that painting with painter() will be
   double buffered.

   \value ExternalPainter indicates that painter() will return a
   painter that was not created by QSharedDoubleBuffer.
*/

/* \internal
   \class QSharedDoubleBuffer

   This class provides a single, reusable double buffer.  This class
   is used internally by Qt widgets that need double buffering, which
   prevents each individual widget form creating a double buffering
   pixmap.

   Using a single pixmap double buffer and sharing it across all
   widgets is nicer on window system resources.
*/

/* \internal
   Creates a QSharedDoubleBuffer with flags \f.

   \sa DoubleBufferFlags
*/
QSharedDoubleBuffer::QSharedDoubleBuffer( DBFlags f )
    : wid( 0 ), rx( 0 ), ry( 0 ), rw( 0 ), rh( 0 ), flags( f ), state( 0 ),
      p( 0 ), external_p( 0 ), pix( 0 )
{
}

/* \internal
   Creates a QSharedDoubleBuffer with flags \f. The \a widget, \a x,
   \a y, \a w and \a h arguments are passed to begin().

   \sa DoubleBufferFlags begin()
*/
QSharedDoubleBuffer::QSharedDoubleBuffer( QWidget* widget,
					  int x, int y, int w, int h,
					  DBFlags f )
    : wid( 0 ), rx( 0 ), ry( 0 ), rw( 0 ), rh( 0 ), flags( f ), state( 0 ),
      p( 0 ), external_p( 0 ), pix( 0 )
{
    begin( widget, x, y, w, h );
}

/* \internal
   Creates a QSharedDoubleBuffer with flags \f. The \a painter, \a x,
   \a y, \a w and \a h arguments are passed to begin().

   \sa DoubleBufferFlags begin()
*/
QSharedDoubleBuffer::QSharedDoubleBuffer( QPainter* painter,
					  int x, int y, int w, int h,
					  DBFlags f)
    : wid( 0 ), rx( 0 ), ry( 0 ), rw( 0 ), rh( 0 ), flags( f ), state( 0 ),
      p( 0 ), external_p( 0 ), pix( 0 )
{
    begin( painter, x, y, w, h );
}

/* \internal
   Creates a QSharedDoubleBuffer with flags \f. The \a widget and
   \a r arguments are passed to begin().

   \sa DoubleBufferFlags begin()
*/
QSharedDoubleBuffer::QSharedDoubleBuffer( QWidget *widget, const QRect &r, DBFlags f )
    : wid( 0 ), rx( 0 ), ry( 0 ), rw( 0 ), rh( 0 ), flags( f ), state( 0 ),
      p( 0 ), external_p( 0 ), pix( 0 )
{
    begin( widget, r );
}

/* \internal
   Creates a QSharedDoubleBuffer with flags \f. The \a painter and
   \a r arguments are passed to begin().

   \sa DoubleBufferFlags begin()
*/
QSharedDoubleBuffer::QSharedDoubleBuffer( QPainter *painter, const QRect &r, DBFlags f )
    : wid( 0 ), rx( 0 ), ry( 0 ), rw( 0 ), rh( 0 ), flags( f ), state( 0 ),
      p( 0 ), external_p( 0 ), pix( 0 )
{
    begin( painter, r );
}

/* \internal
   Destructs the QSharedDoubleBuffer and calls end() if the buffer is
   active.

   \sa isActive() end()
*/
QSharedDoubleBuffer::~QSharedDoubleBuffer()
{
    if ( isActive() )
        end();
}

/* \internal
   Starts double buffered painting in the area specified by \a x,
   \a y, \a w and \a h on \a painter.  Painting should be done using the
   QPainter returned by QSharedDoubleBuffer::painter().

   The double buffered area will be updated when calling end().

   \sa painter() isActive() end()
*/
bool QSharedDoubleBuffer::begin( QPainter* painter, int x, int y, int w, int h )
{
    if ( isActive() ) {
#if defined(QT_CHECK_STATE)
        qWarning( "QSharedDoubleBuffer::begin: Buffer is already active."
                  "\n\tYou must end() the buffer before a second begin()" );
#endif // QT_CHECK_STATE
        return FALSE;
    }

    external_p = painter;

    if ( painter->device()->devType() == QInternal::Widget )
	return begin( (QWidget *) painter->device(), x, y, w, h );

    state = Active;

    rx = x;
    ry = y;
    rw = w;
    rh = h;

    if ( ( pix = getPixmap() ) ) {
#ifdef Q_WS_X11
	if ( painter->device()->x11Screen() != pix->x11Screen() )
	    pix->x11SetScreen( painter->device()->x11Screen() );
	QPixmap::x11SetDefaultScreen( pix->x11Screen() );
#endif // Q_WS_X11

	state |= BufferActive;
	p = new QPainter( pix );
	if ( p->isActive() ) {
	    p->setPen( external_p->pen() );
	    p->setBackgroundColor( external_p->backgroundColor() );
	    p->setFont( external_p->font() );
	}
    } else {
	state |= ExternalPainter;
	p = external_p;
    }

    return TRUE;
}

/* \internal


   Starts double buffered painting in the area specified by \a x,
   \a y, \a w and \a h on \a widget.  Painting should be done using the
   QPainter returned by QSharedDoubleBuffer::painter().

   The double buffered area will be updated when calling end().

   \sa painter() isActive() end()
*/
bool QSharedDoubleBuffer::begin( QWidget* widget, int x, int y, int w, int h )
{
    if ( isActive() ) {
#if defined(QT_CHECK_STATE)
        qWarning( "QSharedDoubleBuffer::begin: Buffer is already active."
                  "\n\tYou must end() the buffer before a second begin()" );
#endif // QT_CHECK_STATE
        return FALSE;
    }

    state = Active;

    wid = widget;
    rx = x;
    ry = y;
    rw = w <= 0 ? wid->width() : w;
    rh = h <= 0 ? wid->height() : h;

    if ( ( pix = getPixmap() ) ) {
#ifdef Q_WS_X11
	if ( wid->x11Screen() != pix->x11Screen() )
	    pix->x11SetScreen( wid->x11Screen() );
	QPixmap::x11SetDefaultScreen( pix->x11Screen() );
#endif // Q_WS_X11

	state |= BufferActive;
	if ( flags & InitBG ) {
	    pix->fill( wid, rx, ry );
	}
	p = new QPainter( pix, wid );
	// newly created painters should be translated to the origin
	// of the widget, so that paint methods can draw onto the double
	// buffered painter in widget coordinates.
	p->setBrushOrigin( -rx, -ry );
	p->translate( -rx, -ry );
    } else {
	if ( external_p ) {
	    state |= ExternalPainter;
	    p = external_p;
	} else {
	    p = new QPainter( wid );
	}

	if ( flags & InitBG ) {
	    wid->erase( rx, ry, rw, rh );
	}
    }
    return TRUE;
}

/* \internal
   Ends double buffered painting.  The contents of the shared double
   buffer pixmap are drawn onto the destination by calling flush(),
   and ownership of the shared double buffer pixmap is released.

   \sa begin() flush()
*/
bool QSharedDoubleBuffer::end()
{
    if ( ! isActive() ) {
#if defined(QT_CHECK_STATE)
	qWarning( "QSharedDoubleBuffer::end: Buffer is not active."
		  "\n\tYou must call begin() before calling end()." );
#endif // QT_CHECK_STATE
	return FALSE;
    }

    if ( ! ( state & ExternalPainter ) ) {
	p->end();
	delete p;
    }

    flush();

    if ( pix ) {
	releasePixmap();
    }

    wid = 0;
    rx = ry = rw = rh = 0;
    // do not reset flags!
    state = 0;

    p = external_p = 0;
    pix = 0;

    return TRUE;
}

/* \internal
   Paints the contents of the shared double buffer pixmap onto the
   destination.  The destination is determined from the arguments
   based to begin().

   Note: You should not need to call this function, since it is called
   from end().

   \sa begin() end()
*/
void QSharedDoubleBuffer::flush()
{
    if ( ! isActive() || ! ( state & BufferActive ) )
	return;

    if ( external_p )
	external_p->drawPixmap( rx, ry, *pix, 0, 0, rw, rh );
    else if ( wid && wid->isVisible() )
	bitBlt( wid, rx, ry, pix, 0, 0, rw, rh );
}

/* \internal
   Acquire ownership of the shared double buffer pixmap, subject to the
   following conditions:

   \list 1
   \i double buffering is enabled globally.
   \i the shared double buffer pixmap is not in use.
   \i the size specified in begin() is valid, and within limits.
   \endlist

   If all of these conditions are met, then this QSharedDoubleBuffer
   object becomes the owner of the shared double buffer pixmap.  The
   shared double buffer pixmap is resize if necessary, and this
   function returns a pointer to the pixmap.  Ownership must later be
   relinquished by calling releasePixmap().

   If none of the above conditions are met, this function returns
   zero.

   \sa releasePixmap()
*/
QPixmap *QSharedDoubleBuffer::getPixmap()
{
    if ( isDisabled() ) {
	// double buffering disabled globally
	return 0;
    }

    if ( qdb_owner ) {
	// shared pixmap already in use
	return 0;
    }

    if ( rw <= 0 || rh <= 0 ||
	 ( hardLimitWidth > 0 && rw >= hardLimitWidth ) ||
	 ( hardLimitHeight > 0 && rh >= hardLimitHeight ) ) {
	// invalid size, or hard limit reached
	return 0;
    }

    if ( rw >= sharedLimitWidth || rh >= sharedLimitHeight ) {
	if ( flags & Force ) {
#ifdef USE_HUGE_QT_SHARED_DOUBLE_BUFFERS
	    rw = QMIN(rw, 16000);
	    rh = QMIN(rh, 16000);
#else
	    rw = QMIN(rw, 8000);
	    rh = QMIN(rh, 8000);
#endif
	    // need to create a big pixmap and start the cleaner
	    if ( ! qdb_force_pixmap ) {
		qdb_force_pixmap = new QPixmap( rw, rh );
		qdb_pixmap_cleanup.add( &qdb_force_pixmap );
	    } else if ( qdb_force_pixmap->width () < rw ||
			qdb_force_pixmap->height() < rh ) {
		qdb_force_pixmap->resize( rw, rh );
	    }
	    qdb_owner = this;
	    staticCleaner()->start();
	    return qdb_force_pixmap;
	}

	// size is outside shared limit
	return 0;
    }

    if ( ! qdb_shared_pixmap ) {
	qdb_shared_pixmap = new QPixmap( rw, rh );
	qdb_pixmap_cleanup.add( &qdb_shared_pixmap );
    } else if ( qdb_shared_pixmap->width() < rw ||
		qdb_shared_pixmap->height() < rh ) {
	qdb_shared_pixmap->resize( rw, rh );
    }
    qdb_owner = this;
    return qdb_shared_pixmap;
}

/* \internal
   Releases ownership of the shared double buffer pixmap.

   \sa getPixmap()
*/
void QSharedDoubleBuffer::releasePixmap()
{
    if ( qdb_owner != this ) {
	// sanity check

#ifdef QT_CHECK_STATE
	qWarning( "QSharedDoubleBuffer::releasePixmap: internal error."
		  "\n\t%p does not own shared pixmap, %p does.",
		  (void*)this, (void*)qdb_owner );
#endif // QT_CHECK_STATE

	return;
    }

    qdb_owner = 0;
}

/* \internal
   \fn bool QSharedDoubleBuffer::isDisabled()

   Returns TRUE if double buffering is disabled globally, FALSE otherwise.
*/

/* \internal
   \fn void QSharedDoubleBuffer::setDisabled( bool off )

   Disables global double buffering \a off is TRUE, otherwise global
   double buffering is enabled.
*/

/* \internal
   Deletes the shared double buffer pixmap.  You should not need to
   call this function, since it is called from the QApplication
   destructor.
*/
void QSharedDoubleBuffer::cleanup()
{
    qdb_pixmap_cleanup.remove( &qdb_shared_pixmap );
    qdb_pixmap_cleanup.remove( &qdb_force_pixmap );
    delete qdb_shared_pixmap;
    delete qdb_force_pixmap;
    qdb_shared_pixmap = 0;
    qdb_force_pixmap = 0;
    qdb_owner = 0;
}

/* \internal
   \fn bool QSharedDoubleBuffer::begin( QWidget *widget, const QRect &r )
   \overload
*/

/* \internal
   \fn bool QSharedDoubleBuffer::begin( QPainter *painter, const QRect &r )
   \overload
*/

/* \internal
   \fn QPainter *QSharedDoubleBuffer::painter() const

   Returns the active painter on the double buffered area,
   or zero if double buffered painting is not active.
*/

/* \internal
   \fn bool QSharedDoubleBuffer::isActive() const

   Returns TRUE if double buffered painting is active, FALSE otherwise.
*/

/* \internal
   \fn bool QSharedDoubleBuffer::isBuffered() const

   Returns TRUE if painting is double buffered, FALSE otherwise.
*/


// *******************************************************************
// QMembuf declaration and implementation
// *******************************************************************

/*  \internal
    This class implements an efficient buffering of data that is often used by
    asynchronous IO classes like QSocket, QHttp and QProcess.
*/

QMembuf::QMembuf() : _size(0), _index(0)
{
    buf = new QPtrList<QByteArray>;
    buf->setAutoDelete( TRUE );
}

QMembuf::~QMembuf()
{
    delete buf;
}

/*! \internal
    This function consumes \a nbytes bytes of data from the
    buffer and copies it into \a sink. If \a sink is a 0 pointer
    the data goes into the nirvana.
*/
bool QMembuf::consumeBytes( Q_ULONG nbytes, char *sink )
{
    if ( nbytes <= 0 || nbytes > _size )
	return FALSE;
    _size -= nbytes;
    for ( ;; ) {
	QByteArray *a = buf->first();
	if ( _index + nbytes >= a->size() ) {
	    // Here we skip the whole byte array and get the next later
	    int len = a->size() - _index;
	    if ( sink ) {
		memcpy( sink, a->data()+_index, len );
		sink += len;
	    }
	    nbytes -= len;
	    buf->remove();
	    _index = 0;
	    if ( nbytes == 0 )
		break;
	} else {
	    // Here we skip only a part of the first byte array
	    if ( sink )
		memcpy( sink, a->data()+_index, nbytes );
	    _index += nbytes;
	    break;
	}
    }
    return TRUE;
}

/*! \internal
    Scans for any occurrence of '\n' in the buffer. If \a store
    is not 0 the text up to the first '\n' (or terminating 0) is
    written to \a store, and a terminating 0 is appended to \a store
    if necessary. Returns TRUE if a '\n' was found; otherwise returns
    FALSE.
*/
bool QMembuf::scanNewline( QByteArray *store )
{
    if ( _size == 0 )
	return FALSE;
    int i = 0; // index into 'store'
    QByteArray *a = 0;
    char *p;
    int n;
    for ( ;; ) {
	if ( !a ) {
	    a = buf->first();
	    if ( !a || a->size() == 0 )
		return FALSE;
	    p = a->data() + _index;
	    n = a->size() - _index;
	} else {
	    a = buf->next();
	    if ( !a || a->size() == 0 )
		return FALSE;
	    p = a->data();
	    n = a->size();
	}
	if ( store ) {
	    while ( n-- > 0 ) {
		*(store->data()+i) = *p;
		if ( ++i == (int)store->size() )
		    store->resize( store->size() < 256
				   ? 1024 : store->size()*4 );
		switch ( *p ) {
		    case '\0':
			store->resize( i );
			return FALSE;
		    case '\n':
			*(store->data()+i) = '\0';
			store->resize( i );
			return TRUE;
		}
		p++;
	    }
	} else {
	    while ( n-- > 0 ) {
		switch ( *p++ ) {
		    case '\0':
			return FALSE;
		    case '\n':
			return TRUE;
		}
	    }
	}
    }
}

int QMembuf::ungetch( int ch )
{
    if ( buf->isEmpty() || _index==0 ) {
	// we need a new QByteArray
	QByteArray *ba = new QByteArray( 1 );
	buf->insert( 0, ba );
	_size++;
	ba->at( 0 ) = ch;
    } else {
	// we can reuse a place in the buffer
	QByteArray *ba = buf->first();
	_index--;
	_size++;
	ba->at( _index ) = ch;
    }
    return ch;
}