/****************************************************************************
** $Id:  qt/qpixmapcache.cpp   3.0.3   edited Mar 4 11:28 $
**
** Implementation of QPixmapCache class
**
** Created : 950504
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#include "qpixmapcache.h"
#include "qcache.h"
#include "qobject.h"
#include "qcleanuphandler.h"


// REVISED: paul
/*!
  \class QPixmapCache qpixmapcache.h

  \brief The QPixmapCache class provides an application-global cache for
  pixmaps.

  \ingroup environment
  \ingroup graphics
  \ingroup images

  This class is a tool for optimized drawing with QPixmap.  You can
  use it to store temporary pixmaps that are expensive to generate
  without using more storage space than cacheLimit(). Use insert() to
  insert pixmaps, find() to find them and clear() to empty the cache.

  For example, QRadioButton has a non-trivial visual representation so
  we don't want to regenerate a pixmap whenever a radio button is
  displayed or changes state. In the function
  QRadioButton::drawButton(), we do not draw the radio button
  directly. Instead, we first check the global pixmap cache for a
  pixmap with the key "$qt_radio_nnn_", where \c nnn is a numerical
  value that specifies the the radio button state.  If a pixmap is
  found, we bitBlt() it onto the widget and return. Otherwise, we
  create a new pixmap, draw the radio button in the pixmap, and
  finally insert the pixmap in the global pixmap cache, using the key
  above.  The bitBlt() is 10 times faster than drawing the radio
  button.  All radio buttons in the program share the cached pixmap
  since QPixmapCache is application-global.

  QPixmapCache contains no member data, only static functions to access
  the global pixmap cache.  It creates an internal QCache for caching the
  pixmaps.

  The cache associates a pixmap with a string (key).  If two
  pixmaps are inserted into the cache using equal keys, then the last
  pixmap will hide the first pixmap. The QDict and QCache classes do
  exactly the same.

  The cache becomes full when the total size of all pixmaps in the
  cache exceeds cacheLimit().  The initial cache limit is 1024 KByte
  (1 MByte); it is changed with setCacheLimit().  A pixmap takes
  roughly width*height*depth/8 bytes of memory.

  See the \l QCache documentation for more details about the cache mechanism.
*/


static const int cache_size = 149;		// size of internal hash array
#ifdef Q_WS_MAC9
static int cache_limit	  = 256;		// 256 KB cache limit
#else
static int cache_limit	  = 1024;		// 1024 KB cache limit
#endif

class QPMCache: public QObject, public QCache<QPixmap>
{
public:
    QPMCache():
	QObject( 0, "global pixmap cache" ),
	QCache<QPixmap>( cache_limit * 1024, cache_size ),
	id( 0 ), ps( 0 ), t( FALSE )
	{
	    setAutoDelete( TRUE );
	}
   ~QPMCache() {}
    void timerEvent( QTimerEvent * );
    bool insert( const QString& k, const QPixmap *d, int c, int p = 0 );
private:
    int id;
    int ps;
    bool t;
};


/*
  This is supposed to cut the cache size down by about 80-90% in a
  minute once the application becomes idle, to let any inserted pixmap
  remain in the cache for some time before it becomes a candidate for
  cleaning-up, and to not cut down the size of the cache while the
  cache is in active use.

  When the last pixmap has been deleted from the cache, kill the
  timer so Qt won't keep the CPU from going into sleep mode.
*/

void QPMCache::timerEvent( QTimerEvent * )
{
    int mc = maxCost();
    bool nt = totalCost() == ps;
    setMaxCost( nt ? totalCost() * 3 / 4 : totalCost() -1 );
    setMaxCost( mc );
    ps = totalCost();

    if ( !count() ) {
	killTimer( id );
	id = 0;
    } else if ( nt != t ) {
	killTimer( id );
	id = startTimer( nt ? 10000 : 30000 );
	t = nt;
    }
}

bool QPMCache::insert( const QString& k, const QPixmap *d, int c, int p )
{
    bool r = QCache<QPixmap>::insert( k, d, c, p );
    if ( r && !id ) {
	id = startTimer( 30000 );
	t = FALSE;
    }
    return r;
}

static QPMCache *pm_cache = 0;			// global pixmap cache

static QSingleCleanupHandler<QPMCache> qpm_cleanup_cache;

/*!
  Returns the pixmap associated with the \a key in the cache, or null
  if there is no such pixmap.

  <strong>
    Note: if valid, you should copy the pixmap immediately (this is quick).
    Subsequent insertions into the cache could cause the pointer to become
    invalid.  For this reason, we recommend you use
    find(const QString&, QPixmap&) instead.
  </strong>

  Example:
  \code
    QPixmap* pp;
    QPixmap p;
    if ( (pp=QPixmapCache::find("my_previous_copy", pm)) ) {
	p = *pp;
    } else {
	p.load("bigimage.png");
	QPixmapCache::insert("my_previous_copy", new QPixmap(p));
    }
    painter->drawPixmap(0, 0, p);
  \endcode
*/

QPixmap *QPixmapCache::find( const QString &key )
{
    return pm_cache ? pm_cache->find(key) : 0;
}


/*!
    \overload
  Looks for a cached pixmap associated with the \a key in the cache.  If a
  pixmap is found, the function sets \a pm to that pixmap and returns
  TRUE.  Otherwise, the function returns FALSE and does not change \a
  pm.

  Example:
  \code
    QPixmap p;
    if ( !QPixmapCache::find("my_previous_copy", pm) ) {
	pm.load("bigimage.png");
	QPixmapCache::insert("my_previous_copy", pm);
    }
    painter->drawPixmap(0, 0, p);
  \endcode
*/

bool QPixmapCache::find( const QString &key, QPixmap& pm )
{
    QPixmap* p = pm_cache ? pm_cache->find(key) : 0;
    if ( p ) pm = *p;
    return !!p;
}


/*!
  \obsolete
  Inserts the pixmap \a pm associated with \a key into the cache.
  Returns TRUE if successful, or FALSE if the pixmap is too big for the cache.

  <strong>
    Note: \a pm must be allocated on the heap (using \c new).

    If this function returns FALSE, you must delete \a pm yourself.

    If this function returns TRUE, do not use \a pm afterwards or
    keep references to it because any other insertions into the cache,
    whether from anywhere in the application or within Qt itself, could cause
    the pixmap to be discarded from the cache and the pointer to
    become invalid.

    Due to these dangers, we strongly recommend that you use
    insert(const QString&, const QPixmap&) instead.
  </strong>
*/

bool QPixmapCache::insert( const QString &key, QPixmap *pm )
{
    if ( !pm_cache ) {				// create pixmap cache
	pm_cache = new QPMCache;
	Q_CHECK_PTR( pm_cache );
	qpm_cleanup_cache.set( &pm_cache );
    }
    return pm_cache->insert( key, pm, pm->width()*pm->height()*pm->depth()/8 );
}

/*!
  Inserts a copy of the pixmap \a pm associated with the \a key into the cache.

  All pixmaps inserted by the Qt library have a key starting with "$qt".
  Use something else for your own pixmaps.

  When a pixmap is inserted and the cache is about to exceed its limit, it
  removes pixmaps until there is enough room for the pixmap to be inserted.

  The oldest pixmaps (least recently accessed in the cache) are deleted
  when more space is needed.

  \sa setCacheLimit().
*/

bool QPixmapCache::insert( const QString &key, const QPixmap& pm )
{
    if ( !pm_cache ) {				// create pixmap cache
	pm_cache = new QPMCache;
	Q_CHECK_PTR( pm_cache );
	qpm_cleanup_cache.set( &pm_cache );
    }
    QPixmap *p = new QPixmap(pm);
    bool rt = pm_cache->insert( key, p, p->width()*p->height()*p->depth()/8 );
    if ( !rt )
	delete p;

    return rt;
}

/*!
  Returns the cache limit (in kilobytes).

  The default setting is 1024 kilobytes.

  \sa setCacheLimit().
*/

int QPixmapCache::cacheLimit()
{
    return cache_limit;
}

/*!
  Sets the cache limit to \a n kilobytes.

  The default setting is 1024 kilobytes.

  \sa cacheLimit()
*/

void QPixmapCache::setCacheLimit( int n )
{
#ifdef Q_WS_MAC9
    if(n > 256)
        qWarning("QPixmapCache::setCacheLimit: Setting cache limits high is harmfull to mac9's health");
#endif
    cache_limit = n;
    if ( pm_cache )
	pm_cache->setMaxCost( 1024*cache_limit );
}


/*!
  Removes all pixmaps from the cache.
*/

void QPixmapCache::clear()
{
    if ( pm_cache )
	pm_cache->clear();
}
