KPixmapCache Class Reference

from PyKDE4.kdeui import *

Detailed Description

General-purpose pixmap cache for KDE.

The pixmap cache can be used to store pixmaps which can later be loaded from the cache very quickly.

Its most common use is storing SVG images which might be expensive to render every time they are used. With the cache you can render each SVG only once and later use the stored version unless the SVG file or requested pixmap size changes.

KPixmapCache's API is similar to that of the QPixmapCache so if you're already using the latter then all you need to do is creating a KPixmapCache object (unlike QPixmapCache, KPixmapCache doesn't have many static methods) and calling insert() and find() method on that object:

  // Create KPixmapCache object
  KPixmapCache* cache = new KPixmapCache("myapp-pixmaps");
  // Load a pixmap
  QPixmap pix;
  if (!cache->find("pixmap-1", pix)) {
      // Pixmap isn't in the cache, create it and insert to cache
      pix = createPixmapFromData();
      cache->insert("pixmap-1", pix);
  }
  // Use pix

The above example illustrates that you can also cache pixmaps created from some data. In case such data is updated, you might need to discard cache contents using discard() method:

 // Discard the cache if it's too old
 if (cache->timestamp() < mydataTimestamp()) {
     cache->discard();
 }
 // Now the cache contains up-to-date data

As demonstrated, you can use cache's timestamp() method to see when the cache was created. If necessary, you can also change the timestamp using setTimestamp() method.

Enumerations
RemoveStrategy	{ RemoveOldest, RemoveSeldomUsed, RemoveLeastRecentlyUsed }
Methods
	__init__ (self, QString name)
	__init__ (self, KPixmapCache other)
int	cacheLimit (self)
	discard (self)
	ensureInited (self)
bool	find (self, QString key, QPixmap pix)
	insert (self, QString key, QPixmap pix)
bool	isEnabled (self)
bool	isValid (self)
bool	loadCustomData (self, QDataStream stream)
bool	loadCustomIndexHeader (self, QDataStream stream)
QPixmap	loadFromFile (self, QString filename)
QPixmap	loadFromSvg (self, QString filename, QSize size=QSize())
bool	recreateCacheFiles (self)
	removeEntries (self, int newsize=0)
KPixmapCache.RemoveStrategy	removeEntryStrategy (self)
	setCacheLimit (self, int kbytes)
	setRemoveEntryStrategy (self, KPixmapCache.RemoveStrategy strategy)
	setTimestamp (self, long time)
	setUseQPixmapCache (self, bool use)
	setValid (self, bool valid)
int	size (self)
long	timestamp (self)
bool	useQPixmapCache (self)
bool	writeCustomData (self, QDataStream stream)
	writeCustomIndexHeader (self, QDataStream stream)
Static Methods
	deleteCache (QString name)

Method Documentation

__init__	(	self,
		QString	name
	)

Constucts the pixmap cache object.

Parameters:

name

unique name of the cache

__init__	(	self,
		KPixmapCache	other
	)

int cacheLimit ( self )

Returns:: maximum size of the cache (in kilobytes). Default setting is 3 megabytes.

deleteCache	(	QString	name
	)

Deletes a pixmap cache.

Parameters:

name

unique name of the cache to be deleted

discard ( self )

Deletes all entries and reinitializes this cache.

ensureInited ( self )

Makes sure that the cache is initialized correctly.

bool find	(	self,
		QString	key,
		QPixmap	pix
	)

Tries to load pixmap with the specified key from cache.

Returns:: true when pixmap was found and loaded from cache, false otherwise

insert	(	self,
		QString	key,
		QPixmap	pix
	)

Insert specified pixmap into the cache. If the cache already contains pixmap with the specified key then it is overwritten.

bool isEnabled ( self )

Returns:: true when the cache is enabled. Cache will be disabled when e.g. its data file cannot be created or read.

bool isValid ( self )

Returns:: true when the cache is ready to be used. False usually means that some additional initing has to be done before the cache can be used.

bool loadCustomData	(	self,
		QDataStream	stream
	)

Can be used by subclasses to write custom data into the stream.

bool loadCustomIndexHeader	(	self,
		QDataStream	stream
	)

Can be used by subclasses to write custom data into cache's header.

QPixmap loadFromFile	(	self,
		QString	filename
	)

Loads pixmap from given file, using the cache. If file's modified-time is more recent than cache's timestamp() , then the cache is discarded.

QPixmap loadFromSvg	(	self,
		QString	filename,
		QSize	size=QSize()
	)

Same as above, but uses SVG file instead.

Parameters:

size

size of the pixmap where the SVG is render to. If not given then SVG's default size is used.

bool recreateCacheFiles ( self )

Recreates the cache files.

removeEntries	(	self,
		int	newsize=0
	)

Removes some of the entries in the cache according to current removeEntryStrategy().

Parameters:

newsize

wanted size of the cache, in bytes. If 0 is given then current cacheLimit() is used.

Warning: this works by copying some entries to a new cache and then replacing the old cache with the new one. Thus it might be slow and will temporarily use extra disk space.

KPixmapCache.RemoveStrategy removeEntryStrategy ( self )

Returns:: current entry removal strategy. Default is RemoveLeastRecentlyUsed.

setCacheLimit	(	self,
		int	kbytes
	)

Sets the maximum size of the cache (in kilobytes). If cache gets bigger the limit then some entries are removed (according to removeEntryStrategy() ). Setting cache limit to 0 disables automatic cache size limiting.

Note that the cleanup might not be done immediately, so the cache might temporarily (for a few seconds) grow bigger than the limit.

setRemoveEntryStrategy	(	self,
		KPixmapCache.RemoveStrategy	strategy
	)

Sets the removeEntryStrategy used when removing entries.

setTimestamp	(	self,
		long	time
	)

Sets the timestamp of app-specific cache. It's saved in the cache file and can later be retrieved using timestamp() method. By default the timestamp is set to the cache creation time.

setUseQPixmapCache	(	self,
		bool	use
	)

Sets whether QPixmapCache (memory caching) should be used in addition to disk cache. QPixmapCache is used by default.

setValid	(	self,
		bool	valid
	)

Can be used by subclasses to indicate that cache needs some additional initing before it can be used.

int size ( self )

Returns:: approximate size of the cache, in kilobytes.

long timestamp ( self )

Returns:: timestamp of the cache, set using the setTimestamp method. It can be used by the application to check whether app-specific cache has outdated.

bool useQPixmapCache ( self )

Whether QPixmapCache should be used to cache pixmaps in memory in addition to caching them on the disk.

bool writeCustomData	(	self,
		QDataStream	stream
	)

Can be used by subclasses to load custom data from the stream.

writeCustomIndexHeader	(	self,
		QDataStream	stream
	)

Can be used by subclasses to load custom data from cache's header.

Enumeration Documentation

RemoveStrategy

Describes which entries will be removed first during cache cleanup.

RemoveOldest oldest entries are removed first.

RemoveSeldomUsed least used entries are removed first.

RemoveLeastRecentlyUsed least recently used entries are removed first.

Enumerator:

RemoveOldest
RemoveSeldomUsed
RemoveLeastRecentlyUsed

KPixmapCache Class Reference

Detailed Description

Enumerations

Methods

Static Methods

Method Documentation

Enumeration Documentation

Modules