KImageCache Class Reference

#include <kimagecache.h>

Inheritance diagram for KImageCache:

Public Member Functions
	KImageCache (const QString &cacheName, unsigned defaultCacheSize, unsigned expectedItemSize=0)
	~KImageCache ()
void	clear ()
bool	findImage (const QString &key, QImage *destination) const
bool	findPixmap (const QString &key, QPixmap *destination) const
bool	insertImage (const QString &key, const QImage &image)
bool	insertPixmap (const QString &key, const QPixmap &pixmap)
time_t	lastModifiedTime () const
int	pixmapCacheLimit () const
bool	pixmapCaching () const
void	setPixmapCacheLimit (int size)
void	setPixmapCaching (bool enable)
Public Member Functions inherited from KSharedDataCache
	KSharedDataCache (const QString &cacheName, unsigned defaultCacheSize, unsigned expectedItemSize=0)
	~KSharedDataCache ()
void	clear ()
bool	contains (const QString &key) const
EvictionPolicy	evictionPolicy () const
bool	find (const QString &key, QByteArray *destination) const
unsigned	freeSize () const
bool	insert (const QString &key, const QByteArray &data)
void	setEvictionPolicy (EvictionPolicy newPolicy)
void	setTimestamp (unsigned newTimestamp)
unsigned	timestamp () const
unsigned	totalSize () const

Additional Inherited Members
Public Types inherited from KSharedDataCache
enum	EvictionPolicy
Static Public Member Functions inherited from KSharedDataCache
static void	deleteCache (const QString &cacheName)

Detailed Description

A simple wrapping layer over KSharedDataCache to support caching images and pixmaps.

This class can be used to share images between different processes, which is useful when it is known that such images will be used across many processes, or when creating the image is expensive.

In addition, the class also supports caching QPixmaps in a single process using the setPixmapCaching() function.

Tips for use: If you already have QPixmaps that you intend to use, and you do not need access to the actual image data, then try to store and retrieve QPixmaps for use.

On the other hand, if you will need to store and retrieve actual image data (to modify the image after retrieval for instance) then you should use QImage to save the conversion cost from QPixmap to QImage.

KImageCache is a subclass of KSharedDataCache, so all of the methods that can be used with KSharedDataCache can be used with KImageCache, with the exception of KSharedDataCache::insert() and KSharedDataCache::find().

Author

Michael Pyne mpyne.nosp@m.@kde.nosp@m..org

Since

4.5

Definition at line 58 of file kimagecache.h.

Constructor & Destructor Documentation

KImageCache::KImageCache	(	const QString &	cacheName,
		unsigned	defaultCacheSize,
		unsigned	expectedItemSize = 0
	)

Constructs an image cache, named by cacheName, with a default size of defaultCacheSize.

Parameters

cacheName	Name of the cache to use.
defaultCacheSize	The default size, in bytes, of the cache. The actual on-disk size will be slightly larger. If the cache already exists, it will not be resized. If it is required to resize the cache then use the deleteCache() function to remove that cache first.
expectedItemSize	The expected general size of the items to be added to the image cache, in bytes. Use 0 if you just want a default item size.

Definition at line 82 of file kimagecache.cpp.

KImageCache::~KImageCache

(

)

Deconstructor.

Definition at line 92 of file kimagecache.cpp.

Member Function Documentation

void KImageCache::clear

(

)

Removes all entries from the cache.

In addition any cached pixmaps (as per setPixmapCaching()) are also removed.

Definition at line 164 of file kimagecache.cpp.

bool KImageCache::findImage	(	const QString &	key,
		QImage *	destination
	)		const

Copies the cached image identified by key to destination.

If no such image exists destination is unchanged.

Returns

true if the image identified by key existed, false otherwise.

Definition at line 122 of file kimagecache.cpp.

bool KImageCache::findPixmap	(	const QString &	key,
		QPixmap *	destination
	)		const

Copies the cached pixmap identified by key to destination.

If no such pixmap exists destination is unchanged.

Returns

true if the pixmap identified by key existed, false otherwise.

See also

setPixmapCaching()

Definition at line 136 of file kimagecache.cpp.

bool KImageCache::insertImage	(	const QString &	key,
		const QImage &	image
	)

Inserts the image into the shared cache, accessible with key.

This variant is preferred over insertPixmap() if your source data is already a QImage, if it is essential that the image be in shared memory (such as for SVG icons which have a high render time), or if it will need to be in QImage form after it is retrieved from the cache.

Parameters

key	Name to access image with.
image	The image to add to the shared cache.

Returns

true if the image was successfully cached, false otherwise.

Definition at line 97 of file kimagecache.cpp.

bool KImageCache::insertPixmap	(	const QString &	key,
		const QPixmap &	pixmap
	)

Inserts the pixmap given by pixmap to the cache, accessible with key.

The pixmap must be converted to a QImage in order to be stored into shared memory. In order to prevent unnecessary conversions from taking place pixmap will also be cached (but not in stored memory) and would be accessible using findPixmap() if pixmap caching is enabled.

Parameters

key	Name to access pixmap with.
pixmap	The pixmap to add to the cache.

Returns

true if the pixmap was successfully cached, false otherwise.

See also

setPixmapCaching()

Definition at line 111 of file kimagecache.cpp.

time_t KImageCache::lastModifiedTime

(

)

const

Returns

The time that an image or pixmap was last inserted into a cache.

Definition at line 170 of file kimagecache.cpp.

int KImageCache::pixmapCacheLimit

(

)

const

Returns

The highest memory size in bytes to be used by cached pixmaps.

Since

4.6

Definition at line 190 of file kimagecache.cpp.

bool KImageCache::pixmapCaching

(

)

const

Returns

if QPixmaps added with insertPixmap() will be stored in a local pixmap cache as well as the shared image cache. The default is to cache pixmaps locally.

Definition at line 175 of file kimagecache.cpp.

void KImageCache::setPixmapCacheLimit

(

int

size

)

Sets the highest memory size the pixmap cache should use.

Parameters

size	The size in bytes

Since

4.6

Definition at line 195 of file kimagecache.cpp.

void KImageCache::setPixmapCaching

(

bool

enable

)

Enables or disables local pixmap caching.

If it is anticipated that a pixmap will be frequently needed then this can actually save memory overall since the X server or graphics card will not have to store duplicate copies of the same image.

Parameters

enable

Enables pixmap caching if true, disables otherwise.

Definition at line 180 of file kimagecache.cpp.

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The documentation for this class was generated from the following files:

• kimagecache.h
• kimagecache.cpp