ice.storm
Class ImageCache

java.lang.Object
  ice.storm.ImageCache

All Implemented Interfaces:

ResourceOwner

public class ImageCache

extends Object

implements ResourceOwner

Object of this class represents an image cache. In many JVMs instances of Images are cached endlessly until somebody calls flush() on the images that have been cached.

The simplest solution in a browser is to store references to all the images on a page and after user leaves the page, call flush() on all those images. Unfortunately this eliminates image caching completely and may not be desirable when data is loaded over a slow link.

To solve the problem ImageCache class has been introduced. It gives the ability to configure or change image caching behaviour. ICE Browser performs all image loading and unloading using this ImageCache.getInstance().

By default the image cache contains reference counter per image. When the counter reaches zero (nobody has a reference to the image), a timeout is set. During the call to flushImages() the timeout values are checked for images that have reference counter equal zero. All such images are flushed. The timeout value can be set via setExpire() method and is by default 30 seconds.

This image caching mechanism could be extended by for example introducing an 'image collector' thread that would kick from time to time and flush unused images.

To disable the image caching, call setExpire(0); This will make sure that the images are freed as soon as possible after they are not in use any more.

Field Summary

protected HashArray	imageToEntry
protected int	timeout
protected HashArray	uriToEntry

Constructor Summary

protected

ImageCache(Session session)

Method Summary

void	checkForAnimatedImagesBug() Called from the ObjectPool whenever a new animated image is discovered (first time imageUpdate() is called with FRAMEBITS).
void	dispose() Deprecated. Use #disposeResource instead
void	disposeResources()
protected Image	factoryGetImage(URL url)
void	flushImages(boolean all) Flush images in the cache.
static ImageCache	get(Session session)
Toolkit	getAwtToolkit()
int	getExpire() Get timeout value
Image	getImage(String url) Get an image which is loaded from a given URI.
Image	getImage(URL u) Deprecated. Use getImage(String).
void	release(Image img) After the image is no longer needed, this method should be called notifying the image cache.
static ImageCache	set(Session session, ImageCache cache)
void	setExpire(int t) Set value of the timeout (in seconds) after which an unused image will be flushed.
void	setReload(boolean flag)
void	stopLoading(Image img) Call this method if you want to stop loading an image

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

uriToEntry

protected HashArray uriToEntry

imageToEntry

protected HashArray imageToEntry

timeout

protected int timeout

Constructor Detail

ImageCache

protected ImageCache(Session session)

Method Detail

get

public static ImageCache get(Session session)

set

public static ImageCache set(Session session,
                             ImageCache cache)

setReload

public void setReload(boolean flag)

getAwtToolkit

public Toolkit getAwtToolkit()

setExpire

public void setExpire(int t)

Set value of the timeout (in seconds) after which an unused image will be flushed.

getExpire

public int getExpire()

Get timeout value

dispose

public void dispose()

Deprecated. Use #disposeResource instead

disposeResources

public void disposeResources()

Specified by:

disposeResources in interface ResourceOwner

getImage

public Image getImage(URL u)

Deprecated. Use getImage(String).

getImage

public Image getImage(String url)

Get an image which is loaded from a given URI. Reference counter for the image is incremented.

stopLoading

public void stopLoading(Image img)

Call this method if you want to stop loading an image

release

public void release(Image img)

After the image is no longer needed, this method should be called notifying the image cache. The reference counter for this image is decrmented.

flushImages

public void flushImages(boolean all)

Flush images in the cache.

Parameters:

all - if false - only epxired unused images are flushed. If true - all the images in the cache are flushed.

checkForAnimatedImagesBug

public void checkForAnimatedImagesBug()

Called from the ObjectPool whenever a new animated image is discovered (first time imageUpdate() is called with FRAMEBITS).
Is responsible for detecting and trying to resolve the hang caused by the common bug in Sun-derived JVMs as described in http://developer.java.sun.com/developer/bugParade/bugs/4339995.html

factoryGetImage

protected Image factoryGetImage(URL url)