com.openhtmltopdf.outputdevice.helper

Class FontCache

java.lang.Object

com.openhtmltopdf.outputdevice.helper.FontCache

public class FontCache
extends Object

A process wide cache of AWT fonts.

Every call to Font.createFont(int, InputStream) and its siblings registers a font with the JDK font manager that is never released again, see JDK-8239833. Creating the same font over and over - which is what happens when documents using @font-face rules or useFont are rendered repeatedly - therefore leaks memory (and temporary files) until the JVM exits. Caching the created fonts avoids that.

The cache is shared by all renderers and documents. Unlike for example PDFBox fonts, AWT fonts are immutable and safe to use from more than one document.

Method Summary

Modifier and Type	Method and Description
static String	contentCacheKey(byte[] content) A cache key derived from the content itself, for fonts that are only available as bytes and therefore have no stable name to be keyed on.
static Font	get(FSSupplier<Font> fontSupplier) Like get(String, long, FSSupplier) with the key and last modified stamp taken from the supplier itself.
static Font	get(String cacheKey, long lastModified, FSSupplier<Font> fontSupplier) Returns the cached font for the given key, creating it with the supplier if it is not cached yet or if the resource it was created from changed.
static Font	getTrueTypeFont(byte[] fontBytes) Returns the true type font in the given bytes, keyed on a hash of the bytes themselves as there is no name to key them on.
static Font	getTrueTypeFont(File fontFile) Returns the true type font in the given file, keyed on its path and reloaded when the file changes.
static Font	getTrueTypeFont(FSSupplier<InputStream> streamSupplier) Returns the true type font supplied by the given supplier, keyed on FSSupplier.cacheKey().
static Font	getTrueTypeFont(String cacheKey, long lastModified, FSSupplier<InputStream> streamSupplier) Like getTrueTypeFont(FSSupplier) but with an explicit key, so that callers can opt out of caching by passing null.
static void	invalidateAll() Removes every font from the cache, for example because font resources changed in a way this cache can not see, such as a web font served under an unchanged URL.

Methods inherited from class java.lang.Object

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

Method Detail

get

public static Font get(String cacheKey,
                       long lastModified,
                       FSSupplier<Font> fontSupplier)

Returns the cached font for the given key, creating it with the supplier if it is not cached yet or if the resource it was created from changed.

Parameters:

cacheKey - identifies the font resource, or null if the caller can not identify it, in which case the font is created without being cached.

lastModified - a value that changes whenever the font resource changes, or FSSupplier.UNKNOWN_LAST_MODIFIED if that can not be determined, in which case the font is cached until invalidateAll() is called.

Returns:

the font, or null if the supplier could not supply one.

get

public static Font get(FSSupplier<Font> fontSupplier)

Like get(String, long, FSSupplier) with the key and last modified stamp taken from the supplier itself.

getTrueTypeFont

public static Font getTrueTypeFont(File fontFile)
                            throws IOException,
                                   FontFormatException

Returns the true type font in the given file, keyed on its path and reloaded when the file changes. Does not handle true type collections.

Throws:

IOException

FontFormatException

getTrueTypeFont

public static Font getTrueTypeFont(byte[] fontBytes)
                            throws IOException,
                                   FontFormatException

Returns the true type font in the given bytes, keyed on a hash of the bytes themselves as there is no name to key them on.

Throws:

IOException

FontFormatException

getTrueTypeFont

public static Font getTrueTypeFont(FSSupplier<InputStream> streamSupplier)
                            throws IOException,
                                   FontFormatException

Returns the true type font supplied by the given supplier, keyed on FSSupplier.cacheKey().

Throws:

IOException

FontFormatException

getTrueTypeFont

public static Font getTrueTypeFont(String cacheKey,
                                   long lastModified,
                                   FSSupplier<InputStream> streamSupplier)
                            throws IOException,
                                   FontFormatException

Like getTrueTypeFont(FSSupplier) but with an explicit key, so that callers can opt out of caching by passing null.

Returns:

the font, or null if the supplier did not supply a stream.

Throws:

IOException

FontFormatException

contentCacheKey

public static String contentCacheKey(byte[] content)

A cache key derived from the content itself, for fonts that are only available as bytes and therefore have no stable name to be keyed on.

invalidateAll

public static void invalidateAll()

Removes every font from the cache, for example because font resources changed in a way this cache can not see, such as a web font served under an unchanged URL.

Note that fonts already handed to the JDK font manager can not be released, so recreating the same fonts after clearing the cache will increase memory usage.