src/macosx/classes/sun/font/CStrikeDisposer.java

/*
 * Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.font;

import com.apple.concurrent.Dispatch;
import sun.lwawt.macosx.CThreading;

import java.util.concurrent.atomic.AtomicBoolean;

/*
 * This keeps track of data that needs to be cleaned up once a
 * strike is freed.
 * a) The native memory that is the glyph image cache.
 * b) removing the "desc" key from the strike's map.
 * This is safe to do because this disposer is invoked only when the
 * reference object has been cleared, which means the value indexed by
 * this key is just an empty reference object.
 * It is possible that a new FontStrike has been created that would
 * be referenced by the same (equals) key. If it is placed in the map
 * before this disposer is executed, then we do not want to remove that
 * object. We should only remove an object where the value is null.
 * So we first verify that the key still points to a cleared reference.
 * Updates to the map thus need to be synchronized.
 *
 * A WeakHashmap will automatically clean up, but we might maintain a
 * reference to the "desc" key in the FontStrike (value) which would
 * prevent the keys from being discarded. And since the strike is the only
 * place is likely we would maintain such a strong reference, then the map
 * entries would be removed much more promptly than we need.
 */
class CStrikeDisposer extends FontStrikeDisposer {

    long pNativeScalerContext;
    private final AtomicBoolean disposed = new AtomicBoolean(false);

    public CStrikeDisposer(Font2D font2D, FontStrikeDesc desc,
                               long pContext, int[] images)
    {
        super(font2D, desc, 0L, images);
        pNativeScalerContext = pContext;
    }

    public CStrikeDisposer(Font2D font2D, FontStrikeDesc desc,
                               long pContext, long[] images)
    {
        super(font2D, desc, 0L, images);
        pNativeScalerContext = pContext;
    }

    public CStrikeDisposer(Font2D font2D, FontStrikeDesc desc,
                               long pContext)
    {
        super(font2D, desc, 0L);
        pNativeScalerContext = pContext;
    }

    public CStrikeDisposer(Font2D font2D, FontStrikeDesc desc) {
        super(font2D, desc);
    }

    public synchronized void dispose() {
        final Runnable command = () -> {
            if (disposed.compareAndSet(false, true)) {
                if (pNativeScalerContext != 0L) {
                    freeNativeScalerContext(pNativeScalerContext);
                }
                super.dispose();
            }
        };
        // Move disposal code to AppKit thread in order to avoid the
        // following deadlock:
        // 1) CGLGraphicsConfig.getCGLConfigInfo (called from Java2D
        //    disposal thread) takes RenderQueue.lock
        // 2) CGLLayer.drawInCGLContext is invoked on AppKit thread and
        //    blocked on RenderQueue.lock
        // 1) invokes native block on AppKit and wait

        CThreading.executeOnAppKit(command);
    }

    private native void freeNativeScalerContext(long pContext);

    protected static native void removeGlyphInfoFromCache(long glyphInfo);
}