/*
* Copyright (c) 2005, 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
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*/
package sun.java2d.pipe;
import java.util.HashSet;
import java.util.Set;
import sun.awt.SunToolkit;
/**
* The RenderQueue class encapsulates a RenderBuffer on which rendering
* operations are enqueued. Note that the RenderQueue lock must be acquired
* before performing any operations on the queue (e.g. enqueuing an operation
* or flushing the queue). A sample usage scenario follows:
*
* public void drawSomething(...) {
* rq.lock();
* try {
* ctx.validate(...);
* rq.ensureCapacity(4);
* rq.getBuffer().putInt(DRAW_SOMETHING);
* ...
* } finally {
* rq.unlock();
* }
* }
*
* If you are enqueuing an operation that involves 8-byte parameters (i.e.
* long or double values), it is imperative that you ensure proper
* alignment of the underlying RenderBuffer. This can be accomplished
* simply by providing an offset to the first 8-byte parameter in your
* operation to the ensureCapacityAndAlignment() method. For example:
*
* public void drawStuff(...) {
* rq.lock();
* try {
* RenderBuffer buf = rq.getBuffer();
* ctx.validate(...);
* // 28 total bytes in the operation, 12 bytes to the first long
* rq.ensureCapacityAndAlignment(28, 12);
* buf.putInt(DRAW_STUFF);
* buf.putInt(x).putInt(y);
* buf.putLong(addr1);
* buf.putLong(addr2);
* } finally {
* rq.unlock();
* }
* }
*/
public abstract class RenderQueue {
/** The size of the underlying buffer, in bytes. */
private static final int BUFFER_SIZE = 32000;
/** The underlying buffer for this queue. */
protected RenderBuffer buf;
/**
* A Set containing hard references to Objects that must stay alive until
* the queue has been completely flushed.
*/
protected Set refSet;
protected RenderQueue() {
refSet = new HashSet();
buf = RenderBuffer.allocate(BUFFER_SIZE);
}
/**
* Locks the queue for read/write access.
*/
public final void lock() {
/*
* Implementation note: In theory we should have two separate locks:
* one lock to synchronize access to the RenderQueue, and then a
* separate lock (the AWT lock) that only needs to be acquired when
* we are about to flush the queue (using native windowing system
* operations). In practice it has been difficult to enforce the
* correct lock ordering; sometimes AWT will have already acquired
* the AWT lock before grabbing the RQ lock (see 6253009), while the
* expected order should be RQ lock and then AWT lock. Due to this
* issue, using two separate locks is prone to deadlocks. Therefore,
* to solve this issue we have decided to eliminate the separate RQ
* lock and instead just acquire the AWT lock here. (Someday it might
* be nice to go back to the old two-lock system, but that would
* require potentially risky changes to AWT to ensure that it never
* acquires the AWT lock before calling into 2D code that wants to
* acquire the RQ lock.)
*/
SunToolkit.awtLock();
}
/**
* Attempts to lock the queue. If successful, this method returns true,
* indicating that the caller is responsible for calling
* <code>unlock</code>; otherwise this method returns false.
*/
public final boolean tryLock() {
return SunToolkit.awtTryLock();
}
/**
* Unlocks the queue.
*/
public final void unlock() {
SunToolkit.awtUnlock();
}
/**
* Adds the given Object to the set of hard references, which will
* prevent that Object from being disposed until the queue has been
* flushed completely. This is useful in cases where some enqueued
* data could become invalid if the reference Object were garbage
* collected before the queue could be processed. (For example, keeping
* a hard reference to a FontStrike will prevent any enqueued glyph
* images associated with that strike from becoming invalid before the
* queue is flushed.) The reference set will be cleared immediately
* after the queue is flushed each time.
*/
public final void addReference(Object ref) {
refSet.add(ref);
}
/**
* Returns the encapsulated RenderBuffer object.
*/
public final RenderBuffer getBuffer() {
return buf;
}
/**
* Ensures that there will be enough room on the underlying buffer
* for the following operation. If the operation will not fit given
* the remaining space, the buffer will be flushed immediately, leaving
* an empty buffer for the impending operation.
*
* @param opsize size (in bytes) of the following operation
*/
public final void ensureCapacity(int opsize) {
if (buf.remaining() < opsize) {
flushNow();
}
}
/**
* Convenience method that is equivalent to calling ensureCapacity()
* followed by ensureAlignment(). The ensureCapacity() call allows for an
* extra 4 bytes of space in case the ensureAlignment() method needs to
* insert a NOOP token on the buffer.
*
* @param opsize size (in bytes) of the following operation
* @param first8ByteValueOffset offset (in bytes) from the current
* position to the first 8-byte value used in the following operation
*/
public final void ensureCapacityAndAlignment(int opsize,
int first8ByteValueOffset)
{
ensureCapacity(opsize + 4);
ensureAlignment(first8ByteValueOffset);
}
/**
* Inserts a 4-byte NOOP token when necessary to ensure that all 8-byte
* parameters for the following operation are added to the underlying
* buffer with an 8-byte memory alignment.
*
* @param first8ByteValueOffset offset (in bytes) from the current
* position to the first 8-byte value used in the following operation
*/
public final void ensureAlignment(int first8ByteValueOffset) {
int first8ByteValuePosition = buf.position() + first8ByteValueOffset;
if ((first8ByteValuePosition & 7) != 0) {
buf.putInt(BufferedOpCodes.NOOP);
}
}
/**
* Immediately processes each operation currently pending on the buffer.
* This method will block until the entire buffer has been flushed. The
* queue lock must be acquired before calling this method.
*/
public abstract void flushNow();
/**
* Immediately processes each operation currently pending on the buffer,
* and then invokes the provided task. This method will block until the
* entire buffer has been flushed and the provided task has been executed.
* The queue lock must be acquired before calling this method.
*/
public abstract void flushAndInvokeNow(Runnable task);
/**
* Updates the current position of the underlying buffer, and then
* flushes the queue immediately. This method is useful when native code
* has added data to the queue and needs to flush immediately.
*/
public void flushNow(int position) {
buf.position(position);
flushNow();
}
}