gecko/mobile/android/base/gfx/Layer.java

/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla Android code.
 *
 * The Initial Developer of the Original Code is Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2009-2010
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Patrick Walton <pcwalton@mozilla.com>
 *   Chris Lord <chrislord.net@gmail.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

package org.mozilla.gecko.gfx;

import android.graphics.Point;
import android.graphics.PointF;
import android.graphics.RectF;
import android.util.Log;
import java.util.concurrent.locks.ReentrantLock;
import javax.microedition.khronos.opengles.GL10;
import org.mozilla.gecko.FloatUtils;

public abstract class Layer {
    private final ReentrantLock mTransactionLock;
    private boolean mInTransaction;
    private Point mOrigin;
    private Point mNewOrigin;
    private float mResolution;
    private float mNewResolution;
    private LayerView mView;

    public Layer() {
        mTransactionLock = new ReentrantLock();
        mOrigin = new Point(0, 0);
        mResolution = 1.0f;
    }

    /**
     * Updates the layer. This returns false if there is still work to be done
     * after this update. If the layer is not already in a transaction, the
     * lock will be acquired and a transaction will automatically begin and
     * end around the update.
     */
    public final boolean update(GL10 gl, RenderContext context) {
        boolean startTransaction = true;
        if (mTransactionLock.isHeldByCurrentThread()) {
            startTransaction = false;
        }

        // If we're not already in a transaction and we can't acquire the lock,
        // bail out.
        if (startTransaction && !mTransactionLock.tryLock()) {
            return false;
        }

        mInTransaction = true;
        try {
            return performUpdates(gl, context);
        } finally {
            if (startTransaction) {
                mInTransaction = false;
                mTransactionLock.unlock();
            }
        }
    }

    /** Subclasses override this function to draw the layer. */
    public abstract void draw(RenderContext context);

    /** Subclasses override this function to provide access to the size of the layer. */
    public abstract IntSize getSize();

    /** Given the intrinsic size of the layer, returns the pixel boundaries of the layer rect. */
    protected RectF getBounds(RenderContext context, FloatSize size) {
        float scaleFactor = context.zoomFactor / mResolution;
        float x = mOrigin.x * scaleFactor, y = mOrigin.y * scaleFactor;
        float width = size.width * scaleFactor, height = size.height * scaleFactor;
        return new RectF(x, y, x + width, y + height);
    }

    /**
     * Call this before modifying the layer. Note that, for TileLayers, "modifying the layer"
     * includes altering the underlying CairoImage in any way. Thus you must call this function
     * before modifying the byte buffer associated with this layer.
     *
     * This function may block, so you should never call this on the main UI thread.
     */
    public void beginTransaction(LayerView aView) {
        if (mTransactionLock.isHeldByCurrentThread())
            throw new RuntimeException("Nested transactions are not supported");
        mTransactionLock.lock();
        mView = aView;
        mInTransaction = true;
    }

    public void beginTransaction() {
        beginTransaction(null);
    }

    /** Call this when you're done modifying the layer. */
    public void endTransaction() {
        if (!mInTransaction)
            throw new RuntimeException("endTransaction() called outside a transaction");
        mInTransaction = false;
        mTransactionLock.unlock();

        if (mView != null)
            mView.requestRender();
    }

    /** Returns true if the layer is currently in a transaction and false otherwise. */
    protected boolean inTransaction() {
        return mInTransaction;
    }

    /** Returns the current layer origin. */
    public Point getOrigin() {
        return mOrigin;
    }

    /** Sets the origin. Only valid inside a transaction. */
    public void setOrigin(Point newOrigin) {
        if (!mInTransaction)
            throw new RuntimeException("setOrigin() is only valid inside a transaction");
        mNewOrigin = newOrigin;
    }

    /** Returns the current layer's resolution. */
    public float getResolution() {
        return mResolution;
    }

    /**
     * Sets the layer resolution. This value is used to determine how many pixels per
     * device pixel this layer was rendered at. This will be reflected by scaling by
     * the reciprocal of the resolution in the layer's transform() function.
     * Only valid inside a transaction. */
    public void setResolution(float newResolution) {
        if (!mInTransaction)
            throw new RuntimeException("setResolution() is only valid inside a transaction");
        mNewResolution = newResolution;
    }

    /**
     * Subclasses may override this method to perform custom layer updates. This will be called
     * with the transaction lock held. Subclass implementations of this method must call the
     * superclass implementation. Returns false if there is still work to be done after this
     * update is complete.
     */
    protected boolean performUpdates(GL10 gl, RenderContext context) {
        if (mNewOrigin != null) {
            mOrigin = mNewOrigin;
            mNewOrigin = null;
        }
        if (mNewResolution != 0.0f) {
            mResolution = mNewResolution;
            mNewResolution = 0.0f;
        }

        return true;
    }

    public static class RenderContext {
        public final RectF viewport;
        public final FloatSize pageSize;
        public final float zoomFactor;

        public RenderContext(RectF aViewport, FloatSize aPageSize, float aZoomFactor) {
            viewport = aViewport;
            pageSize = aPageSize;
            zoomFactor = aZoomFactor;
        }

        public boolean fuzzyEquals(RenderContext other) {
            if (other == null) {
                return false;
            }
            return RectUtils.fuzzyEquals(viewport, other.viewport)
                && pageSize.fuzzyEquals(other.pageSize)
                && FloatUtils.fuzzyEquals(zoomFactor, other.zoomFactor);
        }
    }
}