michael@0: /* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: package org.mozilla.gecko.gfx;
michael@0: 
michael@0: /**
michael@0:  * A class used to schedule a callback to occur when the next frame is drawn.
michael@0:  * Subclasses must redefine the internalRun method, not the run method.
michael@0:  */
michael@0: public abstract class RenderTask {
michael@0:     /**
michael@0:      * Whether to run the task after the render, or before.
michael@0:      */
michael@0:     public final boolean runAfter;
michael@0: 
michael@0:     /**
michael@0:      * Time when this task has first run, in ns. Useful for tasks which run for a specific duration.
michael@0:      */
michael@0:     private long mStartTime;
michael@0: 
michael@0:     /**
michael@0:      * Whether we should initialise mStartTime on the next frame run.
michael@0:      */
michael@0:     private boolean mResetStartTime = true;
michael@0: 
michael@0:     /**
michael@0:      * The callback to run on each frame. timeDelta is the time elapsed since
michael@0:      * the last call, in nanoseconds. Returns true if it should continue
michael@0:      * running, or false if it should be removed from the task queue. Returning
michael@0:      * true implicitly schedules a redraw.
michael@0:      *
michael@0:      * This method first initializes the start time if resetStartTime has been invoked,
michael@0:      * then calls internalRun.
michael@0:      *
michael@0:      * Note : subclasses should override internalRun.
michael@0:      *
michael@0:      * @param timeDelta the time between the beginning of last frame and the beginning of this frame, in ns.
michael@0:      * @param currentFrameStartTime the startTime of the current frame, in ns.
michael@0:      * @return true if animation should be run at the next frame, false otherwise
michael@0:      * @see RenderTask#internalRun(long, long)
michael@0:      */
michael@0:     public final boolean run(long timeDelta, long currentFrameStartTime) {
michael@0:         if (mResetStartTime) {
michael@0:             mStartTime = currentFrameStartTime;
michael@0:             mResetStartTime = false;
michael@0:         }
michael@0:         return internalRun(timeDelta, currentFrameStartTime);
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Abstract method to be overridden by subclasses.
michael@0:      * @param timeDelta the time between the beginning of last frame and the beginning of this frame, in ns
michael@0:      * @param currentFrameStartTime the startTime of the current frame, in ns.
michael@0:      * @return true if animation should be run at the next frame, false otherwise
michael@0:      */
michael@0:     protected abstract boolean internalRun(long timeDelta, long currentFrameStartTime);
michael@0: 
michael@0:     public RenderTask(boolean aRunAfter) {
michael@0:         runAfter = aRunAfter;
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Get the start time of this task.
michael@0:      * It is the start time of the first frame this task was run on.
michael@0:      * @return the start time in ns
michael@0:      */
michael@0:     public long getStartTime() {
michael@0:         return mStartTime;
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Schedule a reset of the recorded start time next time {@link RenderTask#run(long, long)} is run.
michael@0:      * @see RenderTask#getStartTime()
michael@0:      */
michael@0:     public void resetStartTime() {
michael@0:         mResetStartTime = true;
michael@0:     }
michael@0: }