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Add DebounceExecutor, update ZoneRenderer.java to use debounced repai…
…nt (RPTools#611) dispatcher.
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src/main/java/net/rptools/maptool/client/DebounceExecutor.java
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| /* | ||
| * This software Copyright by the RPTools.net development team, and | ||
| * licensed under the Affero GPL Version 3 or, at your option, any later | ||
| * version. | ||
| * | ||
| * MapTool Source 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. | ||
| * | ||
| * You should have received a copy of the GNU Affero General Public | ||
| * License * along with this source Code. If not, please visit | ||
| * <http://www.gnu.org/licenses/> and specifically the Affero license | ||
| * text at <http://www.gnu.org/licenses/agpl.html>. | ||
| */ | ||
| package net.rptools.maptool.client; | ||
|
|
||
| import java.util.Date; | ||
| import java.util.concurrent.Executors; | ||
| import java.util.concurrent.ScheduledExecutorService; | ||
| import java.util.concurrent.ScheduledFuture; | ||
| import java.util.concurrent.ThreadFactory; | ||
| import java.util.concurrent.TimeUnit; | ||
|
|
||
| /** | ||
| * Manages throttling rapid successive attempts to execute a task. | ||
| * | ||
| * @see <a href="https://stackoverflow.com/a/18758408">Cancelling method calls when the same method | ||
| * is called multiple time</a> | ||
| * @see <a href="https://github.com/ThomasGirard/JDebounce">JDebounce</a> | ||
| * @author Philip Nichols ([email protected]) | ||
| * @version 1.5.3 | ||
| * @since 2019-08-23 | ||
| */ | ||
| public class DebounceExecutor { | ||
|
|
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| /** | ||
| * Thread factory for creating named threads. Other than thread naming, this factory relies on | ||
| * defaultThreadFactory and should not add overhead. | ||
| */ | ||
| private static final ThreadFactory threadFactory = | ||
| (new com.google.common.util.concurrent.ThreadFactoryBuilder()) | ||
| .setNameFormat("debounce-executor-%d") | ||
| .build(); | ||
|
|
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| /** The time, in milliseconds, during which to throttle subsequent requests to run the task. */ | ||
| private final long delay; | ||
|
|
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| /** | ||
| * A {@link ScheduledExecutorService} that will be used to run the debounced task when the delay | ||
| * elapses. | ||
| */ | ||
| private final ScheduledExecutorService executor = | ||
| Executors.newSingleThreadScheduledExecutor(threadFactory); | ||
|
|
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| /** A {@link ScheduledFuture} that represents the debounced task. */ | ||
| private ScheduledFuture<?> future; | ||
|
|
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| /** | ||
| * The synchronization lock used during the critical section for determining how to dispose of any | ||
| * single request. | ||
| */ | ||
| private final Object syncLock = new Object(); | ||
|
|
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| /** A {@link Runnable} representing the task to be managed. */ | ||
| private final Runnable task; | ||
|
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| /** | ||
| * A {@link long} indicating the time, in milliseconds, when the task last entered a pending | ||
| * state. | ||
| */ | ||
| private long taskPendingSince = -1; | ||
|
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| /** A reference to the logging service. */ | ||
| // private static final Logger log = LogManager.getLogger(DebounceExecutor.class); | ||
|
|
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| /** | ||
| * Initializes a new instance of the {@link DebounceExecutor} class. | ||
| * | ||
| * <p>Note that this class swallows later attempted invocations of its managed task. This makes it | ||
| * appropriate for repaint()-like tasks, where even an early-scheduled task will be working with | ||
| * the current backbuffer once it finally executes. <i>It is not appropriate for tasks whose | ||
| * correct execution relies on swallowing early invocations and running the last-posted one.</i> | ||
| * | ||
| * @param delay The time, in milliseconds, during which the DebounceExecutor will wait before | ||
| * executing the <i>task</i> and throttle subsequent requests. | ||
| * @param task The task to be executed after the <i>delay</i> elapses. | ||
| */ | ||
| public DebounceExecutor(long delay, Runnable task) { | ||
| this.delay = delay; | ||
| this.task = task; | ||
| } | ||
|
|
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| /** Dispatches a task to be executed by this {@link DebounceExecutor} instance. */ | ||
| public void dispatch() { | ||
| if (this.task == null) { | ||
| // log.info("Exited debouncer because of a null task."); | ||
| return; | ||
| } | ||
| if (this.delay < 1) { | ||
| this.task.run(); | ||
| return; | ||
| } | ||
| synchronized (syncLock) { | ||
| long now = (new Date()).getTime(); | ||
| if (this.taskPendingSince == -1 || now - this.taskPendingSince >= this.delay) { | ||
| this.taskPendingSince = now; | ||
| this.future = this.executor.schedule(this.task, this.delay, TimeUnit.MILLISECONDS); | ||
| } /* else { | ||
| log.info( | ||
| String.format( | ||
| "Task execution was debounced. (now: %d; taskPendingSince: %d; delay: %d; now - taskPendingSince: %d)", | ||
| now, this.taskPendingSince, this.delay, now - this.taskPendingSince)); | ||
| } */ | ||
| } | ||
| } | ||
| } |
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