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1 | /******************************************************************************* |
2 | * Copyright (c) 2014 Ericsson | |
3 | * | |
4 | * All rights reserved. This program and the accompanying materials are | |
5 | * made available under the terms of the Eclipse Public License v1.0 which | |
6 | * accompanies this distribution, and is available at | |
7 | * http://www.eclipse.org/legal/epl-v10.html | |
8 | * | |
9 | * Contributors: | |
10 | * Alexandre Montplaisir - Initial API and implementation | |
11 | *******************************************************************************/ | |
12 | ||
13 | package org.eclipse.linuxtools.tmf.ui; | |
14 | ||
15 | import java.util.Collection; | |
16 | import java.util.HashMap; | |
17 | import java.util.Map; | |
18 | import java.util.Timer; | |
19 | import java.util.TimerTask; | |
20 | ||
21 | import org.eclipse.linuxtools.tmf.core.component.ITmfComponent; | |
22 | import org.eclipse.swt.widgets.Display; | |
23 | ||
24 | import com.google.common.collect.ImmutableList; | |
25 | ||
26 | /** | |
27 | * This handler offers "coalescing" of UI updates. | |
28 | * | |
29 | * When displaying live experiments containing a high number of traces, every | |
30 | * trace will want to regularly update views with their new available data. This | |
31 | * can cause a high number of threads calling {@link Display#asyncExec} | |
32 | * repeatedly, which can really impede UI responsiveness. | |
33 | * <p> | |
34 | * Instead of calling {@link Display#asyncExec} directly, threads that want to | |
35 | * queue updates to the UI can instead call | |
36 | * {@link TmfUiRefreshHandler#queueUpdate}. This will schedule a UI update, | |
37 | * which will happen after *at least* {@link #UPDATE_PERIOD} milliseconds. | |
38 | * <ul><li> | |
39 | * During that time, new requests received from the same component will replace | |
40 | * the previous one (as we assume the latest UI update request is the most | |
41 | * up-to-date and interesting one). | |
42 | * </li><li> | |
43 | * Requests received from other components will be added to the queue (keeping | |
44 | * only the latest request from each component), and once the timeout expires, | |
45 | * they will all be sent to the UI thread via one single call to | |
46 | * {@link Display#syncExec}. | |
47 | * </li></ul> | |
48 | * | |
49 | * @author Alexandre Montplaisir | |
50 | * @since 3.1 | |
51 | */ | |
52 | public class TmfUiRefreshHandler { | |
53 | ||
54 | /** Throttle update requests to this amount of ms */ | |
55 | public static final long UPDATE_PERIOD = 1000; | |
56 | ||
57 | /** Singleton instance */ | |
58 | private static TmfUiRefreshHandler fInstance = null; | |
59 | ||
60 | private final Map<ITmfComponent, Runnable> fUpdates = new HashMap<>(); | |
61 | private final Timer fTimer; | |
62 | private TimerTask fCurrentTask; | |
63 | ||
64 | ||
65 | /** | |
66 | * Internal constructor | |
67 | */ | |
68 | private TmfUiRefreshHandler() { | |
69 | fTimer = new Timer(); | |
70 | fCurrentTask = null; | |
71 | } | |
72 | ||
73 | /** | |
74 | * Get the handler's instance | |
75 | * | |
76 | * @return The singleton instance | |
77 | */ | |
78 | public static synchronized TmfUiRefreshHandler getInstance() { | |
79 | if (fInstance == null) { | |
80 | fInstance = new TmfUiRefreshHandler(); | |
81 | } | |
82 | return fInstance; | |
83 | } | |
84 | ||
85 | /** | |
86 | * Cancel all current requests and dispose the handler. | |
87 | */ | |
88 | public synchronized void dispose() { | |
89 | fCurrentTask = null; | |
90 | fTimer.cancel(); | |
91 | fTimer.purge(); | |
92 | } | |
93 | ||
94 | /** | |
95 | * Queue a UI update. Threads that want to benefit from "UI coalescing" | |
96 | * should send their {@link Runnable} to this method, instead of | |
97 | * {@link Display#asyncExec(Runnable)}. | |
98 | * | |
99 | * @param source | |
100 | * The component sending the request. Typically callers should | |
101 | * use "this". Only the latest request per component is actually | |
102 | * sent. | |
103 | * @param task | |
104 | * The {@link Runnable} to execute in the UI thread. | |
105 | */ | |
106 | public synchronized void queueUpdate(ITmfComponent source, Runnable task) { | |
107 | fUpdates.put(source, task); | |
108 | if (fCurrentTask == null) { | |
109 | fCurrentTask = new RunAllUpdates(); | |
110 | fTimer.schedule(fCurrentTask, UPDATE_PERIOD); | |
111 | } | |
112 | } | |
113 | ||
114 | /** | |
115 | * Task to empty the current map of updates, and send them to the UI thread. | |
116 | */ | |
117 | private class RunAllUpdates extends TimerTask { | |
118 | @Override | |
119 | public void run() { | |
120 | /* Extract the currently-queued tasks in a local variable */ | |
121 | final Collection<Runnable> updates; | |
122 | synchronized (TmfUiRefreshHandler.this) { | |
123 | updates = ImmutableList.copyOf(fUpdates.values()); | |
124 | fUpdates.clear(); | |
125 | } | |
126 | /* | |
127 | * Release the lock on "this" before we wait on the UI thread below. | |
128 | * This is to prevent deadlocks in case components send their | |
129 | * "queueUpdate()" via the UI thread. | |
130 | */ | |
131 | Display.getDefault().syncExec(new Runnable() { | |
132 | @Override | |
133 | public void run() { | |
134 | for (Runnable update : updates) { | |
135 | update.run(); | |
136 | } | |
137 | } | |
138 | }); | |
139 | ||
140 | synchronized (TmfUiRefreshHandler.this) { | |
141 | if (fUpdates.isEmpty()) { | |
142 | /* | |
143 | * No updates were queued in the meantime, put fCurrentTask | |
144 | * back to null so that a new task can be scheduled. | |
145 | */ | |
146 | fCurrentTask = null; | |
147 | } else { | |
148 | /* | |
149 | * Updates were queued during the syncExec, schedule a new | |
150 | * task to eventually run them. | |
151 | */ | |
152 | fCurrentTask = new RunAllUpdates(); | |
153 | fTimer.schedule(fCurrentTask, UPDATE_PERIOD); | |
154 | } | |
155 | } | |
156 | } | |
157 | } | |
158 | } |