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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 | |
aae89862 | 11 | * Patrick Tasse - Update queue handling |
9c91c317 AM |
12 | *******************************************************************************/ |
13 | ||
14 | package org.eclipse.linuxtools.tmf.ui; | |
15 | ||
aae89862 | 16 | import java.util.LinkedHashMap; |
9c91c317 | 17 | import java.util.Map; |
9c91c317 | 18 | |
9c91c317 AM |
19 | import org.eclipse.swt.widgets.Display; |
20 | ||
9c91c317 AM |
21 | /** |
22 | * This handler offers "coalescing" of UI updates. | |
23 | * | |
24 | * When displaying live experiments containing a high number of traces, every | |
25 | * trace will want to regularly update views with their new available data. This | |
26 | * can cause a high number of threads calling {@link Display#asyncExec} | |
27 | * repeatedly, which can really impede UI responsiveness. | |
28 | * <p> | |
29 | * Instead of calling {@link Display#asyncExec} directly, threads that want to | |
30 | * queue updates to the UI can instead call | |
aae89862 PT |
31 | * {@link TmfUiRefreshHandler#queueUpdate}. If the handler is not currently |
32 | * executing another update it will be scheduled immediately. Otherwise the | |
33 | * update will be queued. | |
34 | * <p> | |
35 | * The handler will only execute one update at a time. While it is busy, new | |
36 | * requests received from a source that is already in the queue will replace the | |
37 | * previous one (as we assume the latest UI update request is the most | |
38 | * up-to-date and interesting one), preserving the previous request order. New | |
39 | * requests received from other sources will be added to the end of the queue | |
40 | * (keeping only the latest request from each source). | |
41 | * <p> | |
42 | * Once the current update is completed, the oldest request in the queue will be | |
43 | * sent to the UI thread via one single call to {@link Display#syncExec}. | |
9c91c317 AM |
44 | * |
45 | * @author Alexandre Montplaisir | |
46 | * @since 3.1 | |
47 | */ | |
48 | public class TmfUiRefreshHandler { | |
49 | ||
9c91c317 AM |
50 | /** Singleton instance */ |
51 | private static TmfUiRefreshHandler fInstance = null; | |
52 | ||
aae89862 PT |
53 | private final Map<Object, Runnable> fUpdates = new LinkedHashMap<>(); |
54 | private Thread fCurrentTask; | |
9c91c317 AM |
55 | |
56 | ||
57 | /** | |
58 | * Internal constructor | |
59 | */ | |
60 | private TmfUiRefreshHandler() { | |
9c91c317 AM |
61 | fCurrentTask = null; |
62 | } | |
63 | ||
64 | /** | |
65 | * Get the handler's instance | |
66 | * | |
67 | * @return The singleton instance | |
68 | */ | |
69 | public static synchronized TmfUiRefreshHandler getInstance() { | |
70 | if (fInstance == null) { | |
71 | fInstance = new TmfUiRefreshHandler(); | |
72 | } | |
73 | return fInstance; | |
74 | } | |
75 | ||
76 | /** | |
77 | * Cancel all current requests and dispose the handler. | |
78 | */ | |
79 | public synchronized void dispose() { | |
aae89862 | 80 | fUpdates.clear(); |
9c91c317 | 81 | fCurrentTask = null; |
9c91c317 AM |
82 | } |
83 | ||
84 | /** | |
85 | * Queue a UI update. Threads that want to benefit from "UI coalescing" | |
86 | * should send their {@link Runnable} to this method, instead of | |
87 | * {@link Display#asyncExec(Runnable)}. | |
88 | * | |
89 | * @param source | |
aae89862 PT |
90 | * The source sending the request. Typically callers should use |
91 | * "this". When multiple requests are queued before being | |
92 | * executed, only the latest request per source is actually sent. | |
9c91c317 AM |
93 | * @param task |
94 | * The {@link Runnable} to execute in the UI thread. | |
95 | */ | |
aae89862 | 96 | public synchronized void queueUpdate(Object source, Runnable task) { |
9c91c317 AM |
97 | fUpdates.put(source, task); |
98 | if (fCurrentTask == null) { | |
99 | fCurrentTask = new RunAllUpdates(); | |
aae89862 | 100 | fCurrentTask.start(); |
9c91c317 AM |
101 | } |
102 | } | |
103 | ||
104 | /** | |
aae89862 | 105 | * Task to empty the update queue, and send each task to the UI thread. |
9c91c317 | 106 | */ |
aae89862 | 107 | private class RunAllUpdates extends Thread { |
9c91c317 AM |
108 | @Override |
109 | public void run() { | |
aae89862 PT |
110 | while (true) { |
111 | Runnable nextTask = null; | |
112 | synchronized (TmfUiRefreshHandler.this) { | |
113 | if (!fUpdates.isEmpty()) { | |
114 | Object firstKey = fUpdates.keySet().iterator().next(); | |
115 | nextTask = fUpdates.get(firstKey); | |
116 | fUpdates.remove(firstKey); | |
117 | } | |
118 | if (nextTask == null) { | |
119 | /* | |
120 | * No updates remaining in the queue, put fCurrentTask | |
121 | * back to null so that a new task can be scheduled. | |
122 | */ | |
123 | fCurrentTask = null; | |
124 | break; | |
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125 | } |
126 | } | |
aae89862 | 127 | Display.getDefault().syncExec(nextTask); |
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128 | } |
129 | } | |
130 | } | |
131 | } |