OpenShot Library | libopenshot-audio 0.2.0
juce_AsyncUpdater.h
1
2/** @weakgroup juce_events-broadcasters
3 * @{
4 */
5/*
6 ==============================================================================
7
8 This file is part of the JUCE library.
9 Copyright (c) 2017 - ROLI Ltd.
10
11 JUCE is an open source library subject to commercial or open-source
12 licensing.
13
14 The code included in this file is provided under the terms of the ISC license
15 http://www.isc.org/downloads/software-support-policy/isc-license. Permission
16 To use, copy, modify, and/or distribute this software for any purpose with or
17 without fee is hereby granted provided that the above copyright notice and
18 this permission notice appear in all copies.
19
20 JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
21 EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
22 DISCLAIMED.
23
24 ==============================================================================
25*/
26
27namespace juce
28{
29
30//==============================================================================
31/**
32 Has a callback method that is triggered asynchronously.
33
34 This object allows an asynchronous callback function to be triggered, for
35 tasks such as coalescing multiple updates into a single callback later on.
36
37 Basically, one or more calls to the triggerAsyncUpdate() will result in the
38 message thread calling handleAsyncUpdate() as soon as it can.
39
40 @tags{Events}
41*/
43{
44public:
45 //==============================================================================
46 /** Creates an AsyncUpdater object. */
48
49 /** Destructor.
50 If there are any pending callbacks when the object is deleted, these are lost.
51 */
52 virtual ~AsyncUpdater();
53
54 //==============================================================================
55 /** Causes the callback to be triggered at a later time.
56
57 This method returns immediately, after which a callback to the
58 handleAsyncUpdate() method will be made by the message thread as
59 soon as possible.
60
61 If an update callback is already pending but hasn't happened yet, calling
62 this method will have no effect.
63
64 It's thread-safe to call this method from any thread, BUT beware of calling
65 it from a real-time (e.g. audio) thread, because it involves posting a message
66 to the system queue, which means it may block (and in general will do on
67 most OSes).
68 */
69 void triggerAsyncUpdate();
70
71 /** This will stop any pending updates from happening.
72
73 If called after triggerAsyncUpdate() and before the handleAsyncUpdate()
74 callback happens, this will cancel the handleAsyncUpdate() callback.
75
76 Note that this method simply cancels the next callback - if a callback is already
77 in progress on a different thread, this won't block until the callback finishes, so
78 there's no guarantee that the callback isn't still running when the method returns.
79 */
80 void cancelPendingUpdate() noexcept;
81
82 /** If an update has been triggered and is pending, this will invoke it
83 synchronously.
84
85 Use this as a kind of "flush" operation - if an update is pending, the
86 handleAsyncUpdate() method will be called immediately; if no update is
87 pending, then nothing will be done.
88
89 Because this may invoke the callback, this method must only be called on
90 the main event thread.
91 */
92 void handleUpdateNowIfNeeded();
93
94 /** Returns true if there's an update callback in the pipeline. */
95 bool isUpdatePending() const noexcept;
96
97 //==============================================================================
98 /** Called back to do whatever your class needs to do.
99
100 This method is called by the message thread at the next convenient time
101 after the triggerAsyncUpdate() method has been called.
102 */
103 virtual void handleAsyncUpdate() = 0;
104
105private:
106 //==============================================================================
110
111 JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AsyncUpdater)
112};
113
114} // namespace juce
115
116/** @}*/
Holds a resizable array of primitive or copy-by-value objects.
Definition juce_Array.h:60
Has a callback method that is triggered asynchronously.
virtual void handleAsyncUpdate()=0
Called back to do whatever your class needs to do.
A smart-pointer class which points to a reference-counted object.
#define JUCE_API
This macro is added to all JUCE public class declarations.