OpenShot Audio Library | OpenShotAudio  0.3.0
juce_AsyncUpdater.cpp
1 /*
2  ==============================================================================
3 
4  This file is part of the JUCE library.
5  Copyright (c) 2017 - ROLI Ltd.
6 
7  JUCE is an open source library subject to commercial or open-source
8  licensing.
9 
10  The code included in this file is provided under the terms of the ISC license
11  http://www.isc.org/downloads/software-support-policy/isc-license. Permission
12  To use, copy, modify, and/or distribute this software for any purpose with or
13  without fee is hereby granted provided that the above copyright notice and
14  this permission notice appear in all copies.
15 
16  JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
17  EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
18  DISCLAIMED.
19 
20  ==============================================================================
21 */
22 
23 namespace juce
24 {
25 
26 class AsyncUpdater::AsyncUpdaterMessage : public CallbackMessage
27 {
28 public:
29  AsyncUpdaterMessage (AsyncUpdater& au) : owner (au) {}
30 
31  void messageCallback() override
32  {
33  if (shouldDeliver.compareAndSetBool (0, 1))
34  owner.handleAsyncUpdate();
35  }
36 
37  AsyncUpdater& owner;
38  Atomic<int> shouldDeliver;
39 
40  JUCE_DECLARE_NON_COPYABLE (AsyncUpdaterMessage)
41 };
42 
43 //==============================================================================
45 {
46  activeMessage = *new AsyncUpdaterMessage (*this);
47 }
48 
50 {
51  // You're deleting this object with a background thread while there's an update
52  // pending on the main event thread - that's pretty dodgy threading, as the callback could
53  // happen after this destructor has finished. You should either use a MessageManagerLock while
54  // deleting this object, or find some other way to avoid such a race condition.
55  jassert ((! isUpdatePending())
57  || MessageManager::getInstanceWithoutCreating()->currentThreadHasLockedMessageManager());
58 
59  activeMessage->shouldDeliver.set (0);
60 }
61 
63 {
64  // If you're calling this before (or after) the MessageManager is
65  // running, then you're not going to get any callbacks!
66  JUCE_ASSERT_MESSAGE_MANAGER_EXISTS
67 
68  if (activeMessage->shouldDeliver.compareAndSetBool (1, 0))
69  if (! activeMessage->post())
70  cancelPendingUpdate(); // if the message queue fails, this avoids getting
71  // trapped waiting for the message to arrive
72 }
73 
75 {
76  activeMessage->shouldDeliver.set (0);
77 }
78 
80 {
81  // This can only be called by the event thread.
82  JUCE_ASSERT_MESSAGE_MANAGER_IS_LOCKED
83 
84  if (activeMessage->shouldDeliver.exchange (0) != 0)
86 }
87 
88 bool AsyncUpdater::isUpdatePending() const noexcept
89 {
90  return activeMessage->shouldDeliver.value != 0;
91 }
92 
93 } // namespace juce
bool isUpdatePending() const noexcept
void cancelPendingUpdate() noexcept
virtual void handleAsyncUpdate()=0
static MessageManager * getInstanceWithoutCreating() noexcept