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juce_AsyncUpdater.cpp
1/*
2 ==============================================================================
3
4 This file is part of the JUCE library.
5 Copyright (c) 2022 - Raw Material Software Limited
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 final : 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//==============================================================================
44 AsyncUpdater::AsyncUpdater()
45{
46 activeMessage = *new AsyncUpdaterMessage (*this);
47}
48
49 AsyncUpdater::~AsyncUpdater()
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())
56 || MessageManager::getInstanceWithoutCreating() == nullptr
57 || MessageManager::getInstanceWithoutCreating()->currentThreadHasLockedMessageManager());
58
59 activeMessage->shouldDeliver.set (0);
60}
61
62 void AsyncUpdater::triggerAsyncUpdate()
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
74 void AsyncUpdater::cancelPendingUpdate() noexcept
75{
76 activeMessage->shouldDeliver.set (0);
77}
78
79 void AsyncUpdater::handleUpdateNowIfNeeded()
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)
85 handleAsyncUpdate();
86}
87
88 bool AsyncUpdater::isUpdatePending() const noexcept
89{
90 return activeMessage->shouldDeliver.value != 0;
91}
92
93} // namespace juce
juce::AsyncUpdater::isUpdatePending
bool isUpdatePending() const noexcept
Definition juce_AsyncUpdater.cpp:88
juce::AsyncUpdater::handleUpdateNowIfNeeded
void handleUpdateNowIfNeeded()
Definition juce_AsyncUpdater.cpp:79
juce::AsyncUpdater::handleAsyncUpdate
virtual void handleAsyncUpdate()=0
juce::AsyncUpdater::~AsyncUpdater
virtual ~AsyncUpdater()
Definition juce_AsyncUpdater.cpp:49
juce::AsyncUpdater::triggerAsyncUpdate
void triggerAsyncUpdate()
Definition juce_AsyncUpdater.cpp:62
juce::AsyncUpdater::cancelPendingUpdate
void cancelPendingUpdate() noexcept
Definition juce_AsyncUpdater.cpp:74
juce::AsyncUpdater::AsyncUpdater
AsyncUpdater()
Definition juce_AsyncUpdater.cpp:44
juce::MessageManager::getInstanceWithoutCreating
static MessageManager * getInstanceWithoutCreating() noexcept
Definition juce_MessageManager.cpp:58
juce::Atomic::compareAndSetBool
bool compareAndSetBool(Type newValue, Type valueToCompare) noexcept
Definition juce_Atomic.h:96