94 lines
3.1 KiB
C++
94 lines
3.1 KiB
C++
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/*
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==============================================================================
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This file is part of the JUCE library.
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Copyright (c) 2020 - Raw Material Software Limited
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JUCE is an open source library subject to commercial or open-source
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licensing.
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The code included in this file is provided under the terms of the ISC license
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http://www.isc.org/downloads/software-support-policy/isc-license. Permission
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To use, copy, modify, and/or distribute this software for any purpose with or
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without fee is hereby granted provided that the above copyright notice and
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this permission notice appear in all copies.
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JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
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EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
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DISCLAIMED.
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==============================================================================
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*/
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namespace juce
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{
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class AsyncUpdater::AsyncUpdaterMessage : public CallbackMessage
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{
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public:
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AsyncUpdaterMessage (AsyncUpdater& au) : owner (au) {}
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void messageCallback() override
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{
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if (shouldDeliver.compareAndSetBool (0, 1))
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owner.handleAsyncUpdate();
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}
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AsyncUpdater& owner;
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Atomic<int> shouldDeliver;
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JUCE_DECLARE_NON_COPYABLE (AsyncUpdaterMessage)
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};
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//==============================================================================
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AsyncUpdater::AsyncUpdater()
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{
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activeMessage = *new AsyncUpdaterMessage (*this);
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}
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AsyncUpdater::~AsyncUpdater()
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{
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// You're deleting this object with a background thread while there's an update
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// pending on the main event thread - that's pretty dodgy threading, as the callback could
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// happen after this destructor has finished. You should either use a MessageManagerLock while
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// deleting this object, or find some other way to avoid such a race condition.
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jassert ((! isUpdatePending())
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|| MessageManager::getInstanceWithoutCreating() == nullptr
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|| MessageManager::getInstanceWithoutCreating()->currentThreadHasLockedMessageManager());
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activeMessage->shouldDeliver.set (0);
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}
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void AsyncUpdater::triggerAsyncUpdate()
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{
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// If you're calling this before (or after) the MessageManager is
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// running, then you're not going to get any callbacks!
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JUCE_ASSERT_MESSAGE_MANAGER_EXISTS
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if (activeMessage->shouldDeliver.compareAndSetBool (1, 0))
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if (! activeMessage->post())
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cancelPendingUpdate(); // if the message queue fails, this avoids getting
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// trapped waiting for the message to arrive
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}
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void AsyncUpdater::cancelPendingUpdate() noexcept
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{
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activeMessage->shouldDeliver.set (0);
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}
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void AsyncUpdater::handleUpdateNowIfNeeded()
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{
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// This can only be called by the event thread.
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JUCE_ASSERT_MESSAGE_MANAGER_IS_LOCKED
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if (activeMessage->shouldDeliver.exchange (0) != 0)
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handleAsyncUpdate();
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}
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bool AsyncUpdater::isUpdatePending() const noexcept
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{
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return activeMessage->shouldDeliver.value != 0;
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}
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} // namespace juce
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