111 lines
4.3 KiB
C
111 lines
4.3 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) 2017 - ROLI Ltd.
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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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//==============================================================================
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/**
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Has a callback method that is triggered asynchronously.
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This object allows an asynchronous callback function to be triggered, for
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tasks such as coalescing multiple updates into a single callback later on.
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Basically, one or more calls to the triggerAsyncUpdate() will result in the
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message thread calling handleAsyncUpdate() as soon as it can.
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@tags{Events}
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*/
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class JUCE_API AsyncUpdater
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{
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public:
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//==============================================================================
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/** Creates an AsyncUpdater object. */
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AsyncUpdater();
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/** Destructor.
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If there are any pending callbacks when the object is deleted, these are lost.
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*/
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virtual ~AsyncUpdater();
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//==============================================================================
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/** Causes the callback to be triggered at a later time.
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This method returns immediately, after which a callback to the
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handleAsyncUpdate() method will be made by the message thread as
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soon as possible.
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If an update callback is already pending but hasn't happened yet, calling
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this method will have no effect.
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It's thread-safe to call this method from any thread, BUT beware of calling
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it from a real-time (e.g. audio) thread, because it involves posting a message
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to the system queue, which means it may block (and in general will do on
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most OSes).
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*/
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void triggerAsyncUpdate();
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/** This will stop any pending updates from happening.
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If called after triggerAsyncUpdate() and before the handleAsyncUpdate()
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callback happens, this will cancel the handleAsyncUpdate() callback.
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Note that this method simply cancels the next callback - if a callback is already
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in progress on a different thread, this won't block until the callback finishes, so
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there's no guarantee that the callback isn't still running when the method returns.
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*/
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void cancelPendingUpdate() noexcept;
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/** If an update has been triggered and is pending, this will invoke it
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synchronously.
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Use this as a kind of "flush" operation - if an update is pending, the
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handleAsyncUpdate() method will be called immediately; if no update is
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pending, then nothing will be done.
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Because this may invoke the callback, this method must only be called on
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the main event thread.
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*/
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void handleUpdateNowIfNeeded();
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/** Returns true if there's an update callback in the pipeline. */
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bool isUpdatePending() const noexcept;
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//==============================================================================
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/** Called back to do whatever your class needs to do.
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This method is called by the message thread at the next convenient time
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after the triggerAsyncUpdate() method has been called.
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*/
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virtual void handleAsyncUpdate() = 0;
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private:
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//==============================================================================
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class AsyncUpdaterMessage;
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friend class ReferenceCountedObjectPtr<AsyncUpdaterMessage>;
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ReferenceCountedObjectPtr<AsyncUpdaterMessage> activeMessage;
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JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AsyncUpdater)
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};
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} // namespace juce
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