102 lines
3.5 KiB
C
102 lines
3.5 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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By using JUCE, you agree to the terms of both the JUCE 5 End-User License
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Agreement and JUCE 5 Privacy Policy (both updated and effective as of the
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27th April 2017).
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End User License Agreement: www.juce.com/juce-5-licence
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Privacy Policy: www.juce.com/juce-5-privacy-policy
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Or: You may also use this code under the terms of the GPL v3 (see
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www.gnu.org/licenses).
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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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Used by the UndoManager class to store an action which can be done
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and undone.
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@see UndoManager
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@tags{DataStructures}
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*/
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class JUCE_API UndoableAction
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{
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protected:
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/** Creates an action. */
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UndoableAction() noexcept {}
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public:
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/** Destructor. */
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virtual ~UndoableAction() {}
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//==============================================================================
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/** Overridden by a subclass to perform the action.
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This method is called by the UndoManager, and shouldn't be used directly by
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applications.
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Be careful not to make any calls in a perform() method that could call
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recursively back into the UndoManager::perform() method
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@returns true if the action could be performed.
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@see UndoManager::perform
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*/
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virtual bool perform() = 0;
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/** Overridden by a subclass to undo the action.
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This method is called by the UndoManager, and shouldn't be used directly by
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applications.
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Be careful not to make any calls in an undo() method that could call
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recursively back into the UndoManager::perform() method
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@returns true if the action could be undone without any errors.
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@see UndoManager::perform
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*/
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virtual bool undo() = 0;
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//==============================================================================
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/** Returns a value to indicate how much memory this object takes up.
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Because the UndoManager keeps a list of UndoableActions, this is used
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to work out how much space each one will take up, so that the UndoManager
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can work out how many to keep.
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The default value returned here is 10 - units are arbitrary and
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don't have to be accurate.
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@see UndoManager::getNumberOfUnitsTakenUpByStoredCommands,
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UndoManager::setMaxNumberOfStoredUnits
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*/
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virtual int getSizeInUnits() { return 10; }
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/** Allows multiple actions to be coalesced into a single action object, to reduce storage space.
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If possible, this method should create and return a single action that does the same job as
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this one followed by the supplied action.
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If it's not possible to merge the two actions, the method should return a nullptr.
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*/
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virtual UndoableAction* createCoalescedAction (UndoableAction* nextAction) { ignoreUnused (nextAction); return nullptr; }
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};
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} // namespace juce
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