| 1 | /*
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| 2 | * Project: MoleCuilder
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| 3 | * Description: creates and alters molecular systems
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| 4 | * Copyright (C) 2010 University of Bonn. All rights reserved.
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| 5 | * Please see the LICENSE file or "Copyright notice" in builder.cpp for details.
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| 6 | */
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| 7 |
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| 8 | /**
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| 9 | * \file actions.dox
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| 10 | *
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| 11 | * Created on: Oct 28, 2011
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| 12 | * Author: heber
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| 13 | */
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| 14 |
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| 15 | /** \page actions Actions
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| 16 | *
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| 17 | * Actions are Command patterns (http://en.wikipedia.org/wiki/Command_pattern)
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| 18 | * to allow for undoing and redoing. Each specific Action derives from this
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| 19 | * class to implement a certain functionality. There is a lot of preprocessor
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| 20 | * magic implemented for making this as easy as possible. In effect you only
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| 21 | * have to create three files of which only one actually contains more than a
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| 22 | * few lines, namely the code of the Action itself.
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| 23 | *
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| 24 | * Each Action has thus three types of functionalty: do, undo, and redo.
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| 25 | *
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| 26 | * The ActionRegistry contains a prototype of each Action under its token
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| 27 | * such that an instance can be retrieved by knowing this token.
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| 28 | *
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| 29 | * Each Action obtains its parameter from a central ValueStorage such that
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| 30 | * they are independent of where the parameter originated from: a command line
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| 31 | * parameter, a value entered in a graphical dialog or given via the keyboard
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| 32 | * in a terminal. That's why each begins with a function call to
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| 33 | * getParametersfromValueStorage() to fill its internal Action::params
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| 34 | * structure.
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| 35 | *
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| 36 | * Also there is a regression test (\ref regression-test) for each Action to
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| 37 | * check that it always behaves the same no matter how much the code
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| 38 | * implementing actually has changed.
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| 39 | *
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| 40 | * \section actions-add To add a new action ...
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| 41 | *
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| 42 | * The following steps have to be done for adding a new action:
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| 43 | * -# Create three new files .cpp, .def, and .hpp
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| 44 | * -# Add the files to \b src/Actions/Makefile.am.
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| 45 | * -# Add the name of the Action to \b src/Actions/GlobalListOfActions.hpp
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| 46 | * such that the ActionRegistry knows about it and can instantiate a
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| 47 | * prototype.
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| 48 | *
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| 49 | * \section actions-undo-redo Undoing and Redoing actions ...
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| 50 | *
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| 51 | * The central points of Actions is that they can be undone and redone. This
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| 52 | * has to be implemented in two more functions beside the "do".
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| 53 | *
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| 54 | * Note that undoing means to get every back to its original state and by whatever
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| 55 | * means seem appropriate, e.g. just remvoing all inserted atoms.
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| 56 | * To make this more elaborate it is usually very useful to store extra information
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| 57 | * in the Action's state such that undo and redo can be accomplished more quickly.
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| 58 | * E.g. if your Action creates some new atoms, store their info as \ref AtomicInfo.
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| 59 | * Then, undo can simply delete the newly created atoms and redo can quickly re-
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| 60 | * create them in the state they have been before.
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| 61 | *
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| 62 | * Have a look at \ref UndoRedoHelpers.hpp for some helper functions on this.
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| 63 | *
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| 64 | *
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| 65 | * \date 2012-04-05
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| 66 | *
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| 67 | */
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