diff options
Diffstat (limited to 'doc/src/qundo.qdoc')
| -rw-r--r-- | doc/src/qundo.qdoc | 113 |
1 files changed, 0 insertions, 113 deletions
diff --git a/doc/src/qundo.qdoc b/doc/src/qundo.qdoc deleted file mode 100644 index 9de2aa9..0000000 --- a/doc/src/qundo.qdoc +++ /dev/null @@ -1,113 +0,0 @@ -/**************************************************************************** -** -** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). -** Contact: Nokia Corporation (qt-info@nokia.com) -** -** This file is part of the documentation of the Qt Toolkit. -** -** $QT_BEGIN_LICENSE:LGPL$ -** No Commercial Usage -** This file contains pre-release code and may not be distributed. -** You may use this file in accordance with the terms and conditions -** contained in the either Technology Preview License Agreement or the -** Beta Release License Agreement. -** -** GNU Lesser General Public License Usage -** Alternatively, this file may be used under the terms of the GNU Lesser -** General Public License version 2.1 as published by the Free Software -** Foundation and appearing in the file LICENSE.LGPL included in the -** packaging of this file. Please review the following information to -** ensure the GNU Lesser General Public License version 2.1 requirements -** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. -** -** In addition, as a special exception, Nokia gives you certain -** additional rights. These rights are described in the Nokia Qt LGPL -** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this -** package. -** -** GNU General Public License Usage -** Alternatively, this file may be used under the terms of the GNU -** General Public License version 3.0 as published by the Free Software -** Foundation and appearing in the file LICENSE.GPL included in the -** packaging of this file. Please review the following information to -** ensure the GNU General Public License version 3.0 requirements will be -** met: http://www.gnu.org/copyleft/gpl.html. -** -** If you are unsure which license is appropriate for your use, please -** contact the sales department at http://qt.nokia.com/contact. -** $QT_END_LICENSE$ -** -****************************************************************************/ - -/*! -\page qundo.html -\title Overview of Qt's Undo Framework -\keyword Undo framework -\ingroup architecture - -\section1 Introduction - -Qt's Undo Framework is an implementation of the Command pattern, for -implementing undo/redo functionality in applications. - -The Command pattern is based on the idea that all editing in -an application is done by creating instances of command objects. -Command objects apply changes to the document and are stored -on a command stack. Furthermore, each command knows how to undo its -changes to bring the document back to its previous state. As long -as the application only uses command objects to change the state of -the document, it is possible to undo a sequence of commands by -traversing the stack downwards and calling undo -on each command in turn. It is also possible to redo a sequence of -commands by traversing the stack upwards and calling -redo on each command. - -\section1 Classes - -The framework consists of four classes: - -\list -\i \l QUndoCommand is the base class of all commands stored on an - undo stack. It can apply (redo) or undo a single change in the document. -\i \l QUndoStack is a list of QUndoCommand objects. It contains all the - commands executed on the document and can roll the document's state - backwards or forwards by undoing or redoing them. -\i \l QUndoGroup is a group of undo stacks. It is useful when an application - contains more than one undo stack, typically one for each opened - document. QUndoGroup provides a single pair of undo/redo slots for all - the stacks in the group. It forwards undo and redo requests to - the active stack, which is the stack associated with the document that - is currently being edited by the user. -\i \l QUndoView is a widget which shows the contents of an undo stack. Clicking - on a command in the view rolls the document's state backwards or - forwards to that command. -\endlist - -\section1 Concepts - -The following concepts are supported by the framework: - -\list -\i \bold{Clean state:} Used to signal when the document enters and leaves a - state that has been saved to disk. This is typically used to disable or - enable the save actions, and to update the document's title bar. -\i \bold{Command compression:} Used to compress sequences of commands into a - single command. - For example: In a text editor, the commands that insert individual - characters into the document can be compressed into a single command that - inserts whole sections of text. These bigger changes are more convenient - for the user to undo and redo. -\i \bold{Command macros:} A sequence of commands, all of which are undone or - redone in one step. - These simplify the task of writing an application, since a set of simpler - commands can be composed into more complex commands. For example, a command - that moves a set of selected objects in a document can be created by - combining a set of commands, each of which moves a single object. -\endlist - -QUndoStack provides convenient undo and redo QAction objects that -can be inserted into a menu or a toolbar. The text properties of these -actions always reflect what command will be undone or redone when -they are triggered. Similarly, QUndoGroup provides undo and redo actions -that always behave like the undo and redo actions of the active stack. -*/ |