qundostack.cpp

奇趣公司比较新的qt/emd版本

/*!
    Returns true if there is a command available for undo; otherwise returns false.

    This function returns false if the stack is empty, or if the bottom command
    on the stack has already been undone.

    Synonymous with index() == 0.

    \sa index() canRedo()
*/

bool QUndoStack::canUndo() const
{
    Q_D(const QUndoStack);
    if (!d->macro_stack.isEmpty())
        return false;
    return d->index > 0;
}

/*!
    Returns true if there is a command available for redo; otherwise returns false.

    This function returns false if the stack is empty or if the top command
    on the stack has already been redone.

    Synonymous with index() == count().

    \sa index() canUndo()
*/

bool QUndoStack::canRedo() const
{
    Q_D(const QUndoStack);
    if (!d->macro_stack.isEmpty())
        return false;
    return d->index < d->command_list.size();
}

/*!
    Returns the text of the command which will be undone in the next call to undo().

    \sa QUndoCommand::text() redoText()
*/

QString QUndoStack::undoText() const
{
    Q_D(const QUndoStack);
    if (!d->macro_stack.isEmpty())
        return QString();
    if (d->index > 0)
        return d->command_list.at(d->index - 1)->text();
    return QString();
}

/*!
    Returns the text of the command which will be redone in the next call to redo().

    \sa QUndoCommand::text() undoText()
*/

QString QUndoStack::redoText() const
{
    Q_D(const QUndoStack);
    if (!d->macro_stack.isEmpty())
        return QString();
    if (d->index < d->command_list.size())
        return d->command_list.at(d->index)->text();
    return QString();
}

#ifndef QT_NO_ACTION

/*!
    Creates an undo QAction object with the given \a parent.

    Triggering this action will cause a call to undo(). The text of this action
    is the text of the command which will be undone in the next call to undo(),
    prefixed by the specified \a prefix. If there is no command available for undo,
    this action will be disabled.

    If \a prefix is empty, the default prefix "Undo" is used.

    \sa createRedoAction(), canUndo(), QUndoCommand::text()
*/

QAction *QUndoStack::createUndoAction(QObject *parent, const QString &prefix) const
{
    QString pref = prefix.isEmpty() ? tr("Undo") : prefix;
    QUndoAction *result = new QUndoAction(pref, parent);
    result->setEnabled(canUndo());
    result->setPrefixedText(undoText());
    connect(this, SIGNAL(canUndoChanged(bool)),
            result, SLOT(setEnabled(bool)));
    connect(this, SIGNAL(undoTextChanged(QString)),
            result, SLOT(setPrefixedText(QString)));
    connect(result, SIGNAL(triggered()), this, SLOT(undo()));
    return result;
}

/*!
    Creates an redo QAction object with the given \a parent.

    Triggering this action will cause a call to redo(). The text of this action
    is the text of the command which will be redone in the next call to redo(),
    prefixed by the specified \a prefix. If there is no command available for redo,
    this action will be disabled.

    If \a prefix is empty, the default prefix "Redo" is used.

    \sa createUndoAction(), canRedo(), QUndoCommand::text()
*/

QAction *QUndoStack::createRedoAction(QObject *parent, const QString &prefix) const
{
    QString pref = prefix.isEmpty() ? tr("Redo") : prefix;
    QUndoAction *result = new QUndoAction(pref, parent);
    result->setEnabled(canRedo());
    result->setPrefixedText(redoText());
    connect(this, SIGNAL(canRedoChanged(bool)),
            result, SLOT(setEnabled(bool)));
    connect(this, SIGNAL(redoTextChanged(QString)),
            result, SLOT(setPrefixedText(QString)));
    connect(result, SIGNAL(triggered()), this, SLOT(redo()));
    return result;
}

#endif // QT_NO_ACTION

/*!
    Begins composition of a macro command with the given \a text description.

    An empty command described by the specified \a text is pushed on the stack.
    Any subsequent commands pushed on the stack will be appended to the empty
    command's children until endMacro() is called.

    Calls to beginMacro() and endMacro() may be nested, but every call to
    beginMacro() must have a matching call to endMacro().

    While a macro is composed, the stack is disabled. This means that:
    \list
    \i indexChanged() and cleanChanged() are not emitted,
    \i canUndo() and canRedo() return false,
    \i calling undo() or redo() has no effect,
    \i the undo/redo actions are disabled.
    \endlist

    The stack becomes enabled and appropriate signals are emitted when endMacro()
    is called for the outermost macro.

    \code
    stack.beginMacro("insert red text");
    stack.push(new InsertText(document, idx, text));
    stack.push(new SetColor(document, idx, text.length(), Qt::red));
    stack.endMacro(); // indexChanged() is emitted
    \endcode

    This code is equivalent to:

    \code
    QUndoCommand *insertRed = new QUndoCommand(); // an empty command
    insertRed->setText("insert red text");

    new InsertText(document, idx, text, insertRed); // becomes child of insertRed
    new SetColor(document, idx, text.length(), Qt::red, insertRed);

    stack.push(insertRed);
    \endcode

    \sa endMacro()
*/

void QUndoStack::beginMacro(const QString &text)
{
    Q_D(QUndoStack);
    QUndoCommand *cmd = new QUndoCommand();
    cmd->setText(text);

    if (d->macro_stack.isEmpty()) {
        while (d->index < d->command_list.size())
            delete d->command_list.takeLast();
        if (d->clean_index > d->index)
            d->clean_index = -1; // we've deleted the clean state
        d->command_list.append(cmd);
    } else {
        d->macro_stack.last()->d->child_list.append(cmd);
    }
    d->macro_stack.append(cmd);

    if (d->macro_stack.count() == 1) {
        emit canUndoChanged(false);
        emit undoTextChanged(QString());
        emit canRedoChanged(false);
        emit redoTextChanged(QString());
    }
}

/*!
    Ends composition of a macro command.

    If this is the outermost macro in a set nested macros, this function emits
    indexChanged() once for the entire macro command.

    \sa beginMacro()
*/

void QUndoStack::endMacro()
{
    Q_D(QUndoStack);
    if (d->macro_stack.isEmpty()) {
        qWarning("QUndoStack::endMacro(): no matching beginMacro()");
        return;
    }

    d->macro_stack.removeLast();

    if (d->macro_stack.isEmpty()) {
        d->checkUndoLimit();
        d->setIndex(d->index + 1, false);
    }
}

/*!
    Returns the text of the command at index \a idx.

    \sa beginMacro()
*/

QString QUndoStack::text(int idx) const
{
    Q_D(const QUndoStack);

    if (idx < 0 || idx >= d->command_list.size())
        return QString();
    return d->command_list.at(idx)->text();
}

/*!
    \property QUndoStack::undoLimit
    \brief the maximum number of commands on this stack.
    \since 4.3

    When the number of commands on a stack exceedes the stack's undoLimit, commands are
    deleted from the bottom of the stack. Macro commands (commands with child commands)
    are treated as one command. The default value is 0, which means that there is no
    limit.

    This property may only be set when the undo stack is empty, since setting it on a
    non-empty stack might delete the command at the current index. Calling setUndoLimit()
    on a non-empty stack prints a warning and does nothing.
*/

void QUndoStack::setUndoLimit(int limit)
{
    Q_D(QUndoStack);

    if (!d->command_list.isEmpty()) {
        qWarning("QUndoStack::setUndoLimit(): an undo limit can only be set when the stack is empty");
        return;
    }

    if (limit == d->undo_limit)
        return;
    d->undo_limit = limit;
    d->checkUndoLimit();
}

int QUndoStack::undoLimit() const
{
    Q_D(const QUndoStack);

    return d->undo_limit;
}

/*!
    \property QUndoStack::active
    \brief the active status of this stack.

    An application often has multiple undo stacks, one for each opened document. The active
    stack is the one associated with the currently active document. If the stack belongs
    to a QUndoGroup, calls to QUndoGroup::undo() or QUndoGroup::redo() will be forwarded
    to this stack when it is active. If the QUndoGroup is watched by a QUndoView, the view
    will display the contents of this stack when it is active. If the stack does not belong to
    a QUndoGroup, making it active has no effect.

    It is the programmer's responsibility to specify which stack is active by
    calling setActive(), usually when the associated document window receives focus.

    \sa QUndoGroup
*/

void QUndoStack::setActive(bool active)
{
#ifdef QT_NO_UNDOGROUP
    Q_UNUSED(active);
#else
    Q_D(QUndoStack);

    if (d->group != 0) {
        if (active)
            d->group->setActiveStack(this);
        else if (d->group->activeStack() == this)
            d->group->setActiveStack(0);
    }
#endif
}

bool QUndoStack::isActive() const
{
#ifdef QT_NO_UNDOGROUP
    return true;
#else
    Q_D(const QUndoStack);
    return d->group == 0 || d->group->activeStack() == this;
#endif
}

/*!
    \fn void QUndoStack::indexChanged(int idx)

    This signal is emitted whenever a command modifies the state of the document.
    This happens when a command is undone or redone. When a macro
    command is undone or redone, or setIndex() is called, this signal
    is emitted only once.

    \a idx specifies the index of the current command, ie. the command which will be
    executed on the next call to redo().

    \sa index() setIndex()
*/

/*!
    \fn void QUndoStack::cleanChanged(bool clean)

    This signal is emitted whenever the stack enters or leaves the clean state.
    If \a clean is true, the stack is in a clean state; otherwise this signal
    indicates that it has left the clean state.

    \sa isClean() setClean()
*/

/*!
    \fn void QUndoStack::undoTextChanged(const QString &undoText)

    This signal is emitted whenever the value of undoText() changes. It is
    used to update the text property of the undo action returned by createUndoAction().
    \a undoText specifies the new text.
*/

/*!
    \fn void QUndoStack::canUndoChanged(bool canUndo)

    This signal is emitted whenever the value of canUndo() changes. It is
    used to enable or disable the undo action returned by createUndoAction().
    \a canUndo specifies the new value.
*/

/*!
    \fn void QUndoStack::redoTextChanged(const QString &redoText)

    This signal is emitted whenever the value of redoText() changes. It is
    used to update the text property of the redo action returned by createRedoAction().
    \a redoText specifies the new text.
*/

/*!
    \fn void QUndoStack::canRedoChanged(bool canUndo)

    This signal is emitted whenever the value of canRedo() changes. It is
    used to enable or disable the redo action returned by createRedoAction().
    \a canUndo specifies the new value.
*/

#endif // QT_NO_UNDOSTACK