自学教程：C++ CanUndo函数代码示例

void CPropTreeItemFileEdit::OnContextMenu(CWnd *pWnd, CPoint point){	CMenu FloatingMenu;	VERIFY(FloatingMenu.LoadMenu(IDR_ME_EDIT_MENU));	CMenu *pPopupMenu = FloatingMenu.GetSubMenu(0);	if (CanUndo()) {		pPopupMenu->EnableMenuItem(ID_EDIT_UNDO, MF_BYCOMMAND | MF_ENABLED);	} else {		pPopupMenu->EnableMenuItem(ID_EDIT_UNDO, MF_BYCOMMAND | MF_DISABLED | MF_GRAYED);	}	DWORD dwSel = GetSel();	if (HIWORD(dwSel) != LOWORD(dwSel)) {		pPopupMenu->EnableMenuItem(ID_EDIT_CUT, MF_BYCOMMAND | MF_ENABLED);		pPopupMenu->EnableMenuItem(ID_EDIT_COPY, MF_BYCOMMAND | MF_ENABLED);		pPopupMenu->EnableMenuItem(ID_EDIT_DELETE, MF_BYCOMMAND | MF_ENABLED);	} else {		pPopupMenu->EnableMenuItem(ID_EDIT_CUT, MF_BYCOMMAND | MF_DISABLED | MF_GRAYED);		pPopupMenu->EnableMenuItem(ID_EDIT_COPY, MF_BYCOMMAND | MF_DISABLED | MF_GRAYED);		pPopupMenu->EnableMenuItem(ID_EDIT_DELETE, MF_BYCOMMAND | MF_DISABLED | MF_GRAYED);	}	pPopupMenu->TrackPopupMenu(TPM_LEFTALIGN | TPM_RIGHTBUTTON, point.x, point.y, this);}

// Undo the last commandvoid PaintModel::Undo() {	if (CanUndo()) {		mRedoStack.push(mUndoStack.top());		mUndoStack.top()->Undo(shared_from_this());		mUndoStack.pop();	}}

    void BatchCommand::Undo()    {        BBAssertDebug(CanUndo());        for (RestorableCommandCollection::reverse_iterator it = restorableCommands.rbegin(); it != restorableCommands.rend(); ++it)            (*it)->Undo();    }

void wxTextCtrl::Undo(){    if (CanUndo())    {        ::SendMessage(GetBuddyHwnd(), EM_UNDO, 0, 0);    }}

void CColorEdit::OnChar(UINT nChar, UINT nRepCnt, UINT nFlags){	// TODO: Add your message handler code here and/or call default	switch (nChar)	{	case 0x01:// Ctrl-A => handle SELECT_ALL		SetSel(0, -1);		return;	case 0x03:// Ctrl-C => handle WM_COPY		Copy();		return;	case 0x16:// Ctrl-V => handle WM_PASTE		Paste();		return;	case 0x18:// Ctrl-X => handle WM_CUT		Cut();		return;	case 0x1A:// Ctrl-Z => handle ID_EDIT_UNDO (EM_UNDO)		if(CanUndo())			Undo();		return;	}	CEdit::OnChar(nChar, nRepCnt, nFlags);}

void wxTextEntry::Undo(){    wxCHECK_RET( GetTextPeer(), "Must create the control first" );    if (CanUndo())        GetTextPeer()->Undo() ;}

bool UTransBuffer::Undo(){	CheckState();	if (!CanUndo())	{		UndoDelegate.Broadcast(FUndoSessionContext(), false);		return false;	}	// Apply the undo changes.	GIsTransacting = true;	{		FTransaction& Transaction = UndoBuffer[ UndoBuffer.Num() - ++UndoCount ];		UE_LOG(LogEditorTransaction, Log,  TEXT("Undo %s"), *Transaction.GetTitle().ToString() );		BeforeRedoUndoDelegate.Broadcast(Transaction.GetContext());		Transaction.Apply();		UndoDelegate.Broadcast(Transaction.GetContext(), true);	}	GIsTransacting = false;	CheckState();	return true;}

void CHistory::Undo(){	if (CanUndo())	{		m_commands[m_nextCommandIndex - 1]->Unexecute(); // может выбросить исключение		--m_nextCommandIndex;	}}

BStringUndoContext::UndoLabel() const{	if (CanUndo())		return ((Action*)fHistory->ItemAt(fAt - 1))->Label();	else		return "";}

void wxTextCtrl::Undo(){    if (CanUndo())    {        if (m_bIsMLE)            ::WinSendMsg(GetHwnd(), MLM_UNDO, 0, 0);        // Simple entryfields cannot be undone    }} // end of wxTextCtrl::Undo

bool History::InternalRollBack(void){	if(!CanUndo())return false;	Undoable *u;	m_curpos--;	u = *m_curpos;	u->RollBack();	return true;}

void wxComboBox::Undo(){    if (CanUndo())    {        HWND hEditWnd = (HWND) GetEditHWND() ;        if ( hEditWnd )            ::SendMessage(hEditWnd, EM_UNDO, 0, 0);    }}

void wxComboBox::Redo(){    if (CanUndo())    {        // Same as Undo, since Undo undoes the undo, i.e. a redo.        HWND hEditWnd = (HWND) GetEditHWND() ;        if ( hEditWnd )            ::SendMessage(hEditWnd, EM_UNDO, 0, 0);    }}

void SnapshotManager::Undo(){  Assert(CanUndo());  if (m_snapshots.size() > 1)  {    m_snapshots.pop_back();  }  SetStateToSnapshot(*(m_snapshots.rbegin()));}

bool	cActionManager::Undo(){ 	if (CanUndo())	{		cAction* action = mUndoList.front();		RemoveTopAction(UNDO);		action->Accept(cUndoActionVisitor::Global());		AddAction(REDO, action);		return true;	}	return false;}

void CUICommandHistory::UICommandAction(CommandType type){	CUICommandNode* pOldNode;	CUICommandNode* pNewNode;	if(type == cmdRedo)	{		if(!CanRedo())			return;		pOldNode = m_lstCommandNodes.GetAt(m_lstCommandNodes.FindIndex(m_nCommandIndex));		pNewNode = new CUICommandNode(pOldNode->m_pBefore, pOldNode->m_pAfter, pOldNode->m_ActionType);		m_nCommandIndex++;	}	else	{		if(!CanUndo())			return;		m_nCommandIndex--;		pOldNode = m_lstCommandNodes.GetAt(m_lstCommandNodes.FindIndex(m_nCommandIndex));		ActionType action;		switch(pOldNode->m_ActionType)		{		case actionAdd:			action = actionDelete;			break;		case actionModify:			action = actionModify;			break;		case actionDelete:			action = actionAdd;			break;		}		pNewNode = new CUICommandNode(pOldNode->m_pAfter, pOldNode->m_pBefore, action);	}	switch(pNewNode->m_ActionType)	{	case actionAdd:		ActionAdd(pNewNode->m_pAfter);		break;	case actionModify:		ActionModify(pNewNode->m_pAfter);		break;	case actionDelete:		ActionDelete(pNewNode->m_pBefore);		break;	}	delete pNewNode;}

//-----------------------------------------------------------------------------// The display code is the only part of the program that knows how wide a// rung will be when it's displayed; so this is the only convenient place to// warn the user and undo their changes if they created something too wide.// This is not very clean.//-----------------------------------------------------------------------------static BOOL CheckBoundsUndoIfFails(int gx, int gy){    if(gx >= DISPLAY_MATRIX_X_SIZE || gx < 0 ||       gy >= DISPLAY_MATRIX_Y_SIZE || gy < 0)    {        if(CanUndo()) {            UndoUndo();            Error(_("Too many elements in subcircuit!"));            return TRUE;        }    }    return FALSE;}

FUndoSessionContext UTransBuffer::GetUndoContext( bool bCheckWhetherUndoPossible ){	FUndoSessionContext Context;	FText Title;	if( bCheckWhetherUndoPossible && !CanUndo( &Title ) )	{		Context.Title = Title;		return Context;	}	const FTransaction* Transaction = &UndoBuffer[ UndoBuffer.Num() - (UndoCount + 1) ];	return Transaction->GetContext();}

void CEditWnd::Undo(){	if (!CanUndo()) return;	CPoint ptCursorPos;	if (m_pTextBuffer->Undo(ptCursorPos))	{		ASSERT_VALIDTEXTPOS(ptCursorPos);		SetAnchor(ptCursorPos);		SetSelection(ptCursorPos, ptCursorPos);		SetCursorPos(ptCursorPos);		EnsureVisible(ptCursorPos);	}}

//-----------------------------------------------------------------------------// Purpose: // Input  : *exp - //-----------------------------------------------------------------------------void CExpression::Undo( void ){	if ( !CanUndo() )		return;	Assert( m_nUndoCurrent < undo.Size() );	CExpUndoInfo *u = undo[ m_nUndoCurrent++ ];	Assert( u );		memcpy( setting, u->setting, GLOBAL_STUDIO_FLEX_CONTROL_COUNT * sizeof( float ) );	memcpy( weight, u->weight, GLOBAL_STUDIO_FLEX_CONTROL_COUNT * sizeof( float ) );}

void CommandManager::Undo(std::string& feedback){	if (CanUndo()){		UndoRedoCount--;		Command* pCommand = getLastUndoCommand();		undoList.pop_back();		if (pCommand->undo(_taskList, feedback)){			AddRedo(pCommand);		} else {			delete pCommand;			pCommand = NULL;		}	}}

 bool NativeTextfieldWin::IsCommandIdEnabled(int command_id) const {     switch(command_id)     {     case IDS_APP_UNDO:       return !textfield_->read_only() && !!CanUndo();     case IDS_APP_CUT:        return !textfield_->read_only() &&                                  !textfield_->IsPassword() && !!CanCut();     case IDS_APP_COPY:       return !!CanCopy() && !textfield_->IsPassword();     case IDS_APP_PASTE:      return !textfield_->read_only() && !!CanPaste();     case IDS_APP_SELECT_ALL: return !!CanSelectAll();     default:                 NOTREACHED();         return false;     } }

void CRichEditCtrlX::OnContextMenu(CWnd* pWnd, CPoint point){	long iSelStart, iSelEnd;	GetSel(iSelStart, iSelEnd);	int iTextLen = GetWindowTextLength();	// Context menu of standard edit control	// 	// Undo	// ----	// Cut	// Copy	// Paste	// Delete	// ------	// Select All	bool bReadOnly = (GetStyle() & ES_READONLY);	CMenu menu;	menu.CreatePopupMenu();	if (!bReadOnly){		menu.AppendMenu(MF_STRING, MP_UNDO, GetResString(IDS_UNDO));		menu.AppendMenu(MF_SEPARATOR);	}	if (!bReadOnly)		menu.AppendMenu(MF_STRING, MP_CUT, GetResString(IDS_CUT));	menu.AppendMenu(MF_STRING, MP_COPYSELECTED, GetResString(IDS_COPY));	if (!bReadOnly){		menu.AppendMenu(MF_STRING, MP_PASTE, GetResString(IDS_PASTE));		menu.AppendMenu(MF_STRING, MP_REMOVESELECTED, GetResString(IDS_DELETESELECTED));	}	menu.AppendMenu(MF_SEPARATOR);	menu.AppendMenu(MF_STRING, MP_SELECTALL, GetResString(IDS_SELECTALL));	menu.EnableMenuItem(MP_UNDO, CanUndo() ? MF_ENABLED : MF_GRAYED);	menu.EnableMenuItem(MP_CUT, iSelEnd > iSelStart ? MF_ENABLED : MF_GRAYED);	menu.EnableMenuItem(MP_COPYSELECTED, iSelEnd > iSelStart ? MF_ENABLED : MF_GRAYED);	menu.EnableMenuItem(MP_PASTE, CanPaste() ? MF_ENABLED : MF_GRAYED);	menu.EnableMenuItem(MP_REMOVESELECTED, iSelEnd > iSelStart ? MF_ENABLED : MF_GRAYED);	menu.EnableMenuItem(MP_SELECTALL, iTextLen > 0 ? MF_ENABLED : MF_GRAYED);	if (point.x == -1 && point.y == -1)	{		point.x = 16;		point.y = 32;		ClientToScreen(&point);	}	menu.TrackPopupMenu(TPM_LEFTALIGN | TPM_RIGHTBUTTON, point.x, point.y, this);}

void ProjectManager::OnMenuUndo(){	//Si on peut annuler la modification	if(CanUndo())	{		if(currentHistoryNavigation==0)		{			PushModificationToHistory(true);			currentHistoryNavigation++;		}		currentHistoryNavigation++;		projetConfig=configHistory[configHistory.size()-currentHistoryNavigation];		LoadCurrentProject(false);		Init();	}}

void wxCommandProcessor::SetMenuStrings(){#if wxUSE_MENUS    if (m_commandEditMenu)    {        wxString undoLabel = GetUndoMenuLabel();        wxString redoLabel = GetRedoMenuLabel();        m_commandEditMenu->SetLabel(wxID_UNDO, undoLabel);        m_commandEditMenu->Enable(wxID_UNDO, CanUndo());        m_commandEditMenu->SetLabel(wxID_REDO, redoLabel);        m_commandEditMenu->Enable(wxID_REDO, CanRedo());    }#endif // wxUSE_MENUS}

bool	cActionManager::Undo(int id){	while (42)	{		if (CanUndo())		{			cAction* action = mUndoList.front();			RemoveTopAction(UNDO);			action->Accept(cUndoActionVisitor::Global());			AddAction(REDO, action);			if (action->m_Id == id)				return true;		}		else			return false;	}	return false;}

bool UTransBuffer::Undo(){	CheckState();	if( !CanUndo() )	{		return false;	}	// Apply the undo changes.	FTransaction& Transaction = UndoBuffer[ UndoBuffer.Num() - ++UndoCount ];	UE_LOG(LogEditorTransaction, Log,  TEXT("Undo %s"), *Transaction.GetTitle().ToString() );	Transaction.Apply();	CheckState();	return true;}

BOOL CCrystalTextBuffer::Undo(CPoint &ptCursorPos){	ASSERT(CanUndo());	ASSERT((m_aUndoBuf[0].m_dwFlags & UNDO_BEGINGROUP) != 0);	for (;;)	{		m_nUndoPosition --;		const SUndoRecord &ur = m_aUndoBuf[m_nUndoPosition];		if (ur.m_dwFlags & UNDO_INSERT)		{#ifdef _ADVANCED_BUGCHECK			//	Try to ensure that we undoing correctly...			//	Just compare the text as it was before Undo operation			CString text;			GetText(ur.m_ptStartPos.y, ur.m_ptStartPos.x, ur.m_ptEndPos.y, ur.m_ptEndPos.x, text);			ASSERT(lstrcmp(text, ur.m_pcText) == 0);#endif			VERIFY(InternalDeleteText(NULL, ur.m_ptStartPos.y, ur.m_ptStartPos.x, ur.m_ptEndPos.y, ur.m_ptEndPos.x));			ptCursorPos = ur.m_ptStartPos;		}		else		{			int nEndLine, nEndChar;			VERIFY(InternalInsertText(NULL, ur.m_ptStartPos.y, ur.m_ptStartPos.x, ur.m_pcText, nEndLine, nEndChar));#ifdef _ADVANCED_BUGCHECK			ASSERT(ur.m_ptEndPos.y == nEndLine);			ASSERT(ur.m_ptEndPos.x == nEndChar);#endif			ptCursorPos = ur.m_ptEndPos;		}		if (ur.m_dwFlags & UNDO_BEGINGROUP)			break;	}	if (m_bModified && m_nSyncPosition == m_nUndoPosition)		SetModified(FALSE);	if (! m_bModified && m_nSyncPosition != m_nUndoPosition)		SetModified(TRUE);	return TRUE;}

void CMyRichEdit::OnRButtonDown(UINT nFlags, CPoint point) {	//设置为焦点	SetFocus();	//创建一个弹出式菜单	CMenu popmenu;	popmenu.CreatePopupMenu();	//添加菜单项目	popmenu.AppendMenu(0, ID_RICH_UNDO, _T("撤消(&U)"));	popmenu.AppendMenu(0, MF_SEPARATOR);	popmenu.AppendMenu(0, ID_RICH_CUT, _T("剪切(&T)"));	popmenu.AppendMenu(0, ID_RICH_COPY, _T("复制(&T)"));	popmenu.AppendMenu(0, ID_RICH_PASTE, _T("粘贴(&P)"));	popmenu.AppendMenu(0, ID_RICH_CLEAR, _T("删除(&D)"));	popmenu.AppendMenu(0, MF_SEPARATOR);	popmenu.AppendMenu(0, ID_RICH_SELECTALL, _T("全选(&A)"));	popmenu.AppendMenu(0, MF_SEPARATOR);	popmenu.AppendMenu(0, ID_RICH_SETFONT, _T("设置字体(&F)"));	//初始化菜单项	UINT nUndo=(CanUndo() ? 0 : MF_GRAYED );	popmenu.EnableMenuItem(ID_RICH_UNDO, MF_BYCOMMAND|nUndo);	UINT nSel=((GetSelectionType()!=SEL_EMPTY) ? 0 : MF_GRAYED) ;	popmenu.EnableMenuItem(ID_RICH_CUT, MF_BYCOMMAND|nSel);	popmenu.EnableMenuItem(ID_RICH_COPY, MF_BYCOMMAND|nSel);	popmenu.EnableMenuItem(ID_RICH_CLEAR, MF_BYCOMMAND|nSel);		UINT nPaste=(CanPaste() ? 0 : MF_GRAYED) ;	popmenu.EnableMenuItem(ID_RICH_PASTE, MF_BYCOMMAND|nPaste);	//显示菜单	CPoint pt;	GetCursorPos(&pt);	popmenu.TrackPopupMenu(TPM_RIGHTBUTTON, pt.x, pt.y, this);	popmenu.DestroyMenu();	CRichEditCtrl::OnRButtonDown(nFlags, point);}