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_EdUndo( ) API Library Routine

  • Artículo

Undoes the single most recent change made to the file in the specified window.

void _EdUndo(WHANDLE wh)
WHANDLE wh;            /* Handle of editing window. */

Remarks

When the user makes changes to a file, these changes are recorded in the undo buffer. _EdUndo( ) can be issued multiple times to undo multiple changes. You can't undo a change made prior to issuing _EdSave( ).

For more information on how to create an API library and integrate it with Visual FoxPro, see Accessing the Visual FoxPro API.

Example

The following example opens a file specified by a parameter for editing. After inserting a new line, it uses _EdUndo( ) to delete the line, and then calls _EdRedo( ) to restore the inserted line.

Visual FoxPro Code

SET LIBRARY TO EDUNDO  
= EDREDO("x")

C Code

#include <pro_ext.h>

FAR Example(ParamBlk FAR *parm)
{
#define pFILENAME ((char FAR *) _HandToPtr(parm->p[0].val.ev_handle))

   WHANDLE wh;

   if (!_SetHandSize(parm->p[0].val.ev_handle,
      parm->p[0].val.ev_length+1))
   {
      _Error(182); // "Insufficient memory"
   }
   pFILENAME[parm->p[0].val.ev_length] = '\0';

   _HLock(parm->p[0].val.ev_handle);
   wh = _EdOpenFile(pFILENAME, FO_READWRITE);
   _HUnLock(parm->p[0].val.ev_handle);

   _EdSetPos(wh, _EdGetLinePos(wh, 13));
   _EdInsert(wh, "Hello, world\n", _StrLen("Hello, world\n"));

   _Execute("WAIT WINDOW 'New line inserted.\
      Press any key to undo.'");
   _EdUndo(wh);

   _Execute("WAIT WINDOW 'Insertion undone.  Press any key to redo.'");
   _EdRedo(wh);
}

FoxInfo myFoxInfo[] = {
   {"EDREDO", (FPFI) Example, 1, "C"},
};
FoxTable _FoxTable = {
   (FoxTable FAR *) 0, sizeof(myFoxInfo)/sizeof(FoxInfo), myFoxInfo
};

See Also

Reference

_EdRedo( ) API Library Routine

_EdUndoOn( ) API Library Routine

_EdSave( ) API Library Routine

Other Resources

API Library Construction

Accessing the Visual FoxPro API