Replacing Items in Collections(IM:XP)

Inside Macintosh: QuickDraw GX Printing /: Chapter 3 - Page Formatting and Dialog Box Customization / Using Printing-Related Collection Objects

Replacing Items in Collections

The MyReplaceCollectionItem function is a generic routine that you could write to replace collection items. In the implementation in Listing 3-5, the data being replaced is returned in a variable pointed to by oldData, unless the pointer is nil. If the item does not exist, the new data is returned via the pointer instead.

Listing 3-5 Replacing collection items

OSErr MyReplaceCollectionItem(void *newData, long collectSize,
                       OSType collectType, long collectID,
                       Collection whichCollection,
                       Ptr *oldData, long *oldDataSize)
{
   OSErr    err;
   long     index;

   /*
      If returning the old data, get it.
      If there is no old data, return a copy of the new data.
   */
   if (oldData)
   {
      err = GetCollectionItemInfo(whichCollection,
                           collectType,
                           collectID,
                           dontWantIndex,
                           oldDataSize,
                           dontWantAttributes);
      if (err)
      {
         *oldDataSize = collectSize;
         *oldData = NewPtrSys(*oldDataSize);
         if (!(err = MemError()))
            BlockMove(newData, *oldData, collectSize);
      }
      else
      {
         *oldData = NewPtrSys(*oldDataSize);
         if (!(err = MemError()))
            err = GetCollectionItem(whichCollection,
                              collectType,
                              collectID,
                              dontWantSize,
                              *oldData);
      }
      nrequire(err, CouldNotSetOldData);
   }

   /* 
      Add a new collection item; otherwise, get the existing
      item's index and replace the old collection item.
   */
   err = AddCollectionItem(whichCollection,
                     collectType,
                     collectID,
                     collectSize,
                     newData);

   if (err == collectionItemLockedErr)
   {
      err = GetCollectionItemInfo(whichCollection,
                           collectType,
                           collectID,
                           &index,
                           dontWantSize,
                           dontWantAttributes);
      if (!err)
         err = ReplaceIndexedCollectionItem(whichCollection,
                                    index,
                                    collectSize,
                                    newData);
   }

CouldNotSetOldData:
   return err;
}