The DM_DRAGOVER message is sent to a target whenever the user drags the pointer into the window. To assess whether a drop can be accepted, the target must use DrgAccessDraginfo to get access to the DRAGINFO data structure. It then determines whether a drop can be accepted for each object. The object must meet the following minimum requirements to exchange data:

• The source and target must share knowledge of at least one common type for the object. The target can make this determination by using DrgVerifyTypeSet or DrgVerifyType.

• The source and target must share at least one common rendering mechanism and format for that type object. The target can make this determination by using DrgVerifyRMF.

DOR_DROP, DOR_NODROP, DOR_NODROPOP, and DOR_NEVERDROP are the four possible responses available to the target when it receives a DM_DRAGOVER message. The target sends these values to the window handle specified in the DRAGINFO data structure.

The following sample code shows how the target determines its response to the DM_DRAGOVER message:

/***********************************************************************//*  Someone's dragging an object over us.                              */
/***********************************************************************/
        case DM_DRAGOVER:
         dragInfo = (PDRAGINFO)mp1;

         /* Get access to the DRAGINFO data structure */
         DrgAccessDraginfo(dragInfo);

         /* Can we accept this drop? */
         switch (dragInfo->usOperation)
         {

          /* Return DOR_NODROPOP if current operation */
          /* is link or unknown                       */
           case DO_UNKNOWN:
              DrgFreeDraginfo(dragInfo);
              return (MRFROM2SHORT(DOR_NODROPOP,0));
              break;

           /* Our default operation is Move */
           case DO_DEFAULT:
              dragItem = DrgQueryDragitemPtr(dragInfo,0);
              ulBytes  = DrgQueryStrName(dragItem->hstrContainerName,
                                                   sizeof(szDir),
                                                   szDir);
              if (!ulBytes)
                return (MRFROM2SHORT(DOR_NODROPOP,0));
              else
                usOp = DO_MOVE;
              break;

           /* Do the requested specific operation */
           case DO_MOVE:
           case DO_COPY:
              usOp = dragInfo->usOperation;
              break;
         }

         usIndicator = DOR_DROP;
         cItems = DrgQueryDragitemCount(dragInfo);

          /* Now, we need to look at each item in turn */
          for (i = 0; i < cItems; i++)
          {
            dragItem = DrgQueryDragitemPtr(dragInfo, i);

            /* Make sure we can move for a Move request */
            /* or copy for a Copy                       */
            if (((dragItem->fsSupportedOps & DO_COPYABLE)   &&
                 (usOp == (USHORT)DO_COPY))                 ||
                ((dragItem->fsSupportedOps & DO_MOVEABLE)   &&
                 (usOp == (USHORT)DO_MOVE)))
            {
               /* Check the rendering format */
               if (DrgVerifyRMF(dragItem, "DRM_OS2FILE", "DRF_UNKNOWN"))
                  usIndicator = DOR_DROP;
               else
                  usIndicator = DOR_NEVERDROP;
            }
            else
               usIndicator = DOR_NODROPOP;
          }

          /* Release the draginfo data structure */
          DrgFreeDraginfo(dragInfo);

          return (MRFROM2SHORT(usIndicator, usOp));
          break;