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		- DRAG & DROP - 
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- This code illustrates one method of implementing drag&drop within a 
  TList control (can also be used between two TList controls).  

  A future version of TList may support internal Drag&Drop without VB 
  code, but we will need to look for feedback from our users first
  to insure that we do this in an appropriate manner.
  
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  To use these DragDrop procedures with TList you should do as follows:
  1. Set DragMode for TList to 0 - Manual.
  2. Set DragIcon to the icon you would like to use. I prefer icons 
     from \DRAGDROP standard VB directory.
  3. Set DragHighlight to True - otherwise items won't be highlighted 
     when the user drags over them.
  4. Set TList.Tag to the string "TREE".
     There is no difference what string is in the Tag, but code in 
     the DragDrop event assumes that this line is ID of TList control.
  5. Add code which is below:
     5.1 Add global variables 
         hTreeBuffer&   - here we store a Tree Buffer for items that 
                          we drag.
         XCheck, YCheck - In these variables we save X and Y coordinates
           of mouse cursor position when the user presses the left mouse 
	   button(MouseDown event). 
      Note, that we cannot start Dragging on the first MouseMove event.
      If we did so, the user would be starting a Drag each time he hit the 
      left mouse button.  Thus, to initiate Dragging, the user must press 
      the left mouse button and move the mouse a little, keeping the left 
      mouse button pressed.  In this code we start Dragging only if user 
      moves the mouse with left button depressed for a distance of at least 
      100 twips.
    5.2 Add code for MouseDown, MouseMove, DragDrop and Form_Unload events.
    5.3 There is also some code for expanding and collapsing items on 
	double-click.
  6. How it works:
    6.1. User presses left mouse button and moves the mouse for the distance 
         more than 100 twips.
         We process MouseDown event - set XCheck & YCheck to 0
         We process MouseMove event until difference in X or Y parameters
         is more than 100 twips.
    6.2. In MouseMove event we do:
      6.2.1 set XCheck & YCheck to 0.
      6.2.2 If (TList has an item, specified by ListIndex property) Then
            6.2.2.1 free Tree Buffer(there can be items from previous 
                    drag/drop operations).
            6.2.2.2 copy item whose index is specified by ListIndex property
                    to the Tree Buffer by CopyItem property. (If you need
                    to copy all selected items use CopySelected property, 
                    if you want to copy only subordinate items 
                    use CopyItemSub property)
            6.2.2.3 remove item that we copy by RemoveItem method.
                    Note, there are extra .Redraw calls - they cause 
                    updating of TList after removing of an item,  
                    otherwise highlighted item isn't drawn 
                    correctly after it.
            EndIf
    6.2. Mouse cursor changes as the user moves it over items of TList
            Items that are dragged over are highlighted automatically.
    6.3. User drops on one of the items, triggering the DragDrop event.
            Within the DragDrop event we check the Source.Tag property and
            if we find the string "TREE", we assume that Source is a TList
            control. Then we do as follows:
              6.3.1 Get target item index from tltSample.DropTarget property
              6.3.2 Set Redraw to False(Prevent control from immediate
                    repainting) 
              6.3.3 Expand target item(It may or may not have items but flag 
                    is set anyway).
              6.3.4 Add items from Tree Buffer using the Add property. 
                    This property adds items which are stored in the 
                    Tree Buffer as subordinate items to the item specified 
                    by index. You can use Insert property to add items 
                    before item specified by index on the same level.
              6.3.5 Turn repainting on by setting Redraw to True.
              6.3.6 Release the TreeBuffer memory