widget/nsIClipboardDragDropHooks.idl

   1 /* ***** BEGIN LICENSE BLOCK *****
   2  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   3  *
   4  * The contents of this file are subject to the Mozilla Public License Version
   5  * 1.1 (the "License"); you may not use this file except in compliance with
   6  * the License. You may obtain a copy of the License at
   7  * http://www.mozilla.org/MPL/
   8  *
   9  * Software distributed under the License is distributed on an "AS IS" basis,
  10  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  11  * for the specific language governing rights and limitations under the
  12  * License.
  13  *
  14  * The Original Code is Mozilla Communicator.
  15  *
  16  * The Initial Developer of the Original Code is
  17  * Netscape Communications.
  18  * Portions created by the Initial Developer are Copyright (C) 2002
  19  * the Initial Developer. All Rights Reserved.
  20  *
  21  * Contributor(s):
  22  *  Mike Pinkerton <pinkerton@netscape.com>
  23  *  Kathleen Brade <brade@netscape.com>
  24  *
  25  * Alternatively, the contents of this file may be used under the terms of
  26  * either the GNU General Public License Version 2 or later (the "GPL"), or
  27  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  28  * in which case the provisions of the GPL or the LGPL are applicable instead
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  35  * the terms of any one of the MPL, the GPL or the LGPL.
  36  *
  37  * ***** END LICENSE BLOCK ***** */
  38
  39 #include "nsISupports.idl"
  40
  41 interface nsITransferable;
  42 interface nsIDragSession;
  43 interface nsIDOMEvent;
  44
  45
  46 /**
  47  * Interfaces for overriding the built-in drag, drop, copy, and paste
  48  * implementations in the content area and editors. Use this to do things
  49  * such as prevent a drag from starting, adding or removing
  50  * data and flavors, or preventing the drop.
  51  *
  52  * Embedders who want to have these hooks made available should implement
  53  * nsIClipboardDragDropHooks and use the command manager to send the
  54  * appropriate commands with these parameters/settings:
  55  *      command:  cmd_clipboardDragDropHook
  56  *
  57  *      params        value type   possible values
  58  *      "addhook"     isupports    nsIClipboardDragDropHooks as nsISupports
  59  *      "removehook"  isupports    nsIClipboardDragDropHooks as nsISupports
  60  *
  61  * Notes:
  62  *  * Overrides/hooks need to be added to each window (as appropriate).
  63  *    Adding them to the first window does not enable them for every window.
  64  *  * If more than one implementation is set for a window, the hooks will be
  65  *    called in the order they are added.
  66  *  * Adding the same hook to the same window will not add a second call.
  67  *    Each hook can only be called once per user action/api.
  68  *  * Not all hooks are guaranteed to be called.  If there are multiple hooks
  69  *    set for a window, any of them has an opportunity to cancel the action
  70  *    so no further processing will occur.
  71  *  * If any errors occur (without setting the boolean result) the default
  72  *    action will occur.
  73  *  * AllowDrop will be called MANY times during drag so ensure that it is
  74  *    efficient.
  75  */
  76
  77
  78 [scriptable,uuid(e03e6c5e-0d84-4c0b-8739-e6b8d51922de)]
  79 interface nsIClipboardDragDropHooks : nsISupports
  80 {
  81   /**
  82    * Prevents the drag from starting
  83    *
  84    * @param event DOM event (drag gesture)
  85    *
  86    * @return TRUE  drag can proceed
  87    * @return FALSE drag is cancelled, does not go to OS
  88    */
  89   boolean allowStartDrag(in nsIDOMEvent event);
  90
  91   /**
  92    * Tells gecko whether a drop is allowed on this content area
  93    *
  94    * @param event   DOM event (drag over)
  95    * @param session the drag session from which client can get
  96    *                   the flavors present or the actual data
  97    *
  98    * @return TRUE  indicates to OS that if a drop does happen on this
  99    *                browser, it will be accepted.
 100    * @return FALSE indicates to OS drop is not allowed. On win32, this
 101    *                will change the cursor to "reject".
 102    */
 103   boolean allowDrop(in nsIDOMEvent event, in nsIDragSession session);
 104
 105   /**
 106    * Alter the flavors or data presented to the OS
 107    * Used for drag and copy actions
 108    * Because this can be called many times, it is highly recommended
 109    * that the implementation be very efficient so user feedback is
 110    * not negatively impacted.
 111    *
 112    * @param event  DOM event (drag drop); null if triggered by copy.
 113    * @param trans  the transferable holding the list of flavors
 114    *               and the data for each flavor
 115    *
 116    * @return TRUE  copy/drag can proceed
 117    * @return FALSE copy/drag is cancelled, does not go to OS
 118    */
 119   boolean onCopyOrDrag(in nsIDOMEvent aEvent, in nsITransferable trans);
 120
 121   /**
 122    * Provide an alternative action to the built-in behavior when
 123    * something is dropped on the browser or in an editor
 124    *
 125    * @param event  DOM event (drag drop); null if triggered by paste.
 126    * @param trans  the transferable holding the list of flavors
 127    *               and the data for each flavor
 128    *
 129    * @return TRUE  action was handled, do not perform built-in
 130    *                behavior
 131    * @return FALSE action was not overridden, do built-in behavior
 132    */
 133   boolean onPasteOrDrop(in nsIDOMEvent event, in nsITransferable trans);
 134 };
 135