widget/nsIClipboardDragDropHooks.idl

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #include "nsISupports.idl"
   6
   7 interface nsITransferable;
   8 interface nsIDragSession;
   9 interface nsIDOMEvent;
  10
  11
  12 /**
  13  * Interfaces for overriding the built-in drag, drop, copy, and paste
  14  * implementations in the content area and editors. Use this to do things
  15  * such as prevent a drag from starting, adding or removing
  16  * data and flavors, or preventing the drop.
  17  *
  18  * Embedders who want to have these hooks made available should implement
  19  * nsIClipboardDragDropHooks and use the command manager to send the
  20  * appropriate commands with these parameters/settings:
  21  *      command:  cmd_clipboardDragDropHook
  22  *
  23  *      params        value type   possible values
  24  *      "addhook"     isupports    nsIClipboardDragDropHooks as nsISupports
  25  *      "removehook"  isupports    nsIClipboardDragDropHooks as nsISupports
  26  *
  27  * Notes:
  28  *  * Overrides/hooks need to be added to each window (as appropriate).
  29  *    Adding them to the first window does not enable them for every window.
  30  *  * If more than one implementation is set for a window, the hooks will be
  31  *    called in the order they are added.
  32  *  * Adding the same hook to the same window will not add a second call.
  33  *    Each hook can only be called once per user action/api.
  34  *  * Not all hooks are guaranteed to be called.  If there are multiple hooks
  35  *    set for a window, any of them has an opportunity to cancel the action
  36  *    so no further processing will occur.
  37  *  * If any errors occur (without setting the boolean result) the default
  38  *    action will occur.
  39  *  * AllowDrop will be called MANY times during drag so ensure that it is
  40  *    efficient.
  41  */
  42
  43
  44 [scriptable,uuid(e03e6c5e-0d84-4c0b-8739-e6b8d51922de)]
  45 interface nsIClipboardDragDropHooks : nsISupports
  46 {
  47   /**
  48    * Prevents the drag from starting
  49    *
  50    * @param event DOM event (drag gesture)
  51    *
  52    * @return TRUE  drag can proceed
  53    * @return FALSE drag is cancelled, does not go to OS
  54    */
  55   boolean allowStartDrag(in nsIDOMEvent event);
  56
  57   /**
  58    * Tells gecko whether a drop is allowed on this content area
  59    *
  60    * @param event   DOM event (drag over)
  61    * @param session the drag session from which client can get
  62    *                   the flavors present or the actual data
  63    *
  64    * @return TRUE  indicates to OS that if a drop does happen on this
  65    *                browser, it will be accepted.
  66    * @return FALSE indicates to OS drop is not allowed. On win32, this
  67    *                will change the cursor to "reject".
  68    */
  69   boolean allowDrop(in nsIDOMEvent event, in nsIDragSession session);
  70
  71   /**
  72    * Alter the flavors or data presented to the OS
  73    * Used for drag and copy actions
  74    * Because this can be called many times, it is highly recommended
  75    * that the implementation be very efficient so user feedback is
  76    * not negatively impacted.
  77    *
  78    * @param event  DOM event (drag drop); null if triggered by copy.
  79    * @param trans  the transferable holding the list of flavors
  80    *               and the data for each flavor
  81    *
  82    * @return TRUE  copy/drag can proceed
  83    * @return FALSE copy/drag is cancelled, does not go to OS
  84    */
  85   boolean onCopyOrDrag(in nsIDOMEvent aEvent, in nsITransferable trans);
  86
  87   /**
  88    * Provide an alternative action to the built-in behavior when
  89    * something is dropped on the browser or in an editor
  90    *
  91    * @param event  DOM event (drag drop); null if triggered by paste.
  92    * @param trans  the transferable holding the list of flavors
  93    *               and the data for each flavor
  94    *
  95    * @return TRUE  action was handled, do not perform built-in
  96    *                behavior
  97    * @return FALSE action was not overridden, do built-in behavior
  98    */
  99   boolean onPasteOrDrop(in nsIDOMEvent event, in nsITransferable trans);
 100 };
 101