include/wx/eventfilter.h

   1 ///////////////////////////////////////////////////////////////////////////////
   2 // Name:        wx/eventfilter.h
   3 // Purpose:     wxEventFilter class declaration.
   4 // Author:      Vadim Zeitlin
   5 // Created:     2011-11-21
   6 // RCS-ID:      $Id$
   7 // Copyright:   (c) 2011 Vadim Zeitlin <vadim@wxwidgets.org>
   8 // Licence:     wxWindows licence
   9 ///////////////////////////////////////////////////////////////////////////////
  10
  11 #ifndef _WX_EVENTFILTER_H_
  12 #define _WX_EVENTFILTER_H_
  13
  14 #include "wx/defs.h"
  15
  16 class WXDLLIMPEXP_FWD_BASE wxEvent;
  17 class WXDLLIMPEXP_FWD_BASE wxEvtHandler;
  18
  19 // ----------------------------------------------------------------------------
  20 // wxEventFilter is used with wxEvtHandler::AddFilter() and ProcessEvent().
  21 // ----------------------------------------------------------------------------
  22
  23 class wxEventFilter
  24 {
  25 public:
  26     // Possible return values for FilterEvent().
  27     //
  28     // Notice that the values of these enum elements are fixed due to backwards
  29     // compatibility constraints.
  30     enum
  31     {
  32         // Process event as usual.
  33         Event_Skip = -1,
  34
  35         // Don't process the event normally at all.
  36         Event_Ignore = 0,
  37
  38         // Event was already handled, don't process it normally.
  39         Event_Processed = 1
  40     };
  41
  42     wxEventFilter()
  43     {
  44         m_next = NULL;
  45     }
  46
  47     virtual ~wxEventFilter()
  48     {
  49         wxASSERT_MSG( !m_next, "Forgot to call wxEvtHandler::RemoveFilter()?" );
  50     }
  51
  52     // This method allows to filter all the events processed by the program, so
  53     // you should try to return quickly from it to avoid slowing down the
  54     // program to a crawl.
  55     //
  56     // Return value should be -1 to continue with the normal event processing,
  57     // or true or false to stop further processing and pretend that the event
  58     // had been already processed or won't be processed at all, respectively.
  59     virtual int FilterEvent(wxEvent& event) = 0;
  60
  61 private:
  62     // Objects of this class are made to be stored in a linked list in
  63     // wxEvtHandler so put the next node ponter directly in the class itself.
  64     wxEventFilter* m_next;
  65
  66     // And provide access to it for wxEvtHandler [only].
  67     friend class wxEvtHandler;
  68
  69     wxDECLARE_NO_COPY_CLASS(wxEventFilter);
  70 };
  71
  72 #endif // _WX_EVENTFILTER_H_