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