EVT_IDLE_ONCE

[Troels]

This class is useful when you need to perform a task well after your dialog is shown and in position. The first time the idle event is fired is a good time to perform such a task. The class provided here takes care of the housekeeping, deactivates itself after the first idle, leaving you to just provide a OnIdleOnce event handler. You'll need to instantiate wxIdleOnceEvtHandler though, as shown below, but it then hooks itself up and deactivates itself automatically.

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class MyDialog : public wxDialog
{
   wxIdleOnceEvtHandler* m_idleonce;
   MyDialog() : wxDialog() { m_idleonce = new wxIdleOnceEvtHandler(this); }
   virtual ~MyDialog() { wxDELETE(m_idleonce) }
   void OnIdleOnce(wxIdleEvent&);
};
BEGIN_EVENT_TABLE(MyDialog, wxDialog)
   EVT_IDLE_ONCE(MyDialog::OnIdleOnce)
END_EVENT_TABLE()

First version of this little piece of code is in the Code Dump thread
"Paint background image in any wxWindow, an elegant way"
http://forums.wxwidgets.org/viewtopic.php?t=10019
Now it is calling Connect instead of overriding ProcessEvent.

Edit: PushEventHandler not needed when using Connect.

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/////////////////////////////////////////////////////////////////////////////
// wxIdleOnceEvtHandler by Troels K
// Thanks to Volker Bartheld and Belgabor.
//
// define a new handler type that will deal with the wxEVT_IDLE event when it arrives in the queue for the *FIRST* time 

class wxIdleOnceEvtHandler : public wxEvtHandler
{
public:
   wxEvtHandler* m_target;

   wxIdleOnceEvtHandler(wxEvtHandler* target);
   bool Disconnect(void);
   bool IsFired(void) const;
   virtual ~wxIdleOnceEvtHandler();
protected:
   void Connect();
   void OnIdle(wxIdleEvent&);
};

extern const wxEventType wxEVT_IDLE_ONCE;
#define EVT_IDLE_ONCE(func) wx__DECLARE_EVT0(wxEVT_IDLE_ONCE, wxIdleEventHandler(func))

Code: Select all

/////////////////////////////////////////////////////////////////////////////
// wxIdleOnceEvtHandler
//
// define a new handler type that will deal with the wxEVT_IDLE event when it arrives in the queue for the *FIRST* time

const wxEventType wxEVT_IDLE_ONCE = wxNewEventType();

wxIdleOnceEvtHandler::wxIdleOnceEvtHandler(wxEvtHandler* target) : wxEvtHandler(), m_target(target)
{
   wxASSERT(target);
   Connect();
}

wxIdleOnceEvtHandler::~wxIdleOnceEvtHandler()
{
   if (!IsFired()) Disconnect();
}

void wxIdleOnceEvtHandler::OnIdle(wxIdleEvent& event)
{
   Disconnect(); // stop the handler
   wxEvtHandler* target = m_target;
   m_target = NULL;
   wxEvent* temp = event.Clone(); // duplicate the event
   temp->SetEventType(wxEVT_IDLE_ONCE); // set correct event type
   ::wxPostEvent(target, *temp); // and reinsert it into parent's queue
   target->ProcessPendingEvents(); // Process now
   wxDELETE(temp)
   event.Skip();
}

bool wxIdleOnceEvtHandler::IsFired(void) const
{
   return (m_target == NULL);
}

void wxIdleOnceEvtHandler::Connect()
{
   m_target->Connect(wxID_ANY, wxEVT_IDLE,
            wxIdleEventHandler(wxIdleOnceEvtHandler::OnIdle),
            NULL, this);
}

bool wxIdleOnceEvtHandler::Disconnect()
{
   return m_target->Disconnect(wxID_ANY, wxEVT_IDLE,
            wxIdleEventHandler(wxIdleOnceEvtHandler::OnIdle),
            NULL, this);
}