audacity/src/AudacityException.cpp

#include "Audacity.h"
#include "AudacityException.h"

#include <wx/atomic.h>
#include <wx/msgdlg.h>

AudacityException::~AudacityException()
{
}

wxAtomicInt sOutstandingMessages {};

MessageBoxException::MessageBoxException( const wxString &caption_ )
   : caption{ caption_ }
{
   wxAtomicInc( sOutstandingMessages );
}

// The class needs a copy constructor to be throwable
// (or will need it, by C++14 rules).  But the copy
// needs to act like a move constructor.  There must be unique responsibility
// for each exception thrown to decrease the global count when it is handled.
MessageBoxException::MessageBoxException( const MessageBoxException& that )
{
   caption = that.caption;
   moved = that.moved;
   that.moved = true;
}

MessageBoxException &MessageBoxException::operator = ( MessageBoxException &&that )
{
   caption = that.caption;
   if ( this != &that ) {
      AudacityException::operator=( std::move(that) );
      if (!moved)
         wxAtomicDec( sOutstandingMessages );

      moved = that.moved;
      that.moved = true;
   }

   return *this;
}

MessageBoxException::~MessageBoxException()
{
   if (!moved)
      // If exceptions are used properly, you should never reach this,
      // because moved should become true earlier in the object's lifetime.
      wxAtomicDec( sOutstandingMessages );
}

SimpleMessageBoxException::~SimpleMessageBoxException()
{
}

wxString SimpleMessageBoxException::ErrorMessage() const
{
   return message;
}

std::unique_ptr< AudacityException > SimpleMessageBoxException::Move()
{
   return std::unique_ptr< AudacityException >
   { safenew SimpleMessageBoxException{ std::move( *this ) } };
}

// This is meant to be invoked via wxEvtHandler::CallAfter
void MessageBoxException::DelayedHandlerAction()
{
   if (!moved) {
      // This test prevents accumulation of multiple messages between idle
      // times of the main even loop.  Only the last queued exception
      // displays its message.  We assume that multiple messages have a
      // common cause such as exhaustion of disk space so that the others
      // give the user no useful added information.
      if ( wxAtomicDec( sOutstandingMessages ) == 0 )
         ::wxMessageBox(
            ErrorMessage(),
            caption.IsEmpty() ? wxMessageBoxCaptionStr : caption,
            wxICON_ERROR
         );
      moved = true;
   }
}