Return NULL from wxWindow::GetCapture() when the capture is being lost.

[wxWidgets.git] / src / common / evtloopcmn.cpp

///////////////////////////////////////////////////////////////////////////////
// Name:        src/common/evtloopcmn.cpp
// Purpose:     common wxEventLoop-related stuff
// Author:      Vadim Zeitlin
// Created:     2006-01-12
// Copyright:   (c) 2006, 2013 Vadim Zeitlin <vadim@wxwindows.org>
//              (c) 2013 Rob Bresalier
// Licence:     wxWindows licence
///////////////////////////////////////////////////////////////////////////////

// for compilers that support precompilation, includes "wx.h".
#include "wx/wxprec.h"

#ifdef __BORLANDC__
    #pragma hdrstop
#endif

#include "wx/evtloop.h"

#ifndef WX_PRECOMP
    #include "wx/app.h"
#endif //WX_PRECOMP

#include "wx/scopeguard.h"
#include "wx/apptrait.h"
#include "wx/private/eventloopsourcesmanager.h"

// ----------------------------------------------------------------------------
// wxEventLoopBase
// ----------------------------------------------------------------------------

wxEventLoopBase *wxEventLoopBase::ms_activeLoop = NULL;

wxEventLoopBase::wxEventLoopBase()
{
    m_isInsideRun = false;
    m_shouldExit = false;

    m_isInsideYield = false;
    m_eventsToProcessInsideYield = wxEVT_CATEGORY_ALL;
}

bool wxEventLoopBase::IsMain() const
{
    if (wxTheApp)
        return wxTheApp->GetMainLoop() == this;
    return false;
}

/* static */
void wxEventLoopBase::SetActive(wxEventLoopBase* loop)
{
    ms_activeLoop = loop;

    if (wxTheApp)
        wxTheApp->OnEventLoopEnter(loop);
}

int wxEventLoopBase::Run()
{
    // event loops are not recursive, you need to create another loop!
    wxCHECK_MSG( !IsInsideRun(), -1, wxT("can't reenter a message loop") );

    // ProcessIdle() and ProcessEvents() below may throw so the code here should
    // be exception-safe, hence we must use local objects for all actions we
    // should undo
    wxEventLoopActivator activate(this);

    // We might be called again, after a previous call to ScheduleExit(), so
    // reset this flag.
    m_shouldExit = false;

    // Set this variable to true for the duration of this method.
    m_isInsideRun = true;
    wxON_BLOCK_EXIT_SET(m_isInsideRun, false);

    // Finally really run the loop.
    return DoRun();
}

void wxEventLoopBase::Exit(int rc)
{
    wxCHECK_RET( IsRunning(), wxS("Use ScheduleExit() on not running loop") );

    ScheduleExit(rc);
}

void wxEventLoopBase::OnExit()
{
    if (wxTheApp)
        wxTheApp->OnEventLoopExit(this);
}

void wxEventLoopBase::WakeUpIdle()
{
    WakeUp();
}

bool wxEventLoopBase::ProcessIdle()
{
    return wxTheApp && wxTheApp->ProcessIdle();
}

bool wxEventLoopBase::Yield(bool onlyIfNeeded)
{
    if ( m_isInsideYield )
    {
        if ( !onlyIfNeeded )
        {
            wxFAIL_MSG( wxT("wxYield called recursively" ) );
        }

        return false;
    }

    return YieldFor(wxEVT_CATEGORY_ALL);
}

#if wxUSE_EVENTLOOP_SOURCE

wxEventLoopSource*
wxEventLoopBase::AddSourceForFD(int fd,
                                wxEventLoopSourceHandler *handler,
                                int flags)
{
#if wxUSE_CONSOLE_EVENTLOOP
    // Delegate to the event loop sources manager defined by it.
    wxEventLoopSourcesManagerBase* const
        manager = wxApp::GetValidTraits().GetEventLoopSourcesManager();
    wxCHECK_MSG( manager, NULL, wxS("Must have wxEventLoopSourcesManager") );

    return manager->AddSourceForFD(fd, handler, flags);
#else // !wxUSE_CONSOLE_EVENTLOOP
    return NULL;
#endif // wxUSE_CONSOLE_EVENTLOOP/!wxUSE_CONSOLE_EVENTLOOP
}

#endif // wxUSE_EVENTLOOP_SOURCE

// wxEventLoopManual is unused in the other ports
#if defined(__WINDOWS__) || defined(__WXDFB__) || ( ( defined(__UNIX__) && !defined(__WXOSX__) ) && wxUSE_BASE)

// ============================================================================
// wxEventLoopManual implementation
// ============================================================================

wxEventLoopManual::wxEventLoopManual()
{
    m_exitcode = 0;
}

bool wxEventLoopManual::ProcessEvents()
{
    // process pending wx events first as they correspond to low-level events
    // which happened before, i.e. typically pending events were queued by a
    // previous call to Dispatch() and if we didn't process them now the next
    // call to it might enqueue them again (as happens with e.g. socket events
    // which would be generated as long as there is input available on socket
    // and this input is only removed from it when pending event handlers are
    // executed)
    if ( wxTheApp )
    {
        wxTheApp->ProcessPendingEvents();

        // One of the pending event handlers could have decided to exit the
        // loop so check for the flag before trying to dispatch more events
        // (which could block indefinitely if no more are coming).
        if ( m_shouldExit )
            return false;
    }

    return Dispatch();
}

int wxEventLoopManual::DoRun()
{
    // we must ensure that OnExit() is called even if an exception is thrown
    // from inside ProcessEvents() but we must call it from Exit() in normal
    // situations because it is supposed to be called synchronously,
    // wxModalEventLoop depends on this (so we can't just use ON_BLOCK_EXIT or
    // something similar here)
#if wxUSE_EXCEPTIONS
    for ( ;; )
    {
        try
        {
#endif // wxUSE_EXCEPTIONS

            // this is the event loop itself
            for ( ;; )
            {
                // give them the possibility to do whatever they want
                OnNextIteration();

                // generate and process idle events for as long as we don't
                // have anything else to do
                while ( !m_shouldExit && !Pending() && ProcessIdle() )
                    ;

                if ( m_shouldExit )
                    break;

                // a message came or no more idle processing to do, dispatch
                // all the pending events and call Dispatch() to wait for the
                // next message
                if ( !ProcessEvents() )
                {
                    // we got WM_QUIT
                    break;
                }
            }

            // Process the remaining queued messages, both at the level of the
            // underlying toolkit level (Pending/Dispatch()) and wx level
            // (Has/ProcessPendingEvents()).
            //
            // We do run the risk of never exiting this loop if pending event
            // handlers endlessly generate new events but they shouldn't do
            // this in a well-behaved program and we shouldn't just discard the
            // events we already have, they might be important.
            for ( ;; )
            {
                bool hasMoreEvents = false;
                if ( wxTheApp && wxTheApp->HasPendingEvents() )
                {
                    wxTheApp->ProcessPendingEvents();
                    hasMoreEvents = true;
                }

                if ( Pending() )
                {
                    Dispatch();
                    hasMoreEvents = true;
                }

                if ( !hasMoreEvents )
                    break;
            }

#if wxUSE_EXCEPTIONS
            // exit the outer loop as well
            break;
        }
        catch ( ... )
        {
            try
            {
                if ( !wxTheApp || !wxTheApp->OnExceptionInMainLoop() )
                {
                    OnExit();
                    break;
                }
                //else: continue running the event loop
            }
            catch ( ... )
            {
                // OnException() throwed, possibly rethrowing the same
                // exception again: very good, but we still need OnExit() to
                // be called
                OnExit();
                throw;
            }
        }
    }
#endif // wxUSE_EXCEPTIONS

    return m_exitcode;
}

void wxEventLoopManual::ScheduleExit(int rc)
{
    wxCHECK_RET( IsInsideRun(), wxT("can't call ScheduleExit() if not running") );

    m_exitcode = rc;
    m_shouldExit = true;

    OnExit();

    // all we have to do to exit from the loop is to (maybe) wake it up so that
    // it can notice that Exit() had been called
    //
    // in particular, do *not* use here calls such as PostQuitMessage() (under
    // MSW) which terminate the current event loop here because we're not sure
    // that it is going to be processed by the correct event loop: it would be
    // possible that another one is started and terminated by mistake if we do
    // this
    WakeUp();
}

#endif // __WINDOWS__ || __WXMAC__ || __WXDFB__