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JAWS fix?: Now do the delay of event handling...

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... Queue, don't immediately process, TrackList events, and if listeners want
to hold pointers to tracks, let them use weak_ptr or shared_ptr
This commit is contained in:
Paul Licameli 2017-06-25 03:09:04 -04:00
parent fb18f6a812
commit d3c9a1decb
3 changed files with 17 additions and 18 deletions
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22
src/Track.cpp
View File

@ -857,19 +857,18 @@ void TrackList::RecalcPositions(TrackNodePointer node)
void TrackList::DeletionEvent()
{
wxCommandEvent e(EVT_TRACKLIST_DELETION);
// PRL: ProcessEvent, not QueueEvent! Listeners may need their last
// chance to examine some removed tracks that are about to be destroyed.
ProcessEvent(e);
auto e = std::make_unique<wxCommandEvent>(EVT_TRACKLIST_DELETION);
// wxWidgets will own the event object
QueueEvent(e.release());
}
void TrackList::ResizingEvent(TrackNodePointer node)
{
wxCommandEvent e(EVT_TRACKLIST_RESIZING);
auto e = std::make_unique<wxCommandEvent>(EVT_TRACKLIST_RESIZING);
if (!isNull(node))
e.SetClientData(node->get());
ProcessEvent(e);
e->SetClientData(node->get());
// wxWidgets will own the event object
QueueEvent(e.release());
}
void TrackList::Permute(const std::vector<TrackNodePointer> &permutation)
@ -951,8 +950,6 @@ auto TrackList::Replace(Track * t, value_type &&with) -> value_type
pTrack->SetOwner(this, node);
RecalcPositions(node);
// PRL: Note: Send the event while t (now in holder) is not yet
// destroyed, so pointers to t that listeners may have are not dangling.
DeletionEvent();
ResizingEvent(node);
}
@ -974,8 +971,6 @@ TrackNodePointer TrackList::Remove(Track *t)
RecalcPositions(result);
}
// PRL: Note: Send the event while t (now in holder) is not yet
// destroyed, so pointers to t that listeners may have are not dangling.
DeletionEvent();
}
}
@ -987,9 +982,6 @@ void TrackList::Clear(bool sendEvent)
ListOfTracks tempList;
tempList.swap( *this );
if (sendEvent)
// PRL: Note: Send the event while tempList is not yet
// destroyed, so pointers to tracks that listeners may have are not
// dangling.
DeletionEvent();
}

3
src/Track.h
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@ -489,9 +489,6 @@ DECLARE_EXPORTED_EVENT_TYPE(AUDACITY_DLL_API, EVT_TRACKLIST_RESIZING, -1);
// Posted when a track has been deleted from a tracklist.
// Also posted when one track replaces another
// When a track has been removed, the event is processed before the track
// is destroyed, so that listeners that stored a pointer to the track can still
// use it and correctly check whether the list still contains it.
DECLARE_EXPORTED_EVENT_TYPE(AUDACITY_DLL_API, EVT_TRACKLIST_DELETION, -1);
class TrackList final : public wxEvtHandler, public ListOfTracks

10
src/TrackPanel.cpp
View File

@ -2534,6 +2534,16 @@ wxRect TrackPanel::FindTrackRect( const Track * target, bool label )
target->GetHeight()
};
// PRL: I think the following very old comment misused the term "race
// condition" for a bug that happened with only a single thread. I think the
// real problem referred to, was that this function could be reached, via
// TrackPanelAx callbacks, during low-level operations while the TrackList
// was not in a consistent state. Therefore GetLinked() did not imply
// that GetLink() was not null.
// Now the problem is fixed by delaying the handling of events generated
// by TrackList.
// Old comment:
// The check for a null linked track is necessary because there's
// a possible race condition between the time the 2 linked tracks
// are added and when wxAccessible methods are called. This is