From 5dd72acc027728d0c70f8358f8f4abdfd71fa04a Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Sat, 4 Nov 2017 13:33:11 -0400
Subject: [PATCH] Bug1770: fix crash applying chains

---
 src/Track.cpp      |  5 ++---
 src/Track.h        | 14 +++++++++++++-
 src/TrackPanel.cpp |  4 ++--
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/src/Track.cpp b/src/Track.cpp
index e30563164..fad10ed10 100644
--- a/src/Track.cpp
+++ b/src/Track.cpp
@@ -882,9 +882,8 @@ void TrackList::DeletionEvent()
 
 void TrackList::ResizingEvent(TrackNodePointer node)
 {
-   auto e = std::make_unique<wxCommandEvent>(EVT_TRACKLIST_RESIZING);
-   if (!isNull(node))
-      e->SetClientData(node->get());
+   auto e = std::make_unique<TrackListEvent>(EVT_TRACKLIST_RESIZING);
+   e->mpTrack = *node;
    // wxWidgets will own the event object
    QueueEvent(e.release());
 }
diff --git a/src/Track.h b/src/Track.h
index f8459db35..7cbe04d0b 100644
--- a/src/Track.h
+++ b/src/Track.h
@@ -518,11 +518,23 @@ class AUDACITY_DLL_API SyncLockedTracksIterator final : public TrackListIterator
  * Clear, and Contains, plus serialization of the list of tracks.
  */
 
+struct TrackListEvent : public wxCommandEvent
+{
+   TrackListEvent(wxEventType commandType = wxEVT_NULL, int winid = 0)
+   : wxCommandEvent{ commandType, winid } {}
+
+   TrackListEvent( const TrackListEvent& ) = default;
+
+   wxEvent *Clone() const override { return new TrackListEvent(*this); }
+
+   std::weak_ptr<Track> mpTrack;
+};
+
 // Posted when tracks are reordered but otherwise unchanged.
 DECLARE_EXPORTED_EVENT_TYPE(AUDACITY_DLL_API, EVT_TRACKLIST_PERMUTED, -1);
 
 // Posted when some track was added or changed its height.
-// The wxCommandEvent::GetClientData() method can be used to retrieve it.
+// Cast to TrackListEvent and examine mpTrack to retrieve it.
 DECLARE_EXPORTED_EVENT_TYPE(AUDACITY_DLL_API, EVT_TRACKLIST_RESIZING, -1);
 
 // Posted when a track has been deleted from a tracklist.
diff --git a/src/TrackPanel.cpp b/src/TrackPanel.cpp
index 1916897d0..680a07c46 100644
--- a/src/TrackPanel.cpp
+++ b/src/TrackPanel.cpp
@@ -1158,10 +1158,10 @@ void TrackPanel::OnPlayback(wxCommandEvent &e)
 // ruler size for the track that triggered the event.
 void TrackPanel::OnTrackListResizing(wxCommandEvent & e)
 {
-   Track *t = (Track *) e.GetClientData();
+   auto t = static_cast<TrackListEvent&>(e).mpTrack.lock();
    // A deleted track can trigger the event.  In which case do nothing here.
    if( t )
-      UpdateVRuler(t);
+      UpdateVRuler(t.get());
    e.Skip();
 }