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Reimplement Track::Pointer using std::enable_shared_from_this...

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... now the Track need not be owned yet by a TrackList
This commit is contained in:
Paul Licameli
2018-11-18 20:50:24 -05:00
parent 3dba70120c
commit 6f89c48873
19 changed files with 74 additions and 73 deletions
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37
src/Track.h
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@@ -190,6 +190,7 @@ private:
class AUDACITY_DLL_API Track /* not final */
: public CommonTrackPanelCell, public XMLTagHandler
, public std::enable_shared_from_this<Track> // see SharedPointer()
{
friend class TrackList;
@@ -227,31 +228,29 @@ class AUDACITY_DLL_API Track /* not final */
void SetId( TrackId id ) { mId = id; }
public:
// Given a bare pointer, find a shared_ptr. But this is not possible for
// a track not owned by any project, so the result can be null.
// Given a bare pointer, find a shared_ptr. Undefined results if the track
// is not yet managed by a shared_ptr. Undefined results if the track is
// not really of the subclass. (That is, trusts the caller and uses static
// not dynamic casting.)
template<typename Subclass = Track>
inline static std::shared_ptr<Subclass> Pointer( Track *t )
inline std::shared_ptr<Subclass> SharedPointer()
{
if (t) {
auto pList = t->mList.lock();
if (pList)
return std::static_pointer_cast<Subclass>(*t->mNode.first);
}
return {};
// shared_from_this is injected into class scope by base class
// std::enable_shared_from_this<Track>
if (!this) return {};
return std::static_pointer_cast<Subclass>( shared_from_this() );
}
template<typename Subclass = const Track>
inline static std::shared_ptr<Subclass> Pointer( const Track *t )
inline auto SharedPointer() const -> typename
std::enable_if<
std::is_const<Subclass>::value, std::shared_ptr<Subclass>
>::type
{
if (t) {
auto pList = t->mList.lock();
if (pList) {
std::shared_ptr<const Track> p{ *t->mNode.first };
// Let you change the type, but not cast away the const
return std::static_pointer_cast<Subclass>(p);
}
}
return {};
// shared_from_this is injected into class scope by base class
// std::enable_shared_from_this<Track>
if (!this) return {};
return std::static_pointer_cast<Subclass>( shared_from_this() );
}
// Find anything registered with TrackList::RegisterPendingChangedTrack and