The platform has no support for libdispatch which is handy when setting up an objective C block,
and also has no Retina, which means it doesn't suffer the problem this code is intended to fix
Ignore latency-updates while removing tracks.
remove_tracks() calls disconnect_all() which can trigger the backend
to perform a latency-recompute in a different thread (process thread).
That calls Session::update_latency() which iterates over all routes
including the one(s) to be deleted.
At the same time disconnect_all() may propagate Port::PostDisconnect()
leading to a lock contention.
(no crash just a lot of unnecessary work. remove_routes() calls
update_latency_compensation() which triggers a recompute if needed)
This prevents an extra call to "redisplay" from TAV::hide() which
triggers handle_gui_changes.
Visible TAVs are positioned using show_at() which unsets _hidden.
For every added Trackview/Mixerstrip, Ardour looks up GUI properties which
results in a total of 13 calls for the initial default items per track:
("height", "visible", "layer-display", "strip-width")
Since the tracks don't yet exist, the properties don't either.
Every lookup result in iterating over all all XMLNotes and for every
"Object". ->property ("id") and ->value () allocates memory.
Adding 64 tracks to an empty session results in 528293 string
allocations and deallocations in XMLNode::property() taking ~30%
of the track creation time.
This commit XMLnode's const method to prevent memory allocation
and caches a pointer to the XMLNode* to skip iterating over object
state.
