On tracks the bottom row of each mixer-strip has three buttons.
Two are provided by the gain-meter (automation, meter-point),
and the size of those is set in GainMeterBase (current 15x15px).
The track-group button size was left unspecified.
The master-bus only has the gain-meter buttons, and hence was
less tall compared to tracks.
On GLIBC systems pbd_stack_size() adds __pthread_get_minstack,
this is no available on mac systems, causing issues with some
libraries used by plugins.
In some rare cases the butler may be busy for a long time
(e.g. seek in a large session may still be active when
export is started).
8 second timeout seems reasonable to prevent the app from hanging
without desktops showing a "unresponsive" popup in case the
timeout is reached for some reason (e.g the engine dies, and
no TFSM transition can happen).
Previously the bindings were given to the Region/* equivalents and made insensitive if there was no selected region.
Given that we have specific actions for nudge-playhead-*, and the ones in Region/ will always work on regions
if there are any selected regions, this provides a better set of possible actions, even if the naming is not
totally consistent.
At present only audio data from disk readers is declicked. MIDI tracks with audio output should
likely also be declicked, at which time Session::need_declick_before_locate() will require
amending
previously this subscription was handle done in
Route::add_routes() -> add_routes_inner() for MIDI tracks only.
Since f6c0b02d9f this was only done when adding
tracks, after any instruments were loaded (and fanned out).
This consolidates instrument creation for midi tracks & routes.
If an instrument is added, output auto-connect is postponed until
after the instrument plugin is added. Also when a multi-channel
instrument is fanned-out, the track outputs are not auto-connected.
This also subscribes MIDI-Busses to auto-connect when an instrument
is loaded or replaced at a later time.
Since fan-out happens (interactively) in the GUI thread,
we need to keep track of this, in order to prevent later
auto-connection of the track to the master-bus.
