This is mostly a simple lexical search+replace but the absence of operator< for
std::weak_ptr<T> leads to some complications, particularly with Evoral::Sequence
and ExportPortChannel.
There already is a shaded coverage frame indicating
if a layer is audible. This leads to a more consistent view.
In addition changing layered mode now has to update the
colors (set_frame_color).
This fixes rendering of opaque MIDI regions (previously
MIDI regions were always transparent). This change provides a
way to "flatten" layered MIDI regions, while still allowing
to show the note-line and grid behind the regions.
In the presence of tempo-changes distinguishing between offsets and
absolute positions is signficant. It is only valid to convert absolute
times using the tempo-map
Furthermore since GUI zoom-factor is time-invariant (samples per pixel),
all GUI operations must explictly use samples (or timecnt). It is not
valid (and problematic) to use use a location dependent timepos.
1. leave tertiary-scroll for navigation and primary scroll for session timeline zoom
2. unmodified scroll in edit mode scrolls contents
3. secondary-scroll zooms in and out on contents (i.e. vertical zoom for MIDI)
4. primary-secondary scroll has the just-one-edge behavior previously provided
This also fixes Menu > Edit Delete "delete MIDI" operation.
Pressing backspace/delete calls "Delete Selection" which is
unrelated to MRV::cut_copy_clear.
Note position in samples must be calculated using absolute position
on the timeline. Otherwise the tempo-map is not applied correctly.
Previously this caused issues since the position was first
offset back by _region->position() - time relative to region left
edge - and then the tempo-map was applied.
Another solution identically would be:
(note_start + session_source_start).samples() - _region->position().samples()
this prevents the case where have enabled snap, and you add a note that
appears to be on a bar line. but actually it is {some Grid value} off,
it just looks right because of pixel rounding.
these functions operate on the _note_diff_command,
which is explicitly a NoteDiff, not a generic DiffCommand
also fix a few thinkos where the ambiguous naming led to errors
