The track-header (gtk) is packed with 1px box spacing. This
is added at the top of each box (best seen by looking at the
group-tab vs track-header alignment in the editor).
However the actual track separator line on the canvas is at the
bottom of each track, aligning with the top of the next track
or automation-lane.
The first track however lacks a separator at the top, which
needs to be provided by the ruler. Once the canvas is scrolled
this ruler/canvas separator overlaps with the bottom separator of
each TAV.
Using ruler Rectangle::set_outline had various issues.
The outline extends outside the rectangle. It bled into the
video-timeline instead of the canvas' top y-axis pixel.
Also the separator was above the video-timeline, not above the
canvas. Hence a dedicated separator Line is preferable.
It also provides a consistent separator if no rulers are visible.
Before nutempo, ::find_next_region_boundary() used to return -1
when no boundary was found (now timepos_t::max is returned).
timepos_t::increment() returns the incremented value, not increments
the variable itself.
When a tempo map change originates from a drag, we know the required redraws have
already been done. Use a new bool member, ignore_map_change, to tell the Editor
to ignore the map change signal. For all other map changes, do the full reset.
We now simply move markers during drags, and do not seek to create/delete markers.
When the map is changed, we rebuild the markers from scratch. This might need optimization to avoid doing
when the editor itself changed the map.
Previously it was possible that the tempo-curve display was rendered
above a tempo-marker (e.g. create a marker in the between of existing
markers). With the tempo-curve in front, markers on the right
became inaccessible.
Code used to just push back new markers to the end of the relevant list, and
this would then the new marker to be deleted soon thereafter. Instead pass
an interator indicating where to place the marker in the list.
Note that we rely on the use of std::list<T> here to keep the iterator to the
existing marker valid.
This used to be a distinct kind of drag, but ended up being refactored into
something that happens during a regular drag. Has not been used in quite some time.
We need to delete all existing region views before we redisplay the track. This
was removed as part of an "experimental performance optimization" in 4f7a4cd233
but playlist switching is a rare and non-performance limited operation
