[Audacity-quality] Time track copy-paste and aup3 import

[Paul L. <pau...@gm...>]

James, please review these details.  Peter, maybe generate some bug issues.

How does copy and paste of time track work, and how should it?

Short answer:  you can copy and paste time track points, even into a
project with an existing time track, though not all the behavior is
intuitive.

Question:  If you import an .aup3 project with a time track, should that do
the same as paste (pasting at time 0 and shifting other control points
right), or should it replace the old time track with a new one (but maybe
losing some of your data)?  James argues for the second solution, I'm not
sure I agree.

We need agreement on that to commit simplified code for aup3 import,
reducing the amount of sqlite3 calls we need to maintain.

Details.


   1. Make new project with a time track and some control points, and some
   generated sound
   2. Select all Ctrl + A
   3. Select time track and deselect wave track with Ctrl + click
   4. Try to copy - dialog box tells you to select some audio

That has been so at least since 2.3.1:  You can't copy if only time track
is selected.

But, if time track is selected and another track -- then is it copied to
clipboard?  Since at least 2.3.1, yes, because then pasting into another
project makes a time track.  So a time track IS copyable.

But in 2.3.1, the time track points were lost.  2.3.2 changed that.  Time
track points may be inserted into a time track that already exists and has
other points.  There may be discontinuities at the edges of the paste,
arguably correct or not.

I also notice that if you have cut time & wave tracks, then paste into a
new project with only a time track -- then, whether the wave track pastes
or not, depends whether the time track is selected or not.  If it was, I
only paste time track.  Undo, click background, paste -- then both paste.