manual/include/pushpull-trimming.html

<p>
  Normally, when you trim regions by dragging with the mouse, it affects
  only the selected regions. Their lengths are directly affected by the
  trim operation, but nothing else is. Sometimes though, you might like
  to trim a region that directly adjoins another, and keep this relationship
  the same&mdash;you are not trying to make one of the regions extend
  over the other&mdash;you would like the junction to move in one
  direction or the other as part of the trim. This requires trimming both
  regions on either side of the junction, in opposite directions.
  <dfn>Push/Pull trim</dfn>, activated by pressing shift key before
  starting the drag, will do just that. Here's a few pictures to show the
  difference in the results of a normal trim and push/pull trim. First,
  the initial situation:
</p>
<img src="/images/a3_before_trim.png" alt="region arrangement before trim" />
<p>
  Here is what happens after we trim the right hand (selected) region by
  dragging its starting position earlier:
</p>
<img src="/images/a3_after_trim.png" alt="region arrangement after a trim" />
<p>
  You can see that it now overlaps the earlier region and a crossfade has
  been created between them.
</p>
<p>
  Lets look now at what happens if we do the same trim, but <kbd
  class="mouse mod3">Left</kbd>-dragging to turn it into a push-pull trim instead:
</p>
<img src="/images/a3_after_push_trim.png" alt="region arrangement after a push trim" />
<p>
  There is no overlap, and the end of the earlier region has been moved
  along with the start of the later region, so that they still directly
  adjoin each other.
</p>