manual/include/pushpull-trimming.html

<p>
  Normally, when trimming 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, when trimming a region
  that directly adjoins another, the desired result is to move the boundary
  between the regions and not to make these regions overlap. This requires trimming both
  regions on either side of the junction, in opposite directions.
  <dfn>Push/Pull trim</dfn>, activated by pressing <kbd class="mod3n"></kbd> key before
  starting the drag, will do just that.
</p>
<p>
  The following pictures show the difference in the results of a normal trim and
  a push/pull trim:
</p>

<figure>
  <img src="/images/before-trim.png" alt="region arrangement before trim" />
  <img src="/images/after-trim.png" alt="region arrangement after a trim" />
  <img src="/images/after-push-trim.png" alt="region arrangement after a push trim" />
  <figcaption>
    Trimming vs. push/pull trimming. Before trimming, After a simple trim, After a push/pull trim
  </figcaption>
</figure>

<p>
  In the initial situation, before trimming, two adjacent regions are present,
  the rightmost-one being selected.
</p>
<p>
  The simple trim, obtained by dragging the selected region's starting position earlier, overlaps
  the earlier region. A crossfade has been manually created between them, so their
  sound will fade from the leftmost region to the rightmost one.
</p>
<p>
  If the same trim is done, but by <kbd class="mod3n"></kbd><kbd class="mouse">Left</kbd>-dragging
  to turn it into a push-pull trim instead, 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. In effect, it is like doing a simple
  trim to reduce the leftmost region, then doing a simple trim to extend the rightmost
  one to fill the gap.
</p>