<b>Cursors</b>

Cursors read values off the traces. There are two kinds: one <i>shared vertical pair</i> that
every row carries at the same time, and <i>horizontal rulers</i>, one pair per row, that belong
to that row alone.

<b>How to reach it</b>

The cursors button in the toolbar, or <tt>c</tt>. The pane below the plot shows the readings and
owns a <b>Reset</b> button. Drag a marker to move it. The mode dropdown offers four modes:
<tt>vertical</tt> (the shared time pair), <tt>horizontal</tt> (the per-row rulers),
<tt>both</tt>, and <tt>mix</tt>.

<b>Worth knowing</b>

• The vertical pair is <i>one</i> time for the whole figure, so moving it on any row moves it on
  all of them. That is what makes <tt>dt</tt> meaningful across rows.
• A ruler belongs to its row and nothing shares it, so two rows' rulers are independent.
• <tt>mix</tt> is the reading mode: one line per <i>bound</i> trace, with the trace's own values
  at each marker and their difference. A slot with a name but no channel behind it is not a
  trace and gets no line.
• A marker past the newest sample reads <tt>--</tt>. With only one marker over data the row
  reads <tt>partial</tt>: a difference between a number and nothing is not a number.
• In <tt>mix</tt> each marker also places a crossing annotation per trace, which is what lets
  you see on the plot which sample a number came from.
• The time row exists only in the modes that show the vertical pair. <tt>horizontal</tt> has no
  time row, by design.

<b>Example</b>

Three traces in <tt>mix</tt> mode with both markers over data: 3 lines and 6 crossing marks,
each line reading like <tt>sine  0.31 V  -0.84 V  -1.15 V</tt>. Move the second marker past the
newest sample and the third column reads <tt>--</tt>.
