The length of the sample line can be controlled by samplen. The sample
length is computed as the sum of the tic length and sample_length
times the
character width. It also affects the positions of point samples in the key
since these are drawn at the midpoint of the sample line, even if the line
itself is not drawn.
Key entry lines are single-spaced based on the current font size.
This can be adjusted by set key spacing line-spacing
.
The width_increment
is a number of character widths to be added to or
subtracted from the length of the string. This is useful only when you are
putting a box around the key and you are using control characters in the text.
gnuplot simply counts the number of characters in the string when computing
the box width; this allows you to correct it.