#24 new pen direction "pairwise"

[Christian Nassau]

The attached patch to bltGrLine.c (from blt2.4z) allows
to set the trace option of a line element to the new
value "pairwise"; with this trace value, lines will
only be drawn between points numbered 2n-1 and 2n.

Here's a sample file that uses this new option:

# illustration for the suggested "pairwise" patch
package require BLT

blt::graph .g
pack .g -expand 1 -fill both

set b {0 0 0 4 0 2 2 3 2 3 0 4 0 0 2 1 2 1 0 2}
set l {3 0 3 4 3 0 6 0}
set t {7.5 0 7.5 4 6 4 9 4}

# randomize a bit:
foreach x [concat $b $l $t] {
lappend dt [expr $x + 0.3 * rand()]
}

.g element create blt -data $dt -trace pairwise

[Christian Nassau]

patch to bltGrLine.c from blt2.4z