+proc clickisonarrow {id y} {
+ global mainline mainlinearrow sidelines lthickness
+
+ set thresh [expr {2 * $lthickness + 6}]
+ if {[info exists mainline($id)]} {
+ if {$mainlinearrow($id) ne "none"} {
+ if {abs([lindex $mainline($id) 1] - $y) < $thresh} {
+ return "up"
+ }
+ }
+ }
+ if {[info exists sidelines($id)]} {
+ foreach ls $sidelines($id) {
+ set coords [lindex $ls 0]
+ set arrow [lindex $ls 2]
+ if {$arrow eq "first" || $arrow eq "both"} {
+ if {abs([lindex $coords 1] - $y) < $thresh} {
+ return "up"
+ }
+ }
+ if {$arrow eq "last" || $arrow eq "both"} {
+ if {abs([lindex $coords end] - $y) < $thresh} {
+ return "down"
+ }
+ }
+ }
+ }
+ return {}
+}
+
+proc arrowjump {id dirn y} {
+ global mainline sidelines canv
+
+ set yt {}
+ if {$dirn eq "down"} {
+ if {[info exists mainline($id)]} {
+ set y1 [lindex $mainline($id) 1]
+ if {$y1 > $y} {
+ set yt $y1
+ }
+ }
+ if {[info exists sidelines($id)]} {
+ foreach ls $sidelines($id) {
+ set y1 [lindex $ls 0 1]
+ if {$y1 > $y && ($yt eq {} || $y1 < $yt)} {
+ set yt $y1
+ }
+ }
+ }
+ } else {
+ if {[info exists sidelines($id)]} {
+ foreach ls $sidelines($id) {
+ set y1 [lindex $ls 0 end]
+ if {$y1 < $y && ($yt eq {} || $y1 > $yt)} {
+ set yt $y1
+ }
+ }
+ }
+ }
+ if {$yt eq {}} return
+ set ymax [lindex [$canv cget -scrollregion] 3]
+ if {$ymax eq {} || $ymax <= 0} return
+ set view [$canv yview]
+ set yspan [expr {[lindex $view 1] - [lindex $view 0]}]
+ set yfrac [expr {$yt / $ymax - $yspan / 2}]
+ if {$yfrac < 0} {
+ set yfrac 0
+ }
+ $canv yview moveto $yfrac
+}
+