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# A small demonstration: drawing chemical structures
#
# NOTE: needs fixing!
#
package require Tk
source ./draw_diagram.tcl
#package require Diagrams
namespace import ::Diagrams::*
pack [canvas .c -width 400 -height 130 -bg white]
#console show
drawin .c
proc ring {} {
set side 20
line $side 60 $side 0 $side -60 $side -120 $side 180 $side 120
}
proc benzene {} {
set item [ring]
foreach {x1 y1 x2 y2} [lindex $item 2] {break}
$::Diagrams::state(canvas) create oval \
[expr {($x1+$x2)/2-12}] [expr {($y1+$y2)/2+12}] \
[expr {($x1+$x2)/2+12}] [expr {($y1+$y2)/2-12}]
return $item
}
proc bond { {angle 0} {item {}} } {
set side 20
set anchor E
switch -- $angle {
"0" { direction E ; set anchor E }
"60" { direction NE ; set anchor NE }
"90" { direction N ; set anchor N }
"120" { direction NW ; set anchor NW }
"180" { direction W ; set anchor W }
"240" { direction SW ; set anchor SW }
"-90" -
"270" { direction S ; set anchor S }
"-60" -
"300" { direction SE ; set anchor SE }
}
if { $item != {} } {
currentpos [getpos $anchor $item]
}
line $side $angle
}
#
# Very primitive chemical formula
# -- order of direction/currentpos important!
#
direction east
currentpos [position 40 60]
benzene; bond;
set Catom [plaintext C]
bond 90 $Catom
direction north
plaintext C
direction east
plaintext OOH
bond -90 $Catom
direction south
plaintext H
bond 0 $Catom
direction east
benzene
bond; direction east
plaintext NH2 ;# UNICODE \u2082 is subscript 2, but that is not
# supported in PostScript
#saveps chemical.eps
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