# macros for chem
#
# Copyright 2006-2020 Free Software Foundation, Inc.
#
# Written by Brian Kernighan <http://cm.bell-labs.com/cm/cs/who/bwk>,
# modified by Bernd Warken <groff-bernd.warken-72@web.de>.
#
# This file is part of chem.
#
# chem is distributed with groff, the GNU roff typesetting system.
#
# groff is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free
# Software Foundation, either version 3 of the License, or (at your
# option) any later version.
#
# groff is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
# for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

########################################################################

pi = 3.141592654
deg = 57.29578
# cr = 0.08		# radius of invis circle at ring vertices (see cr[vh])
# crh = 0.16; crw = 0.12 # ht & wid of invis ellipse around atoms at ring vertices
# dav = 0.015		# vertical shift up for atoms in atom macro

# atom(text, wid, ht, carbon position, crh, crw, dav)
define atom { [
	T: $1 wid $2 ht $3-2*$7
	C: ellipse invis ht $5 wid $6 at T.w + ($4,$7)
	L: ellipse invis ht $5 wid $6 at T.w + (cwid/2,$7)
	R: ellipse invis ht $5 wid $6 at T.e + (-cwid/2,$7)
] }

# bond(length, angle in degrees, whatever)
define bond {
	line $3 by ($1) * sin(($2)/deg), ($1) * cos(($2)/deg)
}

# fancy bonds:  r, theta, from/at
define doublebond {
	line $3 invis by ($1) * sin(($2)/deg), ($1) * cos(($2)/deg)
	V1: last line.start; V2: last line.end; dx = V2.x-V1.x; dy = V2.y-V1.y
	norm = sqrt(dx*dx + dy*dy)
	ny = dx * .02 / norm
	nx = -dy * .02 / norm
	line from V1 + (nx,ny) to V2 + (nx,ny)
	line from V1 - (nx,ny) to V2 - (nx,ny)
	move to V2
}
define triplebond {
	line $3 invis by ($1) * sin(($2)/deg), ($1) * cos(($2)/deg)
	V1: last line.start; V2: last line.end; dx = V2.x-V1.x; dy = V2.y-V1.y
	norm = sqrt(dx*dx + dy*dy)
	ny = dx * .025 / norm
	nx = -dy * .025 / norm
	line from V1 + (nx,ny) to V2 + (nx,ny)
	line from V1 - (nx,ny) to V2 - (nx,ny)
	line from V1 to V2
	move to V2
}
define backbond {
	line $3 invis by ($1) * sin(($2)/deg), ($1) * cos(($2)/deg)
	V1: last line.start; V2: last line.end; dx = V2.x-V1.x; dy = V2.y-V1.y
	norm = sqrt(dx*dx + dy*dy)
	n = norm / .025
	ny = dx * .02 / norm
	nx = -dy * .02 / norm
	for i = 1 to n-1 do {
		XZ: i/n <V1,V2>
		line from XZ + (nx,ny) to XZ - (nx,ny)
	}
	move to V2
}
define frontbond {
	line $3 invis by ($1) * sin(($2)/deg), ($1) * cos(($2)/deg)
	V1: last line.start; V2: last line.end; dx = V2.x-V1.x; dy = V2.y-V1.y
	ah = arrowht; aw = arrowwid; ahead = arrowhead
	arrowht = sqrt(dx*dx + dy*dy)
	arrowwid = 0.05
	arrowhead = 7
	line <- from V1 to V2
	arrowht = ah; arrowwid = aw; arrowhead = ahead
}
# Local Variables:
# mode: Nroff
# End: