### arrowline.py -- arrow-headed lines for reportlab.pdfgen
#
# This uses getLineWidth(), getFillColor() and getStrokeColor(),
# which aren't in the standard pdfgen (yet anyway).  The easiest way
# to do without would be to 
#     send the line width in as a parameter
#     set the fill color before calling
#
# Sorry I'm too lazy to convert this to standalone myself.
#
# Steve Witham ess doubleyou at tiac remove-this dot net.
# http://www.tiac.net/~sw

from reportlab.pdfgen import canvas

from math import sin, cos, pi, sqrt, atan2


def arrowLine( a_canvas, x0, y0, x1, y1, tail=False, head=True, 
               angle=22.5, width=4 ):
    w = a_canvas.getLineWidth()
    dx, dy  =  x1-x0, y1-y0
    d = sqrt( dx*dx + dy*dy )
    if d == 0:  return

    dx, dy  =  dx/d, dy/d
    sc, fc  =  a_canvas.getStrokeColor(), a_canvas.getFillColor()
    if fc != sc:  a_canvas.setFillColor( sc )
    if head:  x1, y1  =  arrowHead( a_canvas, x1, y1, dx, dy, angle, width )
    if tail:  x0, y0  =  arrowHead( a_canvas, x0, y0, -dx, -dy, angle, width )
    if fc != sc:  a_canvas.setFillColor( fc )
    a_canvas.line( x0, y0, x1, y1 )
    

def arrowHead( a_canvas, x, y, dx, dy, wedgeAngle, width ):
    # lineWidth * width = width across the back end of the arrowhead.
    wa = wedgeAngle * pi / 180.0
    s, c  =  sin( wa ), cos( wa )
    lineAngle = atan2( dy, dx ) * 180 / pi
    r = a_canvas.getLineWidth() * width / ( 2 * s )
    a_canvas.wedge( x-r, y-r, x+r, y+r, 
                    lineAngle+180-wedgeAngle, wedgeAngle*2, fill=1, stroke=0 )
    return x - dx * r * c, y - dy * r * c