# NOT RUN {
x <- quadGrob(c(.2, .5, .8), c(.2, .8, .2),
stepFn=function(...) seq(0, 1, length.out=10))
grid.draw(x)
pts <- quadPoints(x)
grid.circle(pts$x, pts$y, default.units="in", r=unit(.5, "mm"),
gp=gpar(fill="black"))
tan <- quadTangent(x)
grid.segments(pts$x, pts$y, pts$x + tan$x, pts$y + tan$y,
default.units="in", gp=gpar(col="green"))
norm <- quadNormal(x)
grid.segments(pts$x, pts$y, pts$x + norm$x, pts$y + norm$y,
default.units="in", gp=gpar(col="red"))
# }
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