[RQt-devel] segment glyph

[Yihui Xie]

Hi,

I want to define a glyph which is a short segment as follows, but when
the slope b=0, the glyph looks weird on screen (it is a filled
square); other slopes are fine. I don't know what's going on:

library(qtpaint)
## x: length; b: slope
qglyphSegment <- function(x = 5, b = 0) {
  glyph <- Qt$QPainterPath()
  x0 <- x * cos(atan(b))
  y0 <- x * sin(atan(b))
  glyph$moveTo(-x0, -y0)
  glyph$lineTo(x0, y0)
#  glyph$closeSubpath()
  glyph
}

s <- qscene()
test_layer <- qlayer(s, function(layer, painter) {
    qdrawGlyph(painter, qglyphSegment(), 1:10, .5, stroke = 'black')
    qdrawGlyph(painter, qglyphSegment(10, 1), 1:10, .7, stroke = 'black')
    qdrawGlyph(painter, qglyphSegment(10, -1), 1:10, .3, stroke = 'black')
}, limits=qrect(0,0,11,1))
qplotView(s)
## see the screenshot attached


Thanks!

Regards,
Yihui
--
Yihui Xie <xieyihui at gmail.com>
Phone: 515-294-2465 Web: http://yihui.name
Department of Statistics, Iowa State University
2215 Snedecor Hall, Ames, IA
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