RosettaCodeData/Task/Bitmap-Bresenhams-line-algo.../Ring/bitmap-bresenhams-line-algo...

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load "guilib.ring"
load "stdlib.ring"
new qapp
{
win1 = new qwidget() {
setwindowtitle("drawing using qpainter")
setwinicon(self,"c:\ring\bin\image\browser.png")
setgeometry(100,100,500,600)
label1 = new qlabel(win1) {
setgeometry(10,10,400,400)
settext("")
}
new qpushbutton(win1) {
setgeometry(200,400,100,30)
settext("draw")
setclickevent("draw()")
}
show()
}
exec()
}
func draw
p1 = new qpicture()
color = new qcolor() {
setrgb(0,0,255,255)
}
pen = new qpen() {
setcolor(color)
setwidth(1)
}
new qpainter() {
begin(p1)
setpen(pen)
line = [[50,100,100,190], [100,190,150,100], [150,100,100,10], [100,10,50,100]]
for n = 1 to 4
x1=line[n][1] y1=line[n][2] x2=line[n][3] y2=line[n][4]
dx = fabs(x2 - x1) sx = sign(x2 - x1)
dy = fabs(y2 - y1) sy = sign(y2 - y1)
if dx < dy e = dx / 2 else e = dy / 2 ok
while true
drawline (x1*2,y1*2,x2*2,y2*2)
if x1 = x2 if y1 = y2 exit ok ok
if dx > dy
x1 += sx e -= dy if e < 0 e += dx y1 += sy ok
else
y1 += sy e -= dx if e < 0 e += dy x1 += sx ok ok
end
next
endpaint()
}
label1 { setpicture(p1) show() }