draw2d/draw2dbase/stroker.go

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// Copyright 2010 The draw2d Authors. All rights reserved.
// created: 13/12/2010 by Laurent Le Goff
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package draw2dbase
import (
"math"
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"github.com/llgcode/draw2d"
)
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type LineStroker struct {
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Flattener Flattener
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HalfLineWidth float64
Cap draw2d.LineCap
Join draw2d.LineJoin
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vertices []float64
rewind []float64
x, y, nx, ny float64
}
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func NewLineStroker(c draw2d.LineCap, j draw2d.LineJoin, flattener Flattener) *LineStroker {
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l := new(LineStroker)
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l.Flattener = flattener
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l.HalfLineWidth = 0.5
l.Cap = c
l.Join = j
return l
}
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func (l *LineStroker) MoveTo(x, y float64) {
l.x, l.y = x, y
}
func (l *LineStroker) LineTo(x, y float64) {
l.line(l.x, l.y, x, y)
}
func (l *LineStroker) LineJoin() {
}
func (l *LineStroker) line(x1, y1, x2, y2 float64) {
dx := (x2 - x1)
dy := (y2 - y1)
d := vectorDistance(dx, dy)
if d != 0 {
nx := dy * l.HalfLineWidth / d
ny := -(dx * l.HalfLineWidth / d)
l.appendVertex(x1+nx, y1+ny, x2+nx, y2+ny, x1-nx, y1-ny, x2-nx, y2-ny)
l.x, l.y, l.nx, l.ny = x2, y2, nx, ny
}
}
func (l *LineStroker) Close() {
if len(l.vertices) > 1 {
l.appendVertex(l.vertices[0], l.vertices[1], l.rewind[0], l.rewind[1])
}
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}
func (l *LineStroker) End() {
if len(l.vertices) > 1 {
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l.Flattener.MoveTo(l.vertices[0], l.vertices[1])
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for i, j := 2, 3; j < len(l.vertices); i, j = i+2, j+2 {
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l.Flattener.LineTo(l.vertices[i], l.vertices[j])
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}
}
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for i, j := len(l.rewind)-2, len(l.rewind)-1; j > 0; i, j = i-2, j-2 {
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l.Flattener.LineTo(l.rewind[i], l.rewind[j])
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}
if len(l.vertices) > 1 {
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l.Flattener.LineTo(l.vertices[0], l.vertices[1])
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}
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l.Flattener.End()
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// reinit vertices
l.vertices = l.vertices[0:0]
l.rewind = l.rewind[0:0]
l.x, l.y, l.nx, l.ny = 0, 0, 0, 0
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}
func (l *LineStroker) appendVertex(vertices ...float64) {
s := len(vertices) / 2
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l.vertices = append(l.vertices, vertices[:s]...)
l.rewind = append(l.rewind, vertices[s:]...)
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}
func vectorDistance(dx, dy float64) float64 {
return float64(math.Sqrt(dx*dx + dy*dy))
}