draw2d/draw2dbase/stroker.go
2015-08-14 22:22:01 +02:00

90 lines
2 KiB
Go

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