go-chart/drawing/stroker.go
2016-07-08 17:57:14 -07:00

86 lines
2.2 KiB
Go

// Copyright 2010 The draw2d Authors. All rights reserved.
// created: 13/12/2010 by Laurent Le Goff
package drawing
// NewLineStroker creates a new line stroker.
func NewLineStroker(c LineCap, j LineJoin, flattener Flattener) *LineStroker {
l := new(LineStroker)
l.Flattener = flattener
l.HalfLineWidth = 0.5
l.Cap = c
l.Join = j
return l
}
// LineStroker draws the stroke portion of a line.
type LineStroker struct {
Flattener Flattener
HalfLineWidth float64
Cap LineCap
Join LineJoin
vertices []float64
rewind []float64
x, y, nx, ny float64
}
// MoveTo implements the path builder interface.
func (l *LineStroker) MoveTo(x, y float64) {
l.x, l.y = x, y
}
// LineTo implements the path builder interface.
func (l *LineStroker) LineTo(x, y float64) {
l.line(l.x, l.y, x, y)
}
// LineJoin implements the path builder interface.
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
}
}
// Close implements the path builder interface.
func (l *LineStroker) Close() {
if len(l.vertices) > 1 {
l.appendVertex(l.vertices[0], l.vertices[1], l.rewind[0], l.rewind[1])
}
}
// End implements the path builder interface.
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:]...)
}