draw2d/path.go

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2015-04-27 10:14:34 +00:00
// Copyright 2010 The draw2d Authors. All rights reserved.
// created: 21/11/2010 by Laurent Le Goff
// Package path implements function to build path
package draw2d
2015-04-27 10:14:34 +00:00
import (
"fmt"
"math"
)
// PathBuilder define method that create path
type PathBuilder interface {
// Return the current point of the current path
LastPoint() (x, y float64)
// MoveTo start a new path at (x, y) position
MoveTo(x, y float64)
// LineTo add a line to the current path
LineTo(x, y float64)
// QuadCurveTo add a quadratic curve to the current path
QuadCurveTo(cx, cy, x, y float64)
// CubicCurveTo add a cubic bezier curve to the current path
CubicCurveTo(cx1, cy1, cx2, cy2, x, y float64)
// ArcTo add an arc to the path
ArcTo(cx, cy, rx, ry, startAngle, angle float64)
// Close the current path
Close()
}
// Component represent components of a path
type Component int
const (
MoveToCmp Component = iota
LineToCmp
QuadCurveToCmp
CubicCurveToCmp
ArcToCmp
CloseCmp
)
// Type Path store path
type Path struct {
Components []Component
Points []float64
x, y float64
}
func (p *Path) Clear() {
p.Components = p.Components[0:0]
p.Points = p.Points[0:0]
return
}
func (p *Path) appendToPath(cmd Component, points ...float64) {
p.Components = append(p.Components, cmd)
p.Points = append(p.Points, points...)
}
// Copy make a clone of the current path and return it
func (src *Path) Copy() (dest *Path) {
dest = new(Path)
dest.Components = make([]Component, len(src.Components))
copy(dest.Components, src.Components)
dest.Points = make([]float64, len(src.Points))
copy(dest.Points, src.Points)
dest.x, dest.y = src.x, src.y
return dest
}
func (p *Path) LastPoint() (x, y float64) {
return p.x, p.y
}
func (p *Path) IsEmpty() bool {
return len(p.Components) == 0
}
func (p *Path) Close() {
p.appendToPath(CloseCmp)
}
func (p *Path) MoveTo(x, y float64) {
p.appendToPath(MoveToCmp, x, y)
p.x = x
p.y = y
}
func (p *Path) LineTo(x, y float64) {
if len(p.Components) == 0 { //special case when no move has been done
p.MoveTo(0, 0)
}
p.appendToPath(LineToCmp, x, y)
p.x = x
p.y = y
}
func (p *Path) QuadCurveTo(cx, cy, x, y float64) {
if len(p.Components) == 0 { //special case when no move has been done
p.MoveTo(0, 0)
}
p.appendToPath(QuadCurveToCmp, cx, cy, x, y)
p.x = x
p.y = y
}
func (p *Path) CubicCurveTo(cx1, cy1, cx2, cy2, x, y float64) {
if len(p.Components) == 0 { //special case when no move has been done
p.MoveTo(0, 0)
}
p.appendToPath(CubicCurveToCmp, cx1, cy1, cx2, cy2, x, y)
p.x = x
p.y = y
}
func (p *Path) ArcTo(cx, cy, rx, ry, startAngle, angle float64) {
endAngle := startAngle + angle
clockWise := true
if angle < 0 {
clockWise = false
}
// normalize
if clockWise {
for endAngle < startAngle {
endAngle += math.Pi * 2.0
}
} else {
for startAngle < endAngle {
startAngle += math.Pi * 2.0
}
}
startX := cx + math.Cos(startAngle)*rx
startY := cy + math.Sin(startAngle)*ry
if len(p.Components) > 0 {
p.LineTo(startX, startY)
} else {
p.MoveTo(startX, startY)
}
p.appendToPath(ArcToCmp, cx, cy, rx, ry, startAngle, angle)
p.x = cx + math.Cos(endAngle)*rx
p.y = cy + math.Sin(endAngle)*ry
}
func (p *Path) String() string {
s := ""
j := 0
for _, cmd := range p.Components {
switch cmd {
case MoveToCmp:
s += fmt.Sprintf("MoveTo: %f, %f\n", p.Points[j], p.Points[j+1])
j = j + 2
case LineToCmp:
s += fmt.Sprintf("LineTo: %f, %f\n", p.Points[j], p.Points[j+1])
j = j + 2
case QuadCurveToCmp:
s += fmt.Sprintf("QuadCurveTo: %f, %f, %f, %f\n", p.Points[j], p.Points[j+1], p.Points[j+2], p.Points[j+3])
j = j + 4
case CubicCurveToCmp:
s += fmt.Sprintf("CubicCurveTo: %f, %f, %f, %f, %f, %f\n", p.Points[j], p.Points[j+1], p.Points[j+2], p.Points[j+3], p.Points[j+4], p.Points[j+5])
j = j + 6
case ArcToCmp:
s += fmt.Sprintf("ArcTo: %f, %f, %f, %f, %f, %f\n", p.Points[j], p.Points[j+1], p.Points[j+2], p.Points[j+3], p.Points[j+4], p.Points[j+5])
j = j + 6
case CloseCmp:
s += "Close\n"
}
}
return s
}
// Flatten convert curves in straight segments keeping join segements
func (path *Path) Flatten(flattener Flattener, scale float64) {
// First Point
var startX, startY float64 = 0, 0
// Current Point
var x, y float64 = 0, 0
i := 0
for _, cmd := range path.Components {
switch cmd {
case MoveToCmp:
x, y = path.Points[i], path.Points[i+1]
startX, startY = x, y
if i != 0 {
flattener.End()
}
flattener.MoveTo(x, y)
i += 2
case LineToCmp:
x, y = path.Points[i], path.Points[i+1]
flattener.LineTo(x, y)
flattener.LineJoin()
i += 2
case QuadCurveToCmp:
TraceQuad(flattener, path.Points[i-2:], 0.5)
x, y = path.Points[i+2], path.Points[i+3]
flattener.LineTo(x, y)
i += 4
case CubicCurveToCmp:
TraceCubic(flattener, path.Points[i-2:], 0.5)
x, y = path.Points[i+4], path.Points[i+5]
flattener.LineTo(x, y)
i += 6
case ArcToCmp:
x, y = TraceArc(flattener, path.Points[i], path.Points[i+1], path.Points[i+2], path.Points[i+3], path.Points[i+4], path.Points[i+5], scale)
flattener.LineTo(x, y)
i += 6
case CloseCmp:
flattener.LineTo(startX, startY)
flattener.Close()
}
}
flattener.End()
}