138 lines
3.3 KiB
Go
138 lines
3.3 KiB
Go
// Copyright 2010 The draw2d Authors. All rights reserved.
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// created: 13/12/2010 by Laurent Le Goff
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package draw2d
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type Cap int
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const (
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RoundCap Cap = iota
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ButtCap
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SquareCap
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)
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type Join int
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const (
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BevelJoin Join = iota
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RoundJoin
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MiterJoin
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)
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type LineStroker struct {
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Next VertexConverter
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HalfLineWidth float64
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Cap Cap
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Join Join
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vertices []float64
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rewind []float64
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x, y, nx, ny float64
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command VertexCommand
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}
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func NewLineStroker(c Cap, j Join, converter VertexConverter) *LineStroker {
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l := new(LineStroker)
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l.Next = converter
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l.HalfLineWidth = 0.5
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l.vertices = make([]float64, 0, 256)
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l.rewind = make([]float64, 0, 256)
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l.Cap = c
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l.Join = j
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l.command = VertexNoCommand
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return l
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}
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func (l *LineStroker) NextCommand(command VertexCommand) {
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l.command = command
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if command == VertexStopCommand {
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l.Next.NextCommand(VertexStartCommand)
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for i, j := 0, 1; j < len(l.vertices); i, j = i+2, j+2 {
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l.Next.Vertex(l.vertices[i], l.vertices[j])
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l.Next.NextCommand(VertexNoCommand)
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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.Next.NextCommand(VertexNoCommand)
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l.Next.Vertex(l.rewind[i], l.rewind[j])
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}
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if len(l.vertices) > 1 {
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l.Next.NextCommand(VertexNoCommand)
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l.Next.Vertex(l.vertices[0], l.vertices[1])
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}
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l.Next.NextCommand(VertexStopCommand)
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// reinit vertices
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l.vertices = l.vertices[0:0]
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l.rewind = l.rewind[0:0]
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l.x, l.y, l.nx, l.ny = 0, 0, 0, 0
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}
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}
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func (l *LineStroker) Vertex(x, y float64) {
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switch l.command {
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case VertexNoCommand:
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l.line(l.x, l.y, x, y)
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case VertexJoinCommand:
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l.joinLine(l.x, l.y, l.nx, l.ny, x, y)
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case VertexStartCommand:
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l.x, l.y = x, y
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case VertexCloseCommand:
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l.line(l.x, l.y, x, y)
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l.joinLine(l.x, l.y, l.nx, l.ny, x, y)
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l.closePolygon()
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}
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l.command = VertexNoCommand
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}
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func (l *LineStroker) appendVertex(vertices ...float64) {
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s := len(vertices) / 2
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if len(l.vertices)+s >= cap(l.vertices) {
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v := make([]float64, len(l.vertices), cap(l.vertices)+128)
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copy(v, l.vertices)
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l.vertices = v
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v = make([]float64, len(l.rewind), cap(l.rewind)+128)
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copy(v, l.rewind)
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l.rewind = v
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}
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copy(l.vertices[len(l.vertices):len(l.vertices)+s], vertices[:s])
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l.vertices = l.vertices[0 : len(l.vertices)+s]
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copy(l.rewind[len(l.rewind):len(l.rewind)+s], vertices[s:])
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l.rewind = l.rewind[0 : len(l.rewind)+s]
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}
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func (l *LineStroker) closePolygon() {
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if len(l.vertices) > 1 {
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l.appendVertex(l.vertices[0], l.vertices[1], l.rewind[0], l.rewind[1])
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}
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}
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func (l *LineStroker) line(x1, y1, x2, y2 float64) {
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dx := (x2 - x1)
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dy := (y2 - y1)
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d := vectorDistance(dx, dy)
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if d != 0 {
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nx := dy * l.HalfLineWidth / d
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ny := -(dx * l.HalfLineWidth / d)
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l.appendVertex(x1+nx, y1+ny, x2+nx, y2+ny, x1-nx, y1-ny, x2-nx, y2-ny)
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l.x, l.y, l.nx, l.ny = x2, y2, nx, ny
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}
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}
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func (l *LineStroker) joinLine(x1, y1, nx1, ny1, x2, y2 float64) {
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dx := (x2 - x1)
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dy := (y2 - y1)
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d := vectorDistance(dx, dy)
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if d != 0 {
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nx := dy * l.HalfLineWidth / d
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ny := -(dx * l.HalfLineWidth / d)
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/* l.join(x1, y1, x1 + nx, y1 - ny, nx, ny, x1 + ny2, y1 + nx2, nx2, ny2)
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l.join(x1, y1, x1 - ny1, y1 - nx1, nx1, ny1, x1 - ny2, y1 - nx2, nx2, ny2)*/
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l.appendVertex(x1+nx, y1+ny, x2+nx, y2+ny, x1-nx, y1-ny, x2-nx, y2-ny)
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l.x, l.y, l.nx, l.ny = x2, y2, nx, ny
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}
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}
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