86 lines
2.2 KiB
Go
86 lines
2.2 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 drawing
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// NewLineStroker creates a new line stroker.
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func NewLineStroker(c LineCap, j 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
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l.Cap = c
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l.Join = j
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return l
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}
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// LineStroker draws the stroke portion of a line.
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type LineStroker struct {
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Flattener Flattener
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HalfLineWidth float64
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Cap LineCap
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Join LineJoin
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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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}
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// MoveTo implements the path builder interface.
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func (l *LineStroker) MoveTo(x, y float64) {
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l.x, l.y = x, y
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}
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// LineTo implements the path builder interface.
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func (l *LineStroker) LineTo(x, y float64) {
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l.line(l.x, l.y, x, y)
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}
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// LineJoin implements the path builder interface.
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func (l *LineStroker) LineJoin() {}
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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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// Close implements the path builder interface.
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func (l *LineStroker) Close() {
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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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// End implements the path builder interface.
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func (l *LineStroker) End() {
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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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}
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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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}
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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
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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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func (l *LineStroker) appendVertex(vertices ...float64) {
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s := len(vertices) / 2
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l.vertices = append(l.vertices, vertices[:s]...)
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l.rewind = append(l.rewind, vertices[s:]...)
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}
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