draw2d/draw2dbase/flattener.go

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// Copyright 2010 The draw2d Authors. All rights reserved.
// created: 06/12/2010 by Laurent Le Goff
package draw2dbase
import (
"github.com/llgcode/draw2d"
)
// Liner receive segment definition
type Liner interface {
// LineTo Draw a line from the current position to the point (x, y)
LineTo(x, y float64)
}
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// Flattener receive segment definition
type Flattener interface {
// MoveTo Start a New line from the point (x, y)
MoveTo(x, y float64)
// LineTo Draw a line from the current position to the point (x, y)
LineTo(x, y float64)
// LineJoin add the most recent starting point to close the path to create a polygon
LineJoin()
// Close add the most recent starting point to close the path to create a polygon
Close()
// End mark the current line as finished so we can draw caps
End()
}
// Flatten convert curves into straight segments keeping join segments info
func Flatten(path *draw2d.Path, flattener Flattener, scale float64) {
// First Point
var startX, startY float64 = 0, 0
// Current Point
var x, y float64 = 0, 0
i := 0
for _, cmp := range path.Components {
switch cmp {
case draw2d.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 draw2d.LineToCmp:
x, y = path.Points[i], path.Points[i+1]
flattener.LineTo(x, y)
flattener.LineJoin()
i += 2
case draw2d.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 draw2d.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 draw2d.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 draw2d.CloseCmp:
flattener.LineTo(startX, startY)
flattener.Close()
}
}
flattener.End()
}
// Transformer apply the Matrix transformation tr
type Transformer struct {
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Tr draw2d.Matrix
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Flattener Flattener
}
func (t Transformer) MoveTo(x, y float64) {
u := x*t.Tr[0] + y*t.Tr[2] + t.Tr[4]
v := x*t.Tr[1] + y*t.Tr[3] + t.Tr[5]
t.Flattener.MoveTo(u, v)
}
func (t Transformer) LineTo(x, y float64) {
u := x*t.Tr[0] + y*t.Tr[2] + t.Tr[4]
v := x*t.Tr[1] + y*t.Tr[3] + t.Tr[5]
t.Flattener.LineTo(u, v)
}
func (t Transformer) LineJoin() {
t.Flattener.LineJoin()
}
func (t Transformer) Close() {
t.Flattener.Close()
}
func (t Transformer) End() {
t.Flattener.End()
}
type SegmentedPath struct {
Points []float64
}
func (p *SegmentedPath) MoveTo(x, y float64) {
p.Points = append(p.Points, x, y)
// TODO need to mark this point as moveto
}
func (p *SegmentedPath) LineTo(x, y float64) {
p.Points = append(p.Points, x, y)
}
func (p *SegmentedPath) LineJoin() {
// TODO need to mark the current point as linejoin
}
func (p *SegmentedPath) Close() {
// TODO Close
}
func (p *SegmentedPath) End() {
// Nothing to do
}