Method optimizeClose

path.go:598–633

optimizeClose removes a superfluous first line segment in-place of a subpath. If both the first and last segment are line segments and are colinear, move the start of the path forward one segment

()

// optimizeClose removes a superfluous first line segment in-place of a subpath. If both the first and last segment are line segments and are colinear, move the start of the path forward one segment
func (p *Path) optimizeClose() {
	if len(p.d) == 0 || p.d[len(p.d)-1] != CloseCmd {
		return
	}

	// find last MoveTo
	end := Point{}
	iMoveTo := len(p.d)
	for 0 < iMoveTo {
		cmd := p.d[iMoveTo-1]
		iMoveTo -= cmdLen(cmd)
		if cmd == MoveToCmd {
			end = Point{p.d[iMoveTo+1], p.d[iMoveTo+2]}
			break
		}
	}

	if p.d[iMoveTo] == MoveToCmd && p.d[iMoveTo+cmdLen(MoveToCmd)] == LineToCmd && iMoveTo+cmdLen(MoveToCmd)+cmdLen(LineToCmd) < len(p.d)-cmdLen(CloseCmd) {
		// replace Close + MoveTo + LineTo by Close + MoveTo if equidirectional
		// move Close and MoveTo forward along the path
		start := Point{p.d[len(p.d)-cmdLen(CloseCmd)-3], p.d[len(p.d)-cmdLen(CloseCmd)-2]}
		nextEnd := Point{p.d[iMoveTo+cmdLen(MoveToCmd)+cmdLen(LineToCmd)-3], p.d[iMoveTo+cmdLen(MoveToCmd)+cmdLen(LineToCmd)-2]}
		if Equal(end.Sub(start).AngleBetween(nextEnd.Sub(end)), 0.0) {
			// update Close
			p.d[len(p.d)-3] = nextEnd.X
			p.d[len(p.d)-2] = nextEnd.Y

			// update MoveTo
			p.d[iMoveTo+1] = nextEnd.X
			p.d[iMoveTo+2] = nextEnd.Y

			// remove LineTo
			p.d = append(p.d[:iMoveTo+cmdLen(MoveToCmd)], p.d[iMoveTo+cmdLen(MoveToCmd)+cmdLen(LineToCmd):]...)
		}
	}
}

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