Function scriptDirection

text.go:244–281

(mode WritingMode, orient TextOrientation, script text.Script, level int, direction text.Direction)

}

func scriptDirection(mode WritingMode, orient TextOrientation, script text.Script, level int, direction text.Direction) (text.Direction, text.Rotation) {
	// override text direction for given writing mode
	// script and level come from ScriptItemizer
	// direction is the explicit direction set on the face
	vertical := false
	rotation := text.NoRotation
	if mode == VerticalLR || mode == VerticalRL {
		if !text.IsVerticalScript(script) && orient == Natural {
			// horizontal script with natural orientation
			rotation = text.CW
		} else if rot := text.ScriptRotation(script); rot != text.NoRotation {
			// rotated horizontal script for vertical mode (such as Mongolian)
			rotation = rot
		} else {
			// horizontal script with upright orientation or vertical script
			vertical = true
		}
	}

	if !vertical {
		if direction != text.LeftToRight && direction != text.RightToLeft {
			if (level % 2) == 1 {
				direction = text.RightToLeft
			} else {
				direction = text.LeftToRight
			}
		}
	} else {
		if direction != text.TopToBottom && direction != text.BottomToTop {
			if (level % 2) == 1 {
				direction = text.BottomToTop
			} else {
				direction = text.TopToBottom
			}
		}
	}
	return direction, rotation
}

func reorderSpans(spans []TextSpan) {
	// find runs of a certain level and deeper (including nested)