Method SpanPosToRuneIndex

paint/textlayout.go:41–55

SpanPosToRuneIndex returns the absolute rune index for a given span, rune index position -- i.e., the inverse of RuneSpanPos. Returns false if given input position is out of range, and returns last valid index in that case.

(si, ri int)

// index position -- i.e., the inverse of RuneSpanPos.  Returns false if given
// input position is out of range, and returns last valid index in that case.
func (tx *Text) SpanPosToRuneIndex(si, ri int) (idx int, ok bool) {
	idx = 0
	for i := range tx.Spans {
		sr := &tx.Spans[i]
		if si > i {
			idx += len(sr.Render)
			continue
		}
		if ri <= len(sr.Render) {
			return idx + ri, true
		}
		return idx + (len(sr.Render)), false
	}
	return 0, false
}

// RuneRelPos returns the relative (starting) position of the given rune
// index, counting progressively through all spans present (adds Span RelPos