00 chars} } 0.0 test textIndex-00.0 {TkTextIndexBackChars} {     # not (charCount < 0)     .t index {0.0 - 0 chars} } 0.0 test textIndex-00.0 {TkTextIndexBackChars: find starting segment} {     # for (segPtr = dstPtr->linePtr->segPtr; ; segPtr = segPtr->nextPtr)     # 