static bool deleteEmptyParagraphMechanism(Cursor & cur,
Cursor & old, bool & need_anchor_change);
/// delete double spaces, leading spaces, and empty paragraphs
/// from \first to \last paragraph
static bool deleteEmptyParagraphMechanism(Cursor & cur,
Cursor & old, bool & need_anchor_change);
/// delete double spaces, leading spaces, and empty paragraphs
/// from \first to \last paragraph