_BlockAt
int32 topBlock = _BlockAt(BPoint(Bounds().left, Bounds().top));
int32 bottomBlock = _BlockAt(BPoint(Bounds().right, Bounds().bottom));
for (int32 i = _BlockAt(updateRect.LeftTop()); i < (int32)kNumUnicodeBlocks;
int32 i = _BlockAt(point);
int32 i = _BlockAt(BPoint(0, top));
int32 _BlockAt(BPoint point) const;