20. The system of claim 18 , wherein the walker is further configured to: identify a left-to-right direction when a text part contains at least one character belonging to a left-to-right script but no characters belonging to a right-to-left script; and identify a right-to-left direction when a text part contains at least one character belonging to a right-to-left script but no characters belonging to a left-to-right script.
20. The system of claim 18 , wherein the walker is further configured to: identify a left-to-right direction when a text part contains at least one character belonging to a left-to-right script but no characters belonging to a right-to-left script; and identify a right-to-left direction when a text part contains at least one character belonging to a right-to-left script but no characters belonging to a left-to-right script. 24. The system of claim 20 , wherein the bidirectional text checker is further configured to identify a mismatch when the intrinsic text direction is left-to-right and the declared text direction is right-to-left or when the intrinsic text direction is right-to-left and the declared text direction is left-to-right.