1. A computer-implemented method of selectively checking a set of text formatting rules for applicability to an input, the method comprising: receiving an input; utilizing a computer processor that is a functional component of the computer to reference a cache to identify a sub-set of the set of text formatting rules, the sub-set containing rules that are specifically applicable to the input, wherein the sub-set is a limited number of rules selected from the set of text formatting rules, the limited number being less than all of the rules in the set of text formatting rules; wherein referencing a cache comprises maintaining an array of pointers to rules indicated in the cache as being associated with at least one glyph contained in the input; applying, to the input, rules indicated by the array of pointers, wherein the rules are applied in the order that they are listed in the set of rules; and dynamically updating the array of pointers to reflect changes made to the input.