An application that acts as a filter can intercept a keystroke
coming from EHLLAPI (either from the keyboard or a source application)
that is targeted for another destination. The keystroke can then be:
Ignored (that is, deleted)
Redirected to another application
Validated
Converted (for example, uppercase to lowercase)
Enhanced (through keyboard macros)
Keystroke Flow provides a simplified representation of the
keystroke flow and the objects within a keyboard enhancement environment.
Figure 1. Keystroke Flow