Here's my take on an auto completer, work in progress so don't be too harsh with me.
The idea is that after a spacebar press, it learns the word that was previously written, and the next time you write, it gets a list of all words that fit into what you're writing, so if the user writes "com", a word that may appear is "complex", that is, if the user has written it anytime in the past.
A popup will show up whenever the user writes with the list of words, the way to select one of the words from the list is to scroll with the mouse wheel, and middle click. The popup timeout is 2.5 secs.
Best regards.
PS for the next step would be nice to save words as they are, for example emails, as it is it doesn't get @ for example.
Completer 1.0.exe
AComp.ico
Completer 1.0.au3