The exact features of this applet have yet to be determined, but it will generally just provide automatic snippet insertion.
The user would be able to configure that a given piece of text is mapped to some other given piece of text.
:D could for instance be mapped to 😄. Then when the applet is enabled, when :D is typed in any program, it will automatically be replaced with the unicode 😄 text.
This applet would require to actively listen to all keypresses of the user when the applet is enabled. We will have to look into how feasible this is (in a stable way without interfering with normal OS keyboard usage) for all of the supported OSes. This technology would also be useful for other applets such as dictionaries or spellcheckers.
Will need to detect clicks, and erase the cached text, in order to prevent incorrect matches.