TODO

-Engine: Mono/Poly mode switching via midi-cc (see notes on petri-foo-devel)

-Engine: Voice modes
    +polyphonic re-trigger mode (new note repetition cuts old note).

-Engine: Keyboard tracking
    +add to lfo's for frequency modulation

-Engine: Velocity sensitivity
    +add to eg's for amplitude modulation (i'm not convinced by this)
     (note this has been coded but was commented out).

-Engine: Logarithmic Amplitudes
    +Fix and remove artefacts arising from use of LAT for log_amplitude
     function in maths.[ch] (research info online about alternatives
     such as curved ADSRs for example).

-GUI: general
    +replace PHAT widgets with something else?
    +custom cairo based widgets?
     Petri-Foo now uses Phin instead of PHAT. Phin is a modified
     fork of PHAT which uses Cairo and avoids deprecated GTK/GDK code,
     with the fans on the sliders disabled but default by allowed to
     be enabled by users of compositing desktop environments.


-GUI: Patch List:
    +use an editible widget: note this has been tried, but getting
     menu->rename to use the functionality of the editible cell
     is just far far far too much hard work for little gain.


-GUI: Sample Editor
    + two tool modes: pointer, and zoom
    + zoom tool: select area and zoom
    + pointer tool: *drag* play/loop point markers
    + zoom in/out/all buttons