This commit adds multi-track functionality without exposing it to the
user.
All I really did was rename AudioEngine to Track and allow more than one
Track in TrackManager. A lot of the changes are just changing widgets to
take a TrackManager and use current_track().
The TrackManager creates Tracks and gives them a read-only reference to
the global time value. When the TrackManager wants to fill a sample in
the buffer (in fill_buffer()), it calls fill_sample() on each Track.
The delay code is slightly different - a Track will fill its
m_delay_buffer with the sample it just created rather than the most
recent sample in the buffer (which used to be the same thing).
TrackManager manages the current octave.
Other than those few things, this is a pretty basic separation of
concerns.
I started adding things to a Draw namespace, but it somehow felt really
wrong seeing Draw::Rect and Draw::Bitmap, etc. So instead, let's rename
the library to LibGfx. :^)
Goals:
- Switch to a more typical LibGUI arrangement
- Separate GUI (MainWidget) and audio (AudioEngine)
- Improve on existing features while retaining the same feature set
Improvements:
- Each GUI element is a separate widget
- The wave (WaveWidget) scales with the window
- The piano roll (RollWidget) scales horizontally and scrolls vertically
- The piano (KeysWidget) fits as many notes as possible
- The knobs (KnobsWidget) are now sliders
- All mouse and key events are handled in constant time
- The octave can be changed while playing notes
- The same note can be played with the mouse, keyboard and roll at the
same time, and the volume of the resulting note is scaled accordingly
- Note frequency constants use the maximum precision available in a
double
