m_roll_notes[] is an array of 2 bools, pressed and playing. A roll note
is highlighted if it is pressed or in the currently playing column, but
the note is only actually played if the roll note is both pressed and
playing.
We change columns every m_tick which is currently 10 frames. The delay
is synchronised with this. change_roll_column() tracks the previous
column and current column to be played. Each roll note in the previous
column is set to "not playing" and the underlying audio note is turned
off if it was pressed. For the current column, each roll note is set to
playing and the underlying audio note is turned on if pressed.
Rather than checking key codes and mouse positions, we should have a
more general way to play notes. You can call note() either with a
KeyCode or a PianoKey directly.
Additionally, m_note_on[] is now an array of integers instead of bools.
This allows multiple sources to play a note. This is kind of like a
"reference counted note": two sources can increment the note and it will
only turn off once they have both decremented it back to 0.
We are now only using keys[] to prevent multiple consecutive calls to
keydown_event() (when a key is held), since that would result in playing
a note many times.
The squad is complete :^)
You can find the equation for the triangle wave here:
https://en.wikipedia.org/wiki/Triangle_wave
We're using this one:
|x mod 4 - 2| - 1
Modifications have been made to correct the frequency and phase:
|(4x + 1) mod 4 - 2| - 1
The white noise is generated by calling rand() and dividing it by
RAND_MAX to get a value from 0 to 1. Then it's adjusted to fit between
-1 and 1.
Instead of LibGUI and WindowServer building their own copies of the drawing
and graphics code, let's it in a separate LibDraw library.
This avoids building the code twice, and will encourage better separation
of concerns. :^)
In order to repaint the GUI after the sound thread has produced some sweet
new waves, we post a CCustomEvent to the main thread's event loop and then
wake up that event loop via CEventLoop::wake().
This frees up the main thread to draw the GUI. The secondary thread uses
a pipe to trick the main thread's event loop to break out of select() and
update() the PianoWidget. :^)
The idea here is to implement a simple synhesizer that allows you to play
music with your keyboard. :^)
It's a huge hack currently but we can improve upon this.
