Processing GUI: add buttons to insert "markers" in data log

[chipaudette]

To ease post-test analysis of the data, it would be great if we could insert "markers" into the data stream. These could be used to mark things like "eyes open", "eyes closed", "relaxed", "flexing left arm", "concentrating on mental math", etc.

One way to enter these markers would be to have clickable buttons on the GUI. Or, you could press keys on the keyboard (say, the function keys).

One could pre-define the message associated with each button ("Eyes Closed"), or one could leave them user-definable (with default messages, of course).

The markers could be stored in the existing data log (the big text file that is generated while recording EEG data). I recommend creating a second file to hold just this log data. I recommend logging a code that identifies which button/key was pressed (the code should something that is easily machine readable), followed by the EEG sample number of when the button was pressed (this acts as the clock for associating with the EEG data), and finally the text message itself.

This will be the first step in our path to enabling people to do automated test protocols so that we can share our EEG data and do some actual science. In the vision for the automated test protocol, the GUI itself could drop markers into this log file to say when the visual stimulus (or whatever) was incremented to the next step in the test protocol.