Give up the attempt to omit the do() notation

User defined function will destroy it,
see main.py for more explanation.
Devise a pygui usage scene

Imagine rewriting study-time-record using pygui.
If this can be implemented, then the code of main.py
should be about three times shorter.
Todo explain the status and features of this project
Implement canvas composition (with bugs...)

can't use the same canvas multiple times with different sizes
maybe other bugs, but i forget...
this is unfinished, but i won't touch it for a long time
so... i'll be back