Oh right, sorry, I'd lost sight of the fact it was in a web browser.
No problem, this thread is full of interesting meanderings.
[snip]
If Johannes commits to Cairo (at least, for now), it seems he could just
subclass the context, add a few convenience methods to make triangles or
do a turtle and such, and you then have something that is easy to use and
*still* powerful.
Good point.
So, from an eXtreme programming point of view ( i.e.
"don't write code or add complexity before you are sure you'll need it"),
I'd suggest then either just go with Cairo as an expected part of the
system, or at most just make a thin simplified wrapper around Cairo, and
if later there is a demand for other back ends, then add the layer then.
(Speaking on his behalf, until he comments on his own :-) That is what he wanted to do. However, when trying to design a "library" that could be used by 7 year-old kids ... I think he found out that it was not as easy as he first thought. For example: how do you introduce cartesian coordinates (for positioning graphics objects) in a simple way?
Any suggestion for what the API should look like would be most welcome!
And with the 100% Cairo approach, then the comment "There is no way it
should be used for real world graphics - its sole purpose is educational."
would no longer be needed.
I could not agree more with this approach (see below).
Kids would start off with this, say,
"EasyCairo" context they can do some simple things with easily, and then,
if they get curious, suddenly they could find themselves drawing warped
text as quick speeds, when they realize it has inherited methods they
could use. Or, not having looked at the implementation of pyCairo, if for
some reason it could not be subclasses, one cold write a wrapper object or
even just plain convenience functions that took it as an argument.
I think there is a subtle point here about educational philosophy I can't
quite put into words. Maybe it is something like, "Making real tools
easier and safer to use so people can learn to do simple things with them
more quickly is good (e.g. convenience functions for Cairo to draw
circles); making "educational" tools that people can only do simple things
with and then hit an artificial ceiling with and then get frustrated about
as then need to move onto something else is bad (e.g . an entirely new
display context you can only draw a few things with)."?
And I think "Python" as a learning environment reflects that point. It is
easy to start using Python, but unlike an "educational" version of, say,
Logo or Basic doesn't force you to jump ship when the going gets tough, or
when you design you want to use something to get real work done with. And
I think that is why it is one of the best choices for people first
learning programming.
Indeed. And, if I may use it as an example, I think this is one of the strength of RUR-PLE in comparison with Guido van Robot (or Logo, or whatever else.) RUR-PLE is Python ... with a few pre-defined commands. In fact, executing a RUR-PLE program is done via something like
exec "user_code" in my_globals()
I do some minor pre-processing of the "user_code" part to disallow import statements and a few others (for security reason in a classroom environment, to prevent kids sharing "dangerous" programs), but pretty much any valid Python code can be executed!
So anyway, looking back at Johannes' original proposal,
http://users.ox.ac.uk/~orie1763/coder-python.pdf
it seems to me that just making Cairo a little easier to use would still
fulfill the intent there (including being cross-platform enough), while
not creating any artificial limits on what kids could do. Installation and
availability still may be an issue, of course, but long term, won't that
be solved for Cairo if Mozilla and GTK use it?
Agreed on both points.
Still, I should admit to being a little self-serving with my argument
here; if Python educators got behind a good cross-platform standards like,
say, Cairo, and GTK, and pygtkglext (for OpenGL), and it got bundled into
the main CPython distribution in the future
http://wiki.python.org/moin/PythonThreeDotOh
(or at least as an easy add-on package for Mac, Win, and GNU/Linux), then
I think there would be enormous value for Python in education to have a
solid GUI, 2D, and 3D display engines which everyone could count on for
being available when introducing people to Python.
I don't consider that having such a library is a self-serving goal :-) However, I am not hopeful that it will get bundled in the main Python distribution. I'll settle for an easy download (and, hopefully, for it to be part of Edubuntu).
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