Code Review Request for Initial Work on gadgets-backend

[GoogleCodeExporter]

Branch name: gadgets-backend

Link to the relevant commit(s):
- 
https://code.google.com/p/oppia/source/detail?r=1ce5378fc72608facae6294d6e3faa64
ba4317db&name=gadgets-backend

Purpose of code changes on this branch:
- Introduces a backend framework for enabling capabilities outlined in Oppia's 
Gadgets design doc: 
https://docs.google.com/document/d/18XKCXbuDb3SkMArxZij8TlGHp6KdeldJt2hvZ8LlmYQ/
edit#

- This class diagram may help prior to review:
https://docs.google.com/presentation/d/1w7dTefVrZCh4h5vAJoNzahx6o_pFJv6gWAx_c_DS
p88/edit#slide=id.g7b65b91f2_05

When reviewing my code changes, please focus on:
- are the BaseGadget methods developers are required to override sufficiently 
easy to understand?
- are panels_properties in extensions.skins.skin_classes sufficiently intuitive 
for skin developers to understand?
- any additional validation or tests stand out as valuable to add on the 
backend?

After the review, I'll merge this branch into: develop

Original issue reported on code.google.com by anu...@google.com on 26 Mar 2015 at 2:54

[GoogleCodeExporter]

Just a quick suggestion - you have some really nice diagrams explaining how 
things work, and if you get a chance at some point to create a 'gadgets' page 
on the wiki and include them there that would be very helpful for new 
contributors. You might want to look at 
https://code.google.com/p/oppia/wiki/CreatingExtensions to see what was written 
for interactions.

Original comment by jacobdav...@gmail.com on 26 Mar 2015 at 3:00

[GoogleCodeExporter]

+Xinyu, Amit, Mike: just wanted to loop you in for a quick opinion with regards 
to naming (please don't worry about the code).

See last few posts in

    https://code.google.com/p/oppia/source/detail?r=1ce5378fc72608facae6294d6e3faa64ba4317db&name=gadgets-backend

Any preferences/thoughts? (Examples of 'gadgets' are a calculator, a score bar, 
an advice-giving character, etc. -- basically, anything exploration-scoped that 
could be a useful adjunct to the exploration.)

Original comment by s...@seanlip.org on 27 Mar 2015 at 1:59

[GoogleCodeExporter]

Hey all,

Just looked over the discussion thread, just want to add that I agree with the 
reasoning people have provided for using 'gadgets', especially since users will 
need to be taught the meanings of these words anyhow. Thanks!

Original comment by amitdeut...@google.com on 1 Apr 2015 at 12:44

[GoogleCodeExporter]

Original comment by s...@seanlip.org on 20 Apr 2015 at 3:52

• Changed state: Done