timeline improvements

[joelburget]

I ported over the remaining exercises that didn't work with the timeline to the custom answer type. I also included a few little timeline improvements that have been bitrotting for a while.

[joelburget]

The ports are still fairly rough, I need to go back and take a second look at them, but I wanted to get this review started.

One problem I know for sure exists is that the orange derivative that shows up when you either get all the points right or ask for that hint in derivative intuition doesn't show up in the timeline. I also noticed on at least one exercise that the guess reverts back to the default when viewing a hint that occured after a guess.

[beneater]

I'm worried this might not work correctly in all browsers. I've always been more comfortable with $("#answers") rather than $(answers)

[joelburget]

I was actually gonna ask about this black magic. I used it in a couple other places too but wasn't sure whether it was kosher.

[beneater]

see http://stackoverflow.com/questions/6381425/should-the-id-of-elements-be-made-global-variables-and/6381766#6381766

seems like a bad idea

[joelburget]

Wow, I've never heard of that before. I discovered that answers was a global by accident and just assumed it was Resig magic. Will revert immediately.

[beneater]

Seems possible there are some floating point precision bugs introduced in some of the validators. I was able to convince myself there weren't any, but there's a chance I'm wrong. You may want to monitor the bug reports a little more closely after shipping this.

[beneater]

Clowncopterize!

[joelburget]

The derivative intuition derivative marker still doesn't show up in timeline mode but I don't think that's a bugle-stopper. Would love if you could take a look.

[beneater]

Probably because raphael's .animate() is doing a setTimeout(0) or equivalent, which defers until after the timeline takes its snapshot.

This works around it if you can stand the hackyness of it:

diff --git i/utils/derivative-intuition.js w/utils/derivative-intuition.js
index 0af13d9..db97d2f 100644
--- i/utils/derivative-intuition.js
+++ w/utils/derivative-intuition.js
@@ -274,7 +274,7 @@ $.extend(KhanUtil, {
             graph.style({
                 stroke: KhanUtil.DDX_COLOR,
                 strokeWidth: 1,
-                opacity: 0
+                opacity: duration === 0 ? 1 : 0
             }, function() {
                 ddxplot = graph.plot(function(x) {
                     return KhanUtil.ddx(x);

[joelburget]

I'm fine with it. There are still problems though. For some reason in timeline some (but not all) of the derivative intuition dots fail to move to the right place. Also, tutorials seem to have caused some rendering bugs but that's not a timeline problem.

[beneater]

this lgtm, then