Twiddla does Replays now. Thanks for the inspiration, Etherpad | Hacker News Reader

Twiddla does Replays now. Thanks for the inspiration, Etherpad

twiddla.com

66 pointsjasonkester25 comments

I got inspired after watching that Etherpad replay demo last night, so this morning I rebuilt Twiddla's replay viewer from scratch and threw it live.

It's still pretty rough, but I think it will make a good addition to the service. Thanks, HN, for the inspiration!

Here'a another good one, by the way: http://www.twiddla.com/Replay.aspx?sessionID=75448&delay...

edit: that one is cartoonishly NSFW in places, but then that has always been a typical use case for Twiddla. Drawing "appendages" onto things.

I've never seen my perceived view of marriage so succinctly summed up with stick figures.

Very well done. It seems to me that Etherpad is a subset of Twiddla. I love Twiddla man.. it's just an amazing tool that pushes browsers to the limits. I can't imagine how much time and effort had to go into it.

Bug: Mine died for several hundred frames. Kept getting the same JS error. This might help you out: http://imgur.com/A82D

That's gold. Gotta love the difference between Reddit and HN. "Meh." vs. "Awesome, even though it broke. Here's a stack trace."

@jason: No kidding.

@sam: Will you be my user too, and send me stack traces when I fuck up? :)

Heh, thanks. I try to follow the Golden Rule.

@gruseom: link me, and I'll check it out :)

Looks great! One thing -

The decay on the "name tag" for a particular stroke seems too long. I can't see what they just drew because their name is in the way. The effect is more pronounced on lightning speed.

Indeed. This is running on the same codebase as Twiddla itself, and those little tags are timed for real people using the thing in real time. You're right that it's a bit overwhelming to have 50 of them onscreen at once. I'll be sure to dial that back.

Maybe just add the ability to toggle the names on/off.

great that was my only complaint on an otherwise very nice looking feature.

Fixed. They now fade out immediately instead of hanging around for a whole second. It's a little easier on the eyes now, and you can actually see what's being drawn without it being lost behind a wall of stickies.

Still seems to be too many of them at 2009-02-27 12:40:10 +0000. Also, playback gradually slows done here on Firefox 3. I gave up after about 1160 on Michelle's replay.

Yeah, Firefox has a somewhat undeserved reputation for being fast. They may have a fast javascript engine, but it's more than made up for by their amazingly slow rendering engine. I might simply sniff on the browser and turn those notes off for FF.

That's some fast turnaround. Well done!

Sorry, I accidentally downmodded you (didn't mean to click there). You can go ahead and hit me too, if you want. :)

Worry not, I adjusted the score ;)

It could use a "go to frame" feature, but otherwise that's quite cool!

Sure could. That's what stopped from building this in the past. I wanted to be able to go forward and backward and hop around to any frame. Turns out, that's a much bigger problem than just playing it forward. Essentially we'd need a perfectly functioning Undo counterparts to every commend we issue.

Now that it's built, I'm not so worried about the lack of a rewind button. If I get another free morning, maybe I'll look into it.

It's probably not the best way to go about it, but couldn't you implement that by just cutting the delay to zero and drawing from the beginning until the requested frame? It probably wouldn't work well if you wanted to step through the page backwards, but for just cutting to a specific frame it seems like it aught to do the job with minimal extra coding.

That's essentially how we do snapshots now. You can look backwards until you find something that clears the screen or loads a new page, and save some work by just drawing from there. So yeah, jumping to a frame isn't too hard. You just run the risk of melting something if you try using that technique to reverse the playback.

Man Jason, you're starting to worry me :).

I didn't believe there was enough utility in a record/playback feature (and am still not completely convinced). But looks like people here find it useful.

That is amazing! Made my fan start screaming, but well worth it!

Really cool stuff! How does the client/server stuff work? Is this a comet based application that gives it the snappy refresh rates? Great work!

This replay tool simply loads up a big batch of actions and plays them from the client. Once the page is out the door, we never hear back from it.

Twiddla itself uses good old-fashioned polling, along with a crazy fast message dispatcher on the server.

I'm still not sold on Comet. It's cool in principle, but you essentially need to build your own webserver if you want to do it. Personally, I'd rather simply handle 2000 tiny requests per second than try to juggle 2000 simultaneous open connections. Naturally, there's a bit more lag with polling, but in Twiddla's case it's hard to notice.

reminds me of old days of Mac programming, when PICT format could store & replay Quickdraw commands

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