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epriestley 5c71da8cdb Quicksand, an ignoble successor to Quickling
Summary:
Ref T2086. Ref T7014. With the persistent column, there is significant value in retaining chrome state through navigation events, because the user may have a lot of state in the chat window (scroll position, text selection, room juggling, partially entered text, etc). We can do this by capturing navigation events and faking them with Javascript.

(This can also improve performance, albeit slightly, and I believe there are better approaches to tackle performance any problems which exist with the chrome in many cases).

At Facebook, this system was "Photostream" in photos and then "Quickling" in general, and the technical cost of the system was //staggering//. I am loathe to pursue it again. However:

  - Browsers are less junky now, and we target a smaller set of browsers. A large part of the technical cost of Quickling was the high complexity of emulating nagivation events in IE, where we needed to navigate a hidden iframe to make history entries. All desktop browsers which we might want to use this system on support the History API (although this prototype does not yet implement it).
  - Javelin and Phabricator's architecture are much cleaner than Facebook's was. A large part of the technical cost of Quickling was inconsistency, inlined `onclick` handlers, and general lack of coordination and abstraction. We will have //some// of this, but "correctly written" behaviors are mostly immune to it by design, and many of Javelin's architectural decisions were influenced by desire to avoid issues we encountered building this stuff for Facebook.
  - Some of the primitives which Quickling required (like loading resources over Ajax) have existed in a stable state in our codebase for a year or more, and adoption of these primitives was trivial and uneventful (vs a huge production at Facebook).
  - My hubris is bolstered by recent success with WebSockets and JX.Scrollbar, both of which I would have assessed as infeasibly complex to develop in this project a few years ago.

To these points, the developer cost to prototype Photostream was several weeks; the developer cost to prototype this was a bit less than an hour. It is plausible to me that implementing and maintaining this system really will be hundreds of times less complex than it was at Facebook.

Test Plan:
My plan for this and D11497 is:

  - Get them in master.
  - Some secret key / relatively-hidden preference activates the column.
  - Quicksand activates //only// when the column is open.
  - We can use column + quicksand for a long period of time (i.e., over the course of Conpherence v2 development) and hammer out the long tail of issues.
  - When it derps up, you just hide the column and you're good to go.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T2086, T7014

Differential Revision: https://secure.phabricator.com/D11507
2015-01-27 14:52:09 -08:00
..
core Fix window-exiting drags and drag-and-hold behaviors in JX.Scrollbar 2015-01-24 16:42:21 -08:00
docs Remove @group annotations 2014-07-10 08:12:48 +10:00
ext Use single quotes in JavaScript files 2015-01-20 08:53:47 +11:00
lib Quicksand, an ignoble successor to Quickling 2015-01-27 14:52:09 -08:00
LICENSE Various linter fixes. 2014-02-26 12:44:58 -08:00
README Move all external JS into webroot/rsrc/externals 2013-04-11 10:06:05 -07:00

Javelin is a performance-oriented Javascript library originally developed at
Facebook. Learn more at <http://www.javelinjs.com/>.

GETTING STARTED

Eat a hearty breakfast. Breakfast is the most important meal of the day!


WHAT IS JAVELIN?

Javelin is a compact Javascript library built around event delegation. Its
primary design goal is performance; it is consequently well-suited to projects
where performance is very important. It is not as good for smaller scale
projects where other concerns (like features or ease of development) are more
important.


PACKAGES

Packages come in two flavors: "dev" and "min". The "dev" packages are intended
for development, and have comments and debugging code. The "min" packages have
the same code, but with comments and debugging information stripped out and
symbols crushed. They are intended for use in production -- ha ha ha!


FILES

  example/    Example code.
  LICENSE     A thrilling narrative.
  pkg/        Ready-built Javelin packages.
  README      Who knows? Could be anything.
  src/        Raw sources for Javelin.
  support/    Support scripts and libraries.