Re: [Gmod-ajax] Openlazlo

[Mitch S. <mit...@be...>]

On Thu, 2007-05-31 at 11:13 -0700, Ian Holmes wrote:
> perhaps a Google Maps-type widget is lurking out there that's 
> exactly what we need (though I doubt any available toolkit can do the 
> scary things that Mitch is currently trying with tracks built entirely 
> out of DIVs)

I've been experimenting with this over the last few weeks, which is part
of the reason I've been so quiet lately.  This is still in an extremely
sketchy state, but there's enough there to get the idea:
http://genome.biowiki.org/test/divbrowser/genome2.html

The features are exons from D. melanogaster chromosome 3R.  There are
about 16,000, of which Firefox is able to show a few thousand on my
hardware before it starts to bog down.  If you zoom out beyond about 3
megabases the zooming gets to be quite slow, but that's above the point
where we're currently switching to a feature density histogram for that
track, anyway.

There's still some low-hanging fruit performance-wise, so I'm optimistic
that it'll scale to a full set of tracks, especially if we're smart
about interval search and attaching and detaching things from the DOM.
And adjusting the threshold where we switch to a density histogram
should accommodate hardware differences.

The rationale for using divs is:
1. reduces server side processing/storage for image tiles
2. allows for a nice client-side feature creation/editing UI
3. zooming is cool, but it's more than just eye candy--it helps you keep
an intuitive sense of where you are
4. client can cache an entire chromosome worth of features (at least for
some tracks)--given where firefox and WHAT-WG are going this may enable
offline use in the future.
5. more cross-browser than SVG (I've been testing in firefox and IE 6/7
and I'll be trying for Safari as well)

Mitch