[udig-devel] An update on WMS-C tiles and uDig

[Graham Davis <gdavis@xxxxxxxxxxxxxxx>]

Hi,

This is just an update on some of the functionality Emily G. and I have 
added to uDig trunk in the last few weeks.  Some of this may be old 
news, but it is a quick run-down of the changes we've been making.

WMS-C Tile servers are now supported in the catalog and there are some 
preferences you can set in regards to this.  On the "WMS-C Tiles" 
preferences page you can set the maximum number of concurrent tile 
requests (ie: if this is set to 8 it will use a thread pool size of 8 
and only send of a max of 8 tile requests at a time and wait before 
sending more), whether to use in-memory cache or on-disk cache, and you 
can also set where to cache tiles on disk or choose to clear the current 
cache.

Additionally, there is an operation that allows you to right-click on 
any WMS-C Tile layer in the catalog view and choose to preload all the 
tiles for that layer and cache them on disk.  This runs in a blocking 
dialog with a progress bar since the layer could potentially contain 
hundreds of thousands of tiles and doing so many continuous requests and 
disk writing can be resource heavy.  These tile requests are sent off in 
groups (default is 16 but this can be tweaked with the "max concurrent 
requests" preference mentioned above) and can take a while.  Beware that 
the onslaught of so many continuous requests could potentially bog down 
the WMS-C server you are loading the tiles from.

There is also a new tiled rendering system that can be used for 
rendering any data in uDig.  This can be turned on in the "Rendering" 
preference page.  It provides a cleaner flicker-free panning experience 
when viewing maps in uDig.  Emily has mentioned this before via email, 
but there is also a new Scroll Pan Tool which works very well when tiled 
rendering is turned on.  Emily has also cleaned up the rendering stack a 
lot, including removing some unnecessary render events.

--
Graham Davis
Refractions Research Inc.
gdavis@xxxxxxxxxxxxxxx