[Xastir] Rtree

[James Ewen]

> The very first time a shapefile is drawn in a window that's smaller than
> the full file extent, every shape in the file is read and its extents 
> saved
> in the rtree index for that file.  Then, any shape that's in the current
> window is read in and drawn --- that's why the first draw of a file is 
> slower.

Sounds almost exactly like what I did by chopping the dataset up into 
smaller bits. Xastir looks at the extent of each file and only uses the ones 
within the viewing window. I could increase efficiency a little more by 
chopping the files into smaller chunks again.

I did spend a couple hours chopping the file up with the program you created 
Tom, but I think it was worth the effort! I'm saving a bit of wear and tear 
in the hard drive too!

James