[sugar] clarification of SUGAR_ACTIVITY_ROOT

[Paul Fox]

hi --

newbie activity developer here.  i'm trying to get an existing app
working as an activity, and i'm trying to keep it "well behaved"

i don't quite understand the SUGAR_ACTIVITY_ROOT variable.

the wiki says that it's "Writable space for the activity.... 
Activities are prohibited from writing anywhere else in the file
system.", and at http://wiki.laptop.org/go/Low-level_Activity_API#Security
it refers to three "virtual" subdirectories, and describes the "data",
"instance", and "tmp" directories.

when i track down its value while my activity runs, it leads to
three very un-virtual subdirectories somewhere beneath
/home/olpc/.sugar.

so...

    - what's the "virtual" part mean?  can the directories referred
	to by SUGAR_ACTIVITY_ROOT move around?

    - what if my activity might have larger data needs than
	can be accomodated on the root fs?  what if i'd like to
	use space on a removeable device?  is there a way to
	manage this?  the activity is a street mapping program,
	with the ability to download map data.  map data always
	takes tens, if not hundreds, of megabytes.  (i.e.  all of
	texas takes 300M, all of rhode island takes 8M.)

paul
=---------------------
 paul fox, pgf at foxharp.boston.ma.us (arlington, ma, where it's 32.4 degrees)