id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
10738	Background Imagery: please more aggressive caching and smarter download queening for slow connections	RicoZ	RicoZ	"Hi,

background imagery over slow connections is painful. Even with UMTS+, eg PCN 2012 Italy is not a great joy and much worse with EDGE or GPRS.
I am wondering if there is room for improvement?

* josm does cache tiles - but it appears in many cases the tiles are redownloaded even if they are in cache and not yet ""aged""?
* tile downloads are apparently queued - and it seems with slow connections the queening could do smarter:
* when zooming in/out or panning the dl queue apparently isn't discarded quickly enough and josm keeps downloading tiles which are no longer in focus?
* when zooming there are often long delays even to redisplay tiles that were already downloaded in the same session. Perhaps a single file that needs to be downloaded blocks the display of many precached tiles? Is there some expensive cache revalidation?

Perhaps following would also help:
* when zooming in/out or panning don't immediately start downloading tiles, then start with downloading tile under mouse or around center
* limit downloading to fewer zoom levels, especially when zooming out.. client side scaling is much better than a black screen and long delays.


"	enhancement	closed	major	15.08	Core imagery		fixed	cache