[FOSS-GPS] Re: Download-progress callbacks in osm-gps-map

[Sander van Grieken]

On Monday 17 May 2010 23:12:45 John Stowers wrote:
> On Mon, 2010-05-17 at 17:47 +0200, Sander van Grieken wrote:
> > 
> > For whoever is interested, I have put online my working branch where I'm integrating 
the 
> > OsmGpsMap widget here :
> > 
> > http://www.outrightsolutions.nl/~sander/foxtrotgps/ogm-widget/
> > 
> > Currently I have migrated GPS updates and the map popup menu, so it is runnable and 
gives 
> > an idea of how it'll become. The rest of the functionality is not yet in a working 
state, 
> > so expect no POIs, photos, friends etc.
> 
> Cool, sounds great!

In the meantime..
- rendering the waypoint flag now works
- toolbar buttons now work
- zoom slider now works
- autocenter fixed and gconf-ed

It's already shaping up quite nicely :)

> > Some things I noticed :
> > 
> > It seems the tiles-queued signal is only triggered when downloading tiles 'on-demand', 
> > i.e. when dragging the map around. There are no events triggered when doing an 
explicit 
> > map download.
> 
> OK, this sounds like a bug.

If I recall correctly, tangogps used 2 queues for downloading tiles, a low priority one 
for the bulk map-download, and a high priority one for the on-demand tiles.

> > Also I triggered a 'bug', where I had a huge bbox en a high zoom level (I accidently 
used 
> > the old global_zoom variable instead of the internal zoom variable) when starting a 
map 
> > download. It ate all my memory. This normally shouldn't happen, because the app will 
use a 
> > sane zoom level w.r.t. the bounding box, but maybe some sort of sanity check in OGM is 
a 
> > good idea.
> 
> Yeah, I have had this before, where it goes and calculates a million
> tiles to download if you try and cache the whole world at all zoom
> levels.
> 
> What do you think a sensible sanity check would be?

what about capping the max-zoom-level at a value where the bounding box contains at most 
128 tiles in either dimension? Would cap the queue to 16384 for a perfectly square 
bounding box (still quite a lot), and it matches the max 7 zoom levels download of 
foxtrotgps.

grtz,
Sander