[OpenLayers-Dev] singleTile optimization

Christopher Schmidt crschmidt at metacarta.com
Thu Oct 4 12:16:26 EDT 2007

On Thu, Oct 04, 2007 at 11:09:34AM -0500, Erik Uzureau wrote:
> There we go. What David's said here is what I was grasping for earlier here.
> If you use a singleTile layer that is gridded, *eventully* the user is
> going to pan the map such that the corners of the grid are in the
> viewbox. At that point, the only option is to load 4 tiles, at which
> point, we're back to gridded, in which case you might as well just use
> a normal gridded layer with a very big tilesize and a buffer:0

I think Paul is imagining a singleTile which matches the grid of a
*smaller* set of tiles -- so the gridded tile is 'snapped' to a corner
of a smaller grid. For example, you could imagine the grid existing at
0.5 degree increments all the way across the world, and the tile would
snap to the closest one. The tile no longer has equal buffer space on all 
outside edges, but is more cachable. 

The size of a single grid square must be smaller than the smallest area 
that can outside the map at any given time, so when the new area is
requested, the tile 'jumps' to fill it, but positions itself based on
the grid instead of based on the map center.

Christopher Schmidt

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