map requests tiles outside bounds of tilingScheme

[tbranyen]

Heya,

I downloaded this plugin and attempted to use it, but all tiles come back as failures.

http://otile2.mqcdn.com/tiles/1.0.0/osm/0/1/0.png << unable to serve request.

[tbranyen]

This appears to be directly related with the zoom property. Setting zoom: 3 seems to be the sweet spot without causing errors. However, users can still zoom out on their own which causes errors.

[mprins]

at level 0 there is only 1 tile which is http://otile1.mqcdn.com/tiles/1.0.0/osm/0/0/0.png the requested tile does not exist.

[ryanttb]

Do you still have an issue? If your div is larger than the world at your zoom level, be requests for tiles that don't exist. They can be ignored. For example a 512x512px map element at zoom 0 will center tile http://otile1.mqcdn.com/tiles/1.0.0/osm/0/0/0.png and request invalid tiles around it from MapQuest Open.

[ryanttb]

I would still like to limit the request errors but there are a few design choices to make to do it properly.

• To stop requesting invalid top and left images, don't request tiles with negative indexes. However, devs may want to eventually repeat tiles along the X plane so we may need an option to allow for negative X indexes to return tiles from the right side of the map (which has its own issues mentioned below)
• To stop requesting invalid right and bottom images in a tilingScheme, we would have to know how many rows and columns the server supports on each zoom level. We currently do not have that ability. There is no way to query the server and there are no properties in our tilingScheme object that allows a developer to tell us how many rows/cols. With web mercator, we can assume that it starts with one row & column at zoom level 0 and doubles in each direction per zoom level, however we cannot assume that for every tilingScheme the dev can throw at us.

A possible solution is two new properties for the tilingScheme object:

baseTileCount - used in conjunction with levels; the number of rows and columns at level zero, doubled in each direction per level

tileCounts - used in conjunction with pixelSizes; the number of tile rows/columns per element in the pixelSizes array, i.e., per zoom level