404 raster tiles turn black and cover anything underneath it in the sort order

[burritojustice]

TANGRAM VERSION:

0.13.3

ENVIRONMENT:

10.12.4 (16E195), Chrome, Safari

TO REPRODUCE THE ISSUE, FOLLOW THESE STEPS:

define a limited (non-global) set raster tileset as a source in Tangram

test case:

https://meetar.github.io/raster-overlay/#15/40.7159/-73.9976

this came about trying to display tiled Sanborn maps:

https://mapzen.com/tangram/play/?#16.65417/37.80467/-122.29981

individual Sanborns generally cover a few city blocks, approximately 3x3 z17 tiles. even when lat/lon bounds: are included as a url: argument, empty tiles just outside the bounds are requested.

note that some tile renderers will generate a 'sparse' set of raster tiles that do not include empty tiles (common when the street grid is not north/south).

RESULT:

a 404 raster tile turns black and covers anything underneath it in the sort order, no matter what the raster style's blend mode is.

EXPECTED RESULT:

any 404 raster tiles should not impact the rest of the map.

[bcamper]

Will be fixed in #599, for v0.14.0

[bcamper]

Released in v0.14.0.