aspect_fix_mode = 0 acting as ADJUST_BBOX_HEIGHT in WSG84

[4ng37]

When moving node-mapnik-sample-code from sphericalmercator to WSG84, the map has rendered as it had to adjusted the height.

postgis_settings = {
'srid' : '4326',
'table' : 'mytable' // has SRID 4326 anyway
}
…
var proj4 = '+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs';
// var proj4 = mercator.proj4;
var map = new mmapnik.Map(256, 256, proj4 );
var layer = new mapnik.Layer('tile', proj4 );
…
// var bbox = mercator.xyz_to_envelope(parseInt(params.x),parseInt(params.y),parseInt(params.z), false);
var bbox = tilebelt.tileToBBOX([parseInt(params.x),parseInt(params.y),parseInt(params.z)]);
…
map.aspect_fix_mode=8; // without this line, the coordinates are extended on height ...
map.extent = bbox; // ... when setting the map extent to the Bbox

I may have misused something, but setting aspect_fix_mode to 8 works fine, while leaving it to 0 changes the heigth coordinates

[lightmare]

First, use the named constants, not their values, in your code.

node-mapnik/src/mapnik_map.cpp

Lines 147 to 164 in 7e5997b

	NODE_MAPNIK_DEFINE_CONSTANT(lcons->GetFunction(),
	"ASPECT_GROW_BBOX",mapnik::Map::GROW_BBOX)
	NODE_MAPNIK_DEFINE_CONSTANT(lcons->GetFunction(),
	"ASPECT_GROW_CANVAS",mapnik::Map::GROW_CANVAS)
	NODE_MAPNIK_DEFINE_CONSTANT(lcons->GetFunction(),
	"ASPECT_SHRINK_BBOX",mapnik::Map::SHRINK_BBOX)
	NODE_MAPNIK_DEFINE_CONSTANT(lcons->GetFunction(),
	"ASPECT_SHRINK_CANVAS",mapnik::Map::SHRINK_CANVAS)
	NODE_MAPNIK_DEFINE_CONSTANT(lcons->GetFunction(),
	"ASPECT_ADJUST_BBOX_WIDTH",mapnik::Map::ADJUST_BBOX_WIDTH)
	NODE_MAPNIK_DEFINE_CONSTANT(lcons->GetFunction(),
	"ASPECT_ADJUST_BBOX_HEIGHT",mapnik::Map::ADJUST_BBOX_HEIGHT)
	NODE_MAPNIK_DEFINE_CONSTANT(lcons->GetFunction(),
	"ASPECT_ADJUST_CANVAS_WIDTH",mapnik::Map::ADJUST_CANVAS_WIDTH)
	NODE_MAPNIK_DEFINE_CONSTANT(lcons->GetFunction(),
	"ASPECT_ADJUST_CANVAS_HEIGHT",mapnik::Map::ADJUST_CANVAS_HEIGHT)
	NODE_MAPNIK_DEFINE_CONSTANT(lcons->GetFunction(),
	"ASPECT_RESPECT",mapnik::Map::RESPECT)

The default in mapnik is GROW_BBOX, which may act as ADJUST_BBOX_HEIGHT or ADJUST_BBOX_WIDTH depending on the dimensions that are to be adjusted. What you refer to as 8 is RESPECT which means no adjustment is made.

In short, working as intended.