Why is ArcGIS API for JavaScript Map.setExtent snapping my extent?

Question

I'm having some problems setting the Map extent using ArcGIS API for JavaScript 3.18.

Whenever I call setExtent with myExtent, the Map ends up at some extent that is close to, but significantly different than myExtent. For example I call setExtent with:

myExtent = Object {type: "extent", xmin: -13486723.42416174, ymin: 6046817, xmax: -11828314.857440159, ymax: 8563452}

Then I handle the extent-change event to log the actual extent:

actualExtent = Object {type: "extent", xmin: -13334853.828803658, ymin: 6277279.110955888, xmax: -11980184.45279824, ymax: 8332989.889044112}

In this example the actualExtent is significantly more zoomed in than myExtent. But sometimes it's more zoomed out, sometimes it's more north, etc. Basically the Map seems to be snapping myExtent to certain zoom levels and positions.

Our server is ArcGIS Server 10.4.1. I have an ArcGIS API for Silverlight client connected to the same server doing the same work but it doesn't have this snapping problem. Can anyone suggest why this is happening and how to stop it?

UPDATE: To clarify how I build and set myExtent, it goes a little like this:

let myExtent = angular.copy(this.map.extent);
myExtent.xmin = -13486723.42416174; // calculated
myExtent.ymin = 6046817; // calculated
myExtent.xmax = -11828314.857440159; // calculated
myExtent.ymax = 8563452; // calculated
this.map.setExtent(myExtent);

• Midavalo: Are you using a Cached service?
• Corey: @Midavalo, no I'm not.
• Brian: Have you tried setting the extent with the spatial reference defined in the extent object?
• Corey: Great questions. I should have clarified in my original post. @Brian, before I call setExtent I get the current Map.extent, clone it with angular.copy, then set the xmin, xmax, ymin, ymax properties. I figured this was the safest way not to break anything. Could this actually be causing a problem?
• Corey: I found this snapToZoom setting in [version 4.1][2] that defaults to true. I'm pretty sure this is exactly what I'd like to set to false to fix my problem. But version 3.18 doesn't have this setting so I think I'm out of luck. [2]: developers.arcgis.com/javascript/latest/api-reference/…

Answer 1

If you'd like a guarantee that the input extent will be shown completely on the map when calling setExtent() you should pass the value true as the second (optional) fit parameter.

map.setExtent(myExtent, true);

https://developers.arcgis.com/javascript/3/jsapi/map-amd.html#setextent

• Corey: Thanks, but the docs say that is for Tiled map layers. I'm using Dynamic (I should have mentioned this in my original post). Also, that wouldn't really help as I'm trying to get actualExtent to match myExtent, not just include myExtent.
• john gravois: perhaps im missing something, but there's no way to guarantee that ratio of height x width of a passed extent is going to align exactly with the ratio of the window in which the map is being displayed.
• Corey: I calculate myExtent to match the aspect ratio of the map element.