in SVG export, give top layer g element id="<filename>-<layername>"

[cedricsam]

• To facilitate CSS/JS-targeting using ID when layers order and complement change frequently
• Also easier to keep track of layers in Illustrator

[mbloch]

What about just using the original layer names as ids in SVG output, rather than concatenating the file name with the layer name? (I think that's what I originally intended to do.)

[cedricsam]

The reason why I'd prefer also having the file name in there was to get an id attribute that's as unique as possible, in the scenario where multiple SVGs made from mapshaper, with the same layer names, were to be embedded on a webpage. But then again, id attributes of features already often share the same values in a general multi-layer (let alone multi-SVG) scenario.

Do you prefer just having the layer name because it'd be shorter and perhaps easier to see in a layer list on Illustrator? I don't feel strongly about the file name, but a layer name as the g's id would be a nice improvement. :)

[mbloch]

As you point out, even if you create unique layer ids, collisions could still occur between the ids of map features and other elements in a document. (This is when you're including an SVG map "inline" on a web page, as opposed to embedding as an <object> or <img>, right?)

One simple solution would be to add an option to the -o command to apply a prefix to all the ids in an SVG document, including both layer and feature ids. Sort of a crude namespace. It could be called something like svg-namespace= or id-prefix=. I would prefer this to generating complex layer ids. What do you think?

[cedricsam]

Yes, collisions will still occur. There’s also the case of when several features use the same id-field (which is more a matter of how you pick your id-field), but I see how it could be disruptive to Illustrator scripts that depend on the ID just being a single-value attribute, without anything else.

That said, I like the idea of a svg-namespace= or id-prefix, and to provide control over the naming, rather than reuse the filename. Do you want to discard this PR and start over your way, or wouldn’t mind if I looked into this? (And what do you think of the point-symbol=square improvements? #241 #243)