L.EditToolbar.Edit decides how to handle layers based on the layer type. The process goes like this:

• If layer instanceof L.Marker is true, then L.EditToolbar.Edit does a series of marker-specific editing actions.
• Otherwise, L.EditToolbar.Edit does a few style tweaks, then calls layer.editing.enable(), delegating the specific editing behavior to the handler for that layer (i.e. L.Edit.Rectangle, L.Edit.Circle, L.Edit.Polyline, etc.). This means that layer.editing.enable() is not called if layer inherits from L.Marker.

This was a problem for me because I have a complex layer, L.Illustrate.Textbox, which inherits from L.Marker, but needs to have custom editing behavior.

As I looked at the code for L.EditToolbar.Edit, it seemed that the differential handling of layers into based on marker / non-marker type was fairly arbitrary. Furthermore, there were two lengthy marker-specific methods - _toggleMarkerHighlight and _offsetMarker - in L.EditToolbar.Edit that didn't seem to belong to a general-purpose editing class.

I have refactored L.EditToolbar.Edit to address these issues, moving marker-specific behavior into a new L.Edit.Marker class. This is nice because it makes layer.editing.enable() a universal method for turning on editing behavior, regardless of the layer type. As a bonus, it also makes it easy for plugin developers to override the default editing behavior for classes extending L.Marker.