Why are custom elements in SVG invisible?
Composing Svg with Aurelia is similar to composing html. You have to make sure though that any custom elements are implemented containerless (either by decorating the ViewModel with the `@containerless' attribute or adding an attribute 'containerless' to the custom element tag. SVG is picky about elements that are not defined in the specification and attributes that have the wrong value type.
Even if you have taken care of making them containerless it is still possible the custom elements do not show, even though they are added to the DOM.
Checkout this GistRun. You would expect two white rectangles, that are present in the DOM, above the other elements. But they are not visible.