Earlier we added some Paper.js code to our example/index.html page, but we really would like that functionality to live in our component. In order to access the Paper.js functionality we need to appy a mixin.
Unfortunately, as it turns out, Paper.js uses an architecture that makes everything a global object. This conflicts with the scoped nature of web components and it will not be possible to use Paper.js as a mixin for this component. This does not mean that we can’t use Paper.js as a dependency, but our component will not be self contained and we are forced to make a decision about whether we want to go down that path.
Some libraries are created using a pattern that conflicts with Viewdir's approach to component design. When a library creates a global, singleton API, we are not able to create new instances. This goes against the assumption that we can have multiple instances of web components on a page. This does not mean that we can't use these libraries. We just can't include them as Mixins. More on the singleton pattern can be found in Addy Osmani's JavaScript Design Patterns.
An example of a drawing library that can be included as a Mixin would be Etch. Here’s an example component that demonstrates how Etch can be used as a mixin.