Remove canvas dependency for core Vega

Requiring canvas dependency (or any other lib that uses native node bindings and requires C++ compilation) is always a challenge. I think it would greatly simplify Vega integration into large existing projects if it didn’t require canvas, but offered it as either a separate package, e.g. vega-server, or used some other npm install magic. Or we could create vega-no-canvas?

The moment I add vega lib as a dependency every user who wants to contribute to my project is required to install several native libraries/packages. And the instruction is complex and different for each OS / version. The issue also shows up for build integration (my project now has to specify complex travis configuration, or alter Jenkins, …).

[jheer]

I’ve added a new vega-canvas module that centralizes instantiation of canvas instances. It does not include explicit dependencies / optional dependencies on node-canvas libraries, deferring to parent projects to include node-canvas when desired.

The vega-scenegraph and vega-wordcloud modules now depend on vega-canvas, and so do not directly import node-canvas (other than as a dev dependency for testing).

Vega 3.0.10 has been released and now includes explicit optionalDependencies on canvas and canvas-prebuilt. This is done to maintain compatibility, such that node.js use and command line utilities continue to work as expected. To create a Vega variant that does not attempt to import node-canvas, you can basically copy the main Vega repo and remove the optionalDependencies from package.json.

I’m considering adding a new vega-client module to the Vega org that does exactly this, which would then replace Yuri’s vega-nocanvas. Feel free to share any additional thoughts here.

[jheer]

I’ll redirect that question to @kanitw and @domoritz. I believe Vega-Lite only depends on Vega for testing purposes, so canvas should only be an issue there if you are loading the devDependencies to run test cases.

Another question is vega-embed. That project should probably just import vega-lib instead of vega proper, but I’ll leave that question to the devs on that project.

Feel free to file issues directly on the relevant repos!