I currently have a Firefox extension/plugin combo that works well, and was written with a combination of NPAPI (Firebreath) C++ code and Javascript. The extension works by defining a browser overlay (overlay.xul/overlay.js) that is loaded on every webpage via a script src="overlay.js" tag.
I need to adapt it for the upcoming changes for Firefox Webextensions and deprecation of XPCOM/XUL.
From what I understand, Webextensions will be primarily Javascript based. How would I be able to continue using the C++ portion of my extension? Note that porting the C++ NPAPI library to Javascript would be a non-starter for various reasons.