This means that Browsh can now be entirely run just by running the CLI
binary. The client launches Firefox as a subprocess, then connects to it
via the Marionette protocol, installs the webextension and finally
triggers a new tab with, currently, the Google homepage in it.
I was trying to set this up for automated testing as well by installing
the built webextension as a temporary addon, because otherwise you need
to sign the extension everytime with a unique semantic version. However
for some reason I can't quite recreate the environment that MDN's
`web-ext` creates. The extension installs fine but fails to load the
`content.js` script, I can't find a backtrace or any other details about
the failure. So for now, we're just going to have to use `web-ext` as
seperate process and have the client connect to that. Which is what one
should do during development anyway, so it's not a huge loss.
Using JS's `getComputedStyle()` for every character is too CPU
intensive, so instead I'm experimenting with using a custom font
to take the canvas snapshot. The font is made up of only the unicode
block character, which basically fills the entire space given to a
monospace glyph. This also means that we can fairly reliably work out
the visibility (whether it's obscured or hidden with CSS) of text.
