Like previous "state PRs", this moves app-wide logic relating to
our "composer" widget to its own "state" class, which can be
referenced and called from all parts of the app. This lets us
avoid storing component instances, which we cannot do any longer
once we update to Mithril v2.
This was not as trivial as some of the other state changes, as we
tried to separate DOM effects (e.g. animations) from actual state
changes (e.g. minimizing or opening the composer).
New features:
- A new `app.screen()` method returns the current responsive screen
mode. This lets us check what breakpoint we're on in JS land
without hardcoding / duplicating the actual breakpoints from CSS.
- A new `SuperTextarea` util exposes useful methods for directly
interacting with and manipulating the text contents of e.g. our
post editor.
- A new `ConfirmDocumentUnload` wrapper component encapsulates the
logic for asking the user for confirmation when trying to close
the browser window or navigating to another page. This is used in
the composer to prevent accidentally losing unsaved post content.
There is still potential for future cleanups, but we finally want
to unblock the Mithril update, so these will have to wait:
- Composer height change logic is very DOM-based, so should maybe
not sit in the state.
- I would love to experiment with using composition rather than
inheritance for the `ComposerBody` subclasses.
* Replace gulp with webpack and npm scripts for JS compilation
* Set up Travis CI to commit compiled JS
* Restructure `js` directory; only one instance of npm, forum/admin are "submodules"
* Refactor JS initializers into Application subclasses
* Maintain partial compatibility API (importing from absolute paths) for extensions
* Remove minification responsibility from PHP asset compiler
* Restructure `less` directory
