* Simplify scrollbar refresh and measurement by using imperative DOM
manipulation instead of React to hide/show scrollbars.
* Rename `::performInitialMeasurement` to `::becameVisible`
* Break `::checkForVisibilityChange` out of `::pollDOM` and use it in
to check for the element becoming visible in `componentWillUpdate`.
* Don't rely on stored visibility state anywhere. Always check again.
This could potentially be cached for an update cycle but being wrong
about this is disastrous so I'm being conservative.
This moves observation of the config keys to Editor, which assigns the
invisibles hash or null on the TokenizedBuffer via the DisplayBuffer to
control whether we render invisibles or not.
This commit also extends config.get to merge default values into the
returned object if both the assigned and default values are objects.
This allows 'atom.invisibles' to be treated as an object that always has
the default values filled in.
Per the discussion with @kevinsawicki in #3168, I have added a config
option `editor.confirmCheckoutHead` that defaults to `true`. When the
`editor:checkout-head-revision` command is executed, a confirmation
dialog now shows that states which file is to be reverted and asks the
user to "Revert" or "Cancel". If the config option is set to `false`,
the old behavior, simply reverting without prompting, is used.
I also added tests to ensure that the confirmation dialog is displayed
or not in the right configurations.
Check enabled names against the bundled names and ensure
one bundled UI and one bundled syntax theme are enabled,
defaulting to the dark themes when necessary.
Previously, each editor observed font-related config values on its own
and applied inline styles to honor them. This made it difficult to style
the editor like a normal element with CSS.
Moving this to a global stylesheet that targets editors via the .editor
selector means that the font size setting can be overridden in specific
contexts, such as when using mini editors.
