* Replace backdrop with simple noop mouse listener
As discussed in https://github.com/twbs/bootstrap/pull/22422 the current
approach of injecting a backdrop (to work around iOS' broken event
delegation for the `click` event) has annoying consequences on
touch-enabled laptop/desktop devices.
Instead of a backdrop `<div>`, here we simply add extra empty/noop
mouse listeners to the immediate children of `<body>` (and remove
them when the dropdown is closed) in order to force iOS to properly
bubble a `click` resulting from a tap (essentially, method 2 from
https://www.quirksmode.org/blog/archives/2014/02/mouse_event_bub.html)
This is sufficient (except in rare cases where the user does manage to tap
on the body itself, rather than any child elements of body - which is not
very likely in an iOS phone/tablet scenario for most layouts) to get iOS to
get a grip and do the correct event bubbling/delegation, meaning the regular
"click" event will bubble back to the `<body>` when tapping outside of the dropdown,
and the dropdown will close properly (just like it already does, even without
this fix, in non-iOS touchscreen devices/browsers, like Chrome/Android and
Windows on a touch laptop).
This approach, though a bit hacky, has no impact on the DOM structure, and
has no unforeseen side effects on touch-enabled laptops/desktops. And crucially,
it works just fine in iOS.
* Remove dropdown backdrop styles
* Update doc for dropdowns and touch-enabled devices
* Drop -x and -y as they're all the same
- Also move -width to elsewhere in the vars because it makes no sense by spacers.
- Update values of -x and -y across main Sass and docs Sass.
* Update docs to reflect changes; link to spacing utils from options page
The actual available size of the navbar toggler icon is 30px, but the
SVG uses a 32 unit grid. This commit uses a 30 unit grid and updates
icon accordingly.
- <progress> element didn't allow animation, labels overlaid, multiple bars, etc.
- Revamps CSS to use something more similar to v3's implementation
- Ditches variant mixin for `bg-` utils
- Rebuilds docs to match, including adding a new Height section for customizing that.
Only potential remaining todo is adding `.sr-only` instances to within the bar. Unsure if that's necessary.
- Overhauls the states, including the link/button variants, for list groups to better match how we handle .btn states.
- Moved the .list-group-item-action styles before the .list-group-item so that we don't have to do as much overriding.
- Removed the plain-hover-focus mixins from the disabled and active states since they're unnecessary.
- Added support for :active states on the .list-group-item-action variant (for the current click state).
- Removed the heading and text classes and variables since we can accomplish the same thing with utilities.
- Added support for :disabled on the .list-group-item-action as well since we can use those with button elements.
- Rearranged docs to reflect all the above changes.
- Reformatted some Sass variables.
- No need to set hover and focus on disabled or active elements. Disabled has no interactivity and active will inherit the focus.
- Also removes two now unused vars.
