Previously deprecated in v4.x, this clears out the now unused Sass option and removes some unused mixins. Arguably we could remove more, but I like the hover-focus mixin and we make extensive use of it across the project.
Explicitly re-adds the "hand" `cursor:pointer` for non-disabled `.btn`, `.close`, `.navbar-toggler` elements, as well as forcing `page-link` pagination controls to always have the "hand" cursor (even if an author uses it on, say, `<button>` elements for a dynamically updating in-page pagination).
Controversial, as everybody jumped on the bandwagon following this article https://medium.com/simple-human/buttons-shouldnt-have-a-hand-cursor-b11e99ca374b - which does have its merits of course, but there are also counter-arguments like http://kizu.ru/en/issues/cursor-pointer/
And seeing the amount of issues we've seen following the change, and the potential complexity needed to consistently address the cursor issue (see https://github.com/twbs/bootstrap/issues/24156 where i explore how the cursor needs to be based on "intent", and how that's tough to determine), I'm favouring an opinionated take here of just reintroducing the `cursor:pointer`.
* Update the form focus mixin to use a manual `$enable-shadows` check so we can always ensure a focus state for accessibility and consistency
* - Add new `$input-btn-focus-width` and `$input-btn-focus-color` variables.
- Replace separate `$btn-focus-box-shadow` and `$input-focus-box-shadow`
variables with unified `$input-btn-focus-box-shadow` to match our
combined variables approach elsewhere.
* Put new focus width var to use in buttons mixins
* use new button input-box shadow var
* Add a new mixin for quickly adding linear gradient to components when $enable-gradients is set to true
* use correct var
* fix focus shadows in button mixins
* Add opt-in gradients to alerts, buttons, carousel, custom radios and checkboxes, custom file input, and dropdown items
* Generate .bg-gradient- utilities
* add headings to colors page and document bg-gradient utils
* update the button color for active status, check with yiq as it's done for basic state and hover state
Uses some if/else action to ensure there's readable text on hover. Swapped out a hex value to a variable while I was in there.
Fixes#23398, fixes#23351.
When focused, these buttons styled as links still give good visible focus indication through the underline, so this should not be a concern. Closes#22655
- removes original outline removal (hah)
- replaces it with an explicit `outline: 0` on `.btn`
- instead of replicating `:hover` for `:focus`, uses custom and themed `box-shadow` for an "outline"
- not mapped to the `$enable-shadows` variable because accessibility
