Bootstrap4正式版发布！带来新的示例和新的主题

Bootstrap 4.0.0 正式版现已发布，更新内容方面，相对于之前的测试版，正式版没有重大的改变，但做出了一些关键的改进，并解决了一些棘手的错误，以及带来新的示例和新的主题！

新的示例

几乎每个示例都经过稳定的 v4 版本的重大修改，其中删除了一些过时的示例，添加了一些新的示例，并且彻底改变了其他一些示例。

当然，稳定版中依然有一些已知的问题尚未修复，预计在下一个小版本更新时会修复，如 Input groups, validation, 和 rounded corners。

主题方面，Bootstrap 的主题今年将得到重大更新，官方表示将会推出十个全新的主题。当前的目标是第一季度推出的主题都建立在 Bootstrap 4 上（都没有 v3 版本的）。

Bootstrap 4 的示例和迁移说明。

最新版下载地址：Bootstrap 4

Highlights

Brand new examples and overhauls for existing ones.
Additional border utilities have been added and the default border-color for them darkened from $gray-200 to $gray-300.
Pagination focus styles now match button and input focus state.
Added responsive .order-0 classes to reset column order.
Improved examples of form validation documentation by adding tooltip examples and more.
New documentation added for using our CSS variables to the Theming page.
Improved consistent across browsers when printing.
Sass map extends and docs
New and improved print display utilities

CSS

#24710: $component-active-bg and $component-active-color are partially useful.
#24821: Mixins form-control-focus and button-variant output invalid box-shadow value with shadows enabled.
#24915: Added new .order-last grid classes to match existing .grid-first ones.
#25021: Expand border utilities to include top, right, bottom, left.
#25035: Add variables for popover and tooltip font-size.
#25072: Move alert theme-color() levels to variables.
#25101: Extend $spacers and $sizes Sass maps the same way as we do our color maps to allow modifying, removing, and replacing key-value pairs.
#25117: Remove hardcoded value for navbar's .nav-link horizontal padding.
#25123: Darken $gray-600 by 10% for AA contrast.
#25137: Add .order-0 to the flexbox grid ordering helpers.
#25145: Update outline buttons to match default buttons—only show focus styles for the focused active state and not the normal active state.
#25149: Update pagination focus styles.
#25152: Reimplement input group addon support for textareas.
#25164: Improve printing cross-browser with the addition of new styles and variables.
#25167: Fixed color for disabled buttons.
#25169: Using the $custom-select-height variable to set the custom select height instead of $input-height.
#25173: Remove double borders for custom select and custom file.
#25177: Patch fractional viewport widths to work around Safari rounding bug.
#25210: Add validation feedback/tooltip support to .form-check-inputs.
#25250: Remove touch-action:manipulation click optimization.
#25264: Fix breakpoint mixins for custom breakpoint maps.
#25269: Prevent print utility display classes from overriding all other display utilities.
#25270: Deprecate hover media query shim and mixins.
#25279: Add direct children selectors to avoid cascading styles into a menu form.
#25308: Add display utilities to bootstrap-grid.scss.
#25317: Consistently use :disabled rather than [disabled] selector.
#25338: Use .list-group-item-action for list group item variant.
#25339: Outline button hover color.

JS

#25121: Allow nested structure for accordions.
#25146: Improve ESLint rules.
#25161: Multiple accordion support.
#25199: Check for window before window.QUnit.

Docs

#24751: Add Wall of Browser Bugs entry for Chrome SVG performance bug (#24673).
#24821: Mixins form-control-focus and button-variant output invalid box-shadow value with shadows enabled.
#24898: Overhaul existing and add new examples.
#24994: Add docs about active menu items.
#25071: Show JS button behaviors work on single buttons and button groups.
#25095: Add examples of disabled tooltip and popover triggers.
#25099: Wall of Browser Bugs: position:sticky support landed in MS Edge.
#25108: Update Theming docs for removing map items.
#25111: Add .modal-dialog-centered class to vertically centered modal example.
#25113: Update markup for new custom files in input groups.
#25115: Updated docs for translating "Browse" text into other languages.
#25116: Remove unnecessary align-middle class from Navbar docs.
#25138: docs: fix double copy button.
#25140: Move inline JS outside of HTML.
#25142: Fix overflow issue in IE.
#25143: Add tooltip and valid feedback validation examples.
#25144: Mention $custom-file-text change in Migration docs.
#25148: Document border utilities.
#25162: Remove incorrect roles from accordion, tweak/expand accessibility info, use buttons for accordion.
#25163: Expand keyboard advice for tooltips, clarify what manual trigger does in table.
#25165: Add new Approach docs page.
#25176: Add some documentation on using CSS variables to our Theming docs page.
#25229: Update browser compatibility note for position: sticky since Edge supports it now.
#25244: Fix invalid "constraint validation API" URL in docs.
#25261: Fix variable name in display utility class naming.
#25282: Use the SRI hashes for the live site's assets.
#25289: Add .list-group-flush` to list group docs.
#25302: Add example of a Spanish translation for custom file input.
#25325: Mention .input-group-text in migration docs for Beta 3.
#25355: Remove note about Opera 12 not supporting CSS3 animations.

Build

#25083, #25192: Update devDependencies and gems.
#25139: Add docs-github-serve script for local serving the github target.

Meta

#25080: Include JavaScript map files in NuGet packages.