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twbs--bootstrap/docs/components/reboot.md
Mark Otto f58143e7d6 editing intro
2015-04-17 12:39:39 -07:00

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layout title
page Reboot

Part of Bootstrap's job is to provide an elegant, consistent, and simple baseline to build upon. We use Reboot, a collection of element-specific CSS changes in a single file, to kickstart that.

Reboot builds upon Normalize, providing many HTML elements with somewhat opinionated styles using only element selectors. Additional styling is done only with classes. For example, we reboot some <table> styles for a simpler baseline and later provide .table, .table-bordered, and more.

Approach

Here are our guidelines and reasons for choosing what to override in Reboot:

  • Use rems and ems for units, nothing else.
  • Avoid margin-top. Vertical margins can collapse, yielding unexpected results. More importantly though, a single direction of margin is a simpler mental model.
  • For easier scaling across device sizes, block elements should use rems for margins.
  • Keep declarations of font-related properties to a minimal, using inherit whenever possible.

Page defaults

The <html> and <body> elements are updated to provide better page-wide defaults. More specifically:

  • The box-sizing is globally set on every element—including *:before and *after, to border-box. This ensures that the declared width of element is never exceeded due to padding or border.
  • A base font-size: 16px is declared on the <html> and font-size: 1rem on the <body> for easy responsive type-scaling via media queryies.
  • The <body> also sets a global font-family and line-height. This is inherited later by some form elements to prevent font inconsistencies.
  • For safety, the <body> has a declared background-color, defaulting to #fff.

Headings and paragraphs

All heading elements—e.g., <h1>—and <p> are reset to have their margin-top removed. Headings have margin-bottom: .5rem added and paragraphs margin-bottom: 1rem for easy spacing.

{% markdown %} # h1 heading Curabitur blandit tempus porttitor. Aenean eu leo quam. Pellentesque ornare sem lacinia quam venenatis vestibulum.

h2 heading

Curabitur blandit tempus porttitor. Aenean eu leo quam. Pellentesque ornare sem lacinia quam venenatis vestibulum.

h3 heading

Curabitur blandit tempus porttitor. Aenean eu leo quam. Pellentesque ornare sem lacinia quam venenatis vestibulum.

h4 heading

Curabitur blandit tempus porttitor. Aenean eu leo quam. Pellentesque ornare sem lacinia quam venenatis vestibulum.

h5 heading

Curabitur blandit tempus porttitor. Aenean eu leo quam. Pellentesque ornare sem lacinia quam venenatis vestibulum.

h6 heading

Curabitur blandit tempus porttitor. Aenean eu leo quam. Pellentesque ornare sem lacinia quam venenatis vestibulum. {% endmarkdown %}

Lists

All lists—<ul>, <ol>, and <dl>—have their margin-top removed and a margin-bottom: 1rem. Nested lists have no margin-bottom.

{% markdown %} * Lorem ipsum dolor sit amet * Consectetur adipiscing elit * Integer molestie lorem at massa * Facilisis in pretium nisl aliquet * Nulla volutpat aliquam velit * Phasellus iaculis neque * Purus sodales ultricies * Vestibulum laoreet porttitor sem * Ac tristique libero volutpat at * Faucibus porta lacus fringilla vel * Aenean sit amet erat nunc * Eget porttitor lorem
  1. Lorem ipsum dolor sit amet
  2. Consectetur adipiscing elit
  3. Integer molestie lorem at massa
  4. Facilisis in pretium nisl aliquet
  5. Nulla volutpat aliquam velit
  6. Faucibus porta lacus fringilla vel
  7. Aenean sit amet erat nunc
  8. Eget porttitor lorem {% endmarkdown %}

For simpler styling, clear hierarchy, and better spacing, description lists have updated margins. <dd>s reset margin-left to 0 and add margin-bottom: .5rem. <dt>s are bolded.

{% markdown %}
Description lists
A description list is perfect for defining terms.
Euismod
Vestibulum id ligula porta felis euismod semper eget lacinia odio sem.
Donec id elit non mi porta gravida at eget metus.
Malesuada porta
Etiam porta sem malesuada magna mollis euismod.
{% endmarkdown %}

Preformatted text

The <pre> element is reset to remove its margin-top and use rem units for its margin-bottom.

{% markdown %} 
.element {
  margin-bottom: 1rem;
}
{% endmarkdown %}

Tables

Tables are slightly adjusted to style <caption>s and ensure consistent text-align throughout.

This is an example table, and this is it's caption to describe the contents.
Table heading Table heading Table heading Table heading
Table cell Table cell Table cell Table cell
Table cell Table cell Table cell Table cell
Table cell Table cell Table cell Table cell

Forms

Various form elements have been rebooted for simpler base styles. Here are some of the most notable changes:

  • <fieldset>s have no borders, padding, or margin so they can be easily used as wrappers for individual inputs or groups of inputs. = <legend>s, like fieldsets, have also been restyled to be displayed as a heading of sorts.
  • <label>s are set to display: inline-block to allow margin to be applied.
  • <input>s, <selects>s, <textareas>s, and <buttons>s are mostly addressed by Normalize, but Reboot removes their margin and sets line-height: inherit, too.
  • <textarea>s are modified to only be resizeble vertically as horizontal resizing often "breaks" page layout.

These changes, and more, are demonstrated below.

Example legend 
<p>
  <label for="input">Example input</label>
  <input type="text" id="input" placeholder="Example input">
</p>

<p>
  <label for="select">Example select</label>
  <select id="select">
    <option value="">Choose...</option>
    <optgroup label="Option group 1">
      <option value="">Option 1</option>
      <option value="">Option 2</option>
      <option value="">Option 3</option>
    </optgroup>
    <optgroup label="Option group 2">
      <option value="">Option 4</option>
      <option value="">Option 5</option>
      <option value="">Option 6</option>
    </optgroup>
  </select>
</p>

<p>
  <label>
    <input type="checkbox" value="">
    Check this checkbox
  </label>
</p>

<p>
  <label>
    <input type="radio" name="optionsRadios" id="optionsRadios1" value="option1" checked>
    Option one is this and that
  </label>
  <label>
    <input type="radio" name="optionsRadios" id="optionsRadios2" value="option2">
    Option two is something else that's also super long to demonstrate the wrapping of these fancy form controls.
  </label>
  <label>
    <input type="radio" name="optionsRadios" id="optionsRadios3" value="option3" disabled>
    Option three is disabled
  </label>
</p>

<p>
  <label for="textarea">Example textarea</label>
  <textarea id="example" rows="3"></textarea>
</p>

<p>
  <label for="time">Example temporal</label>
  <input type="date">
</p>

<p>
  <label for="time">Example output</label>
  <output name="result">100</output>
</p>

<p>
  <button type="submit">Button submit</button>
  <input type="submit" value="Input submit button">
  <input type="button" value="Input button">
</p>

<p>
  <button type="submit" disabled>Button submit</button>
  <input type="submit" value="Input submit button" disabled>
  <input type="button" value="Input button" disabled>
</p>

Misc elements

Address

The <address> element is updated to reset the browser default font-style from italic to normal. line-height is also now inherited, and margin-bottom: 1rem has been added.

Twitter, Inc.
795 Folsom Ave, Suite 600
San Francisco, CA 94107
P: (123) 456-7890 Full Name
first.last@example.com

Blockquote

The default margin on blockquotes is 1em 40px, so we reset that to 0 0 1rem for something more consistent with other elements.

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer posuere erat a ante.

Someone famous in Source Title

Inline elements

The <abbr> element receives basic styling to make it stand the amongst paragraph text.

Nulla attr vitae elit libero, a pharetra augue.