aboutsummaryrefslogtreecommitdiffstats
path: root/vendor/twbs/bootstrap/site/docs/4.5/layout/overview.md
blob: 2f6efc65afc3599e7173a1a99fe95b2b544e26fa (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
---
layout: docs
title: Overview
description: Components and options for laying out your Bootstrap project, including wrapping containers, a powerful grid system, a flexible media object, and responsive utility classes.
group: layout
redirect_from: "/docs/4.5/layout/"
toc: true
---

## Containers

Containers are the most basic layout element in Bootstrap and are **required when using our default grid system**. Containers are used to contain, pad, and (sometimes) center the content within them. While containers *can* be nested, most layouts do not require a nested container.

Bootstrap comes with three different containers:

- `.container`, which sets a `max-width` at each responsive breakpoint
- `.container-fluid`, which is `width: 100%` at all breakpoints
- `.container-{breakpoint}`, which is `width: 100%` until the specified breakpoint

The table below illustrates how each container's `max-width` compares to the original `.container` and `.container-fluid` across each breakpoint.

See them in action and compare them in our [Grid example]({{ site.baseurl }}/docs/{{ site.docs_version }}/examples/grid/#containers).

<table class="table text-left">
  <thead>
    <tr>
      <th></th>
      <th>
        Extra small<br>
        <span class="font-weight-normal">&lt;576px</span>
      </th>
      <th>
        Small<br>
        <span class="font-weight-normal">&ge;576px</span>
      </th>
      <th>
        Medium<br>
        <span class="font-weight-normal">&ge;768px</span>
      </th>
      <th>
        Large<br>
        <span class="font-weight-normal">&ge;992px</span>
      </th>
      <th>
        Extra large<br>
        <span class="font-weight-normal">&ge;1200px</span>
      </th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td><code>.container</code></td>
      <td class="text-muted">100%</td>
      <td>540px</td>
      <td>720px</td>
      <td>960px</td>
      <td>1140px</td>
    </tr>
    <tr>
      <td><code>.container-sm</code></td>
      <td class="text-muted">100%</td>
      <td>540px</td>
      <td>720px</td>
      <td>960px</td>
      <td>1140px</td>
    </tr>
    <tr>
      <td><code>.container-md</code></td>
      <td class="text-muted">100%</td>
      <td class="text-muted">100%</td>
      <td>720px</td>
      <td>960px</td>
      <td>1140px</td>
    </tr>
    <tr>
      <td><code>.container-lg</code></td>
      <td class="text-muted">100%</td>
      <td class="text-muted">100%</td>
      <td class="text-muted">100%</td>
      <td>960px</td>
      <td>1140px</td>
    </tr>
    <tr>
      <td><code>.container-xl</code></td>
      <td class="text-muted">100%</td>
      <td class="text-muted">100%</td>
      <td class="text-muted">100%</td>
      <td class="text-muted">100%</td>
      <td>1140px</td>
    </tr>
    <tr>
      <td><code>.container-fluid</code></td>
      <td class="text-muted">100%</td>
      <td class="text-muted">100%</td>
      <td class="text-muted">100%</td>
      <td class="text-muted">100%</td>
      <td class="text-muted">100%</td>
    </tr>
  </tbody>
</table>

### All-in-one

Our default `.container` class is a responsive, fixed-width container, meaning its `max-width` changes at each breakpoint.

{% highlight html %}
<div class="container">
  <!-- Content here -->
</div>
{% endhighlight %}

### Fluid

Use `.container-fluid` for a full width container, spanning the entire width of the viewport.

{% highlight html %}
<div class="container-fluid">
  ...
</div>
{% endhighlight %}

### Responsive

Responsive containers are new in Bootstrap v4.4. They allow you to specify a class that is 100% wide until the specified breakpoint is reached, after which we apply `max-width`s for each of the higher breakpoints. For example, `.container-sm` is 100% wide to start until the `sm` breakpoint is reached, where it will scale up with `md`, `lg`, and `xl`.

{% highlight html %}
<div class="container-sm">100% wide until small breakpoint</div>
<div class="container-md">100% wide until medium breakpoint</div>
<div class="container-lg">100% wide until large breakpoint</div>
<div class="container-xl">100% wide until extra large breakpoint</div>
{% endhighlight %}

## Responsive breakpoints

Since Bootstrap is developed to be mobile first, we use a handful of [media queries](https://developer.mozilla.org/en-US/docs/Web/CSS/Media_Queries/Using_media_queries) to create sensible breakpoints for our layouts and interfaces. These breakpoints are mostly based on minimum viewport widths and allow us to scale up elements as the viewport changes.

Bootstrap primarily uses the following media query ranges—or breakpoints—in our source Sass files for our layout, grid system, and components.

{% highlight scss %}
// Extra small devices (portrait phones, less than 576px)
// No media query for `xs` since this is the default in Bootstrap

// Small devices (landscape phones, 576px and up)
@media (min-width: 576px) { ... }

// Medium devices (tablets, 768px and up)
@media (min-width: 768px) { ... }

// Large devices (desktops, 992px and up)
@media (min-width: 992px) { ... }

// Extra large devices (large desktops, 1200px and up)
@media (min-width: 1200px) { ... }
{% endhighlight %}

Since we write our source CSS in Sass, all our media queries are available via Sass mixins:

{% highlight scss %}
// No media query necessary for xs breakpoint as it's effectively `@media (min-width: 0) { ... }`
@include media-breakpoint-up(sm) { ... }
@include media-breakpoint-up(md) { ... }
@include media-breakpoint-up(lg) { ... }
@include media-breakpoint-up(xl) { ... }

// Example: Hide starting at `min-width: 0`, and then show at the `sm` breakpoint
.custom-class {
  display: none;
}
@include media-breakpoint-up(sm) {
  .custom-class {
    display: block;
  }
}
{% endhighlight %}

We occasionally use media queries that go in the other direction (the given screen size *or smaller*):

{% highlight scss %}
// Extra small devices (portrait phones, less than 576px)
@media (max-width: 575.98px) { ... }

// Small devices (landscape phones, less than 768px)
@media (max-width: 767.98px) { ... }

// Medium devices (tablets, less than 992px)
@media (max-width: 991.98px) { ... }

// Large devices (desktops, less than 1200px)
@media (max-width: 1199.98px) { ... }

// Extra large devices (large desktops)
// No media query since the extra-large breakpoint has no upper bound on its width
{% endhighlight %}

{% include callout-info-mediaqueries-breakpoints.md %}

Once again, these media queries are also available via Sass mixins:

{% highlight scss %}
@include media-breakpoint-down(xs) { ... }
@include media-breakpoint-down(sm) { ... }
@include media-breakpoint-down(md) { ... }
@include media-breakpoint-down(lg) { ... }
// No media query necessary for xl breakpoint as it has no upper bound on its width

// Example: Style from medium breakpoint and down
@include media-breakpoint-down(md) {
  .custom-class {
    display: block;
  }
}
{% endhighlight %}

There are also media queries and mixins for targeting a single segment of screen sizes using the minimum and maximum breakpoint widths.

{% highlight scss %}
// Extra small devices (portrait phones, less than 576px)
@media (max-width: 575.98px) { ... }

// Small devices (landscape phones, 576px and up)
@media (min-width: 576px) and (max-width: 767.98px) { ... }

// Medium devices (tablets, 768px and up)
@media (min-width: 768px) and (max-width: 991.98px) { ... }

// Large devices (desktops, 992px and up)
@media (min-width: 992px) and (max-width: 1199.98px) { ... }

// Extra large devices (large desktops, 1200px and up)
@media (min-width: 1200px) { ... }
{% endhighlight %}

These media queries are also available via Sass mixins:

{% highlight scss %}
@include media-breakpoint-only(xs) { ... }
@include media-breakpoint-only(sm) { ... }
@include media-breakpoint-only(md) { ... }
@include media-breakpoint-only(lg) { ... }
@include media-breakpoint-only(xl) { ... }
{% endhighlight %}

Similarly, media queries may span multiple breakpoint widths:

{% highlight scss %}
// Example
// Apply styles starting from medium devices and up to extra large devices
@media (min-width: 768px) and (max-width: 1199.98px) { ... }
{% endhighlight %}

The Sass mixin for targeting the same screen size range would be:

{% highlight scss %}
@include media-breakpoint-between(md, xl) { ... }
{% endhighlight %}

## Z-index

Several Bootstrap components utilize `z-index`, the CSS property that helps control layout by providing a third axis to arrange content. We utilize a default z-index scale in Bootstrap that's been designed to properly layer navigation, tooltips and popovers, modals, and more.

These higher values start at an arbitrary number, high and specific enough to ideally avoid conflicts. We need a standard set of these across our layered components—tooltips, popovers, navbars, dropdowns, modals—so we can be reasonably consistent in the behaviors. There's no reason we couldn't have used `100`+ or `500`+.

We don't encourage customization of these individual values; should you change one, you likely need to change them all.

{% highlight scss %}
$zindex-dropdown:          1000 !default;
$zindex-sticky:            1020 !default;
$zindex-fixed:             1030 !default;
$zindex-modal-backdrop:    1040 !default;
$zindex-modal:             1050 !default;
$zindex-popover:           1060 !default;
$zindex-tooltip:           1070 !default;
{% endhighlight %}

To handle overlapping borders within components (e.g., buttons and inputs in input groups), we use low single digit `z-index` values of `1`, `2`, and `3` for default, hover, and active states. On hover/focus/active, we bring a particular element to the forefront with a higher `z-index` value to show their border over the sibling elements.