Layout component

.changeset/empty-kangaroos-learn.md

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+---
+"@primer/css": minor
+---
+
+Adding new Layout component

docs/content/components/layout.md

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+---
+title: Layout
+path: components/layout
+status: Experimental
+source: 'https://github.com/primer/css/tree/main/src/layout/layout.scss'
+bundle: layout
+---
+
+
+Build responsive-friendly page layouts with 2 columns.
+
+Use with .container-xx classes to limit the overall layout structure size.
+
+## Elements
+
+- `Layout-main`
+- `Layout-sidebar`
+- `Layout-divider`
+- `Layout-main-centered-md`
+- `Layout-main-centered-lg`
+- `Layout-main-centered-xl`
+
+Use `Layout-main-centered-xx` to wrap `container-xx` elements inside
+`Layout-main` so the content remains centered on the screen regardless
+of the sidebar position.
+
+## Default
+
+```html live
+<div class="Layout">
+  <div class="Layout-main border">
+    .Layout-main
+  </div>
+
+  <div class="Layout-sidebar border">
+    .Layout-sidebar
+  </div>
+</div>
+```
+
+### Dividers
+
+Add `Layout--divided` to the `Layout` to show the dividers.
+
+```html live
+<div class="Layout Layout--divided">
+  <div class="Layout-main border">main content</div>
+  <div class="Layout-divider"></div>
+  <div class="Layout-sidebar border">divider shown</div>
+</div>
+<div class="Layout">
+  <div class="Layout-main border">main content</div>
+  <div class="Layout-divider"></div>
+  <div class="Layout-sidebar border">divider hidden</div>
+</div>
+```
+
+### Centered content
+
+```html live
+<div class="Layout">
+  <div class="Layout-main border">
+    <div class="Layout-main-centered-md">
+      <div class="container-md border color-border-info">
+        centered md
+      </div>
+    </div>
+  </div>
+  <div class="Layout-sidebar border">sidebar</div>
+</div>
+<div class="Layout">
+  <div class="Layout-main border">
+    <div class="Layout-main-centered-lg">
+      <div class="container-lg border color-border-info">
+        centered lg
+      </div>
+    </div>
+  </div>
+  <div class="Layout-sidebar border">sidebar</div>
+</div>
+<div class="Layout">
+  <div class="Layout-main border">
+    <div class="Layout-main-centered-xl">
+      <div class="container-xl border color-border-info">
+        centered xl
+      </div>
+    </div>
+  </div>
+  <div class="Layout-sidebar border">sidebar</div>
+</div>
+```
+
+## Modifiers
+
+### Sidebar sizing
+
+- Default: [md: 256px, lg: 296px, xl: 320px]
+- `Layout--sidebar-narrow` [md: 240px, lg: 256px, xl: 296px]
+- `Layout--sidebar-wide` [md: 296px, lg: 320px, xl: 344px]
+
+```html live
+<div class="Layout Layout--sidebar-narrow">
+  <div class="Layout-main border">
+    Layout--sidebar-narrow
+  </div>
+
+  <div class="Layout-sidebar border">
+    sidebar
+  </div>
+</div>
+<div class="Layout Layout--sidebar-wide">
+  <div class="Layout-main border">
+    Layout--sidebar-wide
+  </div>
+
+  <div class="Layout-sidebar border">
+    sidebar
+  </div>
+</div>
+```
+
+### Column gutter
+
+- Default: [md: 16px, lg: 24px]
+- `Layout--gutter-none`: 0px
+- `Layout--gutter-condensed` 16px
+- `Layout--gutter-spacious` [md: 16px, lg: 32px, xl: 40px]
+
+```html live
+<div class="Layout Layout--gutter-none">
+  <div class="Layout-main border">
+    Layout--gutter-none
+  </div>
+
+  <div class="Layout-sidebar border">
+    sidebar
+  </div>
+</div>
+<div class="Layout Layout--gutter-condensed">
+  <div class="Layout-main border">
+    Layout--gutter-condensed
+  </div>
+
+  <div class="Layout-sidebar border">
+    sidebar
+  </div>
+</div>
+<div class="Layout">
+  <div class="Layout-main border">
+    Default
+  </div>
+
+  <div class="Layout-sidebar border">
+    sidebar
+  </div>
+</div>
+<div class="Layout Layout--gutter-spacious">
+  <div class="Layout-main border">
+    Layout--gutter-spacious
+  </div>
+
+  <div class="Layout-sidebar border">
+    sidebar
+  </div>
+</div>
+```
+
+### Sidebar positioning
+
+- `Layout--sidebarPosition-start` (default): sidebar to the left
+- `Layout--sidebarPosition-end`: sidebar to the right
+
+```html live
+<div class="Layout Layout--sidebarPosition-start">
+  <div class="Layout-main border">main</div>
+  <div class="Layout-sidebar border">sidebar</div>
+</div>
+<div class="Layout Layout--sidebarPosition-end">
+  <div class="Layout-main border">main</div>
+  <div class="Layout-sidebar border">sidebar</div>
+</div>
+```
+
+### Layout stacking
+
+- Default: stacks when container is `sm`.
+- `Layout--flowRow-until-md`: stacks when container is `md`.
+- `Layout--flowRow-until-lg`: stacks when container is `lg`.
+
+```html live
+<div class="Layout Layout--flowRow-until-md">
+  <div class="Layout-main border">main</div>
+  <div class="Layout-sidebar border">sidebar</div>
+</div>
+<div class="Layout Layout--flowRow-until-lg">
+  <div class="Layout-main border">main</div>
+  <div class="Layout-sidebar border">sidebar</div>
+</div>
+```
+
+### Nesting Layouts
+
+It is possible to nest `Layout` components to generate 3-column layouts.
+
+```html live
+<div class="Layout">
+  <div class="Layout-main ">
+    <div class="Layout Layout--sidebarPosition-end Layout--sidebar-narrow">
+      <div class="Layout-main border">main content</div>
+      <div class="Layout-sidebar border">metadata sidebar</div>
+    </div>
+  </div>
+  <div class="Layout-sidebar border">default sidebar</div>
+</div>
+<div class="Layout">
+  <div class="Layout-main ">
+    <div class="Layout Layout--sidebarPosition-end Layout--flowRow-until-lg Layout--sidebar-narrow">
+      <div class="Layout-main border">main content</div>
+      <div class="Layout-sidebar border">metadata sidebar</div>
+    </div>
+  </div>
+  <div class="Layout-sidebar border">default sidebar</div>
+</div>
+```
+
+## Accessibility and keyboard navigation
+
+Keyboard navigation follows the markup order. Decide carefully how the
+focus order should be be by deciding whether `Layout-main` or `Layout-sidebar`
+comes first in code. The code order won’t affect the visual position.

docs/src/@primer/gatsby-theme-doctocat/nav.yml

@@ -83,6 +83,8 @@
       url: /components/header
     - title: Labels
       url: /components/labels
+    - title: Layout
+      url: /components/layout
     - title: Links
       url: /components/links
     - title: Loaders