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docs(multiple): revise and expand a11y docs (#23581)
This change updates the accessibility docs for 21 components for correctness, comprehensiveness, and clarity. I have intentionally omitted several other components either because they're being worked on by someone else or have signifcant changes pending.
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‎src/material/autocomplete/autocomplete.md‎

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@@ -100,10 +100,12 @@ autocomplete is attached to using the `matAutocompleteOrigin` directive together
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```
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### Keyboard interaction
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- <kbd>DOWN_ARROW</kbd>: Next option becomes active
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- <kbd>UP_ARROW</kbd>: Previous option becomes active
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- <kbd>ENTER</kbd>: Selects currently active item
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- <kbd>ESCAPE</kbd>: Closes the autocomplete panel
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- <kbd>Down Arrow</kbd>: Next option becomes active
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- <kbd>Up Arrow</kbd>: Previous option becomes active
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- <kbd>Enter</kbd>: Selects currently active item
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- <kbd>Escape</kbd>: Closes the autocomplete panel
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- <kbd>Alt + Up Arrow</kbd>: Closes the autocomplete panel
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- <kbd>Alt + Down Arrow</kbd>: Open the autocomplete panel if there are any matching options.
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### Option groups
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`mat-option` can be collected into groups using the `mat-optgroup` element:
@@ -112,8 +114,16 @@ autocomplete is attached to using the `matAutocompleteOrigin` directive together
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"region":"mat-autocomplete"}) -->
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### Accessibility
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The input for an autocomplete without text or labels should be given a meaningful label via
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`aria-label` or `aria-labelledby`.
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The autocomplete trigger is given `role="combobox"`. The trigger sets `aria-owns` to the
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autocomplete's id, and sets `aria-activedescendant` to the active option's id.
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`MatAutocomplete` implements the ARIA combobox interaction pattern. The text input trigger specifies
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`role="combobox"` while the content of the pop-up applies `role="listbox"`. Because of this listbox
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pattern, you should _not_ put other interactive controls, such as buttons or checkboxes, inside
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an autocomplete option. Nesting interactive controls like this interferes with most assistive
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technology.
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Always provide an accessible label for the autocomplete. This can be done
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via `<mat-label>` inside of `<mat-form-field>`, a native `<label>` element, the `aria-label`
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attribute, or the `aria-labelledby` attribute.
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`MatAutocomplete` preserves focus on the text trigger, using `aria-activedescendant` to support
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navigation though the autocomplete options.

‎src/material/bottom-sheet/bottom-sheet.md‎

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@@ -96,20 +96,49 @@ for `MAT_BOTTOM_SHEET_DEFAULT_OPTIONS` in your application's root module.
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### Accessibility
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By default, the bottom sheet has `role="dialog"` on the root element and can be labelled using the
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`ariaLabel` property on the `MatBottomSheetConfig`.
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When a bottom sheet is opened, it will move focus to the first focusable element that it can find.
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In order to prevent users from tabbing into elements in the background, the Material bottom sheet
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uses a [focus trap](https://material.angular.io/cdk/a11y/overview#focustrap) to contain focus
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within itself. Once a bottom sheet is closed, it will return focus to the element that was focused
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before it was opened.
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`MatBottomSheet` creates modal dialogs that implement the ARIA `role="dialog"` pattern. This root
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dialog element should be given an accessible label via the `ariaLabel` property of
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`MatBottomSheetConfig`.
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#### Keyboard interaction
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By default, the escape key closes `MatBottomSheet`. While you can disable this behavior by using
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the `disableClose` property of `MatBottomSheetConfig`, doing this breaks the expected interaction
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pattern for the ARIA `role="dialog"` pattern.
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#### Focus management
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By default, the first tabbable element within the bottom sheet will receive focus upon open.
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This can be configured by setting the `cdkFocusInitial` attribute on another focusable element.
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#### Keyboard interaction
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By default pressing the escape key will close the bottom sheet. While this behavior can
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be turned off via the `disableClose` option, users should generally avoid doing so
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as it breaks the expected interaction pattern for screen-reader users.
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When opened, `MatBottomSheet` traps browser focus such that it cannot escape the root
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`role="dialog"` element. By default, the first tabbable element in the bottom sheet receives focus.
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You can customize which element receives focus with the `autoFocus` property of
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`MatBottomSheetConfig`, which supports the following values.
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| Value | Behavior |
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|------------------|--------------------------------------------------------------------------|
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| `first-tabbable` | Focus the first tabbable element. This is the default setting. |
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| `first-header` | Focus the first header element (`role="heading"`, `h1` through `h6`) |
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| `dialog` | Focus the root `role="dialog"` element. |
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| Any CSS selector | Focus the first element matching the given selector. |
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While the default setting applies the best behavior for most applications, special cases may benefit
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from these alternatives. Always test your application to verify the behavior that works best for
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your users.
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#### Focus restoration
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When closed, `MatBottomSheet` restores focus to the element that previously held focus when the
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bottom sheet opened. However, if that previously focused element no longer exists, you must
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add additional handling to return focus to an element that makes sense for the user's workflow.
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Opening a bottom sheet from a menu is one common pattern that causes this situation. The menu
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closes upon clicking an item, thus the focused menu item is no longer in the DOM when the bottom
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sheet attempts to restore focus.
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You can add handling for this situation with the `afterDismissed()` observable from
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`MatBottomSheetRef`.
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```typescript
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const bottomSheetRef = bottomSheet.open(FileTypeChooser);
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bottomSheetRef.afterDismissed().subscribe(() => {
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// Restore focus to an appropriate element for the user's workflow here.
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});
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```

‎src/material/button-toggle/button-toggle.md‎

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@@ -28,17 +28,24 @@ be configured globally using the `MAT_BUTTON_TOGGLE_DEFAULT_OPTIONS` injection t
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`<mat-button-toggle-group>` is compatible with `@angular/forms` and supports both `FormsModule`
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and `ReactiveFormsModule`.
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### Accessibility
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The button-toggles internally use native `button` elements with `aria-pressed` to convey
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their toggled state. The button-toggle-group surrounding the individual buttons applies
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`role="group"` to convey the association between the individual toggles.
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For button toggles containing only icons, each button toggle should be given a meaningful label via
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`aria-label` or `aria-labelledby`.
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For button toggle groups, each group should be given a meaningful label via `aria-label` or
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`aria-labelledby`.
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### Orientation
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The button-toggles can be rendered in a vertical orientation by adding the `vertical` attribute.
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### Accessibility
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`MatButtonToggle` internally uses native `button` elements with `aria-pressed` to convey toggle
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state. If a toggle contains only an icon, you should specify a meaningful label via `aria-label`
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or `aria-labelledby`. For dynamic labels, `MatButtonToggle` provides input properties for binding
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`aria-label` and `aria-labelledby`. This means that you should not use the `attr.` prefix when
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binding these properties, as demonstrated below.
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```html
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<mat-button-toggle [aria-label]="alertsEnabled ? 'Disable alerts' : 'Enable alerts'">
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<mat-icon>notifications</mat-icon>
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</mat-button-toggle>
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```
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The `MatButtonToggleGroup` surrounding the individual buttons applies
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`role="group"` to convey the association between the individual toggles. Each
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`<mat-button-toggle-group>` element should be given a label with `aria-label` or `aria-labelledby`
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that communicates the collective meaning of all toggles. For example, if you have toggles for
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"Bold", "Italic", and "Underline", you might label the parent group "Font styles".

‎src/material/card/card.md‎

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@@ -44,32 +44,36 @@ This element can contain:
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* `<img mat-card-lg-image>`
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### Accessibility
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Cards can be used in a wide variety of scenarios and can contain many different types of content.
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Due to this dynamic nature, the appropriate accessibility treatment depends on how `<mat-card>` is
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used.
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Cards serve a wide variety of scenarios and may contain many different types of content.
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Due to this flexible nature, the appropriate accessibility treatment depends on how you use
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`<mat-card>`.
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#### Group, region, and landmarks
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There are several ARIA roles that communicate that a portion of the UI represents some semantically
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meaningful whole. Depending on what the content of the card means to your application,
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[`role="group"`][0], [`role="region"`][1], or [one of the landmark roles][2] should typically be
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applied to the `<mat-card>` element.
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meaningful whole. Depending on what the content of the card means to your application, you can apply
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one of [`role="group"`][role-group], [`role="region"`][role-region], or
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[one of the landmark roles][aria-landmarks] to the `<mat-card>` element.
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A role is not necessary when the card is used as a purely decorative container that does not
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You do not need to apply a role when using a card as a purely decorative container that does not
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convey a meaningful grouping of related content for a single subject. In these cases, the content
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of the card should follow standard practices for document content.
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#### Focus
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Depending on how cards are used, it may be appropriate to apply a `tabindex` to the `<mat-card>`
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element. If cards are a primary mechanism through which user interacts with the application,
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`tabindex="0"` is appropriate. If attention can be sent to the card, but it's not part of the
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document flow, `tabindex="-1"` is appropriate.
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If the card acts as a purely decorative container, it does not need to be tabbable. In this case,
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the card content should follow normal best practices for tab order.
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Depending on how cards are used, it may be appropriate to apply a `tabindex` to the `<mat-card>`
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element.
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* If cards are a primary mechanism through which user interacts with the application, `tabindex="0"`
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may be appropriate.
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* If attention can be sent to the card, but it's not part of the document flow, `tabindex="-1"` may
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be appropriate.
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* If the card acts as a purely decorative container, it does not need to be tabbable. In this case,
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the card content should follow normal best practices for tab order.
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Always test your application to verify the behavior that works best for your users.
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[0]: https://www.w3.org/TR/wai-aria/#group
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[1]: https://www.w3.org/TR/wai-aria/#region
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[2]: https://www.w3.org/TR/wai-aria/#landmark
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[role-group]: https://www.w3.org/TR/wai-aria/#group
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[role-region]: https://www.w3.org/TR/wai-aria/#region
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[aria-landmarks]: https://www.w3.org/TR/wai-aria/#landmark

‎src/material/checkbox/checkbox.md‎

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@@ -56,9 +56,18 @@ The color of a `<mat-checkbox>` can be changed by using the `color` property. By
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use the theme's accent color. This can be changed to `'primary'` or `'warn'`.
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### Accessibility
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The `<mat-checkbox>` uses an internal `<input type="checkbox">` to provide an accessible experience.
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`MatCheckbox` uses an internal `<input type="checkbox">` to provide an accessible experience.
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This internal checkbox receives focus and is automatically labelled by the text content of the
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`<mat-checkbox>` element.
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`<mat-checkbox>` element. Avoid adding other interactive controls into the content of
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`<mat-checkbox>`, as this degrades the experience for users of assistive technology.
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Always provide an accessible label via `aria-label` or `aria-labelledby` for checkboxes without
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descriptive text content. For dynamic labels, `MatCheckbox` provides input properties for binding
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`aria-label` and `aria-labelledby`. This means that you should not use the `attr.` prefix when
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binding these properties, as demonstrated below.
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Checkboxes without text or labels should be given a meaningful label via `aria-label` or
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`aria-labelledby`.
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```html
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<mat-checkbox [aria-label]="isSubscribedToEmailsMessage">
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</mat-checkbox>
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```

‎src/material/datepicker/datepicker.md‎

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@@ -562,72 +562,80 @@ value can be anything that is accepted by `ngClass`.
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### Accessibility
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The `MatDatepickerInput` and `MatDatepickerToggle` directives add the `aria-haspopup` attribute to
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the native input and toggle button elements respectively, and they trigger a calendar dialog with
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`role="dialog"`.
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The `MatDatepicker` pop-up uses the `role="dialog"` interaction pattern. This dialog then contains
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multiple controls, the most prominent being the calendar itself. This calendar implements the
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`role="grid"` interaction pattern.
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`MatDatepickerIntl` includes strings that are used for `aria-label`s. The datepicker input
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should have a placeholder or be given a meaningful label via `aria-label`, `aria-labelledby` or
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The `MatDatepickerInput` and `MatDatepickerToggle` directives both apply the `aria-haspopup`
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attribute to the native input and button elements, respectively.
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`MatDatepickerIntl` includes strings that are used for `aria-label` attributes. Always provide
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the datepicker text input a meaningful label via `<mat-label>`, `aria-label`, `aria-labelledby` or
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`MatDatepickerIntl`.
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`MatDatepickerInput` adds <kbd>>Alt</kbd> + <kbd>Down Arrow</kbd> as a keyboard short to open the
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datepicker pop-up. However, ChromeOS intercepts this key combination at the OS level such that the
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browser only receives a `PageDown` key event. Because of this behavior, you should always include an
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additional means of opening the pop-up, such as `MatDatepickerToggle`.
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#### Keyboard interaction
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The datepicker supports the following keyboard shortcuts:
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| Shortcut | Action |
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|----------------------|-------------------------------------------|
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| `ALT` + `DOWN_ARROW` | Open the calendar pop-up |
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| `ESCAPE` | Close the calendar pop-up |
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| Shortcut | Action |
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|----------------------------------------|----------------------------|
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| <kbd>ALT</kbd> + <kbd>DOWN_ARROW</kbd> | Open the calendar pop-up |
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| <kbd>ESCAPE</kbd> | Close the calendar pop-up |
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In month view:
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| Shortcut | Action |
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|----------------------|-------------------------------------------|
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| `LEFT_ARROW` | Go to previous day |
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| `RIGHT_ARROW` | Go to next day |
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| `UP_ARROW` | Go to same day in the previous week |
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| `DOWN_ARROW` | Go to same day in the next week |
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| `HOME` | Go to the first day of the month |
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| `END` | Go to the last day of the month |
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| `PAGE_UP` | Go to the same day in the previous month |
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| `ALT` + `PAGE_UP` | Go to the same day in the previous year |
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| `PAGE_DOWN` | Go to the same day in the next month |
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| `ALT` + `PAGE_DOWN` | Go to the same day in the next year |
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| `ENTER` | Select current date |
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| Shortcut | Action |
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|---------------------------------------|------------------------------------------|
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| <kbd>LEFT_ARROW</kbd> | Go to previous day |
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| <kbd>RIGHT_ARROW</kbd> | Go to next day |
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| <kbd>UP_ARROW</kbd> | Go to same day in the previous week |
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| <kbd>DOWN_ARROW</kbd> | Go to same day in the next week |
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| <kbd>HOME</kbd> | Go to the first day of the month |
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| <kbd>END</kbd> | Go to the last day of the month |
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| <kbd>PAGE_UP</kbd> | Go to the same day in the previous month |
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| <kbd>ALT</kbd> + <kbd>PAGE_UP</kbd> | Go to the same day in the previous year |
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| <kbd>PAGE_DOWN</kbd> | Go to the same day in the next month |
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| <kbd>ALT</kbd> + <kbd>PAGE_DOWN</kbd> | Go to the same day in the next year |
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| <kbd>ENTER</kbd> | Select current date |
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In year view:
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| Shortcut | Action |
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|----------------------|-------------------------------------------|
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| `LEFT_ARROW` | Go to previous month |
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| `RIGHT_ARROW` | Go to next month |
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| `UP_ARROW` | Go up a row (back 4 months) |
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| `DOWN_ARROW` | Go down a row (forward 4 months) |
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| `HOME` | Go to the first month of the year |
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| `END` | Go to the last month of the year |
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| `PAGE_UP` | Go to the same month in the previous year |
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| `ALT` + `PAGE_UP` | Go to the same month 10 years back |
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| `PAGE_DOWN` | Go to the same month in the next year |
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| `ALT` + `PAGE_DOWN` | Go to the same month 10 years forward |
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| `ENTER` | Select current month |
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| Shortcut | Action |
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|---------------------------------------|-------------------------------------------|
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| <kbd>LEFT_ARROW</kbd> | Go to previous month |
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| <kbd>RIGHT_ARROW</kbd> | Go to next month |
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| <kbd>UP_ARROW</kbd> | Go up a row (back 4 months) |
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| <kbd>DOWN_ARROW</kbd> | Go down a row (forward 4 months) |
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| <kbd>HOME</kbd> | Go to the first month of the year |
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| <kbd>END</kbd> | Go to the last month of the year |
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| <kbd>PAGE_UP</kbd> | Go to the same month in the previous year |
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| <kbd>ALT</kbd> + <kbd>PAGE_UP</kbd> | Go to the same month 10 years back |
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| <kbd>PAGE_DOWN</kbd> | Go to the same month in the next year |
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| <kbd>ALT</kbd> + <kbd>PAGE_DOWN</kbd> | Go to the same month 10 years forward |
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| <kbd>ENTER</kbd> | Select current month |
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In multi-year view:
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| Shortcut | Action |
619-
|----------------------|-------------------------------------------|
620-
| `LEFT_ARROW` | Go to previous year |
621-
| `RIGHT_ARROW` | Go to next year |
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| `UP_ARROW` | Go up a row (back 4 years) |
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| `DOWN_ARROW` | Go down a row (forward 4 years) |
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| `HOME` | Go to the first year in the current range |
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| `END` | Go to the last year in the current range |
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| `PAGE_UP` | Go back 24 years |
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| `ALT` + `PAGE_UP` | Go back 240 years |
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| `PAGE_DOWN` | Go forward 24 years |
629-
| `ALT` + `PAGE_DOWN` | Go forward 240 years |
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| `ENTER` | Select current year |
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| Shortcut | Action |
627+
|---------------------------------------|-------------------------------------------|
628+
| <kbd>LEFT_ARROW</kbd> | Go to previous year |
629+
| <kbd>RIGHT_ARROW</kbd> | Go to next year |
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| <kbd>UP_ARROW</kbd> | Go up a row (back 4 years) |
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| <kbd>DOWN_ARROW</kbd> | Go down a row (forward 4 years) |
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| <kbd>HOME</kbd> | Go to the first year in the current range |
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| <kbd>END</kbd> | Go to the last year in the current range |
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| <kbd>PAGE_UP</kbd> | Go back 24 years |
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| <kbd>ALT</kbd> + <kbd>PAGE_UP</kbd> | Go back 240 years |
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| <kbd>PAGE_DOWN</kbd> | Go forward 24 years |
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| <kbd>ALT</kbd> + <kbd>PAGE_DOWN</kbd> | Go forward 240 years |
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| <kbd>ENTER</kbd> | Select current year |
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### Troubleshooting
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