f10/sdk/fidl/fuchsia.accessibility.virtualkeyboard/README.md

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# fuchsia.accessibility.virtualkeyboard

<div class="fidl-version-div"><span class="fidl-attribute fidl-version">Added: 7</span></div>


## **PROTOCOLS**

## Listener {#Listener}
*Defined in [fuchsia.accessibility.virtualkeyboard/virtual_keyboard.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.accessibility.virtualkeyboard/virtual_keyboard.fidl;l=60)*
<p>Provides the ability to inform an interested party (&quot;listener&quot;) of changes
in virtual keyboard state (e.g. visibility).</p>
<h1>Roles</h1>
<p>This protocol will typically be:</p>
<ul>
<li>Implemented by platform components which implement accessibility.
For example, a11y_manager.</li>
<li>Consumed by components which provide a GUI affordance for text input.</li>
</ul>
<h1>Notes</h1>
<p>When the consumer of this protocol observes that the channel is closed,
it (the protocol consumer) should retry <code>Registry.Register()</code>, applying
back-off logic to avoid tight loops.</p>


### OnVisibilityChanged {#Listener.OnVisibilityChanged}

<p>Informs the <code>Listener</code> of a change in keyboard visibility.</p>
<p>Consumers of this protocol should wait for each call to be acknowledged
before calling again, to avoid queueing large numbers of updates.</p>



#### Request {#Listener.OnVisibilityChanged_Request}

<table>
    <tr><th>Name</th><th>Type</th></tr>
        <tr>
            <td><code>updated_visibility</code></td>
            <td>
                <code>bool</code>
            </td>
        </tr>
</table>


#### Response {#Listener.OnVisibilityChanged_Response}

&lt;EMPTY&gt;

## Registry {#Registry}
*Defined in [fuchsia.accessibility.virtualkeyboard/virtual_keyboard.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.accessibility.virtualkeyboard/virtual_keyboard.fidl;l=21)*
<p>Provides the ability to register a virtual keyboard.</p>
<p>This protocol exists to bind <code>Listener</code>s to <code>View</code>s (via <code>ViewRef</code>s).
The binding allows, e.g., the accessibility subsystem determine if an
interaction with the <code>View</code> should result in a focus transfer.</p>
<h1>Roles</h1>
<p>This protocol will typically be:</p>
<ul>
<li>Implemented by platform components which implement accessibility.
For example, a11y_manager.</li>
<li>Consumed by components which provide a GUI affordance for text input.</li>
</ul>


### Register {#Registry.Register}

<p>Registers the <code>View</code> referenced by <code>view_ref</code> as a <code>View</code>
which may contain a virtual keyboard.</p>
<p>The presence or absence of a virtual keyboard within the <code>View</code>
may change dynamically.</p>
<ul>
<li>The initial state is indicated by <code>is_visible</code>.</li>
<li>The <code>Registry</code> consumer will update state by invoking
methods on the provided <code>request&lt;Listener&gt;</code>.</li>
</ul>
<h1>Notes</h1>
<ul>
<li>The implementer may limit the number of simultaneous registrations
allowed (e.g. only allowing a single registration at a time).</li>
<li>The implementer should monitor the provided <code>ViewRef</code> for a
<code>ZX_EVENTPAIR_PEER_CLOSED</code> signal (see documentation for
<code>fuchsia.ui.views.ViewRefControl</code>).</li>
<li>If the request would exceed the simultaneous registration limit,
or when the <code>ViewRef</code> receives <code>ZX_EVENTPAIR_PEER_CLOSED</code>, the
implementer should dispose of <code>listener</code>.</li>
</ul>



#### Request {#Registry.Register_Request}

<table>
    <tr><th>Name</th><th>Type</th></tr>
        <tr>
            <td><code>view_ref</code></td>
            <td>
                <code><a class='link' href='../fuchsia.ui.views/'>fuchsia.ui.views</a>/<a class='link' href='../fuchsia.ui.views/#ViewRef'>ViewRef</a></code>
            </td>
        </tr>
        <tr>
            <td><code>is_visible</code></td>
            <td>
                <code>bool</code>
            </td>
        </tr>
        <tr>
            <td><code>listener</code></td>
            <td>
                <code>server_end&lt;<a class='link' href='#Listener'>Listener</a>&gt;</code>
            </td>
        </tr>
</table>