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# fuchsia.ui.pointerinjector
<div class="fidl-version-div"><span class="fidl-attribute fidl-version">Added: 7</span></div>
## **PROTOCOLS**
## Device {#Device}
*Defined in [fuchsia.ui.pointerinjector/device.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/device.fidl;l=79)*
<p>The channel for injecting pointer events into a target.
The associated |Config| applies to injected pointer events.</p>
<p>A |Device| may <em>inject</em> pointer events into a target in the scene, but the
<em>dispatch</em> of pointer events to UI clients within that target's view tree
will depend on the dispatch policy and the scene topology.</p>
### Inject {#Device.Inject}
<p>Injects events into a target.</p>
<p>Batching: The caller is expected to batch-inject all events that share the
same timestamp (e.g., multiple finger samples). There may be multiple such
batches per injection call.</p>
<p>Flow control: The caller is allowed at most one in-flight |Inject| call
at at time: subsequent |Inject| calls must wait until the acknowledgment
returns. Non-compliance results in channel closure.</p>
#### Request {#Device.Inject_Request}
<table>
<tr><th>Name</th><th>Type</th></tr>
<tr>
<td><code>events</code></td>
<td>
<code>vector&lt;<a class='link' href='#Event'>Event</a>&gt;[128]</code>
</td>
</tr>
</table>
#### Response {#Device.Inject_Response}
&lt;EMPTY&gt;
## Registry {#Registry}
*Defined in [fuchsia.ui.pointerinjector/device.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/device.fidl;l=57)*
<p>A coordination mechanism to clearly define the <em>injecting</em> of pointer events
into the scene (injection policy, injection context, etc), for <em>dispatching</em>
pointer events to UI clients (referenced by |fuchsia.ui.views.ViewRef|).</p>
<p>NOTE WELL! ONLY COMPONENTS IN THE TRUSTED COMPUTING BASE SHOULD BE GRANTED
ACCESS TO THIS PROTOCOL.
(1) The injector device acts with the user's authority. UI clients cannot
tell the difference between a real user and an injector device.
(2) The context is self-specified when registering the injector device. An
injector device that gains access to a sensitive context will operate in
that scope.
(3) The injected events may be arbitrary. An injector device can inject
whatever it wants to the clients it can reach.</p>
<p>This protocol defines the context and target for an injector |Device|,
places a viewport in spatial relation to the target, and connects the
|Device| to the viewport. These parameters are set up in the |Config|. A
|Device| may <em>inject</em> pointer events on the viewport, but the <em>dispatch</em> of
pointer events to UI clients in the target will depend on the dispatch
policy and the scene topology.</p>
<p>A |Device| operates within a context, and it serves two purposes:
(1) Scoping. It confirms the |Device|'s authority to inject pointer events
on the specified target.
(2) Coordinate system. It provides the reference coordinate system to define
the viewport's position and size, relative to the target.</p>
<p>Guarantees. A |Device| is directed at a specified target in the scene, and
such a target is afforded some guarantees against snooping and interference
from UI clients outside the target's view tree (&quot;non-target clients&quot;).
Non-target clients never have injected events dispatched to them: a |Device|
preserves <em>confidentiality</em> for target clients. Non-target clients never
block injected events from reaching the target on injection, or from
reaching target clients on dispatch: a |Device| preserves <em>integrity</em> and
<em>availability</em> for target clients. However, the |Device| itself is subject
to disruption by ancestor views of the target (see connectivity invariant).</p>
<p>Note. This protocol, and its policies, are <em>not</em> a sufficient guard against
UI redress attacks! The confidentiality, integrity, and availability
guarantees apply only with respect to non-target clients. Within a
target, UI redress attacks can still happen, between target clients.</p>
<p>Connectivity invariant. A |Device| operates in a stable view tree that is
connected to the root view. When either the target, or both context and
target, are disconnected from the view tree by a UI client, the |Device|
channel is closed. If an event stream was in flight, the server dispatches a
final CANCEL event following channel closure; this CANCEL event is then
propagated according to dispatch policy.</p>
### Register {#Registry.Register}
<p>Sets up a context for a |Device|, the target for the |Device|, and
directs the |Device| at the target via a viewport, positioned in the
context. These parameters are specified in a |Config|.</p>
<p>If |config| is invalid (e.g., missing important data), the |Device|
request will be denied: the channel will be closed.</p>
<p>The return event tells the caller that (1) the server has processed the
call, and (2) the |Device| is connected.</p>
#### Request {#Registry.Register_Request}
<table>
<tr><th>Name</th><th>Type</th></tr>
<tr>
<td><code>config</code></td>
<td>
<code><a class='link' href='#Config'>Config</a></code>
</td>
</tr>
<tr>
<td><code>injector</code></td>
<td>
<code>server_end&lt;<a class='link' href='#Device'>Device</a>&gt;</code>
</td>
</tr>
</table>
#### Response {#Registry.Register_Response}
&lt;EMPTY&gt;
## **ENUMS**
### DeviceType [strict](/fuchsia-src/reference/fidl/language/language.md#strict-vs-flexible){:.fidl-attribute} {#DeviceType data-text="DeviceType"}
Type: <code>uint32</code>
*Defined in [fuchsia.ui.pointerinjector/config.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/config.fidl;l=85)*
<p>A characterization of a device that issues pointer event streams.</p>
<table>
<tr><th>Name</th><th>Value</th><th>Description</th></tr>
<tr id="DeviceType.TOUCH">
<td><h3 id="DeviceType.TOUCH" class="add-link hide-from-toc">TOUCH</h3></td>
<td><code>1</code></td>
<td><p>A device intended for manipulation by direct contact over its surface.</p>
</td>
</tr>
<tr id="DeviceType.MOUSE">
<td><h3 id="DeviceType.MOUSE" class="add-link hide-from-toc">MOUSE</h3></td>
<td><code>2</code></td>
<td><p>A device intended for manipulation by precise movement over a surface.</p>
</td>
</tr>
</table>
### DispatchPolicy [strict](/fuchsia-src/reference/fidl/language/language.md#strict-vs-flexible){:.fidl-attribute} {#DispatchPolicy data-text="DispatchPolicy"}
Type: <code>uint32</code>
*Defined in [fuchsia.ui.pointerinjector/config.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/config.fidl;l=182)*
<p>A specification of the UI clients that may have injected events dispatched
to them in an |Target|. One is specified in |Config|.</p>
<p>A useful concept is &quot;latching&quot;, where one or more clients may start
receiving the pointer event stream, prior to assignment of stream ownership.
After ownership is assigned (e.g., through a gesture disambiguation
protocol), non-owning clients have their latch terminated -- they stop
receiving the pointer event stream.</p>
<ul>
<li>A client's latch does not itself confer stream ownership (receiving the
entire pointer event stream); gesture disambiguation or device termination
may prematurely end the stream dispatched to that client.</li>
<li>It's possible for a client to latch while hidden from the user (i.e.,
manipulate a surface that is invisible to the user), where the occluding
surface is owned by a client outside of |Target|. Conversely, these
occluding clients cannot latch, because latched clients must be in
|Target|'s view tree.</li>
</ul>
<table>
<tr><th>Name</th><th>Value</th><th>Description</th></tr>
<tr id="DispatchPolicy.EXCLUSIVE_TARGET">
<td><h3 id="DispatchPolicy.EXCLUSIVE_TARGET" class="add-link hide-from-toc">EXCLUSIVE_TARGET</h3></td>
<td><code>1</code></td>
<td><p>A single client latches onto a pointer event stream, where:</p>
<ul>
<li>the pointer event stream starts within the viewport rectangle,</li>
<li>the latch happens on the ADD phase of the pointer event stream,</li>
<li>the client is the |Target| itself.
Ownership is assigned immediately to the client.</li>
</ul>
<p>Note: This policy guarantees confidentiality, integrity, and
availability of dispatch to the client, but by itself, does <em>not</em>
confer immunity against UI redress attacks.</p>
</td>
</tr>
<tr id="DispatchPolicy.TOP_HIT_AND_ANCESTORS_IN_TARGET">
<td><h3 id="DispatchPolicy.TOP_HIT_AND_ANCESTORS_IN_TARGET" class="add-link hide-from-toc">TOP_HIT_AND_ANCESTORS_IN_TARGET</h3></td>
<td><code>2</code></td>
<td><p>Multiple clients may latch onto a pointer stream, where:</p>
<ul>
<li>the pointer stream starts within the viewport rectangle,</li>
<li>a hit test is performed on the ADD phase of the pointer event stream,
which returns the top-most surface (in paint order) in the |Target|'s
view tree,</li>
<li>the top-most surface's client latches onto the pointer stream,</li>
<li>the client's ancestors in the |Target|'s view tree also latch onto the
pointer stream.</li>
</ul>
<p>With multiple latches, a pointer stream is dispatched in parallel to
each latched client, until ownership is assigned via gesture
disambiguation. The owner client will continue to receive the pointer
stream, and non-owners will receive a final CANCEL event for the stream.</p>
<p>Note: It's possible for no clients to latch, if the hit test fails to
hit any surface in any sub-view of |Target|.
Note: Each client will have its own copy of the viewport, placed
accordingly in its own coordinate system.</p>
</td>
</tr>
<tr id="DispatchPolicy.MOUSE_HOVER_AND_LATCH_IN_TARGET">
<td><h3 id="DispatchPolicy.MOUSE_HOVER_AND_LATCH_IN_TARGET" class="add-link hide-from-toc">MOUSE_HOVER_AND_LATCH_IN_TARGET</h3></td>
<td><code>3</code></td>
<td><p>The top hit client in the |Target|'s view tree receives hover events when
a cursor is positioned over it, unless the mouse is latched to a specific
client.</p>
<p>A mouse initiates a latch via button down, and until the release of that
latch, mouse events are delivered to that latched client; other clients
do not receive hover events in the latch duration.</p>
<p>Note: It's possible for no client to latch, if the hit test fails to
hit any surface in any sub-view of |Target|.
Note: Each client will have its own copy of the viewport, placed
accordingly in its own coordinate system.</p>
</td>
</tr>
</table>
### EventPhase [strict](/fuchsia-src/reference/fidl/language/language.md#strict-vs-flexible){:.fidl-attribute} {#EventPhase data-text="EventPhase"}
Type: <code>uint32</code>
*Defined in [fuchsia.ui.pointerinjector/event.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/event.fidl;l=13)*
<p>The possible states of a pointer event stream's state machine.</p>
<p>A typical pointer will move through this state machine:
ADD - CHANGE* - REMOVE</p>
<table>
<tr><th>Name</th><th>Value</th><th>Description</th></tr>
<tr id="EventPhase.ADD">
<td><h3 id="EventPhase.ADD" class="add-link hide-from-toc">ADD</h3></td>
<td><code>1</code></td>
<td><p>The device has started tracking the pointer.</p>
</td>
</tr>
<tr id="EventPhase.CHANGE">
<td><h3 id="EventPhase.CHANGE" class="add-link hide-from-toc">CHANGE</h3></td>
<td><code>2</code></td>
<td><p>The device has reported an update to the pointer state.</p>
</td>
</tr>
<tr id="EventPhase.REMOVE">
<td><h3 id="EventPhase.REMOVE" class="add-link hide-from-toc">REMOVE</h3></td>
<td><code>3</code></td>
<td><p>The device has stopped tracking the pointer.</p>
</td>
</tr>
<tr id="EventPhase.CANCEL">
<td><h3 id="EventPhase.CANCEL" class="add-link hide-from-toc">CANCEL</h3></td>
<td><code>4</code></td>
<td><p>The event stream is no longer available.</p>
</td>
</tr>
</table>
## **TABLES**
### Config [resource](/fuchsia-src/reference/fidl/language/language.md#value-vs-resource){:.fidl-attribute} {#Config data-text="Config"}
*Defined in [fuchsia.ui.pointerinjector/config.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/config.fidl;l=28)*
<p>A specification for an injector |Device|.</p>
<p>All fields required.</p>
<table>
<tr><th>Ordinal</th><th>Field</th><th>Type</th><th>Description</th></tr>
<tr id="Config.device_id">
<td><h3 id="Config.device_id" class="add-link hide-from-toc">1</h3></td>
<td><code>device_id</code></td>
<td>
<code>uint32</code>
</td>
<td><p>An identifier for the pointer device that issues pointer event streams.</p>
</td>
</tr>
<tr id="Config.device_type">
<td><h3 id="Config.device_type" class="add-link hide-from-toc">2</h3></td>
<td><code>device_type</code></td>
<td>
<code><a class='link' href='#DeviceType'>DeviceType</a></code>
</td>
<td><p>A characterization of the pointer device.</p>
</td>
</tr>
<tr id="Config.context">
<td><h3 id="Config.context" class="add-link hide-from-toc">3</h3></td>
<td><code>context</code></td>
<td>
<code><a class='link' href='#Context'>Context</a></code>
</td>
<td><p>The scope and coordinate system of the injector |Device|.</p>
<p>Note: To avoid circular injection scenarios, |context| must be a
strict ancestor of |target|.</p>
</td>
</tr>
<tr id="Config.target">
<td><h3 id="Config.target" class="add-link hide-from-toc">4</h3></td>
<td><code>target</code></td>
<td>
<code><a class='link' href='#Target'>Target</a></code>
</td>
<td><p>The region where dispatch is attempted for injected events.</p>
<p>Note: To avoid circular injection scenarios, |target| must be a strict
descendant of |context|.</p>
</td>
</tr>
<tr id="Config.viewport">
<td><h3 id="Config.viewport" class="add-link hide-from-toc">5</h3></td>
<td><code>viewport</code></td>
<td>
<code><a class='link' href='#Viewport'>Viewport</a></code>
</td>
<td><p>The initial viewport for injected events. Subsequent modifications to
the viewport can also be sent synchronously with injected events.</p>
</td>
</tr>
<tr id="Config.dispatch_policy">
<td><h3 id="Config.dispatch_policy" class="add-link hide-from-toc">6</h3></td>
<td><code>dispatch_policy</code></td>
<td>
<code><a class='link' href='#DispatchPolicy'>DispatchPolicy</a></code>
</td>
<td><p>A specification of the UI clients in |target| that may have injected
events dispatched to them.</p>
<p>For example, if |dispatch_policy| is |EXCLUSIVE|, then only |target| may
have injected events dispatched to it, regardless of other factors, such
as surface occlusion by clients inside and outside of |target|.</p>
</td>
</tr>
<tr id="Config.relative_motion_range">
<td><h3 id="Config.relative_motion_range" class="add-link hide-from-toc">10</h3></td>
<td><code>relative_motion_range</code></td>
<td>
<code><a class='link' href='#RelativeMotionRange'>RelativeMotionRange</a></code>
</td>
<td><p>Range of X and Y motion by a mouse device.</p>
</td>
</tr>
<tr id="Config.scroll_v_range">
<td><h3 id="Config.scroll_v_range" class="add-link hide-from-toc">7</h3></td>
<td><code>scroll_v_range</code></td>
<td>
<code><a class='link' href='../fuchsia.input.report/'>fuchsia.input.report</a>/<a class='link' href='../fuchsia.input.report/#Axis'>Axis</a></code>
</td>
<td><p>Range of vertical scroll values issued by the device.</p>
</td>
</tr>
<tr id="Config.scroll_h_range">
<td><h3 id="Config.scroll_h_range" class="add-link hide-from-toc">8</h3></td>
<td><code>scroll_h_range</code></td>
<td>
<code><a class='link' href='../fuchsia.input.report/'>fuchsia.input.report</a>/<a class='link' href='../fuchsia.input.report/#Axis'>Axis</a></code>
</td>
<td><p>Range of horizontal scroll values issued by the device.</p>
</td>
</tr>
<tr id="Config.buttons">
<td><h3 id="Config.buttons" class="add-link hide-from-toc">9</h3></td>
<td><code>buttons</code></td>
<td>
<code>vector&lt;uint8&gt;[32]</code>
</td>
<td><p>Mouse button identifiers issued by the device, in priority order.</p>
<p>The priority order of mouse buttons is a policy choice enacted by the injector.
This priority order is conveyed verbatim to UI clients via
<a class='link' href='#fuchsia.ui.pointer.MouseDeviceInfo.buttons'>fuchsia.ui.pointer.MouseDeviceInfo.buttons</a>, so button priority is shared consistently
between multiple UI clients. For example, to swap the left-side (0x1) and right-side (0x2)
physical buttons from their traditional roles of primary and secondary mouse buttons, the
injector can specify [0x2, 0x1, ... ] in this <a class='link' href='#buttons'>buttons</a> vector.</p>
<p>Note that preserving the physical button ID is also a policy choice. If preserved, a
discerning UI client can distinguish between the ground truth (which physical button was
pressed) versus the desired interpretation (what priority does that physical button have, on
the current system).</p>
</td>
</tr>
</table>
### Event {#Event data-text="Event"}
*Defined in [fuchsia.ui.pointerinjector/event.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/event.fidl;l=85)*
<table>
<tr><th>Ordinal</th><th>Field</th><th>Type</th><th>Description</th></tr>
<tr id="Event.timestamp">
<td><h3 id="Event.timestamp" class="add-link hide-from-toc">1</h3></td>
<td><code>timestamp</code></td>
<td>
<code><a class='link' href='../zx/'>zx</a>/<a class='link' href='../zx/#time'>time</a></code>
</td>
<td><p>The time when this event was observed.</p>
<p>Required.</p>
</td>
</tr>
<tr id="Event.data">
<td><h3 id="Event.data" class="add-link hide-from-toc">2</h3></td>
<td><code>data</code></td>
<td>
<code><a class='link' href='#Data'>Data</a></code>
</td>
<td><p>The event's data.</p>
<p>Required.</p>
</td>
</tr>
<tr id="Event.trace_flow_id">
<td><h3 id="Event.trace_flow_id" class="add-link hide-from-toc">3</h3></td>
<td><code>trace_flow_id</code></td>
<td>
<code>uint64</code>
</td>
<td><p>An identifier to correlate this event's send/receive occurrence across
component boundaries or abstraction layers.</p>
</td>
</tr>
</table>
### PointerSample {#PointerSample data-text="PointerSample"}
*Defined in [fuchsia.ui.pointerinjector/event.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/event.fidl;l=33)*
<p>A description of each sampled data point for a pointer device.</p>
<table>
<tr><th>Ordinal</th><th>Field</th><th>Type</th><th>Description</th></tr>
<tr id="PointerSample.pointer_id">
<td><h3 id="PointerSample.pointer_id" class="add-link hide-from-toc">1</h3></td>
<td><code>pointer_id</code></td>
<td>
<code>uint32</code>
</td>
<td><p>An identifier of the pointer that issued this event.
It is unique only to a specific pointer device.</p>
</td>
</tr>
<tr id="PointerSample.phase">
<td><h3 id="PointerSample.phase" class="add-link hide-from-toc">2</h3></td>
<td><code>phase</code></td>
<td>
<code><a class='link' href='#EventPhase'>EventPhase</a></code>
</td>
<td><p>The state of this event in the pointer event stream's state machine.</p>
</td>
</tr>
<tr id="PointerSample.position_in_viewport">
<td><h3 id="PointerSample.position_in_viewport" class="add-link hide-from-toc">3</h3></td>
<td><code>position_in_viewport</code></td>
<td>
<code><a class='link' href='#Point2'>Point2</a></code>
</td>
<td><p>The position of this event, in the viewport's coordinate system.</p>
</td>
</tr>
<tr id="PointerSample.relative_motion">
<td><h3 id="PointerSample.relative_motion" class="add-link hide-from-toc">7</h3></td>
<td><code>relative_motion</code></td>
<td>
<code><a class='link' href='#RelativeMotion'>RelativeMotion</a></code>
</td>
<td><p>The movement of a mouse, independent of the viewport's coordinate
system.</p>
</td>
</tr>
<tr id="PointerSample.scroll_v">
<td><h3 id="PointerSample.scroll_v" class="add-link hide-from-toc">4</h3></td>
<td><code>scroll_v</code></td>
<td>
<code>int64</code>
</td>
<td><p>Relative vertical scrolling displacement by detent.</p>
</td>
</tr>
<tr id="PointerSample.scroll_h">
<td><h3 id="PointerSample.scroll_h" class="add-link hide-from-toc">5</h3></td>
<td><code>scroll_h</code></td>
<td>
<code>int64</code>
</td>
<td><p>Relative horizontal scrolling displacement by detent.</p>
</td>
</tr>
<tr id="PointerSample.scroll_v_physical_pixel">
<td><h3 id="PointerSample.scroll_v_physical_pixel" class="add-link hide-from-toc">8</h3></td>
<td><code>scroll_v_physical_pixel</code></td>
<td>
<code>float64</code>
</td>
<td><p>Recommended vertical scrolling displacement by physical pixel, it is
computed with accelerator, detent / mm to pixel ratio, etc.</p>
</td>
</tr>
<tr id="PointerSample.scroll_h_physical_pixel">
<td><h3 id="PointerSample.scroll_h_physical_pixel" class="add-link hide-from-toc">9</h3></td>
<td><code>scroll_h_physical_pixel</code></td>
<td>
<code>float64</code>
</td>
<td><p>Recommended horizontal scrolling displacement by physical pixel, it
is computed with accelerator, detent / mm to pixel ratio, etc.</p>
</td>
</tr>
<tr id="PointerSample.is_precision_scroll">
<td><h3 id="PointerSample.is_precision_scroll" class="add-link hide-from-toc">10</h3></td>
<td><code>is_precision_scroll</code></td>
<td>
<code>bool</code>
</td>
<td><p>Indicated if the scroll event is from a precision scroll device (HI_RES
mouse or touchpad). Clients may want to play interpolation animations
on non precision scroll device for smooth scrolling.</p>
</td>
</tr>
<tr id="PointerSample.pressed_buttons">
<td><h3 id="PointerSample.pressed_buttons" class="add-link hide-from-toc">6</h3></td>
<td><code>pressed_buttons</code></td>
<td>
<code>vector&lt;uint8&gt;[32]</code>
</td>
<td><p>Identifiers of currently pressed buttons.</p>
</td>
</tr>
</table>
### Viewport {#Viewport data-text="Viewport"}
*Defined in [fuchsia.ui.pointerinjector/config.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/config.fidl;l=148)*
<p>A rectangular region that directs injected events into a target.</p>
<p>The viewport relates a pointer's position across multiple independent
coordinate systems: the context, the viewport, and the dispatch clients.
Intuitively, the viewport is how a pointer's position is mapped to an
interactive part of the scene.</p>
<p>A matrix is used to relate the viewport coordinate system to the context
coordinate system. A pair of extents defines the viewport's size in the
viewport coordinate system. Together, they define the viewport's placement
in the context coordinate system.</p>
<p>The viewport coordinate system is used to convey a pointer's coordinates in
a scale-invariant way to dispatch clients, so that pointer movement can be
interpreted correctly under effects like magnification. The context defines
the viewport's minimal and maximal extents in the viewport coordinate
system.</p>
<ul>
<li>The boundary of the viewport, a rectangle, is axis aligned with the
viewport coordinate system; however it may otherwise be freely positioned
(&quot;float&quot;) within it: there is translation and scaling, but no rotation.</li>
<li>Floating gives the injector some choice in how to convey coordinates, such
as in Vulkan NDC, or in display pixel coordinates.</li>
<li>The viewport rectangle defines a latch region used in dispatch (described
below).</li>
</ul>
<p>A dispatch client receives a pointer's coordinates in the viewport
coordinate system, along with a matrix to convert coordinates from the
viewport coordinate system to the dispatch client's coordinate system.</p>
<p>All fields required.</p>
<p>TODO(fxbug.dev/81800): Rename Viewport, it is used in Flatland.</p>
<table>
<tr><th>Ordinal</th><th>Field</th><th>Type</th><th>Description</th></tr>
<tr id="Viewport.extents">
<td><h3 id="Viewport.extents" class="add-link hide-from-toc">1</h3></td>
<td><code>extents</code></td>
<td>
<code><a class='link' href='#Extents'>Extents</a></code>
</td>
<td><p>The viewport's minimal and maximal extents in the viewport coordinate
system.</p>
</td>
</tr>
<tr id="Viewport.viewport_to_context_transform">
<td><h3 id="Viewport.viewport_to_context_transform" class="add-link hide-from-toc">2</h3></td>
<td><code>viewport_to_context_transform</code></td>
<td>
<code><a class='link' href='#Mat3'>Mat3</a></code>
</td>
<td><p>A transformation matrix that describes how to map the viewport
coordinate system to the context coordinate system.</p>
<p>This transform, together with |extents|, defines the viewport's
placement in the context coordinate system.</p>
<p>This transform must be an invertible matrix (i.e., has a non-zero
determinant), which guarantees it describes a bijection between the
viewport coordinate system and the context coordinate system. A
non-invertible matrix is rejected.</p>
</td>
</tr>
</table>
## **UNIONS**
### Context [strict](/fuchsia-src/reference/fidl/language/language.md#strict-vs-flexible){:.fidl-attribute} [resource](/fuchsia-src/reference/fidl/language/language.md#value-vs-resource){:.fidl-attribute} {#Context data-text="Context"}
*Defined in [fuchsia.ui.pointerinjector/config.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/config.fidl;l=100)*
<p>The region from which injection is attempted for injected events. As the
context, it serves two purposes:
(1) Scoping. It confirms the |Device|'s authority to inject pointer events
on the specified target. Specifically, the context must be a view-tree
ancestor of the target.
(2) Coordinate System. It provides the reference coordinate system to define
the viewport's position and size, relative to the target.</p>
<table>
<tr><th>Ordinal</th><th>Variant</th><th>Type</th><th>Description</th></tr>
<tr id="Context.view">
<td><h3 id="Context.view" class="add-link hide-from-toc">1</h3></td>
<td><code>view</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>
<td><p>A Scenic view from which injection is attempted for injected events.</p>
<ul>
<li>This view must be connected to the scene graph for injection.</li>
<li>Injected events are confined to this view and its sub-views.</li>
</ul>
</td>
</tr>
</table>
### Data [flexible](/fuchsia-src/reference/fidl/language/language.md#strict-vs-flexible){:.fidl-attribute} {#Data data-text="Data"}
*Defined in [fuchsia.ui.pointerinjector/event.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/event.fidl;l=73)*
<p>A selection of FIFO data sent over the channel.
Each data may have a different issuance policy.</p>
<table>
<tr><th>Ordinal</th><th>Variant</th><th>Type</th><th>Description</th></tr>
<tr id="Data.viewport">
<td><h3 id="Data.viewport" class="add-link hide-from-toc">1</h3></td>
<td><code>viewport</code></td>
<td>
<code><a class='link' href='#Viewport'>Viewport</a></code>
</td>
<td><p>The parameters of the viewport, sufficient for a client to correctly
interpret the position and scale of pointer events dispatched to it.</p>
<ul>
<li>It is issued on every change to the viewport.</li>
</ul>
</td>
</tr>
<tr id="Data.pointer_sample">
<td><h3 id="Data.pointer_sample" class="add-link hide-from-toc">2</h3></td>
<td><code>pointer_sample</code></td>
<td>
<code><a class='link' href='#PointerSample'>PointerSample</a></code>
</td>
<td><p>A description of each sampled data point in a pointer event stream.</p>
<ul>
<li>It is issued on every sample in the pointer event stream.</li>
</ul>
</td>
</tr>
</table>
### Target [strict](/fuchsia-src/reference/fidl/language/language.md#strict-vs-flexible){:.fidl-attribute} [resource](/fuchsia-src/reference/fidl/language/language.md#value-vs-resource){:.fidl-attribute} {#Target data-text="Target"}
*Defined in [fuchsia.ui.pointerinjector/config.fidl](https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/config.fidl;l=109)*
<p>The region in which dispatch is attempted for injected events.
The particular dispatch policy is specified in |Config|.</p>
<table>
<tr><th>Ordinal</th><th>Variant</th><th>Type</th><th>Description</th></tr>
<tr id="Target.view">
<td><h3 id="Target.view" class="add-link hide-from-toc">1</h3></td>
<td><code>view</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>
<td><p>A Scenic view in which dispatch is attempted for injected events.</p>
<ul>
<li>This view must be connected to the scene graph for dispatch.</li>
<li>Injected events are confined to this view and its sub-views.</li>
</ul>
</td>
</tr>
</table>
## **CONSTANTS**
<table>
<tr><th>Name</th><th>Value</th><th>Type</th><th>Description</th></tr>
<tr id="MAX_INJECT">
<td><a href="https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/device.fidl;l=6">MAX_INJECT</a></td>
<td>
<code>128</code>
</td>
<td><code>uint32</code></td>
<td></td>
</tr>
</table>
## **TYPE ALIASES**
<table>
<tr><th>Name</th><th>Value</th><th>Description</th></tr>
<tr id="Extents">
<td><a href="https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/config.fidl;l=15">Extents</a></td>
<td>
<code>array</code>[<code>2</code>]</td>
<td><p>A floating-point pair of points, representing minimal and maximal extents.</p>
<ul>
<li>The values are placed in (minimal, maximal) order.</li>
</ul>
</td>
</tr>
<tr id="Mat3">
<td><a href="https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/config.fidl;l=19">Mat3</a></td>
<td>
<code>array</code>[<code>9</code>]</td>
<td><p>A floating-point 3x3 matrix.</p>
<ul>
<li>The values are placed in column-major order.</li>
</ul>
</td>
</tr>
<tr id="Point2">
<td><a href="https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/config.fidl;l=11">Point2</a></td>
<td>
<code>array</code>[<code>2</code>]</td>
<td><p>A floating-point two-dimensional point.</p>
<ul>
<li>The values are placed in (x, y) order.</li>
</ul>
</td>
</tr>
<tr id="RelativeMotion">
<td><a href="https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/event.fidl;l=30">RelativeMotion</a></td>
<td>
<code>array</code>[<code>2</code>]</td>
<td><p>The relative motion performed by a mouse device.</p>
<ul>
<li>The valid range is defined in <a class='link' href='#Config.RelativeMotionRange'>Config.RelativeMotionRange</a>.</li>
<li>The values are placed in (x, y) order.</li>
</ul>
</td>
</tr>
<tr id="RelativeMotionRange">
<td><a href="https://cs.opensource.google/fuchsia/fuchsia/+/main:sdk/fidl/fuchsia.ui.pointerinjector/config.fidl;l=23">RelativeMotionRange</a></td>
<td>
<code>array</code>[<code>2</code>]</td>
<td><p>The valid values of relative motion for a mouse device.</p>
<ul>
<li>The ranges are placed in (x, y) order.</li>
</ul>
</td>
</tr>
</table>