Editar

Compartir a través de

Gaze Interaction Library

  • Artículo

Microsoft announced native support for eye tracking in Windows in the Windows 10 Fall Creators Update. In the Windows 10 April 2018 update, Microsoft added developer support by releasing Windows Gaze Input APIs to build UWP applications that can interact with gaze input and eye trackers.

This Gaze Interaction Library is built on top of the Windows Gaze Input APIs and provides a set of developer helper classes to more easily enable UWP applications to respond to where the user is looking on the screen. This library is intended to abstract away some of the complexities of dealing with the raw stream of gaze input coming from the eye tracking device exposed through the Windows APIs.

Try it in the sample app

Prerequisites

In order to use the Windows 10 Gaze Input APIs or this Gaze Interaction Library, you need to have the following:

To use the gaze input APIs, you must register the gazeInput capability in the app manifest. Add the following DeviceCapability to the Capabilities node in the Package.appxmanifest file of your project (you can do this by checking Gaze Input in the Capabilities tab in Visual Studio when you have Package.appxmanifest open in the App Manifest Designer):

<Capabilities>
   <DeviceCapability Name="gazeInput" />
</Capabilities>

Supported Features

The Gaze Interaction Library currently supports the following features:

  • Dwell based activation of XAML button and toggle button controls
  • Enabling gaze interactions for the entire XAML page or for a portion of it (like a single control)
  • Customizing the dwell times associated with specific controls
  • Controlling repetition of the dwell invocation of controls

Gaze Concepts

Below are a few eye gaze related concepts that are helpful in order to better understand the rest of the document:

  • Saccade. A saccade is a rapid movement of the eyes from one fixation point to another. Our eyes alternate between fixations and saccades.
  • Fixation. A fixation is the collection of gaze points on a single location of the screen for a relatively short amount of time (roughly around 200ms). This happens after a saccade when the eye comes to rest upon an object and it comes into sharp focus.
  • Dwell. A dwell is the conscious fixation by the user for a duration greater than the fixation time. This mechanism is typically used to identify user intent when the user is using only their eyes as an input method. The dwell time duration can be application and control dependent.
  • Enter/Exit. These are states and properties specific to this API to help manage gaze related interactions and refer to the time elapsed since the first recorded gaze sample and the last recorded gaze sample on a particular control (Button, ToggleButton etc.)

The Gaze Interaction Library enables dwell based gaze interactions on the page by reading the data from the eye tracker over the page invoking specific controls when the user's gaze dwells on a control for a specific time. The application can configure this time based on its usage scenario.

PointerState Properties

The Windows Gaze Input APIs delivers a stream of timestamped gaze point coordinates of the user's gaze location on the screen. This library aggregates these samples over each control and converts the stream into gaze events. Corresponding to these events, are the following states:

Property Type Description
Enter enum A user's gaze has entered the control
Fixation enum A user eye's are focused on the control.
Dwell enum A user is consciously dwelling on the control and has exceeded the dwell time. This is interpreted as the user's intent to activate or invoke the control, e.g. click a button
Exit enum A user's gaze is no longer within the control

GazeInput Properties

If the XAML page is enabled for gaze based interactions, the visibility and size of the gaze cursor, and the timings associated with the states above can be configured using the properties below:

Property Type Description
IsDeviceAvailable bool Returns whether a compatible eye tracker is connected. When this property changes an IsDeviceAvailableChanged event is fired.
Interaction enum Gets or sets the status of gaze interaction over that particular XAML element. There are three options:
  • Enabled. Gaze interaction is enabled on this element and all its children
  • Disabled Gaze interaction is disabled on this element and all its children
  • Inherited Gaze interaction status is inherited from the nearest ancestor
CursorVisible bool The gaze cursor shows where the user is looking at on the screen. This boolean property shows the gaze cursor when set to true and hides it when set to false. The default value is false
CursorRadius int Gets or sets the size of the gaze cursor radius. The default value is X
ThresholdDuration TimeSpan This duration controls when the PointerState moves to either the Enter state or the Exit state. When this duration has elapsed after the user's gaze first enters a control, the PointerState is set to Enter. And when this duration has elapsed after the user's gaze has left the control, the PointerState is set to Exit. In both cases, a StateChanged event is fired. The default value is 50ms.
FixationDuration TimeSpan Gets or sets the duration for the control to transition from the Enter state to the Fixation state. At this point, a StateChanged event is fired with PointerState set to Fixation. This event should be used to control the earliest visual feedback the application needs to provide to the user about the gaze location. The default value is 350ms.
DwellDuration TimeSpan Gets or sets the duration for the control to transition from the Fixation state to the Dwell state. At this point, a StateChanged event is fired with PointerState set to Dwell. The Enter and Fixation states are typically achieved too rapidly for the user to have much control over. In contrast Dwell is a more conscious activity. This is the point at which the control is invoked, e.g. a button click. The application can modify this property to control when a gaze enabled UI element gets invoked after a user starts looking at it. The default value is 400 ms.
MaxDwellRepeatCount int The maximum amount of times the control will invoked repeatedly without the user's gaze having to leave and re-enter the control. The default value is zero which disables repeated invocation of a control. Developers can set a higher value to enable repeated invocation.
DwellRepeatDuration TimeSpan Gets or sets the duration of repeated dwell invocations, should the user continue to dwell on the control. The first repeat will occur after an additional delay specified by RepeatDelayDuration. Subsequent repeats happen after every period of DwellRepeatDuration. A control is invoked repeatedly only if MaxDwellRepeatCount is set to greater than zero.
RepeatDelayDuration TimeSpan Gets or sets the additional duration for the first repeat to occur. This prevents inadvertent repeated invocation. See above for details.
IsSwitchEnabled bool Gets or sets whether switch activation is enabled. When Switch support is enabled, the currently fixated element will not transition to the dwell state. Further, when the GazePointer.Click() method is called the currently fixated element will be invoked.

GazeElement Events

Add description here.

Events Description
StateChanged This event is raised in response to each of the states associated with PointerState (except for the DwellRepeat state). An application can add a handler for this event to customize gaze related processing with respect to the various gaze pointer states mentioned above.
DwellProgressFeedback This event is fired to indicate progress towards a dwell event. An application can handle this event to either customize visual feedback and/or turn off the default animation for dwell by setting DwellProgressEventArgs.Handled to true
Invoked This event is fired when the library is about to invoke the control in response to a dwell event. An application can handle this even to perform custom processing before invocation, and/or suppress invocation by setting the DwellInvokedRoutedEventArgs.Handled to true

StateChangedEventArgs Properties

This parameter is passed to the StateChanged event which is fired when the PointerState changes.

Property Type Description
PointerState GazePointerState The GazePointerState associated with this event
ElapsedTime TimeSpan The time the user has spent looking at the control to reach the specific pointer state above

DwellProgressEventArgs Properties

This parameter is passed to the event handling the DwellProgressFeedback event.

Property Type Description
State enum This enum indicates the state of the control towards dwell in three values Idle, Progressing and Complete
Progress double A value between 0 and 1 that indicates the fractional progress towards completing dwell
Handled bool If an application sets this value to true the default animation provided by the library is suppressed

DwellInvokedRoutedEventArgs Properties

This parameter is passed to the GazeElement::Invoked event and allows the application to prevent default invocation when the user dwells on a control.

Property Type Description
Handled bool This parameter is passed to the GazeElement.Invoked event. If set to true the library will suppress invoking the control on a dwell event

Examples

To enable gaze interactions on the entire XAML page

Add the following lines to your Page element to enable gaze interaction on the entire page.

    xmlns:gaze="using:Microsoft.Toolkit.Uwp.Input.GazeInteraction"
    gaze:GazeInput.Interaction="Enabled"

For e.g.

    <Page
    x:Class="UwpApp.MainPage"
    xmlns="https://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="https://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="https://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:gaze="using:Microsoft.Toolkit.Uwp.Input.GazeInteraction"
    gaze:GazeInput.Interaction="Enabled"
    mc:Ignorable="d">

To enable gaze interactions on a portion of the page

Gaze interaction can also be enabled only on a portion of the page by adding the same attributes to any XAML element on the page.

To enable only a subset of the page, e.g. just one Grid on the page:

    <Grid gaze:GazeInput.Interaction="Enabled">
        <Button Content="Click Me" />
    <Grid />

In the above example, the button will be clicked when the user looks at the button in the grid for a period equal to the default dwell time.

To change the dwell time for a control

The code below sets the Dwell time duration for the button to be 500ms. This means the button will be clicked 500ms after the control enters the Fixation state. (See PointerState for details)

    <Button Content="Click Me" gaze:GazeInput.DwellDuration="00:00:00.500">

Animations

This library provides a default animation of a shriniking rectangle over the control to indicate progress towards a dwell event. The style of animation can be customized in two ways:

  • If you wish to retain the animation style, but change the colors used:
    • Set the GazeInput.DwellFeedbackEnterBrush property to add a rectangle over controls immediately gaze is detected on them
    • Change the GazeInput.DwellFeedbackProgressBrush property to change the color of the progress rectangle
    • Change the GazeInput.DwellFeedbackCompletedBrush property to change the color of the completed brush
  • If you wish to completely disable or override the default animation, add an event handler for DwellProgressFeedback on GazeElement and set Handled to True as follows
<Button Content="Click Me">
    <gaze:GazeInput.GazeElement>
        <gaze:GazeElement DwellProgressFeedback="OnInvokeProgress" />
    </gaze:GazeInput.GazeElement>
</Button>

private void OnInvokeProgress(object sender, DwellProgressEventArgs e)
{
    e.Handled = true;
}

Sample Project

GazeInteractionPage. You can see this in action in the Windows Community Toolkit Sample App.

Requirements

Device family Universal,10.0.17134.1 or higher
Namespace Microsoft.Toolkit.Uwp.Input.GazeInteraction
NuGet package NuGet package

API