The Gamepad specification defines a low-level interface that represents gamepad devices.

This is a work in progress.

Introduction

Some [=user agent=]s have connected gamepad devices. These devices are desirable and suited to input for gaming applications, and for "10 foot" user interfaces (presentations, media viewers).

Currently, the only way for a gamepad to be used as input would be to emulate mouse or keyboard events, however this would lose information and require additional software outside of the [=user agent=] to accomplish emulation.

Meanwhile, native applications are capable of accessing these devices via system APIs.

The Gamepad API provides a solution to this problem by specifying interfaces that allow web applications to directly act on gamepad data.

Scope

Interfacing with external devices designed to control games has the potential to become large and intractable if approached in full generality. In this specification we explicitly choose to narrow scope to provide a useful subset of functionality that can be widely implemented and broadly useful.

Specifically, we choose to only support the functionality required to support gamepads. Support for gamepads requires two input types: buttons and axes. Both buttons and axes are reported as analog values, buttons ranging from [0..1], and axes ranging from [-1..1].

While the primary goal is support for gamepad devices, supporting these two types of analog inputs allows support for other similar devices common to current gaming systems including joysticks, driving wheels, pedals, and accelerometers. As such, the name "gamepad" is exemplary rather than trying to be a generic name for the entire set of devices addressed by this specification.

We specifically exclude support for more complex devices that may also be used in some gaming contexts, including those that that do motion sensing, depth sensing, video analysis, gesture recognition, and so on.

Gamepad interface

This interface defines an individual gamepad device.

        [Exposed=Window, SecureContext]
        interface Gamepad {
          readonly attribute DOMString id;
          readonly attribute long index;
          readonly attribute boolean connected;
          readonly attribute DOMHighResTimeStamp timestamp;
          readonly attribute GamepadMappingType mapping;
          readonly attribute FrozenArray<double> axes;
          readonly attribute FrozenArray<GamepadButton> buttons;
        };
      

The algorithms used to communicate with the system typically complete asynchronously, queuing work on the gamepad task source.

Instances of {{Gamepad}} are created with the internal slots described in the following table:

Internal slot Initial value Description (non-normative)
[[\connected]] `false` A flag indicating that the device is connected to the system
[[\timestamp]] undefined The last time data for this {{Gamepad}} was updated
[[\axes]] An empty [=sequence=] A [=sequence=] of {{double}} values representing the current state of axes exposed by this device
[[\buttons]] An empty [=sequence=] A [=sequence=] of {{GamepadButton}} objects representing the current state of buttons exposed by this device
[[\exposed]] `false` A flag indicating that the {{Gamepad}} object has been exposed to script
[[\axisMapping]] An empty [=ordered map=] Mapping from unmapped axis index to an index in the {{Gamepad/axes}} array
[[\axisMinimums]] An empty [=list=] A [=list=] containing the minimum logical value for each axis
[[\axisMaximums]] An empty [=list=] A [=list=] containing the maximum logical value for each axis
[[\buttonMapping]] An empty [=ordered map=] Mapping from unmapped button index to an index in the {{Gamepad/buttons}} array
[[\buttonMinimums]] An empty [=list=] A [=list=] containing the minimum logical value for each button.
[[\buttonMaximums]] An empty [=list=] A [=list=] containing the maximum logical value for each button
id attribute

An identification string for the gamepad. This string identifies the brand or style of connected gamepad device.

The exact format of the {{Gamepad/id}} string is left unspecified. It is RECOMMENDED that the [=user agent=] select a string that identifies the product without uniquely identifying the device. For example, a USB gamepad may be identified by its `idVendor` and `idProduct` values. Unique identifiers like serial numbers or Bluetooth device addresses MUST NOT be included in the {{Gamepad/id}} string.

index attribute
The index of the gamepad in the {{Navigator}}. When multiple gamepads are connected to a [=user agent=], indices MUST be assigned on a first-come, first-serve basis, starting at zero. If a gamepad is disconnected, previously assigned indices MUST NOT be reassigned to gamepads that continue to be connected. However, if a gamepad is disconnected, and subsequently the same or a different gamepad is then connected, the lowest previously used index MUST be reused.
connected attribute

Indicates whether the physical device represented by this object is still connected to the system. When a gamepad becomes unavailable, whether by being physically disconnected, powered off or otherwise unusable, the {{Gamepad/connected}} attribute MUST be set to `false`.

The {{Gamepad/connected}} getter steps are:

  1. Return [=this=].{{Gamepad/[[connected]]}}.
timestamp attribute

The {{Gamepad/timestamp}} allows the author to determine the last time the {{Gamepad/axes}} or {{Gamepad/buttons}} attribute for this gamepad was updated. The value MUST be set to the [=current high resolution time=] each time the system [=receives new button or axis input values=] from the device. If no data has been received from the hardware, {{Gamepad/timestamp}} MUST be the [=current high resolution time=] at the time when the {{Gamepad}} was first made available to script.

[=User agent=]s SHOULD set a minimum resolution of |gamepad|'s {{Gamepad/timestamp}} attribute to 5 microseconds, following [[HR-TIME]]'s clock resolution recommendation.

The {{Gamepad/timestamp}} getter steps are:

  1. Return [=this=].{{Gamepad/[[timestamp]]}}.
mapping attribute

The mapping in use for this device. If the user agent has knowledge of the layout of the device, then it SHOULD indicate that a mapping is in use by setting {{Gamepad/mapping}} to the corresponding {{GamepadMappingType}} value.

To select a mapping for a gamepad device, run the following steps:

  1. If the button and axis layout of the gamepad device corresponds with the [=Standard Gamepad=] layout, then return {{GamepadMappingType/"standard"}}.
  2. Return {{GamepadMappingType/""}}.
axes attribute

Array of values for all axes of the gamepad. All axis values MUST be linearly normalized to the range [-1.0 .. 1.0]. If the controller is perpendicular to the ground with the directional stick pointing up, -1.0 SHOULD correspond to "forward" or "left", and 1.0 SHOULD correspond to "backward" or "right". Axes that are drawn from a 2D input device SHOULD appear next to each other in the axes array, X then Y. It is RECOMMENDED that axes appear in decreasing order of importance, such that element 0 and 1 typically represent the X and Y axis of a directional stick. The same object MUST be returned until the [=user agent=] needs to return different values (or values in a different order).

The {{Gamepad/axes}} getter steps are:

  1. Return [=this=].{{Gamepad/[[axes]]}}.
buttons attribute

Array of button states for all buttons of the gamepad. It is RECOMMENDED that buttons appear in decreasing importance such that the primary button, secondary button, tertiary button, and so on appear as elements 0, 1, 2, ... in the buttons array. The same object MUST be returned until the [=user agent=] needs to return different values (or values in a different order).

The {{Gamepad/buttons}} getter steps are:

  1. Return [=this=].{{Gamepad/[[buttons]]}}.

Receiving inputs

When the system receives new button or axis input values, run the following steps:

  1. Let |gamepad:Gamepad| be the {{Gamepad}} object representing the device that received new button or axis input values.
  2. [=Queue a task=] on the [=gamepad task source=] to [=update gamepad state=] for |gamepad|.

To update gamepad state for |gamepad:Gamepad|, run the following steps:

  1. Let |now:DOMHighResTimeStamp| be the [=current high resolution time=].
  2. Set |gamepad|.{{Gamepad/[[timestamp]]}} to |now|.
  3. Run the steps to [=map and normalize axes=] for |gamepad|.
  4. Run the steps to [=map and normalize buttons=] for |gamepad|.
  5. Let |navigator:Navigator| be |gamepad|'s [=relevant global object=]'s {{Navigator}} object.
  6. If |navigator|.{{Navigator/[[hasGamepadGesture]]}} is `false` and |gamepad| [=contains a gamepad user gesture=]:
    1. Set |navigator|.{{Navigator/[[hasGamepadGesture]]}} to `true`.
    2. [=list/For each=] |connectedGamepad:Gamepad?| of |navigator|.{{Navigator/[[gamepads]]}}:
      1. If |connectedGamepad| is not equal to `null`:
        1. Set |connectedGamepad|.{{Gamepad/[[exposed]]}} to `true`.
        2. Set |connectedGamepad|.{{Gamepad/[[timestamp]]}} to |now|.
        3. Let |document:Document?| be |gamepad|'s [=relevant global object=]'s [=associated `Document`=]; otherwise `null`.
        4. If |document| is not `null` and is [=Document/fully active=], then [=queue a task=] on the [=gamepad task source=] to [=fire an event=] named {{gamepadconnected}} at |gamepad|'s [=relevant global object=] using {{GamepadEvent}} with its {{GamepadEvent/gamepad}} attribute initialized to |connectedGamepad|.

To map and normalize axes for |gamepad:Gamepad|, run the following steps:

  1. Let |axisValues:list| be a [=list=] of {{unsigned long}} values representing the most recent logical axis input values for each axis input of the device represented by |gamepad|.
  2. Let |maxRawAxisIndex:long| be the [=list/size=] of |axisValues| − 1.
  3. [=list/For each=] |rawAxisIndex:long| of [=the range=] from 0 to |maxRawAxisIndex|:
    1. Let |mappedIndex:long| be |gamepad|.{{Gamepad/[[axisMapping]]}}[|rawAxisIndex|].
    2. Let |logicalValue:unsigned long| be |axisValues|[|rawAxisIndex|].
    3. Let |logicalMinimum:unsigned long| be |gamepad|.{{Gamepad/[[axisMinimums]]}}[|rawAxisIndex|].
    4. Let |logicalMaximum:unsigned long| be |gamepad|.{{Gamepad/[[axisMaximums]]}}[|rawAxisIndex|].
    5. Let |normalizedValue:double| be 2 (|logicalValue| − |logicalMinimum|) / (|logicalMaximum| − |logicalMinimum|) − 1.
    6. Set |gamepad|.{{Gamepad/[[axes]]}}[|axisIndex|] to be |normalizedValue|.

To map and normalize buttons for |gamepad:Gamepad|, run the following steps:

  1. Let |buttonValues:list| be a [=list=] of {{unsigned long}} values representing the most recent logical button input values for each button input of the device represented by |gamepad|.
  2. Let |maxRawButtonIndex:long| be the [=list/size=] of |buttonValues| − 1.
  3. [=list/For each=] |rawButtonIndex:long| of [=the range=] from 0 to |maxRawButtonIndex|:
    1. Let |mappedIndex:long| be |gamepad|.{{Gamepad/[[buttonMapping]]}}[|rawButtonIndex|].
    2. Let |logicalValue:unsigned long| be |buttonValues|[|rawButtonIndex|].
    3. Let |logicalMinimum:unsigned long| be |gamepad|.{{Gamepad/[[buttonMinimums]]}}[|rawButtonIndex|].
    4. Let |logicalMaximum:unsigned long| be |gamepad|.{{Gamepad/[[buttonMaximums]]}}[|rawButtonIndex|].
    5. Let |normalizedValue:double| be (|logicalValue| − |logicalMinimum|) / (|logicalMaximum| − |logicalMinimum|).
    6. Let |button:GamepadButton| be |gamepad|.{{Gamepad/[[buttons]]}}[|mappedIndex|].
    7. Set |button|.{{GamepadButton/[[value]]}} to |normalizedValue|.
    8. If the button has a digital switch to indicate a pure pressed or released state, set |button|.{{GamepadButton/[[pressed]]}} to `true` if the button is pressed or `false` if it is not pressed.

      Otherwise, set |button|.{{GamepadButton/[[pressed]]}} to `true` if the value is above the [=button press threshold=] or `false` if it is not above the threshold.

    9. If the button is capable of detecting touch, set |button|.{{GamepadButton/[[touched]]}} to `true` if the button is currently being touched.

      Otherwise, set |button|.{{GamepadButton/[[touched]]}} to |button|.{{GamepadButton/[[pressed]]}}.

Constructing a `Gamepad`

A new `Gamepad` representing a connected gamepad device is constructed by performing the following steps:

  1. Let |gamepad:Gamepad| be a newly created {{Gamepad}} instance:
    1. Initialize |gamepad|'s {{Gamepad/id}} attribute to an identification string for the gamepad.
    2. Initialize |gamepad|'s {{Gamepad/index}} attribute to the result of [=selecting an unused gamepad index=] for |gamepad|.
    3. Initialize |gamepad|'s {{Gamepad/mapping}} attribute to the result of [=selecting a mapping=] for the gamepad device.
    4. Initialize |gamepad|.{{Gamepad/[[connected]]}} to `true`.
    5. Initialize |gamepad|.{{Gamepad/[[timestamp]]}} to the [=current high resolution time=].
    6. Initialize |gamepad|.{{Gamepad/[[axes]]}} to the result of [=initializing axes=] for |gamepad|.
    7. Initialize |gamepad|.{{Gamepad/[[buttons]]}} to the result of [=initializing buttons=] for |gamepad|.
  2. Return |gamepad|.

To select an unused gamepad index for |gamepad:Gamepad|, run the following steps:

  1. Let |navigator:Navigator| be |gamepad|'s [=relevant global object=]'s {{Navigator}} object.
  2. Let |maxGamepadIndex:long| be the [=list/size=] of |navigator|.{{Navigator/[[gamepads]]}} − 1.
  3. [=list/For each=] |gamepadIndex:long| of [=the range=] from 0 to |maxGamepadIndex|:
    1. If |navigator|.{{Navigator/[[gamepads]]}}[|gamepadIndex|] is `null`, then return |gamepadIndex|.
  4. [=list/Append=] `null` to |navigator|.{{Navigator/[[gamepads]]}}.
  5. Return the [=list/size=] of |navigator|.{{Navigator/[[gamepads]]}} − 1.

To initialize axes for |gamepad:Gamepad|, run the following steps:

  1. Let |inputCount:long| be the number of axis inputs exposed by the device represented by |gamepad|.
  2. Set |gamepad|.{{Gamepad/[[axisMinimums]]}} to a [=list=] of {{unsigned long}} values with [=list/size=] equal to |inputCount| containing minimum logical values for each of the axis inputs.
  3. Set |gamepad|.{{Gamepad/[[axisMaximums]]}} to a [=list=] of {{unsigned long}} values with [=list/size=] equal to |inputCount| containing maximum logical values for each of the axis inputs.
  4. Initialize |unmappedInputList| to be an empty [=list=].
  5. Initialize |mappedIndexList| to be an empty [=list=].
  6. Initialize |axesSize:long| to be 0.
  7. [=list/For each=] |rawInputIndex:long| of [=the range=] from 0 to |inputCount| − 1:
    1. If the the gamepad axis at index |rawInputIndex| [=represents a Standard Gamepad axis=]:
      1. Let |canonicalIndex:long| be the [=canonical index=] for the axis.
      2. If |mappedIndexList| [=list/contain=]s |canonicalIndex|, then append |rawInputIndex| to |unmappedInputList|.

        Otherwise:

        1. Set |gamepad|.{{Gamepad/[[axisMapping]]}}[|rawInputIndex|] to |canonicalIndex|.
        2. [=list/Append=] |canonicalIndex| to |mappedIndexList|.
        3. If |canonicalIndex| + 1 is greater than |axesSize|, then set |axesSize| to |canonicalIndex| + 1.

      Otherwise, [=list/append=] |rawInputIndex| to |unmappedInputList|.

  8. Initialize |axisIndex:long| to be 0.
  9. [=list/For each=] |rawInputIndex:long| of |unmappedInputList|:
    1. While |mappedIndexList| [=list/contain=]s |axisIndex|:
      1. Increment |axisIndex|.
    2. Set |gamepad|.{{Gamepad/[[axisMapping]]}}[|rawInputIndex|] to |axisIndex|.
    3. [=list/Append=] |axisIndex| to |mappedIndexList|.
    4. If |axisIndex| + 1 is greater than |axesSize|, then set |axesSize| to |axisIndex| + 1.
  10. Initialize |axes| to be an empty [=list=].
  11. [=list/For each=] |axisIndex:long| of [=the range=] from 0 to |axesSize| − 1, [=list/append=] 0 to |axes|.
  12. Return |axes|.

To initialize buttons for a gamepad, run the following steps:

  1. Let |inputCount:long| be the number of button inputs exposed by the device represented by |gamepad|.
  2. Set |gamepad|.{{Gamepad/[[buttonMinimums]]}} to be a [=list=] of {{unsigned long}} values with [=list/size=] equal to |inputCount| containing minimum logical values for each of the button inputs.
  3. Set |gamepad|.{{Gamepad/[[buttonMaximums]]}} to be a [=list=] of {{unsigned long}} values with [=list/size=] equal to |inputCount| containing maximum logical values for each of the button inputs.
  4. Initialize |unmappedInputList| to be an empty [=list=].
  5. Initialize |mappedIndexList| to be an empty [=list=].
  6. Initialize |buttonsSize:long| to be 0.
  7. [=list/For each=] |rawInputIndex:long| of [=the range=] from 0 to |inputCount| − 1:
    1. If the the gamepad button at index |rawInputIndex| [=represents a Standard Gamepad button=]:
      1. Let |canonicalIndex:long| be the [=canonical index=] for the button.
      2. If |mappedIndexList| [=list/contain=]s |canonicalIndex|, then append |rawInputIndex| to |unmappedInputList|.

        Otherwise:

        1. Set |gamepad|.{{Gamepad/[[buttonMapping]]}}[|rawInputIndex|] to |canonicalIndex|.
        2. [=list/Append=] |canonicalIndex| to |mappedIndexList|.
        3. If |canonicalIndex| + 1 is greater than |buttonsSize|, then set |buttonsSize| to |canonicalIndex| + 1.

      Otherwise, [=list/append=] |rawInputIndex| to |unmappedInputList|.

    2. Increment |rawInputIndex|.
  8. Initialize |buttonIndex:long| to be 0.
  9. [=list/For each=] |rawInputIndex:long| of |unmappedInputList|:
    1. While |mappedIndexList| [=list/contain=]s |buttonIndex|:
      1. Increment |buttonIndex|.
    2. Set |gamepad|.{{Gamepad/[[buttonMapping]]}}[|rawInputIndex|] to |buttonIndex|.
    3. [=list/Append=] |buttonIndex| to |mappedIndexList|.
    4. If |buttonIndex| + 1 is greater than |buttonsSize|, then set |buttonsSize| to |buttonIndex| + 1.
  10. Initialize |buttons| to be an empty [=list=].
  11. [=list/For each=] |buttonIndex:long| of [=the range=] from 0 to |buttonsSize| − 1, [=list/append=] a [=new=] {{GamepadButton}} to |buttons|.
  12. Return |buttons|.

GamepadButton Interface

This interface defines the state of an individual button on a gamepad device.

        [Exposed=Window, SecureContext]
        interface GamepadButton {
          readonly attribute boolean pressed;
          readonly attribute boolean touched;
          readonly attribute double value;
        };
      

Instances of {{GamepadButton}} are created with the internal slots described in the following table:

Internal slot Initial value Description (non-normative)
[[\pressed]] `false` A flag indicating that the button is pressed
[[\touched]] `false` A flag indicating that the button is touched
[[\value]] 0.0 A {{double}} representing the button value scaled to the range [0.0 .. 1.0]
pressed attribute

The pressed state of the button. This property MUST be `true` if the button is currently pressed, and `false` if it is not pressed. For buttons which do not have a digital switch to indicate a pure pressed or released state, the [=user agent=] MUST choose a button press threshold to indicate the button as pressed when its value is above a certain amount. If the platform API gives a recommended value, the user agent SHOULD use that. In other cases, the user agent SHOULD choose some other reasonable value.

The {{GamepadButton/pressed}} getter steps are:

  1. Return [=this=].{{GamepadButton/[[pressed]]}}.
touched attribute

The touched state of the button. If the button is capable of detecting touch, this property MUST be `true` if the button is currently being touched, and `false` otherwise. If the button is not capable of detecting touch and is capable of reporting an analog value, this property MUST be `true` if the value property is greater than 0, and `false` if the value is 0. If the button is not capable of detecting touch and can only report a digital value, this property MUST mirror the {{GamepadButton/pressed}} attribute.

The {{GamepadButton/touched}} getter steps are:

  1. Return [=this=].{{GamepadButton/[[touched]]}}.
value attribute

For buttons that have an analog sensor, this property MUST represent the amount which the button has been pressed. All button values MUST be linearly normalized to the range [0.0 .. 1.0]. 0.0 MUST mean fully unpressed, and 1.0 MUST mean fully pressed. For buttons without an analog sensor, only the values 0.0 and 1.0 for fully unpressed and fully pressed respectively, MUST be provided.

The {{GamepadButton/value}} getter steps are:

  1. Return [=this=].{{GamepadButton/[[value]]}}.

GamepadMappingType enum

This enum defines the set of known mappings for a Gamepad.

        enum GamepadMappingType {
          "",
          "standard",
          "xr-standard",
        };
      
""
The empty string indicates that no mapping is in use for this gamepad.
`"standard"`
The Gamepad's controls have been mapped to the [=Standard Gamepad=] layout.
`"xr-standard"`
The Gamepad's controls have been mapped to the [="xr-standard" gamepad mapping=]. This mapping is reserved for use by the [[[webxr-gamepads-module-1]]]. Gamepads returned by {{Navigator/getGamepads()}} MUST NOT report a {{Gamepad/mapping}} of {{GamepadMappingType/"xr-standard"}}.

Extensions to the `Navigator` interface

        [Exposed=Window]
        partial interface Navigator {
          sequence<Gamepad?> getGamepads();
        };
      

Instances of {{Navigator}} are created with the internal slots described in the following table:

Internal slot Initial value Description (non-normative)
[[\hasGamepadGesture]] `false` A flag indicating that a [=gamepad user gesture=] has been observed
[[\gamepads]] `[]` A `sequence<Gamepad?>` with each {{Gamepad}} present at the index specified by its {{Gamepad/index}} attribute, or `null` for unassigned indices.

getGamepads() method

The gamepad state returned from {{Navigator/getGamepads()}} does not reflect disconnection or connection until after the {{gamepaddisconnected}} or {{gamepadconnected}} events have fired.

To mitigate fingerprinting, {{Navigator/getGamepads()}} returns an empty [=list=] before a [=gamepad user gesture=] has been seen. [[FINGERPRINTING-GUIDANCE]]

The {{Navigator/getGamepads()}} method steps are:

  1. If the [=current settings object=]'s [=environment settings object / responsible document=] is not [=allowed to use=] the `"gamepad"` permission, then [=exception/throw=] a {{"SecurityError"}} {{DOMException}} and abort these steps.
  2. If [=this=].{{Navigator/[[hasGamepadGesture]]}} is `false`, then return an empty [=list=].
  3. Let |now:DOMHighResTimeStamp| be the [=current high resolution time=].
  4. [=list/For each=] |gamepad:Gamepad| of [=this=].{{Navigator/[[gamepads]]}}:
    1. If |gamepad| is not `null` and |gamepad|.{{Gamepad/[[exposed]]}} is `false`:
      1. Set |gamepad|.{{Gamepad/[[exposed]]}} to `true`.
      2. Set |gamepad|.{{Gamepad/[[timestamp]]}} to |now|.
  5. Return |gamepads|.

A |gamepad:Gamepad| contains a gamepad user gesture if the current input state indicates that the user is currently interacting with the gamepad. The [=user agent=] MUST provide an algorithm to check if the input state contains a gamepad user gesture. For buttons that support a neutral default value and have reported a {{GamepadButton/pressed}} value of `false` at least once, a {{GamepadButton/pressed}} value of `true` SHOULD be considered interaction. If a button does not support a neutral default value (for example, a toggle switch), then a {{GamepadButton/pressed}} value of `true` SHOULD NOT be considered interaction. If a button has never reported a {{GamepadButton/pressed}} value of `false` then it SHOULD NOT be considered interaction. Axis movements SHOULD be considered interaction if the axis supports a neutral default value, the current displacement from neutral is greater than a threshold chosen by the [=user agent=], and the axis has reported a value below the threshold at least once. If an axis does not support a neutral default value (for example, an axis for a joystick that does not self-center), or an axis has never reported a value below the axis gesture threshold, then the axis SHOULD NOT be considered when checking for interaction. The axis gesture threshold SHOULD be large enough that random jitter is not considered interaction.

GamepadEvent Interface

        [Exposed=Window, SecureContext]

        interface GamepadEvent: Event {
          constructor(DOMString type, GamepadEventInit eventInitDict);
          [SameObject] readonly attribute Gamepad gamepad;
        };
      
gamepad
The {{GamepadEvent/gamepad}} attribute provides access to the associated gamepad data for this event.

GamepadEventInit dictionary

        dictionary GamepadEventInit : EventInit {
          required Gamepad gamepad;
        };
      
gamepad member
The {{Gamepad}} associated with this event.

Remapping

Each device manufacturer creates many different products and each has unique styles and layouts of buttons and axes. It is intended that the [=user agent=] support as many of these as possible.

Additionally there are de facto standard layouts that have been made popular by game consoles. When the [=user agent=] recognizes the attached device, it is RECOMMENDED that it be remapped to a canonical ordering when possible. Devices that are not recognized should still be exposed in their raw form.

There is currently one canonical layout, the Standard Gamepad. When remapping, the indices in {{Gamepad/axes}} and {{Gamepad/buttons}} should correspond as closely as possible to the physical locations in the diagram below. Additionally, {{Gamepad/mapping}} SHOULD be set to {{GamepadMappingType/"standard"}}.

The [=Standard Gamepad=] buttons are laid out in a left cluster of four buttons, a right cluster of four buttons, a center cluster of three buttons, and a pair of front facing buttons on the left and right side of the gamepad. The four axes of the "Standard Gamepad" are associated with a pair of analog sticks, one on the left and one on the right. The following table describes the buttons/axes and their physical locations.

An axis input represents a Standard Gamepad axis if it reports the input value for a thumbstick axis, the thumbstick is located in approximately the same location as the corresponding [=Standard Gamepad=] thumbstick, and the orientation of the axis (up-down or left-right) matches the orientation of the [=Standard Gamepad=] axis. If there are multiple axes that represent the same [=Standard Gamepad=] axis, then the [=user agent=] SHOULD select one to be the [=Standard Gamepad=] axis and assign a different index to the other axis.

A button input represents a Standard Gamepad button if it reports the input value for a button or trigger, and the button or trigger is located in approximately the same location as the corresponding [=Standard Gamepad=] button.

If an axis or button input represents a [=Standard Gamepad=] axis or button, then its canonical index is the index of the corresponding [=Standard Gamepad=] axis or button.

Button/Axis Location
buttons[0] Bottom button in right cluster
buttons[1] Right button in right cluster
buttons[2] Left button in right cluster
buttons[3] Top button in right cluster
buttons[4] Top left front button
buttons[5] Top right front button
buttons[6] Bottom left front button
buttons[7] Bottom right front button
buttons[8] Left button in center cluster
buttons[9] Right button in center cluster
buttons[10] Left stick pressed button
buttons[11] Right stick pressed button
buttons[12] Top button in left cluster
buttons[13] Bottom button in left cluster
buttons[14] Left button in left cluster
buttons[15] Right button in left cluster
buttons[16] Center button in center cluster
axes[0] Horizontal axis for left stick (negative left/positive right)
axes[1] Vertical axis for left stick (negative up/positive down)
axes[2] Horizontal axis for right stick (negative left/positive right)
axes[3] Vertical axis for right stick (negative up/positive down)
Visual representation of a [=Standard Gamepad=] layout.

Usage Examples

The example below demonstrates typical access to gamepads. Note the relationship with the {{AnimationFrameProvider/requestAnimationFrame()}} method.

        function runAnimation() {
            window.requestAnimationFrame(runAnimation);
            for (const pad of navigator.getGamepads()) {
              // todo; simple demo of displaying pad.axes and pad.buttons
              console.log(pad);
            }
        }

        window.requestAnimationFrame(runAnimation);
      
Coordination with requestAnimationFrame()

Interactive applications will typically be using the {{AnimationFrameProvider/requestAnimationFrame()}} method to drive animation, and will want coordinate animation with user gamepad input. As such, the gamepad data should be polled as closely as possible to immediately before the animation callbacks are executed, and with frequency matching that of the animation. That is, if the animation callbacks are running at 60Hz, the gamepad inputs should also be sampled at that rate.

The gamepadconnected event

When a gamepad becomes available on the system, run the following steps:

  1. Let |document:Document?| be the [=current settings object=]'s [=environment settings object / responsible document=]; otherwise `null`.
  2. If |document| is not `null` and is not [=allowed to use=] the `"gamepad"` permission, then abort these steps.
  3. [=Queue a task=] on the [=gamepad task source=] to perform the following steps:
    1. Let |gamepad:Gamepad| be [=a new `Gamepad`=] representing the gamepad.
    2. Let |navigator:Navigator| be |gamepad|'s [=relevant global object=]'s {{Navigator}} object.
    3. Set |navigator|.{{Navigator/[[gamepads]]}}[|gamepad|.{{Gamepad/index}}] to |gamepad|.
    4. If |navigator|.{{Navigator/[[hasGamepadGesture]]}} is `true`:
      1. Set |gamepad|.{{Gamepad/[[exposed]]}} to `true`.
      2. If |document| is not `null` and is [=Document/fully active=], then [=fire an event=] named {{gamepadconnected}} at |gamepad|'s [=relevant global object=] using {{GamepadEvent}} with its {{GamepadEvent/gamepad}} attribute initialized to |gamepad|.

User agents implementing this specification must provide a new DOM event, named {{gamepadconnected}}. The corresponding event MUST be of type {{GamepadEvent}} and MUST fire on the {{Window}} object.

A [=user agent=] MUST dispatch this event type to indicate the user has connected a gamepad. If a gamepad was already connected when the page was loaded, the {{gamepadconnected}} event SHOULD be dispatched when the user presses a button or moves an axis.

The gamepaddisconnected event

When a gamepad becomes unavailable on the system, run the following steps:

  1. Let |gamepad:Gamepad| be the {{Gamepad}} representing the unavailable device.
  2. [=Queue a task=] on the [=gamepad task source=] to perform the following steps:
    1. Set |gamepad|.{{Gamepad/[[connected]]}} to `false`.
    2. Let |document:Document?| be |gamepad|'s [=relevant global object=]'s [=associated `Document`=]; otherwise `null`.
    3. If |gamepad|.{{Gamepad/[[exposed]]}} is `true` and |document| is not `null` and is [=Document/fully active=], then [=fire an event=] named {{gamepaddisconnected}} at |gamepad|'s [=relevant global object=] using {{GamepadEvent}} with its {{GamepadEvent/gamepad}} attribute initialized to |gamepad|.
    4. Let |navigator:Navigator| be |gamepad|'s [=relevant global object=]'s {{Navigator}} object.
    5. Set |navigator|.{{Navigator/[[gamepads]]}}[|gamepad|.{{Gamepad/index}}] to `null`.
    6. While |navigator|.{{Navigator/[[gamepads]]}} [=list/is not empty=] and the last [=list/item=] of |navigator|.{{Navigator/[[gamepads]]}} is `null`, [=list/remove=] the last [=list/item=] of |navigator|.{{Navigator/[[gamepads]]}}.

User agents implementing this specification must provide a new DOM event, named {{gamepaddisconnected}}. The corresponding event MUST be of type {{GamepadEvent}} and MUST fire on the {{Window}} object.

When a gamepad is disconnected from the [=user agent=], if the [=user agent=] has previously dispatched a {{gamepadconnected}} event for that gamepad to a {{Window}}, a {{gamepaddisconnected}} event MUST be dispatched to that same {{Window}}.

Other events

More discussion needed, on whether to include or exclude axis and button changed events, and whether to roll them more together (`"gamepadchanged"`?), separate somewhat (`"gamepadaxischanged"`?), or separate by individual axis and button.

Extensions to the `WindowEventHandlers` Interface Mixin

This specification extends the {{WindowEventHandlers}} interface mixin from HTML to add [=event handler IDL attributes=] to facilitate the event handler registration.

        partial interface mixin WindowEventHandlers {
          attribute EventHandler ongamepadconnected;
          attribute EventHandler ongamepaddisconnected;
        };
      

Integration with Permissions Policy

This specification defines a policy-controlled feature identified by the string "gamepad". Its [=default allowlist=] is `'self'`.

A [=document=]’s [=Document/permissions policy=] determines whether any content in that document is allowed to access {{Navigator/getGamepads()}}. If disabled in any document, no content in the document will be [=allowed to use=] {{Navigator/getGamepads()}}, nor will the {{gamepadconnected}} and {{gamepaddisconnected}} events fire.

Acknowledgements

The following people contributed to the development of this document.