The Gamepad specification defines a low-level interface that represents gamepad devices.
This is a work in progress.
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.
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.
This interface defines an individual gamepad device.
[Exposed=Window] 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; [SameObject] readonly attribute GamepadHapticActuator vibrationActuator; };
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 |
[[\vibrationActuator]] | undefined | A {{GamepadHapticActuator}} object capable of generating a haptic effect that vibrates the entire gamepad |
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.
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:
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:
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:
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:
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:
A {{GamepadHapticActuator}} object that represents the device's primary vibration actuator.
The {{Gamepad/vibrationActuator}} getter steps are:
When the system receives new button or axis input values, run the following steps:
To update gamepad state for |gamepad:Gamepad|, run the following steps:
To map and normalize axes for |gamepad:Gamepad|, run the following steps:
To map and normalize buttons for |gamepad:Gamepad|, run the following steps:
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.
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]]}}.
A new `Gamepad` representing a connected gamepad device is constructed by performing the following steps:
To select an unused gamepad index for |gamepad:Gamepad|, run the following steps:
To initialize axes for |gamepad:Gamepad|, run the following steps:
Otherwise:
Otherwise, [=list/append=] |rawInputIndex| to |unmappedInputList|.
To initialize buttons for a gamepad, run the following steps:
Otherwise:
Otherwise, [=list/append=] |rawInputIndex| to |unmappedInputList|.
This interface defines the state of an individual button on a gamepad device.
[Exposed=Window] 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] |
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:
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:
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:
This enum defines the set of known mappings for a Gamepad.
enum GamepadMappingType { "", "standard", "xr-standard", };
A {{GamepadHapticActuator}} corresponds to a configuration of motors or other actuators that can apply a force for the purposes of haptic feedback.
[Exposed=Window] interface GamepadHapticActuator { [SameObject] readonly attribute FrozenArray<GamepadHapticEffectType> effects; Promise<GamepadHapticsResult> playEffect( GamepadHapticEffectType type, optional GamepadEffectParameters params = {} ); Promise<GamepadHapticsResult> reset(); };
Instances of {{GamepadHapticActuator}} are created with the internal slots described in the following table:
Internal slot | Initial value | Description |
---|---|---|
[[\effects]] | An empty [=list=] of {{Gamepad/GamepadHapticEffectType}}. | Represents the effects supported by the actuator. |
[[\playingEffectPromise]] | `null` | The {{Promise}} to play some effect, or `null` if no effect is playing. |
Array of {{Gamepad/GamepadHapticEffectType}} values representing all the types of haptic effects that the actuator supports. This property lists the {{Gamepad/GamepadHapticEffectType}} values that the actuator supports, unless the [=user agent=] does not support playing effects of that type.
The {{GamepadHapticActuator/effects}} getter steps are:
The {{GamepadHapticActuator/playEffect()}} method steps, called with {{GamepadHapticEffectType}} |type:GamepadHapticEffectType| and {{GamepadEffectParameters}} |params:GamepadEffectParameters |, are:
The {{GamepadHapticActuator/reset()}} method steps are:
A {{GamepadHapticActuator}} can play effects with type |type:GamepadHapticEffectType| if |type:GamepadHapticEffectType| can be found in the {{GamepadHapticActuator/[[effects]]}} [=list=].
To check if an effect with {{GamepadHapticEffectType}} |type:GamepadHapticEffectType| and {{GamepadEffectParameters}} |params:GamepadEffectParameters| describes a valid effect, run the following steps:
To issue a haptic effect on an actuator, the [=user agent=] MUST send a command to the device to render an effect of |type:GamepadHapticEffectType| and try to make it use the provided |params:GamepadEffectParameters|. The [=user agent=] SHOULD use the provided |playEffectTimestamp:DOMHighResTimestamp| for more precise playback timing when |params|.{{GamepadEffectParameters/startDelay}} is not `0.0`. The [=user agent=] MAY modify the effect to increase compatibility. For example, an effect intended for a rumble motor may be transformed into a waveform-based effect for a device that supports waveform haptics but lacks rumble motors.
To stop haptic effects on an actuator, the [=user agent=] MUST send a command to the device to abort any effects currently being played. If a haptic effect was interrupted, the actuator SHOULD return to a motionless state as quickly as possible.
When the |document|'s [=Document/visibility state=] becomes `"hidden"`, run these steps for each {{GamepadHapticActuator}} |actuator:GamepadHapticActuator|:
A new |gamepadHapticActuator:GamepadHapticActuator| representing a {{Gamepad}}'s primary vibration actuator is constructed by performing the following steps:
enum GamepadHapticsResult { "complete", "preempted" };
The haptic effected completed playing.
The current effect was stopped or replaced (i.e., "preempted") by another effect.
The effect type defines how the effect parameters are interpreted by the actuator.
enum GamepadHapticEffectType { "dual-rumble", "trigger-rumble" };
{{GamepadHapticEffectType/"dual-rumble"}} describes a haptic configuration with an eccentric rotating mass (ERM) vibration motor in each handle of a standard gamepad. In this configuration, either motor is capable of vibrating the whole gamepad. The vibration effects created by each motor are unequal so that the effects of each can be combined to create more complex haptic effects.
A {{GamepadHapticEffectType/"dual-rumble"}} effect is a fixed-duration, constant-intensity vibration effect intended for an actuator of this type. {{GamepadHapticEffectType/"dual-rumble"}} effects are defined by {{GamepadEffectParameters/startDelay}}, {{GamepadEffectParameters/duration}}, {{GamepadEffectParameters/strongMagnitude}}, and {{GamepadEffectParameters/weakMagnitude}}, none of which are required because they default to 0.
{{GamepadEffectParameters/strongMagnitude}} and {{GamepadEffectParameters/weakMagnitude}} set the intensity levels for the low-frequency and high-frequency vibrations, normalized to the range `[0,1]`, defaulting to 0.
Given {{GamepadEffectParameters}} |params:GamepadEffectParameters|, a valid dual-rumble effect must have a [=valid effect|valid=] {{GamepadEffectParameters/duration}}, a [=valid effect|valid=] {{GamepadEffectParameters/startDelay}}, and both the {{GamepadEffectParameters/strongMagnitude}} and the {{GamepadEffectParameters/weakMagnitude}} must be in the range `[0,1]`.
{{GamepadHapticEffectType/"trigger-rumble"}} describes a haptics configuration with a vibration motor in each of the bottom front buttons of a [=Standard Gamepad=] (buttons with [=canonical indices=] 6 and 7) in addition to the two handle motors used for {{GamepadHapticEffectType/"dual-rumble"}}. These buttons most commonly take the form of spring-loaded triggers. In this configuration, either motor is capable of providing localized haptic feedback on the button's surface.
A {{GamepadHapticEffectType/"trigger-rumble"}} effect is a fixed-duration, constant-intensity vibration effect intended for an actuator of this type. {{GamepadHapticEffectType/"trigger-rumble"}} effects are defined by {{GamepadEffectParameters/startDelay}}, {{GamepadEffectParameters/duration}}, {{GamepadEffectParameters/strongMagnitude}}, {{GamepadEffectParameters/weakMagnitude}}, {{GamepadEffectParameters/leftTrigger}}, and {{GamepadEffectParameters/rightTrigger}}, none of which are required because they default to 0.
{{GamepadEffectParameters/startDelay}}, {{GamepadEffectParameters/duration}}, {{GamepadEffectParameters/strongMagnitude}}, {{GamepadEffectParameters/weakMagnitude}} share the same definition with {{GamepadHapticEffectType/"dual-rumble"}}. {{GamepadEffectParameters/leftTrigger}} and {{GamepadEffectParameters/rightTrigger}}, respectively, set the intensity levels for the left and right bottom front buttons vibrations, normalized to the range `[0,1]`, defaulting to 0.
Given {{GamepadEffectParameters}} |params:GamepadEffectParameters|, a valid trigger-rumble effect must have a [=valid effect|valid=] {{GamepadEffectParameters/duration}}, a [=valid effect|valid=] {{GamepadEffectParameters/startDelay}}, and the {{GamepadEffectParameters/strongMagnitude}}, {{GamepadEffectParameters/weakMagnitude}}, {{GamepadEffectParameters/leftTrigger}}, and {{GamepadEffectParameters/rightTrigger}} must be in the range `[0,1]`.
A GamepadEffectParameters
dictionary contains keys for
parameters used by haptic effects. The meaning of each key is defined
by the haptic effect, and some keys may be unused.
To mitigate unwanted long-running effects, the [=user agent=] MAY limit the total effect duration for a [=valid effect=] to some maximum duration. It is RECOMMENDED that the [=user agent=] use a maximum of 5 seconds.
dictionary GamepadEffectParameters { unsigned long long duration = 0; unsigned long long startDelay = 0; double strongMagnitude = 0.0; double weakMagnitude = 0.0; double leftTrigger = 0.0; double rightTrigger = 0.0; };
[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 empty [=sequence=] of {{Gamepad?}} objects | Each {{Gamepad}} present at the index specified by its {{Gamepad/index}} attribute, or `null` for unassigned indices. |
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:
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.
[Exposed=Window] interface GamepadEvent: Event { constructor(DOMString type, GamepadEventInit eventInitDict); [SameObject] readonly attribute Gamepad gamepad; };
dictionary GamepadEventInit : EventInit { required Gamepad gamepad; };
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.
Type | Index | Location |
---|---|---|
Button | 0 | Bottom button in right cluster |
1 | Right button in right cluster | |
2 | Left button in right cluster | |
3 | Top button in right cluster | |
4 | Top left front button | |
5 | Top right front button | |
6 | Bottom left front button | |
7 | Bottom right front button | |
8 | Left button in center cluster | |
9 | Right button in center cluster | |
10 | Left stick pressed button | |
11 | Right stick pressed button | |
12 | Top button in left cluster | |
13 | Bottom button in left cluster | |
14 | Left button in left cluster | |
15 | Right button in left cluster | |
16 | Center button in center cluster | |
axes | 0 | Horizontal axis for left stick (negative left/positive right) |
1 | Vertical axis for left stick (negative up/positive down) | |
2 | Horizontal axis for right stick (negative left/positive right) | |
3 | Vertical axis for right stick (negative up/positive down) |
Inspecting the capabilities of {{Gamepad}} objects can be used as a means of active fingerprinting. The [=user agent=] MAY alter the device information exposed through the API to reduce the fingerprinting surface. As an example, an implementation can require that a {{Gamepad}} object have exactly the number of buttons and axes defined in the [=Standard Gamepad=] layout even if more or fewer inputs are present on the connected device. [[FINGERPRINTING-GUIDANCE]]
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);
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.
When a gamepad becomes available on the system, run the following steps:
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.
When a gamepad becomes unavailable on the system, run the following steps:
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}}.
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.
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; };
This specification defines a policy-controlled feature identified by the string "gamepad". Its [=policy-controlled feature/default allowlist=] is [=default allowlist/*=].
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.
The following people contributed to the development of this document.