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The Gamepad specification defines a low-level interface that represents gamepad devices.
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This section is non-normative.
Some user agents 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.
Gamepad
interface
This interface defines an individual gamepad device.
WebIDL[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
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
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 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
id
string.
index
attribute
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 connected
attribute MUST be set to
false
.
The connected
getter steps are:
[[connected]]
.
timestamp
attribute
The timestamp
allows the author to determine the last
time the axes
or 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, timestamp
MUST be the current high resolution time at the time when the Gamepad
was first made
available to script.
User agents SHOULD set a minimum resolution of gamepad's
timestamp
attribute to 5 microseconds, following
[HR-TIME]'s clock resolution recommendation.
The timestamp
getter steps are:
[[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 mapping
to the corresponding
GamepadMappingType
value.
To select a mapping for a gamepad device, run the following steps:
standard
".
".
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 axes
getter steps are:
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 buttons
getter steps are:
[[buttons]]
.
When the system receives new button or axis input values, run the following steps:
Gamepad
object representing the
device that received new button or axis input values.
To update gamepad state for gamepad, run the following steps:
[[timestamp]]
to now.
Navigator
object.
[[hasGamepadGesture]]
is false
and
gamepad contains a gamepad user gesture:
[[hasGamepadGesture]]
to
true
.
[[gamepads]]
:
null
:
[[exposed]]
to
true
.
[[timestamp]]
to
now.
Document
; otherwise
null
.
null
and is 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 gamepad
attribute initialized to connectedGamepad.
To map and normalize axes for gamepad, run the following steps:
unsigned long
values
representing the most recent logical axis input values for each axis
input of the device represented by gamepad.
[[axisMapping]]
[rawAxisIndex].
[[axisMinimums]]
[rawAxisIndex].
[[axisMaximums]]
[rawAxisIndex].
[[axes]]
[axisIndex] to be
normalizedValue.
To map and normalize buttons for gamepad, run the following steps:
unsigned long
values
representing the most recent logical button input values for each
button input of the device represented by gamepad.
[[buttonMapping]]
[rawButtonIndex].
[[buttonMinimums]]
[rawButtonIndex].
[[buttonMaximums]]
[rawButtonIndex].
[[buttons]]
[mappedIndex].
[[value]]
to
normalizedValue.
If the button has a digital switch to indicate a pure pressed
or released state, set button.[[pressed]]
to true
if the button is pressed or false
if it is not
pressed.
Otherwise, set button.[[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.[[touched]]
to true
if the
button is currently being touched.
Otherwise, set button.[[touched]]
to
button.[[pressed]]
.
Gamepad
A new Gamepad
representing a connected gamepad device is
constructed by performing the following steps:
Gamepad
instance:
id
attribute to an
identification string for the gamepad.
index
attribute to the
result of selecting an unused gamepad index for gamepad.
mapping
attribute to the
result of selecting a mapping for the gamepad device.
[[connected]]
to true
.
[[timestamp]]
to the
current high resolution time.
[[axes]]
to the result of
initializing axes for gamepad.
[[buttons]]
to the result of
initializing buttons for gamepad.
To select an unused gamepad index for gamepad, run the following steps:
Navigator
object.
[[gamepads]]
− 1.
[[gamepads]]
[gamepadIndex] is
null
, then return gamepadIndex.
null
to navigator.[[gamepads]]
.
[[gamepads]]
− 1.
To initialize axes for gamepad, run the following steps:
[[axisMinimums]]
to a list of
unsigned long
values with size equal to inputCount
containing minimum logical values for each of the axis inputs.
[[axisMaximums]]
to a list of
unsigned long
values with size equal to inputCount
containing maximum logical values for each of the axis inputs.
Otherwise:
[[axisMapping]]
[rawInputIndex] to
canonicalIndex.
Otherwise, append rawInputIndex to unmappedInputList.
[[axisMapping]]
[rawInputIndex] to
axisIndex.
To initialize buttons for a gamepad, run the following steps:
[[buttonMinimums]]
to be a list of
unsigned long
values with size equal to inputCount
containing minimum logical values for each of the button inputs.
[[buttonMaximums]]
to be a list of
unsigned long
values with size equal to inputCount
containing maximum logical values for each of the button inputs.
Otherwise:
[[buttonMapping]]
[rawInputIndex]
to canonicalIndex.
Otherwise, append rawInputIndex to unmappedInputList.
[[buttonMapping]]
[rawInputIndex]
to buttonIndex.
GamepadButton
to
buttons.
GamepadMappingType
enum
This enum defines the set of known mappings for a Gamepad.
WebIDLenum GamepadMappingType
{
"
",
"standard
",
"xr-standard
",
};
""
"standard"
"xr-standard"
getGamepads
()
MUST NOT report a mapping
of
"xr-standard
".
GamepadEvent
Interface
WebIDL[Exposed=Window, SecureContext]
interface GamepadEvent
: Event {
constructor
(DOMString type, GamepadEventInit
eventInitDict);
[SameObject] readonly attribute Gamepad
gamepad
;
};
gamepad
gamepad
attribute provides access to the
associated gamepad data for this event.
GamepadEventInit
dictionary
WebIDLdictionary GamepadEventInit
: EventInit {
required Gamepad
gamepad
;
};
gamepad
member
Gamepad
associated with this event.
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 axes
and
buttons
should correspond as closely as possible to the
physical locations in the diagram below. Additionally,
mapping
SHOULD be set to "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) |
This section is non-normative.
The example below demonstrates typical access to gamepads. Note the
relationship with the
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
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:
null
.
null
and is not allowed to use the
"gamepad"
permission, then abort these steps.
Gamepad
representing the
gamepad.
Navigator
object.
[[gamepads]]
[gamepad.index
]
to gamepad.
[[hasGamepadGesture]]
is true
:
[[exposed]]
to true
.
null
and is fully active, then fire an event named gamepadconnected
at
gamepad's relevant global object using GamepadEvent
with its 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.
When a gamepad becomes unavailable on the system, run the following steps:
Gamepad
representing the
unavailable device.
[[connected]]
to false
.
Document
; otherwise null
.
[[exposed]]
is true
and document
is not null
and is fully active, then fire an event named gamepaddisconnected
at gamepad's relevant global object using GamepadEvent
with its
gamepad
attribute initialized to gamepad.
Navigator
object.
[[gamepads]]
[gamepad.index
]
to null
.
[[gamepads]]
is not empty and the last item of
navigator.[[gamepads]]
is null
, remove
the last item of 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
.
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.
WindowEventHandlers
Interface Mixin
This specification extends the WindowEventHandlers
interface mixin
from HTML to add event handler IDL attributes to facilitate the
event handler registration.
WebIDLpartial interface mixin WindowEventHandlers {
attribute EventHandler ongamepadconnected
;
attribute EventHandler ongamepaddisconnected
;
};
This specification defines a policy-controlled feature identified by
the string "gamepad"
. Its default allowlist is 'self'
.
A document’s permissions policy determines whether
any content in that document is allowed to access
getGamepads
()
. If disabled in any document, no content
in the document will be allowed to use
getGamepads
()
, nor will the gamepadconnected
and
gamepaddisconnected
events fire.
As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.
The key words MUST, MUST NOT, RECOMMENDED, SHOULD, and SHOULD NOT in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
This section is non-normative.
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