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A history of changes to this document can be found at http://dvcs.w3.org/hg/pointerlock/log/default/index.html
Summary of changes since W3C Recommendation 27 October 2016 :
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This document is governed by the 1 March 2019 W3C Process Document .
This section is non-normative.
The Pointer Lock API provides applications the ability to directly interpret mouse movements as an input method, rather than being limited to only read the position of the mouse cursor. A popular example is that of first person movement controls in three dimensional graphics applications such as games: movement of the mouse is interpreted to control the rotation/direction of the player's camera; no mouse cursor is displayed, and the movement is not limited to the traditional boundaries (such as the user agent's window, or the overall screen) that the mouse cursor is usually subject to, meaning that any mouse movements can be tracked indefinitely in any direction.
Pointer Lock is related to Mouse Capture [ MSDN-SETCAPTURE ] [ MDN-SETCAPTURE ] (Mouse Capture is unspecified: bug 14600 ). Capture provides continued event delivery to a target element while a mouse is being dragged, but ceases when the mouse button is released. Pointer Lock differs by being persistent, not limited by screen boundaries, sending events regardless of mouse button state, hiding the cursor, and not releasing until an API call or specific default unlock gesture by the user.
Pointer Lock deals with capturing a single resource and relating it to a single element. This is similar to the Fullscreen API [ FULLSCREEN ], which promotes a single element to be full screen. The Pointer Lock API chooses to pattern the resource capture, state change, and release API as closely as possible after the Fullscreen API.
The Pointer Lock interaction mode was previously referred to as mouse lock. The name was changed as many different controller types besides mice can manipulate the on screen pointing cursor, and they are all impacted.
click
,
but
not
mousemove
.
Engagement
gestures
are
any
events
included
in
the
definition
of
being
triggered
by
user
activation
with
the
addition
of
keypress
and
keyup
.
Note
that
operating
system
level
accessibility
and
internationalization
features
may
intercept
gestures
before
the
user
agent
processes
them
for
interaction
with
a
page.
E.g.
multiple
key
press
codes
used
to
enter
an
extended
international
character.
pointerlockchange
and
pointerlockerror
Events
Two events are used to communicate pointer lock state change or an error in changing state. They are named pointerlockchange and pointerlockerror . If pointer lock is entered or exited for any reason a pointerlockchange event must be sent.
User
agents
must
deliver
these
events
by
queuing
a
task
to
fire
an
event
of
the
appropriate
name
with
its
bubbles
attribute
[
DOM
]
set
to
false
to
the
pointer
lock
target
element's
node
document
.
Magnification software increases the size of content on the screen. It uses the mouse to move the magnified point of focus around. When a pointer lock is initiated, the magnification software needs to switch to using the keyboard to move the magnified point of focus around instead. When a pointerlockchange event is fired, web browsers therefore need to make sure the event is communicated to assistive technologies like screen magnifiers.
Element
Interface
The
Element
interface
is
extended
to
provide
the
ability
to
request
the
the
pointer
be
locked.
partial interface Element {
void requestPointerLock();
};
requestPointerLock()
method
Requests that the pointer be locked to a DOM element target . The user agent determines if pointer lock state will be entered and upon lock state change or error must send either a pointerlockchange or pointerlockerror event respectively.
Pointer lock must not succeed if the document object's active sandboxing flag set has the sandboxed pointer lock browsing context flag set.
Pointer lock must not succeed unless the target 's shadow-including root is the active document of a browsing context which is (or has an ancestor browsing context which is) in focus by a window which is in focus by the operating system's window manager. The target element and its browsing context need not be in focus.
If
a
user
has
exited
pointer
lock
via
the
default
unlock
gesture
,
or
pointer
lock
has
not
previously
been
entered
for
this
document,
an
event
generated
as
a
result
of
an
engagement
gesture
must
be
received
by
the
document
before
will
succeed.
requestPointerLock
()
If any element (including this one), whose shadow-including root is same as this element's shadow-including root , is already locked (or pending lock) the pointer lock target must be updated to this element and a pointerlockchange event sent.
If any element, whose shadow-including root is a different document, is already locked the request must fail and a pointerlockerror event be sent.
Once
in
the
locked
state
the
user
agent
must
fire
all
relevant
user
generated
events
(for
example:
MouseEvent
mousemove
,
mousedown
,
mouseup
,
click
,
and
wheel
)
[
ui-events
]
to
the
target
of
pointer
lock,
and
not
fire
mouse
events
to
other
elements.
Events
that
require
the
concept
of
a
mouse
cursor
must
not
be
dispatched
(for
example:
mouseover
,
mouseout
,
drag
,
and
drop
).
In the locked state the system mouse cursor must be hidden. Movement and button presses of the mouse must not cause the window to lose focus.
Synthetic mouse events created by application script act the same regardless of lock state.
Document
Interface
partial interface Document {
attribute EventHandler onpointerlockchange;
attribute EventHandler onpointerlockerror;
void exitPointerLock();
};
onpointerlockchange
attribute
An event handler idl attribute for pointerlockchange events.
onpointerlockerror
attribute
An event handler idl attribute for pointerlockerror events.
exitPointerLock()
method
Initiates an exit from pointer lock state if currently locked to a target whose shadow-including root is this document, and sends a pointerlockchange event when the lock state has been exited.
The
system
mouse
cursor
must
be
displayed
again
and
positioned
at
the
same
location
that
it
was
when
pointer
lock
was
entered
(the
same
location
that
is
reported
in
screenX
,
screenY
,
when
the
pointer
is
locked).
DocumentOrShadowRoot
Mixin
partial interface mixin DocumentOrShadowRoot {
readonly attribute Element ? pointerLockElement;
};
pointerLockElement
While the pointer is locked, returns the result of retargeting the element, which is the target for mouse events, against the context object if the result and the context object are in the same tree, otherwise returns null.
Returns null if lock is pending or if pointer is unlocked.
<body>
<div id="host1">
<shadow-root id="root1">
<canvas id="canvas1"></canvas>
</shadow-root>
</div>
<div id="host2">
<shadow-root id="root2">
<canvas id="canvas2"></canvas>
</shadow-root>
</div>
</
body
>
Note:
the
example
uses
fictional
shadow-root
element
to
denote
a
shadow
root
instance.
If
#canvas1
is
the
target,
document.pointerLockElement
returns
#host1
,
and
root1.pointerLockElement
returns
#canvas1
.
The
result
of
retargeting
#canvas1
against
#root2
is
#host1
,
but
as
#host1
is
not
in
the
same
tree
as
#root2
,
null
will
be
returned
for
root2.pointerLockElement
.
MouseEvent
Interface
partial interface MouseEvent {
readonly attribute long movementX;
readonly attribute long movementY;
};
movementX
attribute
movementY
attribute
The
attributes
movementX
must
provide
the
change
in
position
of
the
pointer,
as
if
the
values
of
movementY
screenX
,
screenY
,
were
stored
between
two
subsequent
mousemove
events
eNow
and
ePrevious
and
the
difference
taken
movementX
=
eNow.screenX-ePrevious.screenX
.
/
movementX
must
be
zero
for
all
mouse
events
except
movementY
mousemove
.
All
motion
data
must
be
delivered
via
mousemove
events
such
that
between
any
two
mouse
events
earlierEvent
and
currentEvent
the
value
of
currentEvent.screenX-earlierEvent.screenX
is
equivalent
to
the
sum
of
all
movementX
/code>
events
after
movementY
earlierEvent
,
with
the
exception
of
when
screenX
can
not
be
updated
because
the
pointer
is
clipped
by
the
user
agent
screen
boundaries.
/
movementX
must
be
updated
regardless
of
pointer
lock
state.
movementY
When
unlocked,
the
system
cursor
can
exit
and
re-enter
the
user
agent
window.
If
it
does
so
and
the
user
agent
was
not
the
target
of
operating
system
mouse
move
events
then
the
most
recent
pointer
position
will
be
unknown
to
the
user
agent
and
/
movementX
can
not
be
computed
and
must
be
set
to
zero.
movementY
When
pointer
lock
is
enabled
clientX
,
clientY
,
screenX
,
and
screenY
must
hold
constant
values
as
if
the
pointer
did
not
move
at
all
once
pointer
lock
was
entered.
But
/
movementX
must
continue
to
provide
the
change
in
position
of
the
pointer
as
when
the
pointer
is
unlocked.
There
will
be
no
limit
to
movementY
/
movementX
values
if
the
mouse
is
continuously
moved
in
a
single
direction.
The
concept
of
the
mouse
cursor
will
have
been
removed,
and
it
will
not
move
off
the
window
or
be
clamped
by
a
screen
edge.
movementY
The
un-initialized
value
of
/
movementX
must
be
movementY
0
.
Large
movement
values
must
not
appear
in
situations
when
mouse
input
is
interupted,
such
as
the
mouse
cursor
leaving
the
window
and
then
re-entering
at
another
location.
If
a
User
agent
experiences
a
gap
in
receiving
mouse
input
data
from
the
operating
system
then
the
next
generated
mousemove
event
must
have
/
movementX
set
to
movementY
0
.
These
gaps
may
appear
for
example
when
the
User
agent
receives
a
mouse
leaving
event
at
the
window
system
API.
As
an
exception
mouse
capture
may
allow
the
User
agent
to
continue
receiving
mouse
events
when
the
cursor
moves
outside
the
window.
MouseEventInit
Dictionary
partial dictionary MouseEventInit {
long movementX = 0;
long movementY = 0;
};
movementX
member
movementY
member
movementX
and
movementY
are
used
to
initialize
respective
members
of
MouseEvent
.
A default unlock gesture must always be available that will exit pointer lock.
Pointer lock must be exited if the target becomes disconnected , or the user agent , window, or tab loses focus. Moving focus between elements of active documents , including between browsing contexts , does not exit pointer lock. E.g. using the keyboard to move focus between contents of frames or iframes will not exit.
Pointer lock must not be exited when fullscreen [ FULLSCREEN ] is entered or exited unless the pointer is required to enable interaction with the user agent graphical user interface, the default unlock gesture was used to exit both fullscreen and pointer lock, or window or tab focus was lost.
This section is non-normative.
A player on a first/third person game will need to control the view-port orientation. A widely used method is the use of mouse movements to control the viewing angle. This kind of application can use the Pointer Lock API to allow a complete freedom of control over the viewport's yaw and pitch even when the user is not pressing mouse buttons. Those buttons can be used for other actions while constantly providing navigation via mouse movement.
Users of a three dimensional modeling application will need to rotate models. A application can use the Pointer Lock API to enable the author to rotate the model freely in a drag operation without limiting motion. Without pointer lock a drag would stop providing motion data when the mouse cursor is limited by the edge of the screen.
Similarly, absolute motion panning of a large two dimensional image could be permitted in a single drag operation without cursor / screen limits.
A player on a fast reflexes game controls a paddle to bounce back a ball to the opponent, while allowing the same paddle to execute actions based on different mouse buttons being pressed. The application can use the Pointer Lock API to allow the player to react quickly without being concerned about the mouse cursor leaving the game play area and clicking another system application, thus breaking the game flow.
When modifying numerically magnitudes in applications sometimes the user will prefer to "drag" a numeric control by its button handles to increment or decrement the numeric value. E.g. a spinner with a number entry text box and arrows pointing up and down that can be clicked or dragged on to change the value. An application could use the Pointer Lock API to allow modifying the numeric values beyond what the logical screen bounds allow. The same could apply for a control that fast forwards or rewinds a video or audio stream like a "jog".
Some games use a classical cursor, however they want it to be limited or controlled in some manner. E.g. limited to the bounds of the game, or movable by the game. Locking the pointer enables this if the application creates their own cursor. However HTML and DOM should still be available to use for user interface. Synthetic mouse events should be permitted to allow an application defined cursor to interact with DOM. E.g. the following code should permit a custom cursor to send click events while the pointer is locked:
document.addEventListener("click", function (e) {
if (e._isSynthetic)
return;
// send a synthetic click
var ee = document.createEvent("MouseEvents");
ee._isSynthetic = true;
x = myCursor.x;
y = myCursor.y;
ee.initMouseEvent("click", true, true, null, 1,
x + e.screenX - e.clientX,
y + e.screenY - e.clientY,
x,
y);
var target = document.elementFromPoint(x, y);
if (target)
target.dispatchEvent(ee);
});
Note that synthetic clicks may not be permitted by a user agent to produce the same default action as a non-synthetic click. However, application handlers can still take action and provide user interface with existing HTML & DOM mechanisms.
Real Time Strategy games often use this technique. When the player moves the pointer to the view-port borders, if they "push" the border with a mouse movement, the view-port is panned over the game area according to how much they move the mouse. When moving the mouse cursor within the bounds of the view port it acts at is typically would on a system. Applications may choose to implement this using pointer lock and the previous use case of "Synthetic cursor interaction with HTML DOM UI" to bring cursor behavior completely under their control.
Games that use pointer lock may desire a traditional UI and system cursor while players prepare in a game lobby. Games usually start after a short timer when all players are ready. Ideally the game could then switch to pointer lock mode without requiring an engagement gesture . Players should be able to seamlessly move from the game lobby into game navigation.
Game portals, and other sites such as Facebook and Google Plus, host games for users to play. These games may be hosted and served from a different origin from that of the portal site. Embedded games should be able to lock the pointer, even in non-full screen mode.
This section is non-normative.
Security Concerns:
Responses:
Recommendations:
Pointer lock is a required user interaction mode for certain application types, but carries a usability concern if maliciously used. An attacker could remove the ability for a user to control their mouse cursor on their system. User agents will prevent this by always providing a mechanism to exit pointer lock, by informing the user of how, and by limiting how pointer lock can be entered.
User agents will determine their own appropriate policies, which may be specialized per device or differ based on user options.
This section is non-normative.
Mouse Capture [ MDN-SETCAPTURE ] handles low security risk mouse event target lock for the duration of a mouse drag gesture. Pointer lock removes the concept of the cursor and directs all events to a given target. They are related, but different.
If a browser implemented both, it would be reasonable to support a combination of traits: The security simplicity of "automatically release lock when mouse up" and the increased functionality of total control over mouse input and removal of the system cursor. The security trait would allow more permissive use of the feature for applications that only required a short burst of pointer lock during a drag event.
This functionality is omitted from the initial version of this spec because it helps the minor use cases in windowed mode but we still do not have an implementation solving the major ones. And, to implement this a browser must implement both, which none does yet. It is not clear if this feature should live on .lock or on .setCapture. If both were implemented, either API could be augmented fairly easily to offer the hybrid functionality.
Even in non locked state, the delta values of mouse movement are useful. Changing the meaning of .client or .screen based on lock state would also cause easy errors in code not carefully monitoring the lock state.
When the pointer is locked 'wheel' events should be sent to the pointer lock target element just as 'mousemove' events are. There is a naming conflict with .deltaX/Y/Z as defined in DOM 3 'wheel' event .
There are good motivations to provide a more fine grained approach. E.g. the use case "View-port panning by moving a mouse cursor against the bounds of a view-port" doesn't require hiding the mouse cursor, only bounding it and always having delta values available. Also, this specification defines the movement deltas to be taken from how the system mouse cursor moves, which incorporates operating system filtering and acceleration of the mouse movement data. Applications may desire access to a more raw form of movement data prior to adjustments appropriate for a mouse cursor. Also, raw data may provide better than pixel level accuracy for movement, as well as higher frequency updates. Providing the raw delta movement would also not require special permission or mode from a user, and for some set of applications that do not require bounding the cursor may reduce the security barriers and prompts needed.
There are two justifications for postponing this finer grained approach. The first is a concern of specifying what units mouse movement data are provided in. This specification defines .movementX/Y precisely as the same values that could be recorded when the mouse is not under lock by changes in .screenX/Y. Implementations across multiple user agents and operating systems will easily be able to meet that requirement and provide application developers and users with a consistent experience. Further, users are expected to have already configured the full system of hardware input and operating system options resulting in a comfortable control the system mouse cursor. By specifying .movementX/Y in the same units mouse lock API applications will be instantly usable to all users because they have already settled their preferences.
Secondly, the implementation of providing movement data and bounding the mouse cursor is more difficult in the fine grained approach. Bundling the features together gives implementations freedom to use a variety of techniques as appropriate on each operating system and is more practical to implement. Direct APIs do not exist on major desktop platforms (Windows, Mac OS X, Linux) to bound the cursor to a specific rectangle, and prototypes have not yet been developed to demonstrate building that behavior by e.g. invisible windows with Xlib or manual cursor movement on Mac. Unaccelerated Delta values have been proposed to be accessed by reading raw Human Interface Device (HID) data. E.g. WM_INPUT messages on Windows, and USB device APIs on Mac OS X / Linux. The challenge here is interpreting and normalizing the units to some consistent and specifiable scale. Also, most APIs considered to date are limited to USB devices.
It would be reasonable to consider adding these capabilities in the future, as the currently specified pointer lock API would be easy to continue to support if the finer grained delta and confinement features were implemented.
The bundled API is selected for implementation practicality, because the desired use cases are supported, and because it will not conflict with future improvements as discussed here.
Not yet, for the same reasons in the previous question: "Why bundle all functionality (hiding cursor, providing mouse deltas) instead of using CSS to hide the cursor, always providing delta values, and offering an API to restrict the cursor movement to a portion of the web page?" .
When under pointer lock many mouse events remain relevant, e.g. click, mousedown, etc. These all share the same event data structure MouseEvent. If movement data were reported via a new data structure then a new event would be needed for reporting delta movement. The new data structure would have many parallels to MouseEvent to offer the same conveniences, e.g. button and modifier key states. When handling click, down, and up events would the existing mousedown, mouseup be used? If so, they would provide .clientX/Y and .screenX/Y with no useful data, but would lack the convenience of containing the current movement data. Or, new events would also be required for when the mouse is locked.
Also, movementX/Y are convenient even when the mouse is not locked. This spec requires movement members to always be valid, even when the mouse cursor exists. This reduces code required to track the last cursor state and mouseover/mouseout transitions if applications wish to make use of delta motion of the mouse.
The only negative of adding movementX/Y to MouseEvent appears to be the unused values in clientX/Y and screenX/Y when under pointer lock. This does not seem to be a significant problem.
Therefore the minimal change to add movementX/Y to MouseEvent is selected to reduce API and implementation complexity.
Consider a game with a 3D view controlled by moving the mouse cursor, while the user may still chat with other users via a text console. It is reasonable for the application to accept text input to an element that is different than where mouse events are being dispatched. This is similar to pre-existing behavior of receiving mousemove events over any element while typing into a form on a page.
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.
This specification defines conformance criteria that apply to a single product: the user agent that implements the interfaces that it contains.
This section is non-normative.
Many have made contributions to the discussions of this specification: