VirtualKeyboard API

W3C Working Draft

This version:
https://www.w3.org/TR/2021/WD-virtual-keyboard-20210928/
Latest published version:
https://www.w3.org/TR/virtual-keyboard/
Latest editor's draft:
https://w3c.github.io/virtual-keyboard/
Previous version:
https://www.w3.org/TR/2021/WD-virtual-keyboard-20210824/
Editor:
(Microsoft Corporation)
Former editor:
(Microsoft Corporation)
Participate:
GitHub w3c/virtual-keyboard
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Abstract

The VirtualKeyboard API provides authors with greater control over the visibility of the virtual keyboard (VK), and greater ability to adapt the layout of web pages when VK visibility changes.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

This document was published by the Web Editing Working Group as a Working Draft. This document is intended to become a W3C Recommendation.

GitHub Issues are preferred for discussion of this specification. Alternatively, you can send comments to our mailing list. Please send them to public-editing-tf@w3.org (subscribe, archives).

Publication as a Working Draft does not imply endorsement by the W3C Membership.

This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

This document was produced by a group operating under the W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

This document is governed by the 15 September 2020 W3C Process Document.

1. Introduction

This section is non-normative.

The Virtual Keyboard (VK) is the on-screen keyboard used for input in scenarios where a hardware keyboard may not be available. User agents respond to the presence of the VK, without any exposure of this information to web developers in the following way: 1. Repositioning the user agent above the VK 2. Reducing the size of the layout viewport so the VK doesn't occlude it 3. Reducing the size of the visual viewport and padding the layout viewport to ensure it can be shifted above the VK This API provides a fourth option that allows the user agent to leave its layout and visual viewports unchanged and instead provide information about the intersection of the VK and layout viewport so that the author can adapt the layout of their web pages using JavaScript or CSS environment variables.

Figure showing virtual keyboard on dual screen device Figure showing virtual keyboard on dual screen device

Figure showing virtual keyboard on single-touch screen device Figure showing virtual keyboard on single-touch screen device

2. Conformance

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 and MUST 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 specification defines conformance criteria that apply to a single product: the user agent that implements the interfaces that it contains.

Conformance requirements phrased as algorithms or specific steps may be implemented in any manner, so long as the end result is equivalent. (In particular, the algorithms defined in this specification are intended to be easy to follow, and not intended to be performant.)

3. The VirtualKeyboard Interface

WebIDLpartial interface Navigator {
    [SecureContext, SameObject] readonly attribute VirtualKeyboard virtualKeyboard;
};

[Exposed=Window, SecureContext]
interface VirtualKeyboard : EventTarget {
    undefined show();
    undefined hide();
    readonly attribute DOMRect boundingRect;
    attribute boolean overlaysContent;
    attribute EventHandler ongeometrychange;
};

The VirtualKeyboard object has an associated:

boundingRect

A DOMRect, initially has zero values.

overlaysContent

A boolean, initially false. When this attribute is set to true, a user agent MUST NOT resize its document's viewport or visual viewport.

show() method

The method must follow these steps:

  1. Let window be this's relevant global object. Assert that window is a Window object.
  2. If window does not have sticky activation, abort these steps.
  3. If the focused element is not a form control (such as the value of the textarea element), or an editing host (e.g., using contenteditable) then abort these steps.
  4. If the virtualKeyboardPolicy is not manual or inputMode's attribute value is none then abort these steps.
  5. Call the system API to show the VK.
  6. In parallel, follow these steps:
    1. Wait for the virtual keyboard to be shown by the system.
    2. Call set the virtual keyboard bounding rect with the keyboard's OS reported bounding rectangle and the document's viewport rectangle.
    3. Fire an event named "geometrychange" at this.
hide() method

The method must follow these steps:

  1. Let window be this's relevant global object. Assert that window is a Window object.
  2. If window does not have sticky activation, abort these steps.
  3. If the focused element's virtualKeyboardPolicy is not manual or inputMode's attribute value is none then abort these steps.
  4. Call the system API to hide the VK.
  5. In parallel, follow these steps:
    1. Wait for the virtual keyboard to be hidden by the system.
    2. Call set the virtual keyboard bounding rect with the keyboard's OS reported bounding rectangle (which has all 0 values) and the document's viewport rectangle.
    3. Fire an event named "geometrychange" at this.
Note

Platform heuristics may impose additional restrictions on VK show() and hide(). e.g., on Windows the pointer type MUST be touch or pen.

Note

A few people have expressed concerns around show() and hide() methods not being promise-based, but we believe it is a better design for web developers to use ongeometrychange event since it is fired when VK visibility changes, making the return values unnecessary.

overlaysContent

The overlaysContent getter steps are to return this's overlaysContent.

The overlaysContent setter steps are to set this's overlaysContent to the given value.

boundingRect

The attribute reports the intersection of the VK with the document's viewport in client coordinates. Call set the virtual keyboard bounding rect.

set the virtual keyboard bounding rect

To set the virtual keyboard bounding rect, with osk (a DOMRect representing the on-screen keyboard rectangle), and lv (a DOMRect representing the document's viewport rectangle) as inputs, run the following steps:
  1. Let osk be the on-screen keyboard rectangle that is the result of running the algorithm in show() or hide() on this.
  2. Let lv be the document's viewport that is the result of running the algorithm in show() or hide() on this.
  3. Map osk to the coordinate space of lv.
  4. Let bounds be a DOMRect object.
  5. Update bounds by intersecting lv with the osk.
  6. Map bounds to the coordinate space of lv.
  7. Return bounds.

The boundingRect getter steps are to return this's boundingRect.

ongeometrychange

The event is dispatched when the intersection of the VK and the document's viewport changes, e.g., in response to the VK being shown or hidden or the browser window being repositioned.

4. Extensions to the ElementContentEditable mixin

WebIDL partial interface mixin ElementContentEditable {
     [CEReactions] attribute DOMString virtualKeyboardPolicy;
};
Issue 1

Add handling of input and textarea.

The virtualKeyboardPolicy is an enumerated attribute whose keywords are the string, auto, and manual. The IDL attribute must reflect the respective content attributes of the same name. When specified on an element that is a contenteditable host, auto causes the corresponding editable element to automatically show the VK when it is focused or tapped & manual decouples focus and tap on the editable element from changes in the VK’s current state - the VK remains as it was.
The change in setting of any virtualKeyboardPolicy attribute value, negates currently defined behavior, unless it is a change from auto to empty string or vice versa.

Issue 2

Specify timing relative to events like focus.

5. Virtual Keyboard Visibility Change CSS environment variables.

The VirtualKeyboard API proposes six new CSS environment variables that the web developers can utilize to calculate the virtual keyboard's size and adjust layout in a declarative way.

Note

These CSS env should be added to the CSS env variable spec.

5.1 Keyboard inset variables

Name Value
keyboard-inset-top length
keyboard-inset-right length
keyboard-inset-bottom length
keyboard-inset-left length
keyboard-inset-width length
keyboard-inset-height length

The keyboard insets are six environment variables that define a rectangle by its top, right, bottom, and left insets from the edge of the viewport. Default value of the keyboard insets are "0px" if a fallback value is not provided else it gets updated when boundingRect value changes. The width & height insets are calculated from the remaining insets for developer ergonomics.

6. Examples

6.1 Example with usage of VK control APIs.

6.2 Examples with usage of overlaysContent and geometry event as a result of VK showing.

The figure and markup below are a representation of a canvas-based spreadsheet that repositions the active cell when the VK is shown. The geometrychange event triggers a paint request for the canvas. The painting code can then use the boundingRect property to render the active cell in the proper location. Figure showing virtual keyboard on single-touch screen device

The figure below represents a map application that presents a map on one window segment and search results on another. Using the proposal for Window Segments and media queries, the search box shown will increase its bottom margin to remain visible whenever the virtual keyboard appears on the left side of the foldable device. Figure showing virtual keyboard on single-touch screen device

7. Privacy and Security Considerations

Because VirtualKeyboard APIs may reveal some aspects about layout of user's VK, user agents must ensure that no extra information is exposed to the script that it already has through existing APIs. To mitigate potential security and privacy risks, browsers are expected to follow best practices described below.

7.1 hide() and show() methods

7.2 boundingRect, overlaysContent and ongeometrychange attributes

User Agent MUST only allow overlaysContent to be set in a secure, top-level browsing context.

A. IDL Index

WebIDLpartial interface Navigator {
    [SecureContext, SameObject] readonly attribute VirtualKeyboard virtualKeyboard;
};

[Exposed=Window, SecureContext]
interface VirtualKeyboard : EventTarget {
    undefined show();
    undefined hide();
    readonly attribute DOMRect boundingRect;
    attribute boolean overlaysContent;
    attribute EventHandler ongeometrychange;
};

 partial interface mixin ElementContentEditable {
     [CEReactions] attribute DOMString virtualKeyboardPolicy;
};

B. Contributors

Editor's note

Add contributors

C. References

C.1 Normative references

[dom]
DOM Standard. Anne van Kesteren. WHATWG. Living Standard. URL: https://dom.spec.whatwg.org/
[geometry-1]
Geometry Interfaces Module Level 1. Simon Pieters; Chris Harrelson. W3C. 4 December 2018. W3C Candidate Recommendation. URL: https://www.w3.org/TR/geometry-1/
[HTML]
HTML Standard. Anne van Kesteren; Domenic Denicola; Ian Hickson; Philip Jägenstedt; Simon Pieters. WHATWG. Living Standard. URL: https://html.spec.whatwg.org/multipage/
[RFC2119]
Key words for use in RFCs to Indicate Requirement Levels. S. Bradner. IETF. March 1997. Best Current Practice. URL: https://www.rfc-editor.org/rfc/rfc2119
[RFC8174]
Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words. B. Leiba. IETF. May 2017. Best Current Practice. URL: https://www.rfc-editor.org/rfc/rfc8174
[webidl]
Web IDL. Boris Zbarsky. W3C. 15 December 2016. W3C Editor's Draft. URL: https://heycam.github.io/webidl/