Table of contents
Appendices
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A.1 Introduction
Introduction
Each keyboard event references a key using a DOMString
key identifier. The set contained in this appendix is based on the
sets of keycodes from:
While implementations are recommended to use the most relevant
identifier for a key independently of the platform or keyboard
layout mappings, DOM applications should not make assumption on
the ability of keyboard devices to generate them. When using
keyboard events, "consider using numbers and function keys
(F4, F5, and so on) instead of letters in shortcut-key
combinaisons" ([DWW95])
given that most keyboard layouts will provide keys for those.
"U+000000", "U+000001", ...,
"U+FFFFFF" are Unicode based key identifiers ([Unicode30]). When a key cannot be mapped to Unicode, a
specific identifier is used (see also [Guidelines for defining key identifiers]). In
any case, no assumption should be made between the sequence of
keyboard events and the text events. The following three examples
illustrated the concept of keyboard layout mappings and its
relation with keyboard events.
The keystroke "U+000051" (Latin Capital Letter Q key)
will produce (on a PC/AT US keyboard using a US keyboard layout
mapping and without any modifier activated) the Unicode character
q (Latin Small Letter Q):
-
{"http://www.w3.org/2001/xml-events", "keydown"}:
"U+000051" (Latin Capital Letter Q key)
-
{"http://www.w3.org/2001/xml-events", "textInput"}:
"q"
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{"http://www.w3.org/2001/xml-events", "keyup"}:
"U+000051" (Latin Capital Letter Q key)
If the keyboard layout mapping is switched to a french mapping,
pressing the same key will produce:
-
{"http://www.w3.org/2001/xml-events", "keydown"}:
"U+000041"
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{"http://www.w3.org/2001/xml-events", "textInput"}:
"a"
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{"http://www.w3.org/2001/xml-events", "keyup"}:
"U+000041"
If the keyboard layout mapping is switched to a serbian (cyrillic)
mapping, pressing the same key will produce:
-
{"http://www.w3.org/2001/xml-events", "keydown"}:
"U+000409"
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{"http://www.w3.org/2001/xml-events", "textInput"}:
"љ"
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{"http://www.w3.org/2001/xml-events", "keyup"}:
"U+000409"
NOTE:
The order between the text event and keyboard events may differ
depending on the keyboard devices.
Modifier keys[top]
Modifier keys
Keyboard input use modifier keys to change the normal behavior
of a key. The KeyboardEvent interface provides
specific attributes for them:
KeyboardEvent.ctrlKey,
KeyboardEvent.shiftKey,
KeyboardEvent.altKey,
KeyboardEvent.metaKey, and
KeyboardEvent.altGraphKey.
The following example describes a possible sequence of keys to
generate the Unicode character Q (Latin Capital Letter Q)
on a PC/AT US keyboard using a US mapping:
-
{"http://www.w3.org/2001/xml-events", "keydown"}:
"Shift", shiftKey
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{"http://www.w3.org/2001/xml-events", "keydown"}:
"U+000051" (Latin Capital Letter Q key), shiftKey
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{"http://www.w3.org/2001/xml-events", "textInput"}:
"Q"
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{"http://www.w3.org/2001/xml-events", "keyup"}:
"U+000051" (Latin Capital Letter Q key), shiftKey
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{"http://www.w3.org/2001/xml-events", "keyup"}:
"Shift"
The following example describes a possible sequence of keys that
does not generate a Unicode character (using the same configuration):
-
{"http://www.w3.org/2001/xml-events", "keydown"}:
"Control", ctrlKey
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{"http://www.w3.org/2001/xml-events", "keydown"}:
"U+000056" (Latin Capital Letter V key), ctrlKey
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{"http://www.w3.org/2001/xml-events", "keyup"}:
"U+000056" (Latin Capital Letter V key), ctrlKey
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{"http://www.w3.org/2001/xml-events", "keyup"}:
"Control"
Dead keys
Keyboard input use dead keys for the input of composed character
sequences. Unlike the handwriting sequence, in which users type
the base character first, keyboard input require to enter a
special state when a dead key is pressed and emit the
character(s) only when one of a limited number of "legal" base
character is entered.
The dead keys are represented in the key identifiers set using
combining diacritical marks. The sequence of keystrokes
"U+000302" (Combining Circumflex Accent key) and "U+000045"
(Latin Capital Letter E key) will likely produce (on a PC/AT
french keyboard using a french mapping and without any modifier
activated) the Unicode character é (Latin Small Letter E
With Acute) or the composed Unicode character sequence e
(Latin Small Letter E) and 000302 (Combining
Circumflex Accent). In practice, french keyboard input will
generate the Unicode character é instead of the composed
Unicode character sequence, as shown in the following example:
-
{"http://www.w3.org/2001/xml-events", "keydown"}:
"U+000302" (Combining Circumflex Accent key)
-
{"http://www.w3.org/2001/xml-events", "keyup"}:
"U+000302" (Combining Circumflex Accent key)
-
{"http://www.w3.org/2001/xml-events", "keydown"}:
"U+000045" (Latin Capital Letter E key)
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{"http://www.w3.org/2001/xml-events", "textInput"}:
"é"
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{"http://www.w3.org/2001/xml-events", "keyup"}:
"U+000045" (Latin Capital Letter E key)
Input Method Editors[top]
Input Method Editors
Also known as
front end processor, an input method
editor (IME) is an application that performs the conversion
between keystrokes and ideographs or other characters, usually
by user-guided dictionary lookup.
The IMEs function keys are not represented in this set. As an
example, receiving an keydown for the "Accept" key identifier
does not necessarily implies that the text currently selected in
the IME is being accepted. It only indicates that a keystroke
happened, disconnected from the IME Accept
functionality. Depending on the device in use, the IME Accept
functionality can be obtain using the Accept key or the Return
key. Keyboard events cannot be used to determine the current
state of the input method editor.
Keyboard events correspond to the events generated by the input
device after the keyboard layout mapping but before the
processing of the input method editor.
The following example describes a possible sequence of keys to
generate the Unicode character し (Hiragana Letter SI)
using Japanese input methods. This assumes that the input method
editor is activated and in the Japanese-Romaji input mode. The
keys "Convert" and "Accept" may be
replaced by others depending on the input device in use and the
configuration of the IME, e.g. it could be respectively
"U+000020" (Space key) and "Enter".
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{"http://www.w3.org/2001/xml-events", "keydown"}:
"U+000053" (Latin Capital Letter S key)
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{"http://www.w3.org/2001/xml-events", "keyup"}:
"U+000053" (Latin Capital Letter S key)
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{"http://www.w3.org/2001/xml-events", "keydown"}:
"U+000049" (Latin Capital Letter I key)
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{"http://www.w3.org/2001/xml-events", "keyup"}:
"U+000049" (Latin Capital Letter I key)
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{"http://www.w3.org/2001/xml-events", "keydown"}:
"Convert"
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{"http://www.w3.org/2001/xml-events", "keyup"}:
"Convert"
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{"http://www.w3.org/2001/xml-events", "keydown"}:
"Accept"
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{"http://www.w3.org/2001/xml-events", "textInput"}:
"し"
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{"http://www.w3.org/2001/xml-events", "keyup"}:
"Accept"
NOTE:
This specification does not provide a representation of the
input method editor (IME) events, e.g. representing the input
context.
Guidelines for defining key identifiers[top]
Guidelines for defining key identifiers
NOTE:
This section is informative.
The list of key identifiers contained in this appendix is not
exhaustive and input devices may have to define their own key
identifiers. Here is a algorithm to determine which key
identifier to use:
-
Determine a representation for the key by looking at the
keyboard layout mapping in use (and not the keyboard device
in use). This representation should be unique, as human
friendly as possible, platform independent, and
consistent. For example, on PC/AT US keyboards with a US
mapping, the 'Q' key is mapped to the key identifier
"U+000051" (Latin Capital Letter Q key), the '1/!' key is
mapped to the key identifier "U+000031" (Digit One key), the
key '`/~' is mapped to the key identifier "U+000060" (Grave
Accent key), and the 'Enter' key is mapped to the key
identifier "Enter".
-
Find an appropriate mapping in the Unicode character
set. There might not always be an appropriate and obvious
mapping: the Unicode set contains characters and symbols,
the key might generate different characters depending on the
operating system, ... In general, unless the representation
of the key can be mapped to a unique Unicode character, it
is better to create a new one.
-
If no appropriate mapping was found, create an key
identifier as human friendly as possible. As an example, the
Enter key is mapped to the key identifier "Enter" and not to
"U+00000A" (Line Feed), given that this key generates the
character 00000A on Unix operating systems and the
characters 00000D and 00000A on Windows operating systems.
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