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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// @dart = 2.12
part of dart.ui;
/// The type of a key event.
// Must match the KeyEventType enum in ui/window/key_data.h.
enum KeyEventType {
/// The key is pressed.
/// The key is released.
/// The key is held, causing a repeated key input.
/// Information about a key event.
class KeyData {
/// Creates an object that represents a key event.
const KeyData({
required this.timeStamp,
required this.type,
required this.physical,
required this.logical,
required this.character,
required this.synthesized,
/// Time of event dispatch, relative to an arbitrary timeline.
/// For synthesized events, the [timeStamp] might not be the actual time that
/// the key press or release happens.
final Duration timeStamp;
/// The type of the event.
final KeyEventType type;
/// The key code for the physical key that has changed.
final int physical;
/// The key code for the logical key that has changed.
final int logical;
/// Character input from the event.
/// Ignored for up events.
final String? character;
/// If [synthesized] is true, this event does not correspond to a native event.
/// Although most of Flutter's keyboard events are transformed from native
/// events, some events are not based on native events, and are synthesized
/// only to conform Flutter's key event model (as documented in
/// the `HardwareKeyboard` class in the framework).
/// For example, some key downs or ups might be lost when the window loses
/// focus. Some platforms provides ways to query whether a key is being held.
/// If the embedder detects an inconsistency between its internal record and
/// the state returned by the system, the embedder will synthesize a
/// corresponding event to synchronize the state without breaking the event
/// model.
/// As another example, macOS treats CapsLock in a special way by sending
/// down and up events at the down of alterate presses to indicate the
/// direction in which the lock is toggled instead of that the physical key is
/// going. A macOS embedder should normalize the behavior by converting a
/// native down event into a down event followed immediately by a synthesized
/// up event, and the native up event also into a down event followed
/// immediately by a synthesized up event.
/// Synthesized events do not have a trustworthy [timeStamp], and should not be
/// processed as if the key actually went down or up at the time of the
/// callback.
/// [KeyRepeatEvent] is never synthesized.
final bool synthesized;
// Returns the bits that are not included in [valueMask], shifted to the
// right.
// For example, if the input is 0x12abcdabcd, then the result is 0x12.
// This is mostly equivalent to a right shift, resolving the problem that
// JavaScript only support 32-bit bitwise operations and needs to use division
// instead.
static int _nonValueBits(int n) {
const int valueMask = 0x000FFFFFFFF;
// `n >> valueMaskWidth` is equivalent to `n / divisorForValueMask`.
const int divisorForValueMask = valueMask + 1;
const int valueMaskWidth = 32;
// Equivalent to assert(divisorForValueMask == (1 << valueMaskWidth)).
const int _firstDivisorWidth = 28;
assert(divisorForValueMask ==
(1 << _firstDivisorWidth) * (1 << (valueMaskWidth - _firstDivisorWidth)));
// JS only supports up to 2^53 - 1, therefore non-value bits can only
// contain (maxSafeIntegerWidth - valueMaskWidth) bits.
const int maxSafeIntegerWidth = 52;
const int nonValueMask = (1 << (maxSafeIntegerWidth - valueMaskWidth)) - 1;
if (identical(0, 0.0)) { // Detects if we are on the web.
return (n / divisorForValueMask).floor() & nonValueMask;
} else {
return (n >> valueMaskWidth) & nonValueMask;
String _logicalToString() {
final String result = '0x${logical.toRadixString(16)}';
final int planeNum = _nonValueBits(logical) & 0x0FF;
final String planeDescription = (() {
switch (planeNum) {
case 0x000:
return ' (Unicode)';
case 0x001:
return ' (Unprintable)';
case 0x002:
return ' (Flutter)';
case 0x011:
return ' (Android)';
case 0x012:
return ' (Fuchsia)';
case 0x013:
return ' (iOS)';
case 0x014:
return ' (macOS)';
case 0x015:
return ' (GTK)';
case 0x016:
return ' (Windows)';
case 0x017:
return ' (Web)';
case 0x018:
return ' (GLFW)';
return '';
return '$result$planeDescription';
String? _escapeCharacter() {
if (character == null) {
return character ?? '<none>';
switch (character!) {
case '\n':
return r'"\n"';
case '\t':
return r'"\t"';
case '\r':
return r'"\r"';
case '\b':
return r'"\b"';
case '\f':
return r'"\f"';
return '"$character"';
String? _quotedCharCode() {
if (character == null)
return '';
final Iterable<String> hexChars = character!.codeUnits
.map((int code) => code.toRadixString(16).padLeft(2, '0'));
return ' (0x${hexChars.join(' ')})';
String toString() => 'KeyData(key ${_typeToString(type)}, physical: 0x${physical.toRadixString(16)}, '
'logical: ${_logicalToString()}, character: ${_escapeCharacter()}${_quotedCharCode()}${synthesized ? ', synthesized' : ''})';
/// Returns a complete textual description of the information in this object.
String toStringFull() {
return '$runtimeType('
'type: ${_typeToString(type)}, '
'timeStamp: $timeStamp, '
'physical: 0x${physical.toRadixString(16)}, '
'logical: 0x${logical.toRadixString(16)}, '
'character: ${_escapeCharacter()}, '
'synthesized: $synthesized'
static String _typeToString(KeyEventType type) {
switch (type) {
case KeyEventType.up:
return 'up';
case KeyEventType.down:
return 'down';
case KeyEventType.repeat:
return 'repeat';