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[Web] Synthesize key events for modifier keys on pointer events. #36724

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Oct 21, 2022
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[Web] Synthesize key events for modifier keys on pointer events. #36724

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c727189
Synthesize key events for shift key on pointer events.
bleroux Oct 12, 2022
a5c151a
Get the timestamp from the DOM event
bleroux Oct 14, 2022
7bfc20b
Check all modifiers for PointerEvent, MouseEvent and TouchEvent
bleroux Oct 19, 2022
14820cc
Inject KeyboardConverter + add tests
bleroux Oct 19, 2022
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Get the timestamp from the DOM event
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@bleroux
bleroux committed Oct 19, 2022
commit a5c151ab0be675a546c254737aeff70cd4fb4070
9 changes: 5 additions & 4 deletions lib/web_ui/lib/src/engine/keyboard_binding.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -153,14 +153,15 @@ class KeyboardBinding {
}

// Synthesize shift key up or down event only when the known pressing state is different.
void synthesizeShiftKeyIfNeeded(ui.KeyEventType type) {
void synthesizeShiftKeyIfNeeded(ui.KeyEventType type, num eventTimestamp) {
// TODO(bleroux): should we take care of shift left AND shift right?
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@dkwingsmt dkwingsmt Oct 13, 2022

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Yes.

Let's use a "least event dispatched" strategy:

  • If the true state is pressed, and neither key is pressed, press the left key.
  • If the true state is not pressed, and any key is pressed, release these keys.
  • Otherwise, dispatch no events.

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@bleroux bleroux Oct 18, 2022

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Done

final int physicalShift = kWebToPhysicalKey['ShiftLeft']!;
final bool alreadyPressed = _converter._pressingRecords.containsKey(physicalShift);
final bool synthesizeDown = type == ui.KeyEventType.down && !alreadyPressed;
final bool synthesizeUp = type == ui.KeyEventType.up && alreadyPressed;
if (synthesizeDown || synthesizeUp) {
_converter.performDispatchKeyData(_shiftLeftKeyData(type));
final Duration timestamp = _eventTimeStampToDuration(eventTimestamp);
_converter.performDispatchKeyData(_shiftLeftKeyData(type, timestamp));
// Update pressing state
if (synthesizeDown) {
_converter._pressingRecords[physicalShift] = _kLogicalShiftLeft;
Expand All @@ -170,9 +171,9 @@ class KeyboardBinding {
}
}

ui.KeyData _shiftLeftKeyData(ui.KeyEventType type) {
ui.KeyData _shiftLeftKeyData(ui.KeyEventType type, Duration timestamp) {
return ui.KeyData(
timeStamp: Duration.zero,
timeStamp: timestamp,
type: type,
physical: kWebToPhysicalKey['ShiftLeft']!,
logical: _kLogicalShiftLeft,
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@dkwingsmt dkwingsmt Oct 13, 2022

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This magic value is concerning, but for now we don't have other ways than keeping a static map from physical keys to logical keys.

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@bleroux bleroux Oct 18, 2022

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I added _kPhysicalxxx variables (similar to the _kLogicalxxx ones) to centralize those magic values.
Maybe adding a generated enum in key_map.g.dart could help to not dissiminate those magic values and might make it possible to rely on const variables?

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2 changes: 2 additions & 0 deletions lib/web_ui/lib/src/engine/pointer_binding.dart
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Expand Up @@ -613,9 +613,11 @@ class _PointerAdapter extends _BaseAdapter with _WheelEventListenerMixin {
void _checkModifiersState(DomEvent event) {
// TODO(bleroux): add support for 'Meta', 'Ctrl' and 'Alt'
final DomPointerEvent pointerEvent = event as DomPointerEvent;

final bool shiftPressed = pointerEvent.getModifierState('Shift');
KeyboardBinding.instance!.synthesizeShiftKeyIfNeeded(
shiftPressed ? ui.KeyEventType.down : ui.KeyEventType.up,
event.timeStamp!,
);
}

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