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Fabric: core Switch renders but never fires onValueChange on mouse click (new architecture)

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#16,316 0 comentarios 0 reacciones 0 asignados Ver en GitHub

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Evaluación

Dificultad
4/5
Tiempo estimado
3-5 días
Aptitud para principiantes
58/100
Tipo de issue
Error
Claridad
Bastante claro
Estado de actividad
Tranquilo
Stack tecnológico
cpp, react-native
Área
desktop, frontend

Línea de trabajo

Comienza en vnext/Microsoft.ReactNative/Fabric/Composition/SwitchComponentView.cpp, centrándote en OnPointerPressed, OnPointerReleased y las comprobaciones de IsPrimary(). Comprueba si la liberación del ratón llega a la vista y si la condición la acepta; después, añade la prueba de interacción descrita en el issue. Se considera terminado cuando un clic de ratón sintetizado emite SwitchEventEmitter::onChange y actualiza el Switch controlado.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

Needs: Triage :mag:

Environment

  • react-native-windows 0.83.2 (component source unchanged on main as of 2026-07-17), new architecture (Fabric, composition), Win32/HWND host
  • Windows 11, physical mouse input
  • Reproduced in a production app; repro is trivial (any core Switch)

Steps to reproduce

import {Switch} from 'react-native';

function Repro() {
  const [on, setOn] = React.useState(false);
  return <Switch value={on} onValueChange={v => { console.log('onValueChange', v); setOn(v); }} />;
}
  1. Run on react-native-windows with the new architecture enabled.
  2. Click the Switch with the mouse.

Expected

onValueChange fires with the toggled value; the Switch (a controlled component) re-renders in the new state. This is the behavior on Android/iOS.

Actual

The Switch renders correctly (including hover visuals), but onValueChange never fires on mouse click. No JS callback, no state change — the control is effectively inert for mouse users.

Root cause pointer

vnext/Microsoft.ReactNative/Fabric/Composition/SwitchComponentView.cpp (current main):

  • OnPointerReleased (~line 285) is the only mouse path to toggle() (~line 328), which emits facebook::react::SwitchEventEmitter::onChange — the native event behind onValueChange.
  • Both OnPointerPressed (~line 262) and OnPointerReleased early-return unless args.GetCurrentPoint(-1).Properties().IsPrimary() is true.

On our device the emitter never fires for mouse clicks, so either the IsPrimary() gate rejects mouse pointer input on this code path, or OnPointerReleased is never routed to the Switch component view at all (pointer capture/hit-test). We have not stepped through native to disambiguate the two; what is proven on-device is that no onChange event reaches JS for any mouse click, on multiple screens and multiple Switch instances. The keyboard path (OnKeyUp, Space, ~line 318) is separate and was not part of this investigation.

Suggested fix

Ensure the pointer-released path reaches toggle() for mouse input: verify PointerRoutedEventArgs::GetCurrentPoint(-1).Properties().IsPrimary() returns true for mouse-generated pointer events in the composition input pipeline (or drop the IsPrimary() gate for mouse pointer devices), and add an interaction test that asserts SwitchEventEmitter::onChange fires on a synthesized mouse click.

Workaround (what we ship today)

Wrap the Switch in a Pressable that owns the interaction, and make the Switch itself inert:

<Pressable onPress={() => setOn(v => !v)}>
  <Switch value={on} pointerEvents="none" />
</Pressable>

The Pressable receives the click and toggles state; the Switch is display-only. This restores mouse operation but bypasses the control's own accessibility/interaction semantics.

Lenguaje dominante
C++
Estrellas
17.4k
Forks
1.2k
Merge medio
2 d 17 h
PR fusionados (30 d)
13

Preparar el entorno

Primeros pasos

  1. Lee el issue completo y luego la guía de contribución del proyecto.
  2. Comenta en el issue que vas a ocuparte — evita que dos personas hagan lo mismo.
  3. Haz un fork del repositorio y trabaja en una rama.
  4. Abre un pull request que haga referencia al número del issue.

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