Re: [pointerevents] Expose event for pinch gesture (#543)

Awesome :)

I work for a w3c member, so I'm happy to join the WG and the meetings if you think it'd be useful.

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Fwiw, while playing with userland solutions for this I realized that a possible approach is not specific to pinch to zoom and touch gestures.

One could have an event, `zoom`, with the following properties:
- clientX/clientY (and related coordinate systems)
- zoomFactor

1. When performing a pinch-to-zoom gesture, it would fire the event with (x,y) set to the center of the fingers, and with zoomFactor set to the percentage that the difference between the fingers increased/decreased.
1. When performing a Ctrl+wheel, the coordinates would be the mouse coordinates and the zoomFactor would be some platform-specific amount computed based on the "wheel scroll speed".
1. When performing a Ctrl+Plus and Ctrl+Minus, or using the browser's "zoom in/out" buttons, the coordinates would be either NaN or the center of the window, and the zoom factor would again be browser-defined.

Listeners for these events would probably need to be passive by default, unless `passive: false` is explicitly set.

These events would be cancelable, so that user code can define their own zoom behavior. Maybe the event dispatched by the browser zoom buttons should not be cancelable.

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Received on Wednesday, 16 July 2025 16:46:54 UTC