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add PointerDeviceKind to ScaleStartDetails #165096

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add PointerDeviceKind to ScaleStartDetails #165096

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yakagami
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@yakagami yakagami commented Mar 13, 2025 •
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Adds the PointerDeviceKind of the scale start event to ScaleStartDetails, which is currently missing.

This is a bug according to #115061. Additionally, according to the docs:

Having both a pan gesture recognizer and a scale gesture recognizer is redundant; scale is a superset of pan. Just use the scale gesture recognizer.

See also #135936 for similar issues and the PRs fixing them.

If multiple pointers are contacting the screen at scale start, then the PointerDeviceKind of the first pointer is used. In practice this should be good enough as I don't know of any UI that expects you to use two different pointer kinds at the same time. However, if this is an issue, we could either give a list of pointers with their kinds or a set of all active PointerDeviceKinds. I don't think this is necessary though.

Closes #115061.

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@github-actions github-actions bot added framework flutter/packages/flutter repository. See also f: labels. f: gestures flutter/packages/flutter/gestures repository. labels Mar 13, 2025
justinmc
justinmc reviewed Mar 18, 2025
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Looks good except for a small docs change. Thanks for jumping in and making this change. I'm sure a lot of people have struggled with not having this value over the years when someone just needed to add it.

packages/flutter/lib/src/gestures/scale.dart Outdated
Comment on lines 138 to 140
/// The kind of the device that initiated the event. If multiple pointers are
/// touching the screen, the kind of the pointer device that first initiated
/// the event is used.
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The first sentence should be its own paragraph per the styleguide: https://github.com/flutter/flutter/blob/master/docs/contributing/Style-guide-for-Flutter-repo.md#dartdoc-specific-requirements

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done

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I'm sure a lot of people have struggled with not having this value over the years when someone just needed to add it.

Yeah, I was going though the f: gestures issues and noticed I would actually benefit from this myself for my package (https://pub.dev/packages/zoom_view). Right now I use a Listner to get the device kind. The specific reason I need it is because for trackpads you need to disambiguate scaling from panning differently than other pointers. With other pointers you can just check that pointerCount == 1 which is a pan and pointerCount == 2 is a scale. This doesn't work with trackpads because you pan with two fingers on a trackpad. #13102 is related here. I've been thinking if there was a way for the framework to handle that natively and might make another pull request for that.

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How to use scale gesture recognizer instead of pan recognizer
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